ICEINSPACE
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Waxing Gibbous 82.5%
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07-12-2018, 06:43 AM
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Registered User
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Join Date: Dec 2015
Location: Melbourne, Australia
Posts: 349
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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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07-12-2018, 07:08 AM
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Ultimate Noob
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Join Date: Aug 2011
Location: Melbourne
Posts: 6,982
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Quote:
Originally Posted by AstroApprentice
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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The particular issue here is mostly happening within the last 0.5mm on the sensor itself.
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07-12-2018, 08:22 AM
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Registered User
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Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
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I too use the 7nm zwo ha.
Filter orientation hasn't helped me.
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07-12-2018, 08:38 AM
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PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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Quote:
Originally Posted by Benjamin
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.
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No problem, Ben. That definitely looks less ugly.
Quote:
Originally Posted by Lognic04
I too use the 7nm zwo ha.
Filter orientation hasn't helped me.
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Quote:
Originally Posted by kosborn
I have a full set of ZWO filters. This particular image was the ZWO 7nm Ha filter.
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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?
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07-12-2018, 08:52 AM
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Registered User
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Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
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Yes unmounted, but the filter wheels now come with masks so that's not the problem
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07-12-2018, 10:18 AM
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Registered User
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Join Date: Mar 2018
Location: Canberra
Posts: 503
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Quote:
Originally Posted by AstroApprentice
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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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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07-12-2018, 10:20 AM
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Registered User
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Join Date: Mar 2018
Location: Canberra
Posts: 503
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Quote:
Originally Posted by RickS
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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Yes mine are unmounted ZWO filters.
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07-12-2018, 10:50 AM
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Registered User
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Join Date: Dec 2015
Location: Melbourne, Australia
Posts: 349
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spacers
Quote:
Originally Posted by kosborn
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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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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07-12-2018, 07:18 PM
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Registered User
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Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
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Any luck Rick?
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07-12-2018, 10:06 PM
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PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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Quote:
Originally Posted by Lognic04
Any luck Rick?
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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
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08-12-2018, 05:42 PM
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Registered User
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Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
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08-12-2018, 06:09 PM
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Ultimate Noob
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Join Date: Aug 2011
Location: Melbourne
Posts: 6,982
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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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10-12-2018, 09:23 PM
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PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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Quote:
Originally Posted by RickS
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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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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10-12-2018, 09:57 PM
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Registered User
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Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
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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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10-12-2018, 10:11 PM
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PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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Quote:
Originally Posted by Lognic04
Rick what you'e describing is different to colin's method?
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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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10-12-2018, 10:36 PM
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Registered User
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Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
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Oh I see, thanks I'll have a go tomorrow
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16-12-2018, 04:16 PM
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PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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My attempts at a relatively simple and quick solution with a single mask for Kevin & Logan's multiple reflection artefacts did produce an improvement but not enough for me to be happy with the result. Looks like it would need a mask for each ring to do a good job with this strategy and that's going to be time consuming...
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