cannot solve in ASTAP
Stacking program, astrometric (plate) solver, fits file viewer
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It is very strange that in most (although not all) of the cases I cannot solve the astrometry in ASTAP. I entered the expected position of the image or even the exact position. I also downloaded the G18 catalog. For example, in the attached files, the mosaiced image can be solved, while the cropped image cannot (the header contains the correct astrometry information). I also attach another unsolved image which should be not far from M57, the FOV of the image should be about 2.35 deg (height). The screenshot is my setting. Could anyone please help me to check what are the problems? Thank you very much.
The images have a lot of hot pixels. They can be seen as stars. The pixel scale is about 8.8"/pixel so to filter most the hot pixels out, set the minimum star size at 12".
The mosaic solves if the hash tolerance is increased from 0.005 to 0.009. I assume the mosaic introduces some distorsion.
The M71 the image is solved if you use the settings as shown in the screenshot. I would also increase the exposure time from 2 to maybe 5 sec or even higher. You could experiment what works best . It looks like a 8 bit camera. 16 bit should be better but it works.
Tell me if it works reliable with the new settings.
I will delete your files above to save forum space.
Clear skies, Han
Last edit: han.k 2020-09-09
Thank you so much. Now I understand it is the hot pixels causing the problem. I can solve all the images now.
I have now had ASTAP loaded (and re-loaded) for 3 1/2 years. It has never solved where, for a while, Platesolve 3 and in most cases (although painfully slow) Astrometry.net did. I am very frustrated. Whether in the house and using an existing fits file or or on the fly using in the observatory for a night of photography. ASTAP has not worked once in 3 1/2 years. I followed all of the steps outlined on this and its associated web sites. Attached are attempts local (known solvable image) as well as one of the images and last, my program path.
Sure would like some help that works.
The focal length is specified as 51 mm. Looking to your screen shots it should be around 250 mm. Set this value in Nina, then it should work. See attached.
Having an original image would be easier to fault finding. But the 250 mm should work.
Han
Thanks Han. I was almost certain that those numbers had been corrected already. Still appreciate your insight. I have only recently started using the RedCat51. I'd hoped that it would solve. But even with corrected numbers it still is missing something. The ES ED102 @ 714 and F7 does not solve either. Astrometry.net will usually solve and location but at the cost of time. It is very slow.
I will attach an original unstretched fits file
Hi Dawson,
Solving of the image was very easy inless then a second. The only thing you have to change in Nina is change the focal length to 250 mm instead of 51 mm.
You can test it by loading the image in ASTAP. Go to the stack menu (ctrl+A), tab alignment and change the 51 to 250 and press the solve button.
The focal length can be specified in Nina in the settings for the telescope if i remember well. I'm not at my main desktopat this moment so I can not look to Nina.
Does this work for you?
Cheers, Han