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Author Topic: Trouble in PI  (Read 975 times)

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Offline Phillyo

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Trouble in PI
« on: 14:49:44, 12 February, 2015 »
Hello all,

So after a month or so of not being able to image due to a broken piece of kit, I'm now back up and running again. Managed to get out on Monday night and grab some SII and OIII on IC443, however I'm having a nightmare getting them to blend together properly in PI.

The Ha data I have is from the Megrez 72 whereas I got the OIII and SII from the Star 71 so there's a small difference in the focal length making the stars at the corners not line up perfectly, but I'm not too worried about that. After I have aligned the images I use PixelMath to combine them...but no matter what combination I use the stars are always purple or green or whatever and I have no idea how to enhance the colours I want (nebulosity) and make the stars go white!

It's driving me mad. Anyone know any links to vids or tips please?

Thanks,
Phil.
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Trouble in PI
« Reply #1 on: 15:24:07, 12 February, 2015 »
Phil

I assume you are doing Star Alignment on all the frames using a common reference frame? If so, in star alignment turn on Distortion Correction and change the registration model to a 2-d surface spline. You may have to up the number of iterations (50?) to get a valid solution. This will then warp the images to get a best star fit right across the frame. I have successfully brought together frames from very different setups this way.

Dont worry too much about the odd star colour, get everything else right first. Build a decent star mask and then do a seperate colour adjustment on the stars only, often by just destaurating them on NB images. OR cu the stars out completely and add them back at the end (quite a lot of effort!)

If the size of the stars is different between the frames due to focus or just conditions, you can do a decon or run a round of morphology on them to match them up better (lots of trial and error)

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
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Offline Phillyo

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Re: Trouble in PI
« Reply #2 on: 20:21:08, 12 February, 2015 »
Ok thanks Chris. I'll give those a try :)
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline Phillyo

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Re: Trouble in PI
« Reply #3 on: 10:08:44, 21 February, 2015 »
Well I got it to work Chris, but really not happy with the image so I think I'm going  to try and get some more data and try again. To be honest, and maybe this is me being very picky (or i've been spoiled) but I really don't like the images coming out of the Astronomik SII and OIII filters. They look very washed out with HUGE stars everywhere. The Astrodon 3nm Ha is just beautiful and smooth in comparison :)

Might be clear tonight, with no moon so may try getting some more SII and OIII on IC443 tonight :)

Thanks again,
Phil.
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

 

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