Tips on my processing of bode's galaxy!

Hi,

Which software did you use for background extraction?

I usually do stacking in Siril, and then I do background extraction and denoising in GraXpert.

That workflow helps me reduce gradients, noise, etc.

Hope this helps. 😀

——————————————————————————-

Raw stacked image in Siril.

📷 image.pngAfter Background Extraction and Denoising in GraXpert.

📷 image.png

Rick Veregin · Mar 19, 2026 at 07:45 PM

You did not mention doing darks. With an uncooled film camera the sensor gets hot, so aside from read noise the thermal dark noise can be a big problem. Even in winter the sensor can get very hot. In the best of times, darks are needed to help remove noise. Darks should be done with the same exposure and temperature, which means you should do them somewhere when doing your lights. Bare minimum is 10 darks, but more would be better. Just put on the dust cap say after you are done with your lights, and take the darks.

You should also do flats and flat darks, 10 to 20 should be enough. This might help with the uneven red/green patches, this might be sensor variation, though it might also be a problem with how you did your background extraction. By the way, all those dust donuts do not help trying to get a good background extraction, it will be easier to get the background right without them.

You don’t mention how dark your skies are, but if you are using a CLS filter I presume that you don’t have super dark skies. In general, 1.5 hours isn’t enough to overcome the noise to get good details, your image is just too noisy. And if your skies are not dark, you will need to take even more exposure time. I assume you are at f6 or so with your lens? If you search on AB for M81 and 300 mm FL at your fratio you can see how much time people are using, my guess is 10 or more hours to get something that is getting there to bring out detail, but depending on how bright your skies are, maybe even more exposure than that. The 30 sec sub length should be good if you are in suburban skies, just more total exposure is needed.

Hope this helps

Rick

Thank you so much Rick! This does help a lot, I apologize for forgetting to say I did both bias and darks around 20 each. I also do flats on my other images but they sorta have the same gray background. I’m also in bottle 8 skies with a f 5.6 so I’ll look on AB to see how long people are doing it. Thanks again 😀!

Interactive Sky · Mar 19, 2026 at 07:17 PM

Hi,

Which software did you use for background extraction?

I usually do stacking in Siril, and then I do background extraction and denoising in GraXpert.

That workflow helps me reduce gradients, noise, etc.

Hope this helps. 😀

——————————————————————————-

Raw stacked image in Siril.

📷 image.pngAfter Background Extraction and Denoising in GraXpert.

📷 image.png

Thank you so much! I use deepskystacker, I had no clue you can stack in Siril. I’m gonna look for a tutorial on how to and give it a shot right now!

Clear skies!

-Horriblebaby 😀

Rick Veregin · Mar 19, 2026 at 08:16 PM

Horriblebaby · Mar 19, 2026, 07:54 PM

Rick Veregin · Mar 19, 2026 at 07:45 PM

You did not mention doing darks. With an uncooled film camera the sensor gets hot, so aside from read noise the thermal dark noise can be a big problem. Even in winter the sensor can get very hot. In the best of times, darks are needed to help remove noise. Darks should be done with the same exposure and temperature, which means you should do them somewhere when doing your lights. Bare minimum is 10 darks, but more would be better. Just put on the dust cap say after you are done with your lights, and take the darks.

You should also do flats and flat darks, 10 to 20 should be enough. This might help with the uneven red/green patches, this might be sensor variation, though it might also be a problem with how you did your background extraction. By the way, all those dust donuts do not help trying to get a good background extraction, it will be easier to get the background right without them.

You don’t mention how dark your skies are, but if you are using a CLS filter I presume that you don’t have super dark skies. In general, 1.5 hours isn’t enough to overcome the noise to get good details, your image is just too noisy. And if your skies are not dark, you will need to take even more exposure time. I assume you are at f6 or so with your lens? If you search on AB for M81 and 300 mm FL at your fratio you can see how much time people are using, my guess is 10 or more hours to get something that is getting there to bring out detail, but depending on how bright your skies are, maybe even more exposure than that. The 30 sec sub length should be good if you are in suburban skies, just more total exposure is needed.

Hope this helps

Rick

Thank you so much Rick! This does help a lot, I apologize for forgetting to say I did both bias and darks around 20 each. I also do flats on my other images but they sorta have the same gray background. I’m also in bottle 8 skies with a f 5.6 so I’ll look on AB to see how long people are doing it. Thanks again 😀!

Note that flats may look just gray, except for donuts, but there can be subtle variations that are difficult to see in the flat, but nonetheless, do improve image evenness. Remember you will be hugely stretching the image, so it doesn’t take a lot of unevenness to show up in the final stretched result.

Rick

Okay yeah! Next time I won’t forget to do my flats. Thanks for all your help!

Tony Gondola · Mar 19, 2026 at 08:34 PM

Horriblebaby · Mar 19, 2026, 07:56 PM

Interactive Sky · Mar 19, 2026 at 07:17 PM

Hi,

Which software did you use for background extraction?

I usually do stacking in Siril, and then I do background extraction and denoising in GraXpert.

That workflow helps me reduce gradients, noise, etc.

Hope this helps. 😀

——————————————————————————-

Raw stacked image in Siril.

📷 image.pngAfter Background Extraction and Denoising in GraXpert.

📷 image.png

Thank you so much! I use deepskystacker, I had no clue you can stack in Siril. I’m gonna look for a tutorial on how to and give it a shot right now!

Clear skies!

-Horriblebaby 😀

Since you just have lights, put these in a folder and name it lights. Put this in another folder name with the name of your project. In Siril make the project directory your home directory. At that point you can stack using the script “OSC-preprocessing without dbf” It’s really easy…

Thank you! I just finished doing that, and now I’m in graxpert doing background extraction and denoising. It’s actually already looking quite a lot better!

To get the dust lanes on Bodes Galaxy your going to need more intrigration time. Not bad for only 1.5 hours with a Canon T6 I would expect that much noise for that small amount of intrigration time. Can only do some much with a jpg. I used Siril to crop your image down and used Prism Deep to denoise the image and then deconvolution on the stars. Graxpert is great but your image needed a bit more TLC to reduce the noise.