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ASTAP won't open FITS file

2022-09-04
2022-09-06
  • Pierros Papadeas

    I have the attached FITS file that opens OK on other software (ds9, kstars fits viewer etc) but ASTAP refuses to open it.
    Error message: "Access violation. Press OK to ignore and risk data corruption. Press Abort to kill the program."
    Any ideas?

     
  • han.k

    han.k - 2022-09-04

    Hello Pierros,

    That is an interesting but exotic image. It contains four colours. ASTAP can only handle three colours. If I load the image in FV (the NASA fits viewer) it blinks the four images.

    MaximDL viewer crashes. AstroImageJ only show one image.

    I can probably fix ASTAP displaying the first three images in red, green and blue. But it is better to understand what the four images are. Did you use four filters? If so which type of filters and which software was used to create it? Then the question is open how to display four colours in a three colour operating system?

    Cheers, Han

     
  • Pierros Papadeas

    Hey @han59 thanks for checking. Indeed those are some peculiar files that each "channel" is storing the mean, st, max and argmax values of each pixel respectively from multiple files. I understand that this is a peculiar case, but still plotting them as three colors, or just plotting the first channel would be nice, and it would allow us to use astap for plate solving too.

    Would that be possible?

     
  • han.k

    han.k - 2022-09-04

    Try this 2022-09-04 version:

    http://www.hnsky.org/astap_setup.exe

    It will display only the first colour (=mean). Saving will preserve the first colour only!.
    Since "st'", "max" will confuse the solver I decided not to display them.

    Since the field of view is pretty large use the W08 or the V17 star database. Your image solves fine/best with the W08. For very long exposures the V17 is probably better..

    Which software did produce this file?

    Cheers, Han

     
  • Pierros Papadeas

    Thanks a lot @han59 !

    Tried the new version and it works like a charm. Fast solving too!
    The fits files are produced by this open source software we are creating for satellite identification and measurements https://github.com/cbassa/stvid

    We are considering using ASTAP as the plate-solver if it is faster and more efficient than astrometry.net locally.

    Cheers!

     
  • han.k

    han.k - 2022-09-05

    Normally you can use either the standard (astap) or the command-line version of ASTAP (astap-cli) for solving using the command-line. The change hasn't been implemented in the command-line version. I have updated the command-line code but not released a binary. Tell me if this is required and I will release an updated command-line version.

    Han

     
  • Pierros Papadeas

    We are only using the linux version, so the astap command line works perfectly. Any pointers on the best usage of -fov? I am asking because sometimes it is working only if I specify lower fov than the actual one.

     
  • han.k

    han.k - 2022-09-06

    The FOV is for ASTAP is defined as the image height. Your image FOV is 12.6 x7.92 degrees. So for ASTAP the FOV=7.9 degrees. Once ASTAP has solved an image and it will remember the FOV. If it can't be extracted from the image it will use the 7.9 next time. Best if your specify as parameter -FOV 7.9

    The image dimensions 968x608 pixels are too small. If your camera allows it stay above 1280x960 pixels.

    Specifying the expected RA, DEC position will speed up solving. ASTAP will search in a spiral pattern around the specified RA, DEC position.

    I would prefer specifying RA, DEC and FOV (focal length, pixel size in micrometer), in the FITS header but you could also specify it in the command-line.

    You have to experiment which star database works best for you. Either W08 or V17. The W08 goes down to magnitude 8 so if your exposing longer you have to use the V17 which goes down to magnitude 17.

    Han

     

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