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  #21  
Old 07-12-2018, 05:43 AM
AstroApprentice (Jason)
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Filter orientation

Just wondering if you have played with filter orientation? The general rule is that the reflective side should face the sky, but apparently under certain conditions the opposite may help reduce internal reflections:
https://www.baader-planetarium.com/e...the-telescope/
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  #22  
Old 07-12-2018, 06:08 AM
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Quote:
Originally Posted by AstroApprentice View Post
Just wondering if you have played with filter orientation? The general rule is that the reflective side should face the sky, but apparently under certain conditions the opposite may help reduce internal reflections:
https://www.baader-planetarium.com/e...the-telescope/
The particular issue here is mostly happening within the last 0.5mm on the sensor itself.
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  #23  
Old 07-12-2018, 07:22 AM
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I too use the 7nm zwo ha.
Filter orientation hasn't helped me.
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  #24  
Old 07-12-2018, 07:38 AM
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Sorry to jump the gun but was having too much fun trying things! As a first step I followed Ricks advice and created a range mask, isolating the reflections and leaving the star, and then replaced the reflections with an estimate of the background (MMT). I had to soften the mask a little and still ended up with some residual halos. I did this on the three Ha, S2 and O3 tone maps and also on the Luminance (which in this version is just Ha). A start perhaps? Before and after pics below.
No problem, Ben. That definitely looks less ugly.

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Originally Posted by Lognic04 View Post
I too use the 7nm zwo ha.
Filter orientation hasn't helped me.
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Originally Posted by kosborn View Post
I have a full set of ZWO filters. This particular image was the ZWO 7nm Ha filter.
Are they unmounted filters? I remember reading about someone who had to mask the edges of the unmounted ZWO filters but I think that was a different issue - maybe bad flats?
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  #25  
Old 07-12-2018, 07:52 AM
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Yes unmounted, but the filter wheels now come with masks so that's not the problem
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  #26  
Old 07-12-2018, 09:18 AM
kosborn (Kevin)
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Quote:
Originally Posted by AstroApprentice View Post
Just wondering if you have played with filter orientation? The general rule is that the reflective side should face the sky, but apparently under certain conditions the opposite may help reduce internal reflections:
https://www.baader-planetarium.com/e...the-telescope/

Interesting, thanks for the link. I have a field flattener that sits about 20mm in front of the filters. I was very careful to orientate the filters correctly but I might flip the narrow band ones around and see what happens.
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  #27  
Old 07-12-2018, 09:20 AM
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Are they unmounted filters? I remember reading about someone who had to mask the edges of the unmounted ZWO filters but I think that was a different issue - maybe bad flats?

Yes mine are unmounted ZWO filters.
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  #28  
Old 07-12-2018, 09:50 AM
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spacers

Quote:
Originally Posted by kosborn View Post
Interesting, thanks for the link. I have a field flattener that sits about 20mm in front of the filters. I was very careful to orientate the filters correctly but I might flip the narrow band ones around and see what happens.
If the reflections are not exclusively due to the CMOS surface/coverslip, then Thomas' suggestion about adding spacers between the sensor and filters might also help...
https://www.baader-planetarium.com/e...the-telescope/
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  #29  
Old 07-12-2018, 06:18 PM
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Any luck Rick?
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  #30  
Old 07-12-2018, 09:06 PM
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Any luck Rick?
I had the work Christmas party tonight, Logan. I walked home and I'm not going to try driving PI tonight either
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  #31  
Old 08-12-2018, 04:42 PM
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https://cdn.discordapp.com/attachmen...39/unknown.png

Had a go at removing the rings with clonestamp!
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  #32  
Old 08-12-2018, 05:09 PM
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I’ve recently been watching Adam Blocks tutorials on masks and I’ve had an idea on how to remove circular patterns like this.

Create a circular mask that is the same size of the circular patterns. Create a star mask and subtract any stars from within that circular mask. This should create a mask that covers the rings and not the stars. Invert the mask and use a high MMT and it’ll average everything in there.

It’ll keep the Starr’s but remove the rings and diffraction spikes.
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  #33  
Old 10-12-2018, 08:23 PM
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I had the work Christmas party tonight, Logan. I walked home and I'm not going to try driving PI tonight either
Had a busy weekend and it's clear so far tonight. Will get back to messing with data next cloudy night

The technique that Colin mentions for subtracting the bright stuff from a mask is a good one. Something like PixelMath "mask-luminance*0.75" then tweak the 0.75 value for best results... Also use HT to stretch afterwards if the mask becomes too weak.

Cheers,
Rick.
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  #34  
Old 10-12-2018, 08:57 PM
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Rick what you'e describing is different to colin's method?
Colin, your method kind of worked but it just blurred it all out really
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  #35  
Old 10-12-2018, 09:11 PM
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Originally Posted by Lognic04 View Post
Rick what you'e describing is different to colin's method?
Hi Logan,

I was just talking about the part where you remove bright stars, etc. from a mask. It's a useful sub-technique.

Cheers,
Rick.
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  #36  
Old 10-12-2018, 09:36 PM
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Oh I see, thanks I'll have a go tomorrow
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