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Halo effect? Is this light pollution

astrophotography beginner dslr dso
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#1 BazzaAlpine

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Posted 28 October 2020 - 04:22 PM

Hi all,

 

I notice when I'm trying to process my data in pixinsight that a lot of the times when doing a background extraction it leaves a halo effect on the image that I can't seem to get rid of. Can anyone give me some pointers on what is causing this? I'm in a Bortal 5 area and the image attached was while there was a pretty bright half moon in the sky so I'm thinking the overall sky might have been too bright and not helping. I'm using an astro modified Canon 450D, 6.3 reducer spaced correctly but no filter and a Celestron dew shield.

 

This astrophotography is hard work lol.gif

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  • masterLight-BINNING_1-FILTER_NoFilter-EXPTIME_120_halo.jpg

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#2 klaussius

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Posted 28 October 2020 - 04:29 PM

Did you take flats, darks, dark flats, etc?

 

How exactly did you calibrate your subs?

 

It looks like vignetting, background extraction will leave residues like that when there is significant vignetting and light pollution, but it goes away if you do flat/dark claibration right.


Edited by klaussius, 28 October 2020 - 04:29 PM.


#3 Bean614

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Posted 28 October 2020 - 05:34 PM

You should ALWAYS post what scope, and  other equipment you were using when posting photo issues! This may help someone recall an issue they might have heard about.

.    In this particular instance, there are numerous folks who would be able to share some possibilities,  but they would be found in a Different Forum.  The only scope in your signature is a 6SE.  If THAT was the scope you used, there are LOTS of threads on this in the Cats & Casses Forum. 



#4 PirateMike

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Posted 28 October 2020 - 05:41 PM

Could this be the issue?

 

https://www.youtube....441UBNpo&t=146s

 

 

 

Miguel   8-)

 

 

.



#5 TOMDEY

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Posted 28 October 2020 - 06:01 PM

Actually, I like it that way! Just call it ~artistic interpretation~.    Tom



#6 Voska

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Posted 28 October 2020 - 07:15 PM

I'm on the trial of PixInsight and it seems like all of my images that i and trying to redo (from scratch) seem to get this same halo. I use darks, Flats, and Bias. (never done Dark Flats)



#7 BazzaAlpine

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Posted 29 October 2020 - 03:23 AM

Thanks for the responses.

 

Hi Viking, I had taken some darks (10) and biases (20) the same evening but my flats (@30 of them) were a bit older. As for calibrating the subs I'm not sure what you mean? I used the weighted batch process with default settings in pixinsight if that's it.

 

Thank you for the warm welcome Apollo. Yes the 6SE in my signature is the only scope I have and yes I did try a search before posting. Seeing as this was a beginners section to astrophotography this section of the forum felt appropriate. I'll go and see what's in Cats and cases (sounds like a feline meme section confused1.gif ).

 

Thanks' for the link Gemini, I'll have a look. There are so many videos out there on how to use various software it's hard to work out what is best for me.

 

lol.gif Maybe I should put artistic impression next to any images I process.



#8 klaussius

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Posted 29 October 2020 - 12:26 PM

Hi Viking, I had taken some darks (10) and biases (20) the same evening but my flats (@30 of them) were a bit older. As for calibrating the subs I'm not sure what you mean? I used the weighted batch process with default settings in pixinsight if that's it.
Do you leave your image train fully assembled? If nothing has changed, I'd suggest you try taking some fresh flats.
 
The focus needs to be roughly in the same spot as it was during light acquisition, so if you changed focus try to refocus. If you haven't touched anything leaving it as it is may be good enough.
 
If you have disassembled or changed anything, flats from earlier sessions won't work. You have to retake them each time you change something.
 
So if you have indeed disassembled and have no way to take new flats, you could try synthetic flats. You can build them out of your lights with a bit of processing magic.

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#9 Euripides

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Posted 29 October 2020 - 12:50 PM

If I recall correctly I’ve faced 2 times the same issue. Both times I’ve used older flats (from previous night), without disassembling my setup.

Since then I capture new flats for every session and never had this issue again.

So from my point of view: Flats issue, focus changed


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#10 BazzaAlpine

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Posted 29 October 2020 - 03:27 PM

I'll do that then thanks :) unfortunately where I am located I have to take everything inside once I'm finished and while I don't do a complete strip down I do usually take the camera off so the focus point does change. I'd use the white t-shirt method to get flats at the end of the evening but I don't have a good enough light source for that yet.



#11 limeyx

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Posted 29 October 2020 - 03:48 PM

I've had similar issues on a Nikon D5300. For me I *think* it was bad flats but it's been too cloudy for the last two months to check it

 

Did you try stacking just the light frames and seeing if you still see the issue ? When I stacked just the lights, the result looked far better than when I added the bias/flats, so that's what led me into analyzing my flats and getting a tracing pad to make them more repeatable



#12 Euripides

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Posted 30 October 2020 - 01:16 AM

I'll do that then thanks :) unfortunately where I am located I have to take everything inside once I'm finished and while I don't do a complete strip down I do usually take the camera off so the focus point does change. I'd use the white t-shirt method to get flats at the end of the evening but I don't have a good enough light source for that yet.


Do you have an iPad, a tablet?

Just placed 2-3 white papers (or a t shirt) in front of the lens. Open your iPad, turn the brightness to full. open Notes, create a new note then you have all the light you need. Finally place gently the iPad above the papers and you are good to go.

Warning: Your focus should be solid. You do not want to change it at all.


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#13 BazzaAlpine

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Posted 30 October 2020 - 03:50 AM

Do you have an iPad, a tablet?

Just placed 2-3 white papers (or a t shirt) in front of the lens. Open your iPad, turn the brightness to full. open Notes, create a new note then you have all the light you need. Finally place gently the iPad above the papers and you are good to go.

 

I have a surface pro but the screen is not big enough to completely cover the front of the scope. Not sure how much of an impact that would have on the flats. 



#14 Euripides

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Posted 30 October 2020 - 04:04 AM

I have a surface pro but the screen is not big enough to completely cover the front of the scope. Not sure how much of an impact that would have on the flats. 

It has to completely cover the whole area, so this is a no go for you :-( ( example https://astrobackyar...t-field-panel/)


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#15 klaussius

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Posted 30 October 2020 - 10:34 AM

The morning sky is quite good as a light source. When the sky is just getting brighter, you can do your flats right then, placing a paper or t-shirt on the apperture to diffuse the light.

 

The only tricky part is that the sky will be getting brighter and brighter, so you have to account for that when picking the exposure time, or be quick about it.



#16 Voska

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Posted 31 October 2020 - 11:48 AM

BazzaApline, I just wanted to throw this out there for you as I was doing some testing last night (32F or lower temps). I do run a C9.25 with the 6.3 reducer/corrector. I also use the AstroZap dew shield/heater on the front of the telescope. I was looking at my images that seemed to show the same Halo effect in PixInsite (again please note i am still on the trial of it sooo yeah) and decided to check a bunch of my previous images to see how many had that same issue and i found that not ALL of them did. Looking at the notes for each one, the ones that DID have it had the reducer (though i did have 2 that didnt have the halo... but the rest did). SOOO last night i was out just testing a few things out and during this process I took off the reducer and noticed that the reducer had started to fog up... I dont run a dew strap on that and now I am thinking that since this Halo looks like the same affect you would get if the main lenses was starting to fog up I am thinking that the reducer has been fogging up and since i don't disassemble the image train till after I am done with everything (and i take my calibration images later after i have brought it into the garage and in most cases a few hours later after i have gotten some sleep). So I would bet this MIGHT be a reason... I myself am ordering a 2" dew strap for the corrector just to be sure.


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#17 Mike in Rancho

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Posted 31 October 2020 - 02:42 PM

BazzaAlpine I'm glad you posted this here.  I ran into very similar issues just this week after trying out my old telescope (90mm refractor) on my new EQ mount.  I thought it might be the full moon since I was shooting so close to it.

 

After reading some of this thread, I restacked my lights without the flats.  It made a big difference, but of course created new, different rings and halos to deal with lol.  Hopefully improved flat procedures resolves the matter.  The first night I knew right away I made a mistake (D'oh!) taking the camera off the scope to use the body cap and run my darks.  The second night I kept everything together, but still probably knocked the assembly out of focus trying to aim the unmounted scope up against my laptop screen.

 

Camera lens flats seem so much easier!



#18 BazzaAlpine

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Posted 31 October 2020 - 05:52 PM

BazzaApline, I just wanted to throw this out there for you as I was doing some testing last night (32F or lower temps). I do run a C9.25 with the 6.3 reducer/corrector. I also use the AstroZap dew shield/heater on the front of the telescope. I was looking at my images that seemed to show the same Halo effect in PixInsite (again please note i am still on the trial of it sooo yeah) and decided to check a bunch of my previous images to see how many had that same issue and i found that not ALL of them did. Looking at the notes for each one, the ones that DID have it had the reducer (though i did have 2 that didnt have the halo... but the rest did). SOOO last night i was out just testing a few things out and during this process I took off the reducer and noticed that the reducer had started to fog up... I dont run a dew strap on that and now I am thinking that since this Halo looks like the same affect you would get if the main lenses was starting to fog up I am thinking that the reducer has been fogging up and since i don't disassemble the image train till after I am done with everything (and i take my calibration images later after i have brought it into the garage and in most cases a few hours later after i have gotten some sleep). So I would bet this MIGHT be a reason... I myself am ordering a 2" dew strap for the corrector just to be sure.

I never even thought of that. The temps were definitely dipping into the cold side. Something to consider.

 

Hi Mike, I'm definitely going to keep my camera connected to the scope as much as possible now and certainly make sure I find a way to take some flats before making any changes.



#19 Michael Harris

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Posted 01 November 2020 - 07:16 PM

With PixInsight, I had to uncheck the “Optimize” checkbox in the Darks section of Image Integration, or images had central artifacts due to over-correction. Dewing, light pollution, are both possible but your defects are so symmetric within the image that it makes me think more of a PixInsight setting, or maybe the backfocus setting (distance between your focal reducer and the imaging chip) is incorrect, or vignetting from the scope or filter. A lot of this depends on your optics/camera combination, too. Try some integrations of a smaller number of frames to test different settings, and see if that helps.


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