17 replies to this topic

[JustAKidWithATelescope]

What is the weird color around my image?

Don't mind the middle it got messed up from compressing. But I always get this color when processing.

 

Equipment:
Eq Mount: Eqal55i pro


Telescope: Nextstar Evolution 8


Camera: Sony A7r111


Guide camera: asi 120mm guide camera


Guide scope: ZWO - 30mm f/4 Mini Guide Scope - 30F4


Accessories: Field flattener, ASAIR, Dew Shield.
Processing: Siril, Lightroom

Attached Thumbnails

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Edited by JustAKidWithATelescope, 16 June 2025 - 06:50 PM.

[ram812]

What image😯?

[Juno18]

What the heck?

[Phil Perry]

What image?

I'd guess that's NGC 6888, Crescent Nebula. But something really got messed up here! Dirt on the optics, severe vignetting? 

[JustAKidWithATelescope]

I'd guess that's NGC 6888, Crescent Nebula. But something really got messed up here! Dirt on the optics, severe vignetting? 

I do have vignetting but I think its my adapter. I dont know though my vignetting has always been really bad

[Peter Morrison]

Are you calibrating the subs (with darks, flats, bias...)?

 

Peter

[unimatrix0]

I do have vignetting but I think its my adapter. I dont know though my vignetting has always been really bad

8 inch SCT has a viewing opening like 32mm  + adapters + flattener + full frame camera  = your image. 

 

It Checks out. 

 

I think the most replies ever made on this forum is to warn people not to use an SCT on an inadequate mount and no full frame cameras either. Just saying! 

 

You are not the first and surely not the last! Within like 8 hours someone will come and tell us about their difficulty using an SCT or how their image not looking like what they hoped for. 

[JustAKidWithATelescope]

8 inch SCT has a viewing opening like 32mm  + adapters + flattener + full frame camera  = your image. 

 

It Checks out. 

 

I think the most replies ever made on this forum is to warn people not to use an SCT on an inadequate mount and no full frame cameras either. Just saying! 

 

You are not the first and surely not the last! Within like 8 hours someone will come and tell us about their difficulty using an SCT or how their image not looking like what they hoped for. 

What should I do to fix it?

[WadeH237]

The issue here has nothing to do with the common difficulties using an SCT for imaging.  There are a few things going on here.

 

The size of your camera's sensor is much larger than the telescope's imaging circle.  This is why the stars are severely misshapen as they get closer to the corners.

 

There are circular gradients with very sharp definition.  Most often when I've seen this problem, it's been due to calibrating with flats that were compromised by a light leak.  Since you'd not said anything about your processing, I don't know what to recommend here.

 

Finally, there are bizarre colors in the circular gradients.  I have seen colors do some really wonky things when they are over saturated to the extreme.

 

Given that you are using a mirrorless camera, are you sure that you are getting truly raw data from the camera?  Is it possible that the camera is altering the image before your software gets it?  How does the camera display it on its screen before you download it?

[JustAKidWithATelescope]

The issue here has nothing to do with the common difficulties using an SCT for imaging.  There are a few things going on here.

 

The size of your camera's sensor is much larger than the telescope's imaging circle.  This is why the stars are severely misshapen as they get closer to the corners.

 

There are circular gradients with very sharp definition.  Most often when I've seen this problem, it's been due to calibrating with flats that were compromised by a light leak.  Since you'd not said anything about your processing, I don't know what to recommend here.

 

Finally, there are bizarre colors in the circular gradients.  I have seen colors do some really wonky things when they are over-saturated to the extreme.

 

Given that you are using a mirrorless camera, are you sure that you are getting truly raw data from the camera?  Is it possible that the camera is altering the image before your software gets it?  How does the camera display it on its screen before you download it?

I dont think so. My storage is the camera card which is plugged into the asiair. I dont know where it would have been going worng. Would you sugjust shooting witha crop sensor camrea or what else should I do?

[WadeH237]

I dont think so. My storage is the camera card which is plugged into the asiair. I dont know where it would have been going worng. Would you sugjust shooting witha crop sensor camrea or what else should I do?

The corner aberrations would look better with a crop sensor camera, just because the field of view is smaller.  Of course, you don't need to change cameras to do that.  You could just crop the field of the camera that are already using.

 

That said, using a smaller sensor would not do anything to address the weird colors.

 

Can please tell us what processing you have done to the image you posted?  Be very specific.  Details matter in the answers.  In your first post above, you have said "Processing: Siril and Lightroom".  You should definitely not be touching the image in Lightroom for troubleshooting this.

 

The steps that I listed in my earlier response are exactly what I would do.  My next steps would depend entirely on what I found with that.  Without doing the testing that I described above, any other changes to the system (especially gear changes) would be utterly random and only make troubleshooting more difficult.

 

This hobby rewards methodical attention to details.

[JustAKidWithATelescope]

The corner aberrations would look better with a crop sensor camera, just because the field of view is smaller.  Of course, you don't need to change cameras to do that.  You could just crop the field of the camera that are already using.

 

That said, using a smaller sensor would not do anything to address the weird colors.

 

Can please tell us what processing you have done to the image you posted?  Be very specific.  Details matter in the answers.  In your first post above, you have said "Processing: Siril and Lightroom".  You should definitely not be touching the image in Lightroom for troubleshooting this.

 

The steps that I listed in my earlier response are exactly what I would do.  My next steps would depend entirely on what I found with that.  Without doing the testing that I described above, any other changes to the system (especially gear changes) would be utterly random and only make troubleshooting more difficult.

 

This hobby rewards methodical attention to details.

How would I crop the field of the camera that are already using?

[WadeH237]

How would I crop the field of the camera that are already using?

It would be a feature of your image editing software.  I'm pretty sure that both Siril and Lightroom can do it.

 

Also, please note that you have not answered any of the questions to help us better understand your weird color issue.  Cropping images has nothing to do with the problem that you are asking about and is mostly a distraction.

[JustAKidWithATelescope]

It would be a feature of your image editing software.  I'm pretty sure that both Siril and Lightroom can do it.

 

Also, please note that you have not answered any of the questions to help us better understand your weird color issue.  Cropping images has nothing to do with the problem that you are asking about and is mostly a distraction.

I'm sorry, I'm new to all of this. I don't really use Lightroom for processing, but with Siril, I do background extraction and histogram transformation.t I will do background extraction a couple of times.

[WadeH237]

I'm sorry, I'm new to all of this. I don't really use Lightroom for processing, but with Siril, I do background extraction and histogram transformation.t I will do background extraction a couple of times.

Great!  We can rule out Lightroom as the cause.

 

What does the image look like if you do nothing more than calibrate (without flats) and stack?  We want no background extraction, and only a basic histogram transformation to make the target visible.  I've never used Siril, but in PixInsight, an AutoSTF stretch would do it.

[JustAKidWithATelescope]

Great!  We can rule out Lightroom as the cause.

 

What does the image look like if you do nothing more than calibrate (without flats) and stack?  We want no background extraction, and only a basic histogram transformation to make the target visible.  I've never used Siril, but in PixInsight, an AutoSTF stretch would do it.

The image looks better I dont have a picture and I am about to leave for 5 days this will likley be my last thread until saturday. It still has werid color things but not as vibrant and the whole image is a little grey.

[WadeH237]

The image looks better I dont have a picture and I am about to leave for 5 days this will likley be my last thread until saturday. It still has werid color things but not as vibrant and the whole image is a little grey.

No worries.  We'll still be here when you get back.  Just update us when you have something.

[Phil Perry]

I think the first step would be to determine if this is in your optical train (equipment stack) or in the processing. Anything odd looking in the raw flats and lights? If they look reasonably normal, the problem must be in the processing. If they show the strong ring effect and possible dirt/dust, cleaning may be in order, and try without the field flattener. Let us know what you find.