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Strange lines in photos

Acquisition Deep Sky M42 Artifacts Messier Objects
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Jean-David Gadina avatar
Jean-David Gadina avatar
I was taking pictures of M42 last night, and I noticed some strange lines on my photos.
I started taking pictures with my telescope about one week ago, so I’m unsure what’s happening here.

Here’s an unedited example. I just boosted the exposure to make the lines more visible:
I’m using a Celestron Evolution 6 with a stock Canon R7. This time, I also used a .7 reducer.
The picture above is a 25'' exposure at ISO 1000.

I first thought about some fingerprints or dirt on the reducer, but I took a few other pictures of other objects that don’t display the same lines.
But all the M42 pictures from that night do.

I’m taking pictures from my balcony in a Bortle Class 6 area. Is this some reflection from the city lights?

If so, what’s the best way to prevent or mitigate this?
Would a dew shield like the one below help? https://www.celestron.com/products/dew-shield-dx-for-c6-c8
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Brian Puhl avatar
Brian Puhl avatar
That's definitely a new pattern, but since it's radial in nature, I can only assume it's a reflection from somewhere inside your scope.  

I would take a flashlight and shine it down your scope, look for shiny edges that reflect back at you.  You'll probably discover the culprit.
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Ron avatar
Ron avatar
Brian is absolutely correct.  I had the exact problem with my 8" Celestron CPC many years ago.  I consulted with Celestron who told me the problem was that the baffle leading out of the scope was the problem.  They asked me to flock the inside of the exit baffle and the problem was solved.  That's where I's suggest you start looking.

Good luck,
Ron
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Jean-David Gadina avatar
Jean-David Gadina avatar
Thanks a lot for the replies.

I just took other pictures without the reducer, without any lines showing.
As you suggested, I looked into the scope but found nothing useful. I’m not sure what to look for.

I also looked at the reducer with a flashlight, which probably needs some cleaning.
I'll try again next time.

By the way, in the same picture with the reducer, I also noticed a vignetting effect.
Is this something normal/expected with such a reducer?
Here's an exaggerated version:

Sean Mc avatar
Sean Mc avatar
Yeah, a reducer reduces the light cone. I agree that it looks like a reflection, and it also looks like your imaging train might not be straight given the shape of your stars and where the reflection is. 

flats will get rid of the vignette.
Johannes Maximilian Möslein avatar
Johannes Maximilian Möslein avatar
I get the exact same lines when using a reducer! Finally I found someone with the same problem. smile
I guess it's from reflections inside the Reducer. For my setup, it's so far on the edge of the image circle, only the OAG sees it and not the main camera.
Jean-David Gadina avatar
Jean-David Gadina avatar
Johannes Maximilian Möslein:
I get the exact same lines when using a reducer! Finally I found someone with the same problem. 
I guess it's from reflections inside the Reducer. For my setup, it's so far on the edge of the image circle, only the OAG sees it and not the main camera.

Ah, good to know!
Are these lines in all your pictures or just some, like me?

Are you using the Celestron .7 Reducer as well?

After some good cleaning, I'll try again this weekend if the sky is clear.
I'll post my results here.
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Jean-David Gadina avatar
Jean-David Gadina avatar
Sean Mc:
Yeah, a reducer reduces the light cone. I agree that it looks like a reflection, and it also looks like your imaging train might not be straight given the shape of your stars and where the reflection is. 

flats will get rid of the vignette.

Thanks for that information.
I've only tried stacking planets for now, so no flats.
I definitely want to try with DSOs, so good to know!
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Johannes Maximilian Möslein avatar
Johannes Maximilian Möslein avatar
Jean-David Gadina:
Ah, good to know!
Are these lines in all your pictures or just some, like me?

Are you using the Celestron .7 Reducer as well?

After some good cleaning, I'll try again this weekend if the sky is clear.
I'll post my results here.

I'm using a TS 0.67. 

For me, those lines are far enough away from the center, they don't fall onto the camera, so unfortunately I can't help you with getting rid of it, because I haven't tried anything (yet).
I just can see them when looking at the images of the guide cam, which is attached to an Off-Axis Guider.