Old 06-06-2018, 04:55 PM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

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Join Date: Mar 2012
Location: Melbourne
Posts: 2,636
How to get Nice Star colours under LP?

Hi folks,

I'm interested in people's methods for rendering accurate RGB star colours when shooting LRGB under LP.
(Mono cameras, not DSLRs or One shot cameras with a bayer matrix).

I'm currently shooting 15x1 min subs per colour, and while the star colours look ok when processed, I don't think it's deep/long enough exposure time to record enough stars.

I'm thinking I either need to go to 30x 2 min or 60x 1min subs.

I have an IDAS LP filter, but I no longer use it as it messes with the star colours!

I'm using a QSI683 wsg8 camera, and scopes with 70mm, 110mm & 200mm aperture.

My skies are class 6 bortle Mag 19.03 (according to the "Clear Outside" app)



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Old 06-06-2018, 05:03 PM
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multiweb (Marc)
ze frogginator

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Join Date: Oct 2007
Location: Hinchinbrook
Posts: 19,386
Star colors will vary wildly with many factors besides light pollution. Altitude, transparency, natural skyglow. Blues are best shot at the zenith, red and green are not as affected at lower elevations. LP filters, Nebulae filters, etc... will have a red bias usually so what you end up with will always be different. There are some good tools in PI to retrieve the right colors, goodlook as also an excellent color balance algo. If you want to do a little pixel math in PI or CCD Stack the best way to get ball park is to select a part of the sky background without any stars (or very little) and no nebulosity. Look at the parameter called int mode then make a note of it for your red, green and blue channels. Take the highest value channel then calculate the difference to add/subtract to the other two channels and do a pixel math add/subtract to equalise the three channels. Then combine your color with the ratios 1:1:1. That will get you as close as it can be to the true color values.
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Old 06-06-2018, 06:47 PM
LewisM's Avatar
Novichok test rabbit

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Join Date: Aug 2012
Location: Somewhere in the cosmos...
Posts: 9,877
I was gonna answer, but you said NOT OSC, so...I dunno
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