15th Feb 2024: Astro Pixel Processor 2.0.0-beta29 released - macOS native File Chooser, macOS CMD-Q fixed, read-only Fits on network fixed and other bug fixes
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Hi all - I am very new to Astro photography as well as APP. I have watched several video tutorials and done some searching on the forum, but I haven’t found great answers. Please feel free, however, to point me to the right resource.
Quick background: trial license (1.082) on an M1 MacBook Air running Big Sur OS (11.5.2).
My images are very basic. Just a camera (EOS RP) on a tripod. No tracking. Using either a zoom lens (24-105) at 24mm or a wide-angle 14mm prime - both wide open. I have been trying to shoot either M31 or the MilkyWay, and I typically include some ground-based background. Shots are 15 - 30 second exposure time. I have experimented with darks, but haven’t done bias or flats, yet. However, my question centers around registration / alignment.
My initial attempts at stacking lights (usually just 5 to 12 images, but I have even gone to 2 to experiment with APP) to reduce background noise involved hand alignment with Photoshop. However, I was not happy with the linear x-y alignment that is easiest to do by hand (I could align a small part of the image, but other areas would be MSI-aligned). I found APP while trying to get a program that would automatically find the best rotational alignment for my entire image.
So I have tried loading lights into APP, running star analyzer and hitting Registration. The results don’t seem awesome.
One question: is it possible to view exactly what translation was applied to an image during registration? Maybe something like x-y translation amounts and/or coordinates of axis of rotation and degrees of rotation?
During one experiment, I was trying to align 11 lights, and I could clearly see a star trail as if no alignment at all had occurred. On another attempt with just 2 lights where I cropped out the vast majority of the ground-based background, the registration process showed “0 of 2” lights to be stacked even when set at 100%. I’m not sure why the program wouldn’t stack.
I have tried viewing the star analyzer output map. With lots of background, the star analyzer often identifies ground-based background. That’s when I tried the crop approach. Then the star map looked good, but I got the “0 of 2” issue noted above.
Any ideas to basic issues I might be running into?
What types of image transformation will APP do during the registration process?
Thanks, in advance, for any advice / input!
-Trevor
Hi Trevor,
Thanks for trying out APP! I think you may be in the realm of noise too much with the data, without guiding I assume you take exposures of just seconds? The problem with that is that the signal is very much amongst the noise and this is a challenge for the statistics. Using proper darks and bias frames is a very important thing here as APP will then know more about the background noise before analysing the stars. With data in the noise, you're always a bit in an uphill battle for the complete workflow (unless you have a camera with real low noise and are shooting under super dark skies, and even then people tend to shoot 50-100 frames easily).
Apart from all that, the table below shows a lot of the statistics like SNR etc. You can also apply dynamic distortion correction which is super precise if the image indeed is a bit distorted due to the optics. APP in that sense has some of the most precise alignment.
Great, thank you. Can you comment on ground-based background - is it okay for that to be part of the image?
And are there some resources to understand the “goodness” of some of the statistics?
Thanks for the speedy response @vincent-moderator
Trevor
Ground based background is ok, as long as stars are there. Of course that background will become blurry as APP will only look a the stars to align everything. Usually people take a picture with flash of the background and put that over the blurry one. In the future this would be nice to automate in APP as well.
Regarding resources, I think you can find some of that by searching the forum, but at the moment there are not a lot of in depth resources available yet. On top of the forum you can also have a look at the presentations and video tutorials sections.
