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Registration fails... Too many "fake" stars?
I have been using APP successfully several times with the same setup (C8 Evo and ASI 385MC) but it won't process my last capture...When I run 4) register (with pattern recognition set to "triangles") I get an error message "Registration failed on some of the frames!" - which sounds actually almost nice, since in reality it failed on ALL frames.
I'm suspecting that the problem is that it finds far too many "stars" when running 3) analyse stars: the results show typically 200+ stars, while I can only see 10 to 15 stars in each frame (these are short exposure, 10 s each). Sure, a computer can do better than my bare eye, but still, I believe that most of these "detections" are actually noise peaks. And then, trying to find pairs between two images cannot provide any meaningful solution.
I would be happy if there would be a parameter in 3) analyse stars to limit the results to a small number (say, 10 or so) of the brightest stars in the image. In principle, one needs only 3 pairs to fully describe the translation + rotation between two frames. All my light frames are towards the same field, only some small drift (because no guiding) and field rotation (because alt-az mount) can happen, no distortion and no need for mosaicing at this stage...
Any idea what parameter I can change to fix that problem?
After investigating a bit more, I understand the root cause of my problem: the true stars are too big on my images. Somehow, APP assumes that a star has a FWHM of 2 to 3 pixels, but in my case, it's more like 12 to 15. OK, the focus was maybe not perfect, but still, the size of the PSF depends on the pixel size of the camera, the telescope, and the seeing during the observations. Therefore, it would be nice to be able to keep this as a free parameter (within some reasonable limits).
Now, what can I do with my frames so that APP detects the real stars, and not the peaks in the noise?
Thanks for your help!
This sounds like APP is seeing bad pixels as stars and we have seen this before, also with someone who had out of focus data. This has been addressed and will be fixed in the next version. However FWHM of 12 to 15 is big, usually it's not that high even with a different set-up.
So, I have just downloaded version 1.075 and tried it on the same set of data. Unfortunately without success. The problem now occurs earlier, in step 3) analyse stars, where ALL the frames produced an error "analysis failed". I have tried with and without calibrating the frames (I only have darks for that night, no flat and no bias). I have also tried using "super-pixel" as debayer algorithm instead of adaptive Airy disc, so that the PSF looks "smaller" (i.e spread less pixels). None of this did fix the problem...
I would be happy to upload an example frame if you have a chance to look at it 🙂
Yes that seems better, although the noise is still too high for what I would expect. Could you upload some frames to our servermaybe? It is challenging data and that is great for Mabula to see if he can actually make that work. Login/password: appuser and please create a directory with your name on it. Much appreciated!
OK, I uploaded one dark frame and 4 lights in directory SchullerFred.
As I mentioned earlier in this thread, the stars have a PSF as big as 12-15 pixels, due to using a 2xBarlow and certainly not perfect focus. I think that the star detection step is one of the most critical, and it would be nice to have access to a few input parameters, such as the expected typical size of the stars, to give a hint to the programme...
did Mabula have chance to look at some of my problematic frames?
Last night I had clear weather but terrible seeing. I tried to get some images (without Barlow) but again I have the problem that Analyse stars fails on *all* the frames. Here's an example screen shot. The stars look big (because of the seeing) but there are quite a few in the image that APP should be able to detect...
Is there any hope to find a way to process these images?