Odd Horizontal Thick Line Artifacts - Forums

Topic starter

6 hours ago

Hello.

I’ve reached a point of frustration and I’m unsure how to proceed. I have some image stacks that show up with these odd looking horizontal “lines. I cannot figure out what is causing it. I pre-processed in WBPP using lights, darks, bias, flats. The calibration frames were taken this morning after last night’s imaging session.

I think I’m close to narrowing it down to being an issue with my darks. But I don’t know how/what/why. The camera is ASI533MC pro, scope is WO ZS61. I take the darks with the scope cover on it (the one with the clearish bahtinov mask inside) and I cover the whole rig with a couple of shirts/blankets to try to prevent any light leakage. As far as I can tell, it should be total darkness but I keep ending up with this issue.

Any ideas on what is causing this? Why is it happening? How do I prevent it? Are there any WBPP options to deal with it? What are these called?

📷 LinesOfFrustration.jpg

Here are two of the darks that I exaggerated the stretch to highlight the issue:

📷 stretcheddark1.jpg📷 stretcheddark2.jpg

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andrea tasselli

Frequent contributor

6 hours ago

You have a light leak. You need to sort it out. Or process it without darks (just flats and bias) for the time being and pray your flats won't fail you.

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Adam

Topic starter

6 hours ago

Thank you kindly for the response.

I don’t think I’ve seen much about “light leaks”. It’s strange because I have not changed anything in my optics train.

I’m going to experiment processing with no darks and see what I come out with.

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andrea tasselli

Frequent contributor

6 hours ago

This is how a dark should look like for an IMX533:

Adam

Topic starter

5 hours ago

Thanks!

I checked a few of my other darks and they look close to what you have posted. So at least not all is lost!

Now to figure out how to track down and correct this light leak.

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Tony Gondola

Frequent contributor

Exemplary contributor

5 hours ago

I guess I would question the practice of taking darks that way. Its’s how you would do it with a DSLR but you have a cooled camera. If you just make a dark library indoors with the camera capped you’ll be done and won’t have to worry about light leaks or taking away imaging time (or sleep!) just to take darks. You can make your bias frames at the same time. The only calibration frames you need to make with the scope in operation are the flats.

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Adam

Topic starter

5 hours ago

Thanks, Tony. You make an excellent point.

While not ideal or most efficient, I think I’ve learned a lot from my typical process haha.

I usually hope weather is good, check said weather, plan which targets to hit, set up plan, put scope out 30m early to acclimate to temps, polar align, final check, and then start the plan. I’ll follow along and watch the images come in (asiair) for a while and then let the plan go. When I get up in the morning, I bring it closer to the house and use the “autorun” portion of asiair where I have saved the different calibration frames I would like to take. Most often I’ll take the flats first since it requires me to use light panel and cover the lens with a white shirt/etc. Usually the temperature has not changed much (within range of the lights); I’ll then cap the scope and cover it up a bit (light leak prevention (not working well :) )) and run the darks.

It is kind of a pain because then I have to wait a while/etc.

It’s funny that you mention the comparison with the DSLR because I think this is why I do it this way. I started with a DSLR and was always really nervous and anxious about making dang sure I get the calibrations right.

I think I’m learning more and realizing that the darks don’t need to be handled as carefully as I am handling them now—in other words, I can make a dark library and focus on other issues! So, again, thanks for the suggestion.

I’d now also like to learn more about and to address my issue if light leakage. I’m open to tips on how to do so! 😆

Tony Gondola

Frequent contributor

Exemplary contributor

4 hours ago

For light leaks, just go over the rig and look for anyplace light might get in. You could also play a flashlight at night over the suspect areas while looking inside the tube. Any leaks or glows should be easy to see.

On your flat frames, you might look into making sky flats. These are quick and easy and require nothing but your scope and the sunrise or sunset sky. Oh, and, as far as I know flats do not need to be temperature matched to your lights.

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Adam

Topic starter

4 hours ago

Thanks, Tony. I’ll do some research on the “sky flats”. I actually did a variant of that this morning. I first took flats with the light panel, but wanted to experiment with using the sky as a light source. I put a white t-shirt over the scope and pointed up to the blue sky and it it rip.

I would go light leak hunting right now, but I have the rig in a closet taking darks to build this dark library haha

I had good results, too, pre-processing with no darks. So I’m working with a couple of images right now as a result. And then I plan to go and figure out how to process the comet C/2024 E1 images I took last night.

Only have a couple of hours before the sun goes down and I can put the rig out. So I’ll need to plan for that too. Today has been filled with astrophotography and astrophotography adjacent tasks.

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