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Starting Point - Descent Subs

I'm having trouble getting descent subs. I'm new so I haven't had a full year of weather and seeing conditions to work with. I know there are a lot of variables and I'm working through those as I go. But I'm wondering if anybody has any thoughts.

My subs are incredibly noisy and very difficult to work with.

Here's what I'm doing -

I'm in a Bortle 8 area.

Canon T7 ( I have a cooled ASI1600MM on the way, but still on backorder)

Optolong L-extreme dual band filter

tracking and guiding are spot on.

I shoot anywhere from sets of 300 sec to 600 sec subs. I'm only able to get 20 or so. Low number of lights could be part of my problem.

20 Dark

20 Flat

20 Bias

Seeing and Transparency might be another huge factor. Temperatures in the 100's during the day, so the Canon gets pretty hot. I'm thinking a great deal of the noise is just heat.

I also live in California near where all the fires are burning. While it isn't too bad where I am, I'm sure there is some residual smoke in the air.

I'm attaching one of the light subs as a reference.

Any thoughts?

Thanks in advance,

Jim

3 comments

3 Comments

jim

Sep 30, 2021

Hi Antoine, I think my question to you guys was a little premature. At the time, I was still waiting for my ASI16000MM. Well, it came. The difference a cooled sensor can make is apparent. Attached is first light - or a stack of first lights on night one. Basically just 10 S, 10 H and 10 O.

Still the information you gave was good info as I still like knowing what causes issues. Thanks again.

Antoine & Dalia Grelin

Oct 02, 2021

Replying to

Wow, fantastic image! You will have a blast with this camera, have fun!

Antoine & Dalia Grelin

Sep 30, 2021

Hi Jim,

Sorry it took me forever to see this! What I see on your raw image seems to be just a big amount of both read noise or dark current noise. Read noise there isn't much you can do about besides upgrading the camera, but here your main issue is likely all the added dark current noise. This occurs because the camera sensor gets too hot and, like you said, your location in California gets very warm even at night. We often had this issue as well when we were imaging from Vegas during hot Summer nights with our DSLR camera. I attached a raw frame from a hot night just so you can see.

What you could do to improve your noise:

- Let the camera sensor cool down a bit between each frame (so use an interval of a few seconds before each photo).

- Use more calibration frames

- Upgrade to an astronomy dedicated camera that can be cooled

- Image on cooler nights :D

Hope this helps,

Antoine