

                            ASTROMETRICA SHAREWARE
                           


 This is an  unclicensed version of  "Astrometrica".  As usual,  you may use
 this shareware two weeks for free. After you have tested this software, you
 either delete all copies,  or register yourself as licensed user. To do so,
 send at least US$ 25.- to the author of  "Astrometrica"  and you will get a
 licensed copy of the latest version of this shareware.  Please  use  Postal
 Money Order or send Cash in a letter.  Cheques  can not be accepted because
 of the high fees taken by the bank!

 As a shareware author,  you may use  the program  for free,  but you should
 contact the author of  "Astrometrica", too:  After sending a description of
 your  shareware-programs  to the address  given  below,  you will receive a
 licensed copy of the latest version of "Astrometrica", too.

 It is expressly welcome to distribute copies of this demo disk on diskette,
 via bulletin boards or computer networks.

 This unlicensed copy of "Astrometrica"  is a fully operationable version of
 that software, only the number of reference stars is limited to four (while
 a licensed copy allows up to twelve reference stars).

 To order "Astrometrica",  please use the form which is included in the file
 REGISTER.TXT.  The  address  of  the  author,  where you can order licensed 
 versions of "Astrometrica", is:

                                 Herbert Raab
                                Schrammlstr. 8
                                 A-4050 Traun
                                   Austria

                                   e-mail:
                         Herbert.Raab@jk.uni-linz.ac.at

 ----------------------------------------------------------------------------



                               ASTROMETRICA 3.1
                              

  
  A short description of the new features  of  version  3.1  is given in the
  file NEW.TXT!


  ABOUT ASTROMETRICA
  

  "Astrometrica"  1.0  was  implemented  between  February and June 1993  in
  order to check the possibility  of using  CCD cameras for astrometric work
  on minor planets and comets.

  During the development of "Astrometrica",  in the months mentioned above,
  about  150 CCD images of comets were measured successfully.  Thus, it was
  possible to adapt the program to the needs of practical working amateurs.

  Version 1.1 was created in September 1993.  It allowed  loading compressed
  ST-6 files and created a file named  CREPORT.TXT, which is compatible with
  the IAU standard file format for reporting astrometric observations.

  Version 1.2,  which was released in October 1993, supported the comparison
  of two CCD images by electronically blinking them.

  Version 2.0, finished in April 1994, was able to read ST-4 and TIFF files.
  Furthermore,  the methods for astrometric and photometric  data  reduction
  were improved.

  Version 2.1, released in October 1994,  had  an  expanded  file  interface
  which was also able to read FITS files.  Among the many program extensions
  was an expanded blink-comparator and an improved centroiding algorithm.

  Version 3.0 was finished in April 1995. It can read large CCD images up to
  2056 x 1032 Pixels in size.  Under  the  many  improvements is a tool that
  supports the calculation of the time of mid-exposure for composite images,
  an interface  to other star  catalogues,  and the support of the new style
  IAU comet designations.

  Version 3.1, completed in August 1996, added  Super VGA support (800 x 600
  resolution),  a file interface for Cookbook CCD cameras,  a command to re-
  call the last reference star field, and an improved blink comperator.


  WHAT YOU NEED
  

  * PC-compatible computer with 80286 (or later) CPU with at least 1 MB XMS,
    memory (more for large images),  standard VGA graphics card and a Micro-
    soft compatible mouse (original Microsoft mouse driver recommended).

  * MS-DOS 5.0 (or later version).

  * The  "Hubble Space Telescope Guide Star Catalog"  (GSC),  version 1.0 or
    1.1,  on CD-ROM or copied onto the computer's hard disk (with  the  same
    directory structure as on the CD-ROM). "Astrometrica" reads the original
    version only (FITS files on two CD-ROMs),  but won't work with truncated
    or compressed versions of the GSC,  as  shipped with some other software
    packages.
    The two GSC CD-ROM's are available from the following address for  about
    (US) $70 + shipping & handling:

            Astronomical Society of the Pacific
            390 Ashton Ave.
            Dept. AD
            San Francisco, CA 94112      U.S. Phone: (415) 337 2624
            U.S.A.                       U.S. Fax:   (415) 337 5205


  WHAT'S ON THE DISK
  

  The diskette holds the following files:

  * ASTROMET.EXE: The executable program ("Astrometrica").

  * DPMI16BI.OVL, RTM.EXE: These files represent the DOS Protected Mode
    Interface and the Run Time Manager for Protected Mode Applications. Note
    that they must be located in the same directory as ASTROMET.EXE.

  * REGIONS.DAT: A file which holds information on the location of the GSC
    regions.

  * DEMO.CAT: A file with refernce star data for the demo-images. See the
    section 'Using an alternative Star Catalogue' below for information how
    to use these data.

  * README.BAT and README.TXT: The text you are reading and a batch file to
    display it.

  * LIESMICH.BAT and LIESMICH.TXT: The German version of this text, and a 
    batch file to display it.

  * NEW.TXT, NEU.TXT:   A brief description  of the new functions of version
    3.1 in English and German.

  * ASTROMET.PIF, ASTROMT1.ICO, ASTROMT2.ICO: A Program Information File and
    two nice Icons for those who want to run  "Astrometrica"  from  Windows.
    (Please refer to your Windows manual on how to run DOS-Appliactions from
    Windows.)

  * /HGXMOUSE: This subdirectory contains the shreware TSR-tool HGXMOUSE,
    which supports mouse operations in Super VGA graphics modes. Please
    read the file HGXMOUSE.TXT from this directory for further information.

  * /CCD: A subdirectory with sample images and a text file (README.TXT)
    containing some comments about these images.

  * /ELM: A subdirectory with the orbital elements of the objects on the
    sample images.


  INSTALLING ASTROMETRICA
  

  Installing  "Astrometrica"  on  your  computer's  hard disk drive  is very
  simple.  Using  the  MS-DOS  command  MD  (for  Make Directory),  create a
  directory to operate from and then copy the files from your "Astrometrica"
  floppy disk onto your hard disk.  You may also  copy the sample images and
  the orbital elements to the subdirectories where you store your CCD images
  and orbital elements, respectively.

  When you start  "Astrometrica"  for the first time,  a message will appear
  telling  you  that the  file for  initializing  the  software could not be
  found.  You should go through  the 'Options' menu  now  and  configure the
  software, as described later.


  COMMANDS
  

  ͻ
   Menu     Command           Description                               
  ͹
   File     Load Image        Loads, depending on the configuration,    
                              SBIG, Cookbook, FITS or TIFF files from   
                              the disk into the main memory             
           Ķ
            View Text-File    Loads and displays a text file            
           Ķ
            Save Text-File    Writes the contents of the active window  
                              to a text file                            
           Ķ
            Print Text-File   Prints the contents of the active window  
           Ķ
            Printer Setup     Sets printer commands (hex codes)         
           Ķ
            Change Dir        Changes the default directory             
           Ķ
            Delete File       Deletes a file selected by the user       
           Ķ
            DOS Shell         Temporarily exits to DOS                  
           Ķ
            Exit              Exits "Astrometrica" (quits the program)  
  Ķ
   Display  Chart             Displays a chart of a part of the sky     
           Ķ
            Image             Displays the current image, and allows    
                              inspection of its pixels with a crosshair 
           Ķ
            Parameters        Displays information on the current image 
           Ķ
            Negative          Toggles negative display of the CCD image 
           Ķ
            Load User         Loads and sets an alternative color       
            Color Table       table (ST-6 file format)                  
           Ķ
            Set Standard      Sets the standard color table             
            Color Table       (Gray-scale)                              
  Ķ
   Measure  Select Reference  Displays a chart of that part of the sky  
            Stars             seen on the CCD image, in order to select 
                              the reference stars, which will be used   
                              to calculate the position and brightness  
                              of the object in question                 
           Ķ
            Recall Reference  Recalls the last reference star field to  
            Stars             remove stars, or select new ones          
           Ķ
            Measure Position  Displays the current image in order to    
                              measure the position of the reference     
                              stars and the object in question          
           Ķ
            Measure           Displays the current image in order to    
            Position & Mag    measure the position and brightness of    
                              the reference stars and the object in     
                              question                                  
           Ķ
            Remeasure Object  Remeasures the object without remeasuring 
                              the reference stars                       
           Ķ
            Information       Displays information on the last measure- 
                              ment like plate constants, centroid,      
                              contrast index and focal length           
  Ķ
   Utility  Background        Sets the display parameters Background and
            & Range           Range, which control the image contrast   
           Ķ
            Scale             Sets the display parameters so that a     
                              given amount of pixels will appear black  
                              (Low Limit) and white (High Limit)        
           Ķ
            Smooth            Applys a mean value filter to the image   
           Ķ
            Median Filter     Applys a median filter to the image       
           Ķ
            Blink Images      Compares two images by blinking them      
           Ķ
            Edit Parameters   Edits information on the image which is   
                              important for astrometric work.  This     
                              function will also be called after an     
                              image has been loaded from the disk       
           Ķ
            Change Star       Selects a star catalogue (file format de- 
            Catalogue         scribed below) to be used instead of the  
                              GSC                                       
           Ķ
            Default Catalogue Specifies the default star catalogue (GSC)
  Ķ
   Ephem    Load Elements     Loads orbital elements from the disk into 
                              the main memory                           
           Ķ
            Save Elements     Saves the current set of orbital elements 
                              to disk                                   
           Ķ
            Discard Elements  Removes the current orbital elements from 
                              the main memory                           
           Ķ
            Calculate         Calculates an ephemeris from the current  
                              set of orbital elements for a given time, 
                              at the end of evening twilight or at the  
                              beginning of morning twilight             
           Ķ
            Scan Elements     Scans the orbital elements on the disk and
                              displays a "what's up tonight" listing    
           Ķ
            Display Elements  Displays the current set of elements      
           Ķ
            Edit Elements     Allows new orbital elements to be input,  
                              and previously saved elements to be edited
  Ķ
   Options  Directories       Sets the paths for the CCD images, GSC    
                              data, and the files with orbital elements 
           Ķ
            Observatory       Sets the default information on the       
                              observatory's location and equipment      
           Ķ
            CCD               Sets the default information for your CCD 
           Ķ
            Settings          Sets the default values for data reduction
                              and ephemeris calculation                 
           Ķ
            User              Sets the default information on the user  
  Ķ
   Windows  Resize/Move       Changes the size or position of the       
                              active window                             
           Ķ
            Zoom              Enlarges or restores the size of the      
                              active window                             
           Ķ
            Next              Makes the next window active              
           Ķ
            Close             Closes the active window                  
           Ķ
            Tile              Arranges windows by tiling                
           Ķ
            Cascade           Arranges windows by cascading             
  Ķ
   About    About             Displays information about "Astrometrica" 
            Astrometrica                                                
           Ķ
            License Info      Displays the license information          
  ͼ


  USING "ASTROMETRICA"
  

  "Astrometrica" has a dialog-based user interface, and most users are quite
  familiar  with  it  after playing around with it a while.  As  with  other
  programs having a similar user interface,  you can select  the  menues  by
  pressing  the <Alt>-key and highlighted character in the menue's name.  To
  select a command from a menue,  simply  press  the  highlighted key in the
  command's name.  Of  course,  you  may also use the mouse and click on the
  respective names of the menues and commands.

  Within a dialog,  you can activate the input lines by  double-clicking  in
  the respective fields or by a single click on  the  labels  of  the  input
  lines.  You may also press the  <Alt>-key and the highlighted caharcter in
  the label to select the respective input line or button.  Finally, you can
  use the tabulator key to move the focus from one dialog element forward to
  the next (or backwards, when you also hold down the <Shift> key).

  Some users noted that the mouse cursor disappears sometimes.  This problem
  seems to depent on the hard- and software configuration (the graphics card
  and the mouse driver) used. If you encounter that problem, press <Alt>+<Q>
  and the mouse cursor will be visible again  -  or maybe not...   To  avoid
  problems with the mouse,  using  the  original  Microsoft  mouse driver is
  highly recommended.

  Setup - the 'Options' Menu
  

  When you use  "Astrometrica" for the first time, you should go through the
  'Options' menu first.  The following are available under this menu:

  * 'Directory':  Here you can  specify the  path where  the CCD  images are
  stored, the CD-ROM drive which contains the GSC data (or a subdirectory on
  a hard disk,  with the same  tree of subdirectories as on the CD-ROM)  and
  the path where the files holding the orbital elements can be found.

  * 'Observatory':  This is used to set the default information on the loca-
  tion and  equipment of your observatory, which is used during the calcula-
  tion of an ephemeris,  and the preparation of the REPORT-files.  The value
  entered in the  'Time Zone'  field will be  added by the  software  to the
  times given in the image  header to convert  local time to  Universal Time
  (U.T.).  Enter zero if the  clock of the  computer  you  used to  take the
  images is running on U.T.  Otherwise,  note that this value is negative in
  the eastern hemisphere, and positive in the western.

  * 'CCD':  This allows  you to specify  whether  you want to use ST-4, SBIG
  (Type 3), Cookbook, FITS or TIFF files.  The  spectral  band in which your
  CCD works can also be selected here.  While many  CCDs are most  sensitive
  to red light when you don't use filters,  a  sensitivity  to  visual light
  would be desireable,  as the magnitudes given by the GSC are V-magnitudes.
  If the images appear upside-down after  loading  FITS  files,  toggle  the
  'Upside Down' checkbox.

  * 'Settings':  This allows  you to limit the maximum  residuals for refer-
  ence stars to be  used in the  astrometric or  photometric data  reduction
  process, to enter the value of  T = TDT - UT  to be used in the ephemeris
  calculation,  to select the zoom factor,  and to turn  the sound  on & off
  when measuring an image and selecting reference points for blinking.

  * 'User':  This asks you for your name and your address, which will appear
  in the REPORT-file. The name you enter here (the surname, at least) should
  be equal to that of the licensee.  Otherwise,  a message will appear every
  time you start the program,  saying that this copy is not licensed to this
  user.

  * Using the 'File - Printer Setup' dialog, you can configure your printer:
  After entering the page length (in lines),  the  program asks for the hex-
  codes of the printer commands for form feed,  condensed font,  and default
  font. Note that one hex digit must be entered as two characters.


  The Status Window
  

  The Status  Window  appears  on the  bottom of the  desktop when you start
  "Astrometrica". Like other windows, it can be moved around,  but you can't
  close it. It shows the filename  of the image loaded,  the filename of the
  color table loaded,  the binning factor applied to the image, the filename
  of the star catalogue used,  and the number of  selected  reference  stars
  whose data are held in the computer's main memory.  In some  cases,  short
  messages appear within the Status Window.


  Command Line Parameters
  

  These command line parameters may be used to start "Astrometrica"  in some
  special modes. They must be specified when starting the program, following 
  the name of the program, (e.g. "ASTROMET /NoSVGA").

  /MB:  "Astrometrica" will ask for Multiple  Background  measurements. That
        is,  you  have to measure the background for the object and for each
        of the reference seperately.  This  option  may  be  useful for high
        precision photometry,  or  in  case the background in your images is
        not uniform (bad or no flat fielding).

  /ED: "Astrometrica" will display one Extra Digit in both R.A. (to 0.001 s)
        and Decl. (to 0.01").  While this extra digit is not significant for
        absolute positions (note that the positions of  the  GSC  stars  are
        usually accuarte to about 0.2" or so),  it  may  be  significant for
        relative positions (e.g., in case of last minute observations before
        stellar occulations by a minor planet).

  /NoSVGA: "Astrometrica" loads a Standard VGA graphics  driver  instead  of
        the Super VGA driver.  Use this option if your graphics seems not to
        be compatible with the Standard VGA driver.  If you make use of this
        parameter, you can neither use the high resolution 800x600 mode, nor
        blink more than two images.
        In case of problems with the graphics display,  please read the file
        SVGATRBL.TXT!


  Printing Files and Star Charts
  

  By issuing the  'File - Print Text-File'  command,  the  contents  of  the
  currently active window may be printed.  However,  no contol codes will be
  sent  to  the  printer.  Therefore,  the  user has to activate the desired
  printer font. Above all,  make sure a condensed font is used when printing
  an ephemeris generated with "Astrometrica".

  Printing of graphics is not  supported by the above command.  However,  if
  you want to print  the GSC star charts drawn by  "Astrometrica",  you just
  have to load the memory resident, DOS program "GRAPHICS".  Then,  you  can
  print the star  charts by simply hitting the  <Print Screen>  key.  Please
  refer to your DOS  manual for  details on how to configure  "GRAPHICS"  to
  support your printer.


  Loading Images
  

  Using the 'Load Image' command  from the File menu,  you can  load the CCD
  images you want to measure.  "Astrometrica"  3.0  reads ST-4, ST-4X, ST-6,
  ST-7, ST-8 and other  SBIG type 3 images, Cookbook CB 211 (PIX) and CB 245
  (PA/PB or P1/P2/P3), FITS (8, 16 and 32 bit integer)  and  uncompressed  8
  bit or 16 bit gray-scale TIFF images.

  After the image has been loaded,  the  most  important  parameters  (Date,
  Universal Time of mid-exposure, the observer's name,  and the designations
  of the object,  the  latter  with  the  default value given by the orbital
  elements)  will be displayed and may be changed,  if neccessary.  Pressing
  the  'Mid-Ex' button will start a dialog that can be used to calculate the
  mid-exposure of composite images,  or  images made using SBIG's 'Track and
  Accumulate' mode.

  With sufficient memory, it is possible to load images up  to  2056 x 1032
  pixels in size.  If the image can not be displayed  at  full  resolution, 
  2x2,  3x3  or  4x4 pixels will be binned for  display.  All calculations, 
  however,  will  be  done using the full image data available.  Also, note 
  that a magnified portion of the image can be displayed at full resolution 
  using the zoom (F8-key) mode.

  * SBIG ST-4 Images:
  Unlike other SBIG camera images,  which record the  start time and date of
  the exposure in dedicated lines in the image file header, this information
  is instead  recorded  in  the  comment string.  Furthermore,  it should be
  noted that the actual time  recorded is the time the image  finishes down-
  loading to the host computer.  This time can be several seconds later than
  the actual  end time of the image.   "Astrometrica"  tries to  calculate a
  mid-exposure time (by substracting half the exposure time),  however, most
  likely a manual correction will be required.

  * SBIG Type 3 Images:
  The header of these SBIG files gives  information on the time of the start
  and the duration of the exposure.  "Astrometrica"  can therefore calculate
  the time of mid-exposure by adding half the exposure time to the time when
  the exposure was started.
  However, when loading an image taken with the SBIG  'Track and Accumulate'
  mode, this method fails; The time of mid-exposure can  not  be  calculated
  correctly!!  You can start a dialog to calculate  the time of mid-exposure
  by pressing the 'Mid-Ex' button on the 'Edit Parameters' window.

  * Cookbook images:
  The software reads full frame images from both the  CB 211 (PIX-files) and
  the CB 245 (PA/PB, and P1/P2/P3-files).  Any  part of the CB 245 image can
  be selected in order to load the complete image.
  As the Cookbook files do  not include any information on the date and time
  when the image was taken,  the user has to enter the date and time of mid-
  exposure manually!

  * FITS images:
  "Astrometrica" reads 8, 16, and 32 bit integer FITS files.  Here is a list
  with all keywords recogniced by the software:

    Mandatory FITS standard keywords:
    SIMPLE, BITPIX, NAXIS, NAXIS1, NAXIS2, NAXIS3, END

    Optional FITS standard keywords:
    BSACLE, BZERO, BLANK, DATE-OBS, OBJECT, NOTE, OBSERVER

    Optional non-standard keywords:
    TIME-OBS, TIME-BEG, TIME-END, OBS-BEGIN, OBS-START, OBS-END, UT,
    UT-BEGIN, UT-START, UT-END, EXPOSURE, EXPTIME, EXP-TIME

  Note that any date must be given in the form DD/MM/YY,  and  times must be
  in the form HH:MM:SS. Note also that "Astrometrica" can calculate the time
  of mid-exposure only if either both the start  and the end of the exposure
  (e.g., OBS-BEGIN and OBS-END or UT-START and UT-END), or both the start of
  the exposure and it's duration in seconds  (e.g., TIME-OBS and EXPOSURE or
  UT and EXPTIME) is given.  In  case  of  keywords  starting  with 'UT', no
  correction for the local time zone will be applied.

  If you have the choice between various file  formats,  use  your  camera's
  native file format,  if supported by the software.  If you have the choice
  between FITS and TIFF, using FITS is recommended.

  ! ! ! CAUTION ! ! !
  ALWAYS CHECK THE  DATE AND UNIVERSAL TIME (UT)  OF MID-EXPOSURE CAREFULLY!
  Remember that this time should be accurate to one second! Note that it has
  been found that, on some computers,  the time setting may drift by several
  seconds during a long night's observing session.  Checking  the computer's
  clock a few times during the night may be wise.  A  clock  setting  on the
  computer, accurate to the second,  is  especially important when measuring
  fast moving objects!


  Displaying Images
  

  The  'Display - Image'  command  may  be  used  to display the current CCD
  image.  Furthermore, it is possible to obtain pixel data using crosshairs.
  Below the image,  the  coordinates  of  the pixel where the crosshairs are
  located, as well as the pixel's value, will be displayed.  The  crosshairs
  can be moved using the cursor keys, or by a mouse click. Use the F8-key to
  switch to the zoom mode.

  "Astrometrica"  will  display images with an aspect ration of x:y = 1:1.3.
  Images  taken  with CCD cameras having pixels with different aspect ratios
  (with square pixels for example) will therefore appear somewhat distorted.
  This will have no effect on the data reduction procedures  or the  results
  obtained with "Astrometrica".

  If you encounter any problems while displaying CCD images, please read the
  file SVGATRBL.TXT!


  Setting the Image Contrast
  

  There are two ways to set the image contrast in "Astrometrica". First, the
  'Utility - Background & Range' function may be used to set the contrast by
  entering the values for Background and Range.  Pixels  having values below
  "Background"  will appear black,  and the grey scales will be spread among
  those pixels having values between "Background" and "Background + Range".

  The 'Utility - Scale' command, on the other hand, will ask  the  user  for
  the percentage of pixels that should appear black  ("Low"),  and  for  the
  percentage of pixels that should appear white ("High").  In  other  words,
  "Low" is the amount of image  area covered  by blank sky,  while "High" is
  the amount covered by the brightest stars.


  Filtering Images
  

  The  'Smooth'  function  and the  'Median filter'  can be  used to  remove
  specks in the image or reduce the effects of noise.

  The Smooth function  applies a mean value filter to the image,  which sets
  the gray value of each pixel to the mean value of the pixel itself and its
  adjacent neighbors, which blurs the image a bit.

  The Median filter removes specks and noise without  sacrificing  sharpness
  by setting the gray value of each  pixel to the  median of itself  and its
  adjacent  neighbors.   However,  it  takes  about  three  times  longer to
  process the image this way as compared to the smooth function.

  Be  careful  when measuring images processed by filters other than the two
  mentioned above!  Some filters,  such as high  pass filters  ('sharpening'
  filters),  unsharp masking or convolution methods may modify  the image in
  a way that the calculation of the centroid of an image is influenced.

  Scaling of images (that is, changing the pixel values)  will influence the
  results too.  Linear scaling doesn't do much harm, providing care has been
  taken not to loose information.  Other methods,  like logarithmic scaling,
  should not be used on the images you want to measure.

  The 'Scale' and 'Background & Range' functions of  "Astrometrica",  by the
  way,  do not change the values of the  pixels in the image,  and therefore
  may be used safely. They just set the display parameters so that the image
  may be viewed at optimum contrast.

  In general,  you should use unfiltered and unscaled images for astrometric
  work.


  Compare Images
  

  By using the 'Blink Images' command of the 'Utility' menu, two to four CCD
  images can be compared,  in  order  to  detect moving or variable objects.
  First, the number of iamges to compare, and the names of the files holding
  the comparison image must be entered.  Then you have to mark two reference
  points  (stars,  for  example)  on  each image by clicking on them, so the
  images can be aligned. Try to use stars with small diameters, as it easier
  to click at the exact center of their images.  To  make  precise aligments
  easier, the mouse cursor may also be moved by pressing the arrow keys, and
  the <Enter>-key may be used to select the reference point,  instead of the
  mouse button.

  If the two images are not rotated against each other (e.g., the camera has
  not been removed  from the telescope in the time between the images),  the
  selection of a single reference point in each image is sufficient. In that
  case, instead of selecting the second reference point  on the first image,
  press the <Esc> key.

  For comparison,  the images  will be displayed alternately.  The time each
  image will be displayed can be controlled  by the keys '0' to '9'.  Press-
  ing the '1' key will allow each image to be  displayed for 50ms,  while it
  will be displayed  for 450ms  when you press '9'.  When wanting to inspect
  individual images,  pressing the '0' key will pause the blinking  routine,
  and allow the user to manually switch between images, at will, by pressing
  any key (like the <Spacebar>). In this mode, the mouse cursor appears when
  the currently loaded  CCD image is displayed.  When you click at any point
  within the image,  the  image coordinates of the point you clicked on will
  be displayed in a small window.  Close this window by pressing <Esc> or by
  clicking on the "Close" button.

  Use the  F5  key for a contrast-enhanced display of the images (this helps
  when attempting to locate faint objects).   The  F6  key  will restore the
  original contrast.

  Pressing the <Esc> key exits the blinking procedure.

  In case of problems with the graphics display during blinking, please read
  the file SVGATRBL.TXT!


  Selecting Reference Stars
  

  By issuing the 'Measure - Select Reference Stars' command,  you can select
  up to twelve reference stars,  whose data from the GSC  (or an alternative
  ASCII file) are later used to calculate the position and brightness of the
  object in question.

  From the time stored with the CCD image and from the orbital elements, the
  computer is able to select the region of the sky so that the chart and the
  CCD  image can be  displayed  at the same scale.  The aspect  ratio of the
  chart will be similar  to that of the CCD image.  If there are no  orbital
  elements loaded,  the user has to enter the  position of the object at the
  time the image was taken.

  If you have rotated the camera  so that north is not up in the image,  you
  can compensate for this field rotation, so the chart and the CCD image may
  be displayed with the same orientation.  Enter the position angle at which
  the y-axis of the CCD camera was pointing (for example, 45 if your camera
  was oriented so that the  y-axis points  towards northeast,  or,  in other
  words, north is towards the upper right of the image).

  You can also select reference stars from a chart  drawn after you selected
  the  'Display - Chart'  command.  You have to care for the  coordinates of
  the field then. While the computer gives you a suggestion for the scale of
  the chart to fit the CCD image,  the aspect ratio of the chart will not be
  changed to fit the CCD image.  When using the  'Display - Chart'  command,
  you may also key in coordinates for any equinox between J1800 and J2100  -
  they will be converted to the standard epoch J2000.0 by the program.

  you may also enter coordiantes for an aequinox other then J2000.0: The
  program will convert them to

  Select reference stars which are neither underexposed (hardly distinguish-
  able from the background  noise)  nor overexposed  (with a pixel  value of
  65535 for 16 bit images, for example).  Select seven  to  twelve reference
  stars which are evenly distributed around the object, if possible.


  Using an alternative Star Catalogue
  

  Usually, the Hubble Space Telescope Guide Star Catalogue (GSC)  is used as
  the source  for the reference  star data when doing  astrometric work with
  CCD cameras.  Sometimes however, it may be  necessary to use other sources
  for the reference star data  (for example, for "last minute astrometry" in
  preparation for an occulation of a star by a minor planet).

  "Astrometrica"  can read reference star data from files  in  a  format  as
  follows:  The  designation  of the reference star is given in columns 1 to
  13, followed by the Right Ascension (hours, minutes and seconds, separated
  by at least one blank), Declination (degrees with sign, minute and second,
  separated by blanks) and the magnitude. Between Declination and magnitude,
  proper motion data  (in time seconds per year for Right Ascension,  and in
  arc seconds per year for Declination) may be inserted.  Please  note  that
  the data entered must be for equinox J2000 (FK5 reference frame).
  Here are some examples of that file format:

  Column:  1         2         3         4         5         6
  123456789012345678901234567890123456789012345678901234567890
  ------------------------------------------------------------
  Star # 1      13 37 30.33 -00 13 17.3 9.3
  GSC 240601508 05 59 46.35 +31 04 39.9 12.34
  PPM 092899    03 47 29.073 +24 06 18.38 +0.0014 -0.046 2.8
  Sirius         6 45 08.871 -16 42 57.99 -0.0385 -1.205 -1.53

  To make use of such a star catalogue,  select  the  'Utility - Change Star
  Catalogue' command.  Use the 'Utility - Default Catalogue' to use the  GSC
  again.


  Measuring an Image
  

  Before you use  CCD images  for  astrometric purposes,  substract the dark
  frame  and  apply  the  flat field  correction  to  the  image.  Using the
  'Utility - Background & Range'  or  'Utility - Scale'  functions, set  the
  image  contrast  so that the object and reference stars are easily seen on
  a uniform, dark gray background.  If this can't be done, a longer integra-
  tion time may be necessary.  On the other hand,  the reference stars,  and
  above all, the object you want to measure, should not be overexposed (con-
  tain saturated pixels).

  After selecting  the 'Measure Position'  or  'Measure Position & Mag' com-
  mand,  the current CCD image will be displayed,  and a box,  which is used
  to measure the  position  and  magnitude  of the stars on the image,  will
  appear.  The arrow keys are used to move this box in units of one pixel on
  the screen.  Pressing the arrow  keys while holding down the  <Shift>  key
  will move the box in units of one image pixel (for binned images). A mouse
  click can move the box quickly over a larger distance to the  location  of
  the mouse cursor.  The <Enter> key is used to measure the position  and/or
  magnitude.

  The functions of keys F1 to F8 are as follows:

    F1: Decrease x-size of box.
    F2: Increase x-size of box.
    F3: Decrease y-size of box.
    F4: Increase y-size of box.
    F5: Boost image contrast. Makes faint regions easier to see.
    F6: Restore original contrast.
    F7: Scale the image so that the faintest pixel within the box will
        appear black, the brightest pixel within the box will appear white,
        with the grays scaled among the these extremes.
        If the value of the faintest pixel inside the box is larger than the
        threshold value used for astrometric data reduction (see below and
        the section 'Astrometrica Interna'), the latter is substituted by
        that pixel value.
        This function is especially useful when measuring the position of a
        comet with a bright coma (see the 'Tips' section).
    F8: Display a zoomed section of the image, centered on the current
        position of the cursor box.  A dotted cross indicates the centroid
        as calculated by the software.
        You can use the F1..F7 keys, the arrow keys, and the <Enter> key in
        the zoomed mode just as with the normal mode.  Press the <Esc> key
        to return from the zoomed mode to the standard display mode.

  A window displayed  below the image gives you information  on the location
  of the box (x,y coordinates), the value of the central pixel, the  size of
  the cursor box,  and the threshold  values used for photometric and astro-
  metric data reduction (see below, and for more detail, the section 'Astro-
  metrica Interna').

  Before the object of interest and the reference stars can be measured, the
  brightness of the background sky has to be determined.  The thresholds for
  photometric  and  astrometric data reductions will be calculated from that
  value.  Only pixels having values above these thresholds will be used  for
  photometric and astrometric data reduction.

  In order to measure the brightness of the background sky, move the box  to
  a large region free of nebulae and stars,  size the box appropiately,  and
  then press the <Enter> key.  If the background  does not appear  uniformly
  bright,  measure  the  brightness  of  the  background  near the object of
  interest.

  If you have selected the 'Measure Position & Mag' command,  the brightness
  of the  object of interest  will be measured next.  Locate the box so that
  the object lies completely within this box  -  including the faint,  outer
  coma in case of comets  -  and press the <Enter> key again.  If the faint,
  outer region of a comet's coma has not been recorded, the magnitude of the
  comet may be under-estimated by several magnitudes!

  Next, the position of the object of interest will be measured.  Locate the
  box so that the brightest pixels lie near the center of the box,  and size
  the box appropriately, then press the <Enter> key. Using the Zoom function
  (F8-key)  may be useful.  In the case of  comets,  isolating  the  nuclear
  region by using the  F7-key and a small  box may be useful (see the 'Tips'
  section below).

  Now, the reference stars will be measured. As with the object of interest,
  locate the box so that the brightest pixels of  the  stars  lie  near  the
  center of the box, and size the box to fit the size of the reference star.
  If you have selected the  'Measure Position & Mag' command,  the  position
  and brightness of reference stars will be measured simultaneously.

  After the measurement has been completed,  the  results will be displayed.
  For each reference star and the object of interest,  the measured position
  and magnitude will be shown.  For the reference stars,  the O-C  (observed
  minus calculated)  residuals for position  and  magnitude will appear too.
  If you have selected the 'Measure Position' command, no magnitudes will be
  given.  The rectangular pixel coordinates of each object will be displayed
  instead.

  If there are orbital elements loaded, the O-C residuals of the object will
  be shown as compared to the ephemeris.  In contrast to the residuals given
  for  the reference stars,  this value is not the  "true" residual  (as you
  usually measure the position of the object to refine it's orbit,  and thus
  the position  of the object  can't be  calculated  precisely).  Still, the
  motion of the true object and that of a  hypothetical  object in a similar
  orbit,  can be considered as running parallel for the short period of time
  between images taken during one  observing  session.  Thus, incorrect data
  (such as an incorrect time or date for the mid-exposure!)  may be detected
  in this way.

  The results of the measurement will be summarized in the files REPORT.TXT,
  CREPORT.TXT, AREPORT.TXT and ASTROMET.LOG  (see the 'Report- and Log-Files
  section below).

  If your image shows more than one minor planet, or if you want to measure,
  for example,  a comet using both a 5 x 5 and a 3 x 3 box,  you may use the
  'Remeasure Object' command,  which allows you to measure an object without
  having to measure the background and the reference stars again.

  If you measure different objects using the 'Remeasure Object' function, do
  not forget to load the corresponding orbital elements, if you want to com-
  pare your results with the ephemeris.


  Tips and Suggestions
  

  In order to get the best results from your images, keep these simple rules
  in mind:

  *  Measure your images only after you have "calibrated" them  (substracted
     the dark  frame and  applied the  flat-field correction).  While at the
     telescope,  it is best to save your "raw" image, dark frames, and flat-
     fields separately. This will allow you to accurately test for saturated
     pixels on  your raw images later on - prior to creating  the calibrated
     image. (A couple saturated pixels per reference star may be acceptable,
     but a large number may reduce the accuracy of your measurements.)

  *  It is best to use even  numbered integration  times when taking images.
     This will avoid  introducing a half-second rounding  error when "Astro-
     metrica" calculates the time of mid-exposure.  This mainly applies when
     measuring very fast moving objects,  such as near-Earth asteroids or at
     times, comets.

  *  Try to use 7 to 12 reference stars,  roughly equally distributed around
     the object of interest.  The images of  the reference  stars should not
     noisy.  Furthermore,  try to use  reference  stars which have  no close
     companions.

  *  For optimum performance, the images of the stars, as well as the object
     you are measuring,  must cover a minimum  amount of pixels  (usually at
     least 3 x 3).  A short focal length or extremely sharp star images will
     therefore negatively influence the results. While unfavorable observing
     conditions,  like moderate  seeing or  light pollution,  decrease  your
     limiting  magnitude,  they  hardly  harm  the  quality  of  astrometric
     measurements.

  *  Try to locate  the center  of the box  for measuring  the images at the
     brightest pixel of the reference star or object.  The  brightest  pixel
     within the box must be part of the image to be measured.  Size the  box
     to fit the object you are measuring.  Use the zoom function (F8-key) to
     ensure proper placement and sizing of the box.  Hint:  In general,  the
     minimal size for the box can be found by sizing it large enough so that
     if the box is moved one  (or perhaps two)  pixels up,  down,  left,  or
     right, the displayed centroid, as well as the number of pixels contrib-
     uting to that centroid, does not change.

  *  Use the image scaling function  (F7-key)  to locate  the nucleus within
     the coma of a bright comet.  Proceeding like this is recomended:
     Move the cursor box,  with a  size  roughly  equivalent  to the comet's
     coma,  over the  nuclear  region  of the  comet,  and press the F7-key.
     Change to the zoomed mode, using the F8-key. Reduce the box size to 5x5
     or 3 x 3 pixels,  move it over the brightest  portion of the coma,  and
     press the F7-key again. Now, only the brightest pixels, which represent
     the nucleus of the comet,  can be seen.  If some bright  pixels  appear
     outside the box,  resizing the box  appropriately may be useful  before
     you finally measure the comet's position.
     This procedure is based on our experiences measuring ST-6 images (pixel
     size 3.2" x 3.7").  With smaller  pixels  (or  longer  focal  lengths),
     larger box sizes may give optimum results.
     Precisely  determining the position of a bright comet is much more dif-
     ficult than measuring an asteroid,  and frequently the user's judgement
     and common sense is demanded!

  *  An image scale of about  2" per pixel has turned out to be the best for
     astrometry:  Larger pixels will give results not  that  precise,  while
     even smaller pixels increase noise,  and thus affect  the  precision of
     the measurement, too.

  *  If all reference stars have  huge  residuals,  you  have  probably mis-
     identified on or more of them.  If  a  single  reference star has large
     residuals, the catalogue data may be bad. In any case,  you can use the
     'Measure - Recall Reference Stars' command  to  unselect the bad stars,
     and eventually select new ones.

  *  If  the  measured  magnitude  of the  object seems to scatter more than
     usual, or if it seems to be much too faint, the signal/noise ratio  may
     be too low.  Try to use longer exposure times or to co-add some images.
     Be aware that you will  potentially get a more accurate magnitude meas-
     urement if your reference stars have a  wide range of magnitudes,  pre-
     ferably of a range encompassing the object you are measuring.

  *  Should  the object you are  measuring be considerably fainter than your
     reference stars,  and all the reference stars be of very similar magni-
     tude, the program may not be able to accurately extrapolate a magnitude
     for the object you are measuring.  In such a case, it is up to the user
     as to wheter or not to report the calculated magnitude.

  *  The  'Measure - Information'  command  gives  you  information  on  the
     quality  of  the  object's  image  just  measured.   Images  with  mean
     intensities under 3 are too faint to get  reliable data from.  If  the
     image  of the object  is fainter  than  that criteria,  or only  covers
     a small number of pixels, try using a  longer exposure, or co-add  some
     images.

  *  Watch out for large differences in the  "O-C Residuals"  of the object,
     as compared with other observations of that object made during the same
     observing session. If necessary, carefully check the data (date, time!)
     of the observation.

   * The  IAU  Minor Planet Center  offers a fine introduction to CCD astro-
     metry at this WWW site:

             http://cfa-www.harvard.edu/cfa/ps/info/Astrometry.html

     Information on "Astrometrica" is available on these web sites:

             http://mars.planet.co.at/LAG/lag_astrometrica.html
             http://www.bekkoame.or.jp/~makino.astromet.htm

     (Many Thanks to Wolfgang Stroh and Ikufumi Makino for administrating
     the "Astrometrica" pages !)


  Results
  

  Since the beginning of its developement,  "Astrometrica"  has been used by
  the author  and his colleague,  Erich Meyer,  to measure over 1000 precise
  positions of comets and minor planets (between March 1993 and March 1995).
  Using an ST-6 CCD camera on our Schmidt-Cassegrain telescope  (288mm diam-
  eter,  1500mm focal length)  of the private  observatory Obermair / Meyer,
  which lies near Linz, Austria, Europe, (48.4425 north latitude,  14.2753
  east longitude, 815 meters above sea level),  these observations have been
  published regularly (under observatory code 540)  in the Minor Planet Cir-
  culars, and sometimes also in the Minor Planet Electronic Circulars or the
  IAU Circulars.

  Although the pixel size of the ST-6 CCD camera is 3.2" x 3.7" at the focal
  length of 1500mm,  the mean residual of the reference  stars  has  settled
  near 0.2" per coordinate.  However,  these  residuals are minimized by the
  least square fit. Furthermore, there are systematic errors within the GSC.
  Therefore, we may expect higher residuals for the objects we measure.  But
  how large are these errors?

  Between January 1995 and August 1996,the Minor Planet Center published the 
  O-C residuals of 175 CCD-observations made  at  Linz  with  the  equipment 
  described above.  Of these observations,  19% had a total residual of less 
  than 0.25",  39% had a total residual of less than 0.50",  66% had a total 
  residual of less than 0.75",  81%  had  a total residual of less than 1.0" 
  and 93% had a total residual of less than 1.5".  Only  3%  of  the  obser-
  vations had a total residual of more than 2.0",  with the largest residual 
  of 3.5" - just about the size of a pixel.


  Publishing observations
  

  If you have high quality astrometric observations  of  minor  planets  and
  comets,  you may send them to the Minor  Planet  Center,  operated by  the
  International Astronomical Union  (IAU), for publication.  You may  either
  send a printout of the file REPORT.TXT  or a copy of  CREPORT.TXT on a MS-
  DOS disk by mail, or a copy of CREPORT.TXT by electronic mail, to:

                        Minor Planet Center
                        Smithsonian Astrophysical Observatory
                        60 Garden Street
                        Cambridge, MA 02138
                        U.S.A.

                        e-mail: mpc@cfa.harvard.edu
                                bmarsden@cfa.harvard.edu
                                gwilliams@cfa.harvard.edu

  Using  e-mail  is strongly encouraged by the Minor Planet Center.  If  you
  don't have the possibility to use electronic mail,  using  a  DOS  disk is
  recommended.  Submissions on paper are subjected to considerable delay  in
  the processing of your data.

  Be sure to include information on the observer's name, the telescope (dia-
  meter, type and focal ratio)  and the reference star catalogue used.  When
  reporting data for the first time,  you  must  also  include  your  postal
  address, the name and the exact location  (longitude, latitude, and height
  above sea level) of your observing site.  Also, do not give an Observatory
  Code  when  you report data for the first time  -  the Minor Planet Center
  will assign one to your site as soon as your data have been published.

  The  IAU  Minor  Planet  Center collects all astrometric observations, and
  compiles  the  Minor  Planet  Circulars  (M.P.C.s).   The  M.P.C.s  appear
  twelve times  a  year,  and may be described as a batch of paper,  usually
  about  1 cm high,  that  lists  all  astrometric observations reported to,
  and accepted by, the Minor Planet Center during the last month or so,  and
  also new orbital elements of  minor planets  and  comets  calculated  from
  these observations.

  For information on  subscribing to the M.P.C.s or IAU Circulars,  write to
  the postal address given above, or contact the Minor Planet Center at:

    FAX:    617-495-7231
    e-mail: iausubs@cfa.harvard.edu
    www:    http://cfa-www.harvard.edu/cfa/ps/services/Subscriptions.html

  Astrometric observations of (numbered) minor planets are  also  collected,
  published in "The Minor Planet Bulletin",  and  routinely forwarded to the
  IAU Minor Planet Center by the Minor Planet Section of Lunar and Planetary
  Observers (ALPO).  ALPO does also collect and publish photometric observa-
  tions,  done to reveal the period and amplitude of the lightcurve of minor
  planets.

  Astrometric results may be sent as a printout of the file AREPORT.TXT,  or
  as a copy of that file on MS-DOS disk by mail,  or a as a copy of the same
  file by electronic mail, to ALPO. To do so, use the address given below:

                        Frederick Pilcher
                        Department of Physics
                        Illinois College
                        Jacksonville, IL 62650
                        U.S.A.

                        e-mail: rpb@astron.mit.edu

  For  information  on  how  to  subscribe  to  "The Minor Planet Bulletin",
  contact:
                        Derald D. Nye
                        Minor Planet Bulletin
                        10385 East Observatory Drive
                        Corona de Tucson, AZ 85641-2309
                        U.S.A.

                        e-mail: nye@kw-obsv.org


  "Astrometrica" Interna
  

  This section gives a short description of the  data  reduction  algorithms
  used  by " Astrometrica",  for  all those who want to know what's going on
  behind the scenes.

  First, when the image background is measured,  the program calculates both
  the mean pixel value of those pixels  inside  the  cursor  box  (hereafter
  simply called "Sky")  and the standard derivation of these pixels from the
  mean value (hereafter called "SigmaOfSky").

  The brightness of an object is calculated by adding all pixel values with-
  in the cursor box,  after  "Sky" has been subtracted from each.  In  other
  words, the signal from the object is compared to that from an empty region
  of equal  size,  and any excess in intensity is assigned to the light from
  the object.

  The centroid for the object and for the reference stars is calculated from
  a simple center of gravity calculation.  However, only those pixels having
  values larger than a certain threshold are used in that calculation.  That
  threshold  is given by  "Sky+3*SigmaOfSky".  This means  that  only  those
  pixels that are  statistically to 99.7% real information  (not noise)  are
  used in that calculation.  Further, any pixel used in the calculation must
  be  "four connected to the brightest pixel"  within the  cursor box.  Four
  connected to the brightest pixel  means that you can trace a path from the
  brightest pixel to the pixel in question by stepping only from pixels that
  are also above the threshold - by moving up, down, left and right, but not
  diagonally.  This will, for example, prevent light from a nearby star from
  influencing  the centroid  calculation,  as long as the two images are not
  involved with each other.

  The thresholds given by "Sky" (for photometric data reduction)  and "Sky +
  3*SigmaOfSky"  (for astrometric data reduction)  are  displayed  below the
  image during the measurement as "T(mag)" and "T(pos)" respectively.

  After the measurement has been completed,  the positions and magnitudes of
  the reference stars and the object will be calculated.

  In course of the photometric data reduction, the  contrast  index  of  the
  image,  usually denoted as ,  is calculated from a linear regression,  so
  that the brightness ratio of each reference star as compared to the others
  will give the best fit to the ratios as calculated from the data given  by
  the  star  catalogue.  The brightness (or intensity) ratio  I1/I2  for two
  objects of magnitude m1 and m2 is thereby calculated from:

                                     0.4*(m2-m1)
                         I1/I2 = 10

  The data from all reference  stars is then  combined to a single,  virtual
  reference star of a given of intensity I0 with the corresponding magnitude
  m0.  The  magnitude  for  any  object,  with I being the intensity of that
  object, is given by:
                                         I0
                       m = m0 + 2.5*log ----
                                         I

  Using the positions measured for the reference stars,  the plate constants
  a, b, c, d, e, f, g and h will be calculated by means of  a  least  square
  fit. By using these plate constants, the measured x and y  position may be
  transformed into the rectangular standard coordiantes X and Y,  which  are
  independent of the focal length of the  telescope used,  and also from the
  orientation of the frame:

                          X = a*x + b*y + c*xy + d
                          Y = e*x + f*y + g*xy + h

  If you have measured less than five reference stars, the plate constants c
  and g are set equal to zero.

  From  the  rectangular  standard coordinates X and Y,  the  spherical  co-
  ordinates  (,)  of the objects may be calculated,  when  the approximate
  center (0,0) of the frame is known:

                                         -X             
                  = 0 + arctan  --------------------- 
                                   cos(0) - Y*sin(0)  

                                sin(0) + Y*cos(0)  
                    = arcsin  --------------------- 
                                   (1+X+Y)        

  If the program encounters reference stars with residuals larger  than  the
  limit set by the user during the photometric or astrometric data reduction
  process, this process is repeated under exclusion of these stars.


  Editing Orbital Elements
  

  After selecting 'Ephem - Edit Elements' from the menu,  you have to decide
  whether  you want  to edit  the  orbital  elements  of a comet  or a minor
  planet.  If there is  already  a set of orbital elements loaded,  only the
  selection which does not conflict with these elements is possible.  Before
  you  load,  or key in  any  elements,  or  after  selecting  the  'Discard
  Elements' command, both selections are possible.

  The field  asking for the name  of the object  is split in two parts.  The
  first part may be used to enter a name or number for the object, while the
  second part may be used to enter a short designation (see section 'Report-
  and Log - Files'). In case you don't need the  CREPORT  or  AREPORT files,
  which  use  standard formats for reporting astrometric observations to the
  IAU or ALPO, this field may be left blank.

  In the case of minor planets,  there is a button labeled  "n->a"  near the
  input line for the orbit's semi-major axis.  If your source of orbital el-
  ements lists only the mean daily motion (measured in degrees per day), but
  not the semi-major axis,  enter the value given for the mean motion in the
  line for the semi-major axis, and then press this button. The program will
  then calculate the semi-major axis from the mean motion.

  The orbital elements you key in may be given for any equinox  -  they will
  be converted to the standard epoch J2000.0 by the program.


  Orbital Elements File Format
  

  The file format that is used to store orbital elements is a  simple  ASCII
  format, with all the information in a single line:  The name of the object
  is stored as ASCII text in columns 1 to 10,  and the designation is stored
  as ASCII text in columns 11 to 20.  Column  21  holds the character '1' if
  the elements refer to a comet,  or '0' in case of an asteroid.  Then,  the
  perihelion time [JDT],  the perihelion distance [AU],  the excentricity of
  the orbit,  the orbital inclination [radians],  the argument of perihelion
  [radians]  and  the  longitude of the ascending node [radians]  is  given,
  followed by a number  that holds the information for the prediction of the
  object's magnitude.  This number is calculated from m0 + 10000 * k,  where
  m0  is the absolute magnitude of the object,  and  k  is the magnitude co-
  efficient (in case of comets)  or the slope factor (in case of asteroids).
  Two more numbers give the equinox [Year]  and Epoch [JDT] of the elements.
  All the numbers  are seperated  by one or more blanks,  respectively.  The
  Epoch is followed by a single blank and (optional) an ASCII text, up to 25
  characters in length,  holding  reference  information  or  user comments.
  Finally, there is a Carriage Return (Hex 0D) character and a Linefeed (Hex
  0A) character at the end of the line.


  Calculating an Ephemeris
  

  "Astrometrica"  can calculate  a detailed ephemeris  from orbital elements
  keyed in by the user or read from disk.  The ephemeris  may be  calculated
  for a given instance of time, for the end of the astronomical evening twi-
  light or the beginning of astronomical morning twilight.

  The coordinates given are topocentric positions that were calculated with-
  out taking the perturbations of the planets into account.

  The following information is given:

  Date, U.T. .... Date and Universal Time for which the following data are
                  valid.

  R.A., Decl. ... Equatorial coordinates of the object (J2000.0).

  Alt, Az ....... Horizontal coordiantes of the object (equinox of date).

  Airmass ....... Length of the path of light through the Earth's atmos-
                  phere, in units of airmasses at the zenith.  The starlight
                  will be dimmed by about 0.23 magnitude per airmass-unit.

  El ............ Elongation of the object from the Sun.

  Moon .......... Angular distance of the object from the Moon. An asterisk
                  is printed if the Moon is above the horizon at the given
                  instant.

  k ............. Illuminated fraction of the Moon's disk in percent.

  mag ........... Predicted magnitude of the object.

  Ph ............ Phase angle of the object. (For minor planets only.)

  Tail .......... Predicted position angle of the ion-tail. (For comets
                  only.)

  r, d .......... Distance of the object from Sun and Earth in Astronomical
                  Units.

  , P.A. ....... Apparent motion of the object: Angular speed in arcsec.
                  per minute, position angle of the direction of motion.

  t ............. Period for the motor which is used to compensate for the
                  motion of the object. (The period at 1"/min may be entered
                  using the 'Options-Observatory' command.)

  The  results  of the ephemeris calculation  will be displayed in a window.
  You may save the contents of this window by using  the  'File - Save Text-
  File' command.  By using the 'File - Print Text-File' command,  it is also
  possible to send the data to the printer.  Keep in mind that the ephemeris
  table has up to  121 characters per column,  so the user has to activate a
  condensed printer font before printing the file.


  Report- and Log-Files
  

  The file  REPORT.TXT  summarizes the data from your observations.  You may
  print that file if you want to report your observations on paper,  or  for
  your archive.

  This file  CREPORT.TXT  holds the data  from  the astrometric observations
  according to the IAU standard format given on M.P.C.  18847 to 18849 (Oct.
  1991) and M.P.C. 24421 (Jan.1995), and may be used for sending astrometric
  observations to the  IAU  Minor Planet Center  via computer networks or on
  DOS-diskette.  Please note that the file  CREPORT does not include any in-
  formation on your observing site (other than the Observatory Code)  or  on
  your postal address.  Be  sure to include these data when you send data to
  the Minor Planet Center for the first time.
  (CREPORT stands for Computerized Report, by the way.)

  The file  AREPORT.TXT  holds  the data according to the standard format of
  ALPO.  The object designation,  date,  time  and  position  information is
  compatible to the  IAU  format,  but  instead of magnitude and Observatory
  Code, the uncertainties of the positions are given. "Astrometrica" inserts
  the mean reference star residuals here.  If  you use three reference stars
  only (it is highly recommended to use at least four stars,  and  seven  to
  twelve stars would be perfect),  the  reference star  residuals are always
  zero.  The user has to insert  the aestimated uncertanty of the  positions
  manually, then.
  (AREPORT stands for ALPO Reprot, by the way.)

  Both  CREPORT and AREPORT  use a short designation to identify the object,
  which you  can enter when editing the orbital elements.  Here  are  a  few
  examples:

  Name:   [Ceres     ] [00001     ]  --  Minor Planet (1) Ceres
                                         Five digits, note leading zeroes

  Name:   [1990HV4   ] [J90H04V   ]  --  Minor Planet 1990 HV4
                                         J for the century (J = 19)

  Name:   [2000YZ109 ] [K00YA9Z   ]  --  Minor Planet 2000 YZ109
                                         5th character A for 10

  Name    [2001 P-L  ] [PLS2001   ]  --  Minor Planet 2001 P-L
                                         (Palomar-Leiden Asteroid Survey)

  Name:   [4139 T-3  ] [T3S5139   ]  --  Minor Planet 4139 T-3
                                         (3rd Trojan Asteroid Survey)

  Name    [My #2     ] [LNZ002    ]  --  New discovery, no official
                                         designation yet

  Name    [Object X  ] [DC003     ]  --  New discovery, no official
                                         designation yet

  Name:   [P/Encke   ] [0002P     ]  --  Comet 2P/Encke
                                         Four digits (leading zeroes!),
                                         followed by a "P"

  Name:   [51/P-A    ] [0051Pa    ]  --  Comet 51P/Harrington
                                         Component A, marked by the trailing
                                         "a"

  Name:   [C/1994 N1 ] [CJ94N010  ]  --  Comet C/1994 N1 Nakamura-Nishimura-
                                         Machholz
                                         Note trailing zero !

  Name:   [2002 V13  ] [CK02V130  ]  --  Comet C/2002 V13

  Name:   [P/1994P1-D] [PJ94P01d  ]  --  Comet P/1994 P1 Machholz 2,
                                         fragment D, marked by the trailing
                                         "d" (instead of "0")

  Take care to enter the short name correctly!

  Please note that the name of the object will be written to the REPORT.TXT,
  CREPORT.TXT and AREPORT.TXT files only if you have the orbital elements of
  the object loaded  while measuring it's position  (the center of the chart
  for selecting reference stars and the  "O-C residuals" for the object will
  also be calculated by the computer in that case),  or  when  you enter the
  name and designation in the 'Edit Parameters' window  (which appears after
  you load a CCD image).

  Also,  please note  that the information  in  the  headers of  REPORT.TXT,
  CREPORT.TXT  and  AREPORT.TXT  is  created  after the first image has been
  measured.  If you later use a star catalogue other than the GSC, or images
  taken on another telescope,  for example,  you  must  correct  the data in
  these files manually.

  The  file  ASTROMET.LOG,  finally,  holds  detailled  information  on  the
  measurements.


  COPYRIGHT, CREDITS, ETC.
  

  The copyright and all other rights are owned by the author:

                                Herbert Raab
                               Schrammlstr. 8
                                A-4050 Traun
                                  Austria

                   e-mail: Herbert.Raab@jk.uni-linz.ac.at

  "Astrometrica" was implemented using Borland Pascal 7.0 (c).
  The user interface is based on Borland's Turbo Vision 2.0 (c).
  Copyright (c) for DPMI16BI.OVL and RTM.EXE is owned by Borland.
  Copyright (c) for the Super VGA BGI driver is owned by Jordan Hargraphix.
  
  Brand and product names  mentioned  in the text are  usually trademarks or
  registered trademarks of their respective holders.

  "Astrometrica"  is  supplied as is.  The author  disclaims all warranties,
  expressed or implied, including, without limitation,  the warranty of fit-
  ness for any purpose. The author assumes no liability for damages,  direct
  or consequential, which may result from the use of "Astrometrica".

  However,  I tried hard to write  a program which is  easy to use  and does
  what you want it to do.  Years of using it have shown that "Astrometrica",
  in  combination  with  modern CCDs,  is a powerful instrument  which gives
  amateur as well as professional astronomers the opportunity to do valuable
  scientific work on minor planets and comets.

  I  owe  great  thanks to all those who helped to improve this program with
  their suggestions.  Most of all, I want to thank my collegues Erich  Meyer
  and Erwin Obermair for everything, Olivier Hainaut  and  Tim Abbott (Euro-
  pean Southern Observatory)  for  their  help  on improving the centroiding
  algorithm and (in alphabetic order)  Dennis diCicco (Sky Publishing Corp.,
  USA),  Takuo  Kojima  (YGCO Chiyoda Observatory,  Japan),  Ikufumi  Makino
  ("Interactive Astronomy",  Japan),  Larry  Marschall  (Gettysburg College,
  USA) and George R. Viscome (Rand  Observatory, USA)  for their  continuous
  support.

  Last,  but not least,  I want to thank  B. G. Marsden  and  G. V. Williams
  (Minor Planet Center, Cambridge, USA) for (3184)...!

  If you have discovered a bug or have any ideas for improvements to this
  software, please let me know!


                                I hope you enjoy using "Astrometrica" !

                                           Herbert Raab

