Unexpected glow in my image

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Hi all

Just done a quick stack from the other night of M78. As I started stretching I noticed a prominent glow in the bottom right of the image. A quick and dirty process below to show what I mean.

Does anyone know what might be causing this ? At first I thought it might be light from Alnitak, but I assume that would be too far away to cause this ?

The image is OSC, light frames stacked with darks, flats and dark flats in DSS.

Thanks

 

[ONIKKINEN]

Probably glow from Alnitak, or an internal reflection between 2 or more of the lenses in your flattener(?). Could also just be gradient from the sky, difficult to tell.

But its easily removed with a good background extraction tool, i ran this JPEG through the background extraction tool in Siril and its definitely removable:

Didnt pay much attention to the sampler placements, so some actual nebula signal was most likely also lost but run it on the linear file and you will get rid of it easily.

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38 minutes ago, ONIKKINEN said:

Probably glow from Alnitak, or an internal reflection between 2 or more of the lenses in your flattener(?). Could also just be gradient from the sky, difficult to tell.

But its easily removed with a good background extraction tool, i ran this JPEG through the background extraction tool in Siril and its definitely removable:

Wow... That's amazing, thank you. I think I need to learn how to use Siril !

[Ratlet]

6 hours ago, Spaced Out said:

Wow... That's amazing, thank you. I think I need to learn how to use Siril !

Siril is awesome.  I just follow this for my images and it works very well:

https://siril.org/tutorials/tuto-manual/

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5 hours ago, Ratlet said:

Siril is awesome.  I just follow this for my images and it works very well:

https://siril.org/tutorials/tuto-manual/

Thanks, I'll take a look. 👍

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Does anyone think that glow is definitely from Alnitak, or definitely something else ? I'd like to try and understand what it is.  Took some images of M45 the same night, the glow was not visible in the stacked image for that tho.

[Elp]

Looks like light pollution to me. I always get it when imaging R, G, B or OSC. What time was it, Orion rises a bit later in the evening so is low close to the horizon, Pleiades is much higher in the sky so is less affected.

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8 hours ago, Elp said:

Looks like light pollution to me. I always get it when imaging R, G, B or OSC. What time was it, Orion rises a bit later in the evening so is low close to the horizon, Pleiades is much higher in the sky so is less affected.

Hmmmm... This is what I am worried about tbh. I live under fairly dark skies (21.4 SQM-L) and there is usually very little light pollution, but, my neighbours 2 doors down have just put a light in their garden that is solar powered and on all night ! It is not in direct line of sight from my telescope location (a couple of fences sit in between and shield it), but I wondered if this might be the problem ? 

[ONIKKINEN]

1 hour ago, Spaced Out said:

Hmmmm... This is what I am worried about tbh. I live under fairly dark skies (21.4 SQM-L) and there is usually very little light pollution, but, my neighbours 2 doors down have just put a light in their garden that is solar powered and on all night ! It is not in direct line of sight from my telescope location (a couple of fences sit in between and shield it), but I wondered if this might be the problem ? 

Probably, yeah. I try to image only at darksites and my 2 most common spots are SQM 21-ish and SQM 21.3 ish and gradient removal is still something that has to be done on each image. It will take a true darksite and a target at the zenith to not have any gradient, so almost all imagers will have to deal with that.

By the way, you can doublecheck your actual sky conditions with ASTAP. Calibrate a sub, feed it to ASTAP, platesolve it, and then run the SQM tool on the image. It will tell you the actual sky conditions for that particular image you have taken, so if you are wondering whether or not your SQM-L is accurate or not given your neighbors new lights, you could check with ASTAP whether the data agrees with the other measurements.

[Elp]

A background extraction on Siril will normally sort it out very easily.

Maybe also talk to the neighbour to politely ask why their light needs to be on all night and not with a motion sensor. Otherwise if possible try to image nearer to a fence or some sort of shield to minimise the glow.

 

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On 06/11/2022 at 09:12, Elp said:

A background extraction on Siril will normally sort it out very easily.

Maybe also talk to the neighbour to politely ask why their light needs to be on all night and not with a motion sensor. Otherwise if possible try to image nearer to a fence or some sort of shield to minimise the glow.

 

I have already spoken to the neighbours, I was so polite but just got a sort of defensive response, a bit of a brick wall tbh. 🙁

The light they have is a cheap solar thing that stays on all night 'for security'. It isn't directly visible from my garden and I can't see much of a glow from it either tbh, so I was hoping it wouldn't have too much impact on my imaging. I can't move the telescope unfortunately, its a concrete pier. I may have to buy a dew shield to see if that helps and start using Siril.

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On 06/11/2022 at 01:40, ONIKKINEN said:

 so if you are wondering whether or not your SQM-L is accurate or not given your neighbors new lights, you could check with ASTAP whether the data agrees with the other measurements.

Thanks for this info. My readings were usually 21.3 ish (21.4 on a good night) but I haven't taken any readings since the neighbours installed their new lights.