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 Post Posted: Fri Oct 27, 2017 7:28 pm 
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Here's some pics of no filter, OIII and SII filters after flipping over. You can see the huge halo on the filtered shots and nothing on the unfiltered shot.

Dave


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 Post Posted: Sat Oct 28, 2017 6:40 pm 
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I'm rethinking my last post about the huge halo being due to the filter. There has been fairly high humidity as of late and I had the same effect last night after turning the filter back over. I now think that it's some form of light pollution reflecting off the moisture in the air. It could also be a dew problem as my secondary dewed over last night around 2am. The smaller halos around the stars are definitely due to the filters. I'm attaching a shot of the Veil that shows this really well.
Dave


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 Post Posted: Sun Oct 29, 2017 9:55 am 
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Hi Dave,

I don't think that the big halo is a dew or moisture problem. At least I can say: The test pics of all filters in my first posting were taken right after setting up my equipment in the garden. So there shouldn't be any moisture effect yet. I checked all lenses after the test images, and there was no dew.

So what causes the big halo? That's still the question! As soon as I'll get some starry skies here, I will try the following: Take pic without filters and without Coma Corrector (I use GPU).

Cheers, Stephan


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 Post Posted: Sun Oct 29, 2017 10:06 am 
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Hi Dave,

A friend of my mine just told me that there is a "right" and "wrong" side of the filter... see here: https://astronomy-imaging-camera.com/pr ... mm-filter/

This information is new to me. Maybe it was just added recently?

Stephan


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 Post Posted: Sun Oct 29, 2017 4:13 pm 
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Thanks for the link Stephen. I've never seen that before either. I will check my filters today.

Dave


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 Post Posted: Wed Nov 01, 2017 9:02 pm 
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Hi,

I was able to make test this evening. I changed my image train a bit, screwed the 15mm T2 extension between Cam and Filter Wheel (before the extension was between Filter Wheel and OAG). So the filters are now 15mm more away from the chip. Took 240s exposures with R and OIII

Result: The halos are still there, but fainter and bigger. I also flipped the R and OIII filters before, because of the instructions of the ZWO site about what side is wrong. Well, at least when it comes to this problem, the side of filter has no effect.

But it has something to do with the filters. The more reflective a filter is, the more evident is the halo. I also suspect the front glas of the Camera!

Stephan


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R_240s.jpg
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 Post Posted: Mon Nov 13, 2017 12:57 pm 
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Here's an example... I cannot believe that there isn't any solution for it :-(

IC 443, 23 à 240sec H-alpha with a 8" F4 Newtonian


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 Post Posted: Mon Nov 13, 2017 5:11 pm 
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schurig wrote:
Here's an example... I cannot believe that there isn't any solution for it :-(

IC 443, 23 à 240sec H-alpha with a 8" F4 Newtonian


I know what you mean Stephen. I have a few things I want to try, but it been cloudy for the last 2 weeks. I was thinking it might be reflections off my focal reducer, but I'm sure you don't use one on your Newt, but you probably do use a coma corrector.

Also, Sam hasn't said much about this. Hopefully he is looking onto it. I find it hard to believe that we are the only ones with this problem.

What size filters are you using Stephen? I'm using the 31mm unmounted.

Dave


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 Post Posted: Wed Nov 15, 2017 7:29 am 
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davebl wrote:
schurig wrote:
Here's an example... I cannot believe that there isn't any solution for it :-(

IC 443, 23 à 240sec H-alpha with a 8" F4 Newtonian


I know what you mean Stephen. I have a few things I want to try, but it been cloudy for the last 2 weeks. I was thinking it might be reflections off my focal reducer, but I'm sure you don't use one on your Newt, but you probably do use a coma corrector.

Also, Sam hasn't said much about this. Hopefully he is looking onto it. I find it hard to believe that we are the only ones with this problem.

What size filters are you using Stephen? I'm using the 31mm unmounted.

Dave


Hi Dave,

It's definitely not the reducer/coma corrector. I've made tests without coma corrector and it's still there. By the way, we're not alone: https://zwoug.org/viewtopic.php?f=21&t= ... 7dc5a15a97. The posted picture there shows a multiple reflexions pattern, which certainly comes from the microlenses. It's also in my pics.

I use the 36mm ZWO filters.

I wonder why ZWO doesn't show more committment to this issue?! :(

Stephan


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 Post Posted: Wed Nov 15, 2017 7:51 am 
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Thanks for the link Stephen. I noticed he is having multiple reflections and using Baader filters. I'm tempted to remove the cover glass and try that when it clears up here.
Dave


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