TheSkySearchers

Good day all!
I've been struggling with uneven illumination of my background and I think it may be due to my dark frames...
I don't understand why they look like this. By looking at my stretched master dark I would say there was a light leak but I cooled the camera to -10C and my rig was in my garage with no lights on and it was completely dark outside so, aside from the illuminated rocker switch on my power supply, there was no ambient light...

Attached are 2 screenshots. 1 is my stacked image with auto-stretch and normalization applied and the other is my master dark with the same stretch.

Any suggestions?

Thanks!

Larry

I re-stacked this image without the darks and it turned out much better...
I'm going to re-shoot them tonight and see if I can figure out what's going on...

Larry

It definitely look much better Larry. I've never had problems with Darks and, from the description of your approach, there is nothing that appears wrong. Hopefully your problem is a "one of" that goes away.

Best of success in your troubleshooting!

Steve

STEVE333 wrote: ↑Mon May 03, 2021 2:32 am It definitely look much better Larry. I've never had problems with Darks and, from the description of your approach, there is nothing that appears wrong. Hopefully your problem is a "one of" that goes away.

Best of success in your troubleshooting!

Steve

Thanks Steve. I took care to cover the power supply and wrapped the focuser. I'll re-stack everything tonight.

Larry

When I first looked at it I was thinking some sort of amp glow, but seeing how the darks over-corrected the lights, that is out the window. With that in mind some sort of light leak seems more likely. It'll be interesting to see if the new darks behave better.

Bob

Why mess with them, I don't. All my galaxy season shots are 'naked', no darks, flats, bias, or the latest mess-up-your-image-of-the-day method. These new cameras are almost idiot proof, and I'm the proof.

Good luck,
Steve

sdbodin wrote: ↑Mon May 03, 2021 3:10 pm Why mess with them, I don't. All my galaxy season shots are 'naked', no darks, flats, bias, or the latest mess-up-your-image-of-the-day method. These new cameras are almost idiot proof, and I'm the proof.

Good luck,
Steve

I've been debating the necessity of dark frames lately myself... I have an Altair 26C that has very low read noise and zero amp glow...
I've only been at this for about 2 years but I started out with a DSLR and they were necessary and I just got in the habit...

Larry

Larry 1969 wrote: ↑Mon May 03, 2021 9:46 pm

sdbodin wrote: ↑Mon May 03, 2021 3:10 pm Why mess with them, I don't. All my galaxy season shots are 'naked', no darks, flats, bias, or the latest mess-up-your-image-of-the-day method. These new cameras are almost idiot proof, and I'm the proof.

Good luck,
Steve

I've been debating the necessity of dark frames lately myself... I have an Altair 26C that has very low read noise and zero amp glow...
I've only been at this for about 2 years but I started out with a DSLR and they were necessary and I just got in the habit...

Larry

Getting away without Darks maybe, but, for my system the Flats are a necessity. Not only do I have Amp Glow but the corners of my image are darker than the center, so, Flats help my images quite a bit.

Just sayin -

Steve

STEVE333 wrote: ↑Mon May 03, 2021 10:50 pm
Getting away without Darks maybe, but, for my system the Flats are a necessity. Not only do I have Amp Glow but the corners of my image are darker than the center, so, Flats help my images quite a bit.

Just sayin -

Steve

For sure Steve! I would need flats and I would, most likely, shoot dark flats just because they're quick and easy.

Larry

Well, I just re-stacked the image with the new darks and it looks much like the image with no darks at all...
Here's the image followed by the new master dark... I may quit shooting darks entirely...
Although it begs the question: If my darks are suffering from light leakage, my light frames are surely as well, are they not?
I'm going to take more precaution when shooting my lights and I may or may not shoot darks...

Thanks for the feedback!

Larry

Congratulations on resolving your Darks issue.

Since your camera is CMOS your idea of using dark flats is the correct one. With CMOS sensors it is recommended NOT to use Bias frames but to use dark flats for flat frames.

Steve

Larry 1969 wrote: ↑Mon May 03, 2021 11:59 pm

STEVE333 wrote: ↑Mon May 03, 2021 10:50 pm
Getting away without Darks maybe, but, for my system the Flats are a necessity. Not only do I have Amp Glow but the corners of my image are darker than the center, so, Flats help my images quite a bit.

Just sayin -

Steve

For sure Steve! I would need flats and I would, most likely, shoot dark flats just because they're quick and easy.

Larry

Very interesting dialog here as I was just thinking to myself about the need for darks with my ASI2600. Flats yes, since I have vignetting and you can't remove dust shadows without them. I need to do some experimenting.

Larry 1969 wrote: ↑Mon May 03, 2021 9:46 pm
I've been debating the necessity of dark frames lately myself... I have an Altair 26C that has very low read noise and zero amp glow...
I've only been at this for about 2 years but I started out with a DSLR and they were necessary and I just got in the habit...

Larry

Even with the Canon DSLR, I have been debating the need for dark frames. With enough dither positions and a lot of lights, I'm not sure how helpful they are. Still working out that detail on the Nikon.

Like Steve, I rely on flats to handle vignetting and dust.

Bob

I hope you get to the bottom of your dark frame issue Larry.

Here's one of my darks, stretched. The 294MC sensor does this every time! I only use 10 darks in the stack but the amp glow shows if I don't use any.

Regards

Graeme

Graeme1858 wrote: ↑Tue May 04, 2021 5:34 am I hope you get to the bottom of your dark frame issue Larry.
The 294MC sensor does this every time! I only use 10 darks in the stack but the amp glow shows if I don't use any.

Regards

Graeme

Unfortunately, I believe dark frames are the only way to handle amp glow...
Maybe there's a new camera in your future?

Larry

Larry 1969 wrote: ↑Tue May 04, 2021 10:32 am Maybe there's a new camera in your future?

I wish!