Author Topic: Combine RGB offset Problem  (Read 851 times)

Offline Duddd

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Combine RGB offset Problem
« on: 2017 August 24 01:05:37 »
Hi everyone,

i received my new asi1600mmc cam a couple of weeks a ago and finally had the chance to capture the veil nebula. Im very new to RGB processing because i used an OSC (QHY8L) and the asi is my first monochrome camera.

I am stacking each channel seperatly using DeepSkyStacker (shame on me) and then i try to combine them in PI via ChannelCombination. Unfortunetly the channels seem a little unaligned. (Please look at the image attached).

In Fitswork i know i can mark a star on each channels frame before combining them to RGB. Then, fitsworks automatically alignes the channels. How can i achieve this in PI?

Thank you,
Greetings from germany,
Chris

Offline Dimitris Platis

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Re: Combine RGB offset Problem
« Reply #1 on: 2017 August 24 01:36:46 »
Did u align the channels before u combined them in Pixinsight (after Deepskystacker)?

Offline Duddd

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Re: Combine RGB offset Problem
« Reply #2 on: 2017 August 24 04:21:57 »
Hey Dimitris,

nope i did not. How do i do so?

Thank you,
Chris

Offline aworonow

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Re: Combine RGB offset Problem
« Reply #3 on: 2017 August 24 06:08:00 »
Do the alignment suggested above (by picking a single reference frame and aligning all separate RGB raw frames to it). I have often encountered some degree of color dispersion from CFA cameras when the target is fairly low in the sky in some images and less so in others. I attribute that effect, rightly or wrongly, to differential refraction with target elevation. Not sure if PI's "distortion" models are intended to handle that problem or not.
In any case, most of your problem will disappear by make RGB separate images from each raw image and aligning them to one common reference image--I usually use a G image.

AlexW

Offline Geoff

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Re: Combine RGB offset Problem
« Reply #4 on: 2017 August 24 06:27:42 »
Do not align R, G and B separately. Pick the best frame and then align all your colour frames to that one. Same thing if you have L frames. Then form stacks of each colour followed by a combine.
Geoff
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Offline Duddd

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Re: Combine RGB offset Problem
« Reply #5 on: 2017 September 06 07:58:31 »
Wanted to thank you guys, got it now!