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Advice on shooting stars with a mono camera

QHYCCD QHY268 M Processing RGB Monochrome Deep Sky
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RammaN avatar
RammaN avatar
Hello, so to let you know my setup, I shoot nebula with a hyperstar and a qhy 268m. I then shoot rgb stars with an Askar FRA400. 

In the past i have used a OSC camera to gather star data. With a lum filter these stars looked great. Hues of blue and yellow.

with my mono camera i am struggling to get good star colour. Ill admit, i have not shot many nights with the 268 and fra400 combo.

So, i have a set of astronomik deep sky rgb filters as well as an Astronomik L3 lum filter.

my question is, what is the best way to aquire and process stars?

i have tried just rgb so far, 90 second x 90 exposures and i wasnt impressed with the end result.

what should my exposure length be? Should i combine a lum channel as well? What is the best way to process the stars for perfect colour while keeping the stars size to a minimum? How do i process the stars without stretching until clipped or losing star colour?

I have alot of experience with pixinsight and my nebulosity images are good enough where I am happy with the result, now I need to work on my stars! 

thanks alot, any info appreciated
RammaN avatar
RammaN avatar


my latest with hyperstar, fra400 and qhy268m
Joe Linington avatar
Joe Linington avatar
I have only just asked the same questions a few months ago. 90 seconds seems awfully long. My camera will start blowing out stars at anything over 60s. Your camera has a deeper wheel depth and bigger dynamic range but still. I use 15s subs for RGB stars. 15-20 minutes per channel, throw a third away and only stack the best. Some people use 5-10s subs and only capture 5-10minutes per channel.  No lum, simple SPCC and BlurX, then star extract and stretch the stars. I like an initial ArcSinh stretch and then GHS. This seems to preserve colour while preventing blow out.
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RammaN avatar
RammaN avatar
Interesting, i assumed that the longer exposures would help aid in collection of photons, thus adding to the natural colour. So with what you are saying its possible that I am over exposing the stars and this is leading the colours to end up looking very white?

i know i try to balance the RGB OF THE STARS IN PIX, but i cannot get those beautiful blue and yellows i see in alot of images
dkamen avatar
dkamen avatar
It is not just possible, it is certain. Stars are bright and mono collects 2X to 4X more of them per pixel than an equivalent OSC.

i assumed that the longer exposures would help aid in collection of photons, thus adding to the natural colour


As long as you do not saturate, this is true. When the subject is dim, collecting a value of 60% red clearly results in something redder than collecting a value of 20% red.  But stars are hundreds to thousands of times brighter than nebulas. As you keep collecting, too many photons will eventually result in a value of 100% to be recorded by the pixel. 100% blue + 100% red + 100% green = white. With stars, it is best to underexpose. 

Cheers,
Dimitris
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tjm8874 avatar
tjm8874 avatar
Blue and yellow stars like this?

80PHQx0.76 (455mm f/5.7) ASI533MM 
30sec x20 RGB (total 30min) + 180sec x150 SHO (total 7.5hour), 
remove SHO star, HT, channel combination
stack RGB, SPCC, Arcsinh / HT stretch, then extract stars
screen integration ~(~back*~stars)
then go to Photoshop, saturation contrast vibrant...
RammaN avatar
RammaN avatar
heeeeeyyy that what i was looking for, thank you so much!!!