Some images in a series not solved?
Stacking program, astrometric (plate) solver, fits file viewer
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han59
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Hi!
I am calibrating and solving series of images of variable stars. I find
that some images are not solved, while the majority is. On inspection,
they look similar and are of course with the same exposure time and
image scale and so on. Any ideas of what is going on here and how I
could handle it?
An unsolved image is found here:
https://www.dropbox.com/sh/l9h4b34q3dlke1x/AABe-yfs17hAbQZzzvHjXRnKa?dl=0
Magnus
I also get this warning:
"Warning scale was inaccurate! Set FOV=0.38d, scale=1.1", FL=2065mm"
But where in ASTAP do I set these parameter? I find FOV in the Alignment tab, but not scale nor FL.
Magnus
Hello Magnus,
the image, what you loaded into the dropbox, is already solved: The Fits header contains the coordinates. Also ASTAP solves it again without any problems.
Regards Achim
OK. It was solved when taken but that solution is written in "old" format, and I need "new" format. So therefore I try to solve with ASTAP. And my ASTAP fails when trying to solve it. So which parameters do you have?
Magnus
Last edit: Magnus L 2021-06-18
see attachment
ASTAP needs only the FOV for solving in this case 0.38 degrees height. This is calculated from the sensor_size/focal_length ratio. You can override it in tab alignment but every times you load a new image it is overwritten by the values in the FITS header. In the header the focallength is specified as 1900mm resulyting in a FOV of 0.41 degrees height. It should be 2078, so about 9% more.
Solving can be improved by changing the focal length in the FITS header.
1) Make a backup of the files.
2) Load all files in tab images or tab photometry.
3) Select all by ctrl+A
4) With right mouse button, get the popup menu and select "change key word in selected files".
5) Enter for keyword "FOCALLEN", type for value 2078.
Wait till all files are updated. Then try again to solve all.
Han
to override any existing solution, check mark "override existing FITS header solution"
If one or two are not solving you could upload them to nova.astrometry.net or use an local astrometry.net version.
Setting the focal length correctly helps. For your sample, the number of detect quads increases from 3 to 5.