Visible bands during processing?

[herne]

7 hours ago, Budgie1 said:

I've just noticed that you mention in the OP that you're using Darks & Bias calibration frames with Flats. As part of your "experiment", the next time you get a chance to image, shoot Darks, Bias, Flats & Dark-Flats (same exposure settings as the Flats but with the lens cap on, I put it into Tv mode to take these). Then try a stack using all of them and a second stack without the Darks and see if there's an difference, good, bad or none.

I read that for DSLR's, Darks could be replaced with Bias & Dark-Flats because the Darks are temperature related and, unless you have a cooled DSLR, you can't get a set temperature for the session. The ambient air temp will be higher at the start than at the end and sensor temp will be lower at the start than at the end (that's my understanding but I'm more than happy for those with more knowledge to correct me )

I tried it with the 1300D and I didn't notice any difference in the stacked images, so I stopped taking Darks with the DSLR. It means I can use all the time to take more Subs, instead of stopping the session early to take Darks.

Good idea, will try that 👍.  This is part of what makes this so interesting - there's always something new to try out to get the most out of the equipment you have.

7 hours ago, Budgie1 said:

I still have to take Darks for my ZWO OSC camera but the set-point cooling on that means I can build a library of darks for the different exposures & temperatures and just reuse the Master files until something changes.

Haha nice.  I did consider moving to such a camera, however I need to walk before I can run.  Good tip for the future.

[alacant]

11 hours ago, herne said:

overall much better than in the original.

The original looks better to my eyes;) Maybe by processing to remove the banding, you lost detail in the galaxies?

Our dslr method is with Siril. Having first dithered between each light frame:

• use bias and flat frames
• stack using a clipping algorithm

That's it. No dark frames of any type.

We would however recommend at least trying a non compromised camera. This game is hard enough without starting at a disadvantage!

Cheers

Edited July 26, 2021 by alacant

[herne]

1 hour ago, alacant said:

The original looks better to my eyes;) Maybe by processing to remove the banding, you lost detail in the galaxies?

When I said overall much better I mean from the perspective of the banding issue.  I just went overboard with the galaxy processing when using the Camera Raw Filter in PS - I'd already pretty much removed the banding before that without really compromising the galaxy data.

1 hour ago, alacant said:

Our dslr method is with Siril. Having first dithered between each light frame:

• use bias and flat frames
• stack using a clipping algorithm

That's it. No dark frames of any type.

Good tips and something else to try out thanks 👍.

1 hour ago, alacant said:

This game is hard enough without starting at a disadvantage!

Haha agreed and that's the trick - finding a non-compromised camera in the first place.  From what I understand any DSLR can have issues although some may be less prone than others.  Following through your previous advice, the older Canon 1300D at 18mp could be an option (backed up by budgie's experience) or something from Canon's current line up, with the 2000D being the base model.  Even the 60D remains a viable option, or even older equipment, but I'm changing from a 12 year old Sony DSLR and would be concerned that similarly aged equipment might bring their own issues (as I'm now seeing with the Sony, hence the change).  I see no point in investing more into, say the current 850D or 90D, as if I did I may as well just buy a dedicated astro camera as it'd be getting into that price bracket.

[michael8554]

On 25/07/2021 at 09:45, wxsatuser said:

The sensor autofocus only works in Liveview mode or in mirrorless cameras, I believe the whole sensor is used in dual pixel AF.
In view finder mode there is a dedicated autofocus chip, I would assume that one wouldn't use Liveview in AP.

I'm sure you're right, but the autofocus sensors in the imaging sensor that cause the banding are there all the time, whatever mode you use.

Michael

[alacant]

700d: a nice clean sensor. Just noticed for sale.

Or simply remove the banding in software. Interestingly they appear only in the green and blue. Here you're lucky they missed the galaxies:

 

Edited July 26, 2021 by alacant