Possible bugs in version 2025.03.03
Stacking program, astrometric (plate) solver, fits file viewer
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han59
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Hi. I'm new to the forum. I've been using astap for a while now to stack my deep sky frames. I just upgraded to the newest version (2025.03.03) a few days ago and noticed some "flaky" behavior related to the new "quick" checkbox for analyzing lights. I also see bright pixel areas/artifacts that kind of resemble hot pixels that I don't see in the previous version of astap. I'm running astap on Windows 11. Here's a summary:
1) When I check or uncheck the "quick" checkbox, the table of lights kind of gets zeroed put -- lots of columns get replaced with ones or zeros.
2) Using the "quick" checkbox gives different results in the final stack than with "quick" unchecked. This might be because astap chooses a different reference frame, but I didn't think using the "quick" checkbox would do this. But I notice that it does give different values for star counts, background, and hfd.
3) In the new version, I see bright pixel areas/artifacts that kind of resemble hot pixels. I don't recall seeing these when I stacked with the older version (I can't remember what version I used before upgrading). I did some experimenting: the effect is less if you use smaller sigma cutoff. And it seems to go away if you use AstroSimple (I usually just use bilinear.) (I have 100 darks, good flats and flat-darks.) I have attached some pictures.
I tried with AstroC too -- is shows the bright spots same as with bilinear. I was doing this testing using the version from 2024.07.08.
I went back and looked at some of my old images I stacked with astap. I DO see the same kind of bright spots/artifacts -- I just didn't notice them.
Hi Robert,
Thanks for the observations and feedback. In the latest version threads so multiprocessor use was introduced. In ASTAP an image is then processed in horizontal slides. Each slide is processed in a different thread/processor. For bilinear interpolation this is relative easy because you process 4 pixels (RGGB) each time. For the other method it is more dificult due some overlap.
The blue and green pixels in your images are hot pixels which should go away if you lower the sigma factor in tab "stack method". Maybe a sigma of 1.6 or 1.5 will do. More images will also help to exclude outliers/hot pixels. Secondly hot pixels are in most cases eliminated by a dark.
If the stack result is same in the old ASTAP version then I'm glad there is no difference. An coding error is easily made. So any abonormality please report. That helps.
About the option quick. In the current version if you press directly stack the analyse phase is skipped and the first image is used as a reference image. This result in -1 for HFD values. If you want to see the HFD values you first have to press the analyse button. With option quick checked the images are binned and analysed. This roughly halves the analysing time. This is all pretty new in the program and hopefully an improvement. Again feedback is welcome.
Cheers, Han
Hi Han,
First let me say that I should have added a question mark to the title of this topic. I didn't mean to imply that there is definitely bug. I did some experimenting and found that:
(1) the hot pixel areas is less if you use smaller sigma cutoff (I went down as low as 2.0)
(2) and with demosaicing algorithm AstroSimple I don't see those hot pixels at all. (I have usually been using bilinear.)
I am stacking 142 60-sec lights and I have 100 darks, good flats and flat-darks. So I would have thought that my darks would take care of hot pixels.
I'm going to try some older versions of astap to compare. I guess one new feature that would help in such testing is the ability to choose the reference frame.
Thanks for a great program!!
--Bob
I'm looking into it. Sigma clip seems somehow less effective.
Hi.
Han, is it possible to make the variable star list window of adjustable width? Or make it narrower? It covers a significant part of the graph.
Thank you.
Okay. Found a major bug in sigma clip stacking :(
The outliers for colour green and blue where not excluded. This only effects stacking of OSC camera images.
I just fixed and uploaded the version 2025.03.07. Mac version follows next hour..
Selecting manually a file as reference for stacking, I will look into it.
Aleh, the scroll width has been fixed as well.
Thanks all for the feedback.
Han
Many thanks for your work!
Now for the first time I have encountered a situation where the program cannot provide me with a single Comparison star and a single Check star. Can this happen? Or is it some kind of error? I attach one file with an image and screenshots of settings.
P.S. I can not attach my fit this time.
Last edit: Aleh 2025-03-07
They are all variables. Try to increase the limiting magnitude to 15 or 99. See screenshot.
If you can attach the fits. (strange) upload to astrometry.net and share the link
Cheers, Han
Even then the comparison star will be too faint. Strange. No idea at this moment why there are no reference stars. You could call up an AAVSO map from the viewer.