rogerg
09-09-2009, 11:47 PM
G'day all,
A couple of weeks ago I took a few shots of NGC 7090 and am having trouble getting any nice colour variation out of them. I'm not sure why.
The sharpness of the data was good - the nights were nice and clear, and very stable.
I have relatively little experience with combining RGB. I know that I need to measure the exact ratios of my filters by exposing a star of the correct spectrum, which I haven't done. But in the past for some shots such as NGC 1566 I've at last ended up with something better than I have here.
There just seems to be no significant variation between the colour exposures to generate any reasonable amount of contrast between the colours. Yet I look at other shots of this galaxy on the web and there's some nice variation.
I've set the image background to a neutral colour using levels, and used levels and curves to brighten the image, but other than that not done any processing on the stacked (average) files.
I realise my RGB exposure times are short, 40mins max per channel, but surely there should still b some variation apparent, just noisy?
I'm happy to send anyone the 4 stacked LRGB fits if they want to help (all the FITS if you like, but doubt that's necessary).
Full details:
L= 125 mins (100mins of 10 min subs, 25 mins of 5 min subs, two sets averaged then added/summed two sets together)
R,G= 40 mins each
B= 30 mins (one blue was trailed so excluded)
Individual exposures of 10 minutes in all but the 5 luminance at 5min, Luminance all at 1x1, RGB at 2x2 and resized to 1x1 for processing. Approx F/7.5.
Attached is my best effort, which is essentially a yellow grayscale image :(
Thanks for any assistance :thumbsup:
Roger.
A couple of weeks ago I took a few shots of NGC 7090 and am having trouble getting any nice colour variation out of them. I'm not sure why.
The sharpness of the data was good - the nights were nice and clear, and very stable.
I have relatively little experience with combining RGB. I know that I need to measure the exact ratios of my filters by exposing a star of the correct spectrum, which I haven't done. But in the past for some shots such as NGC 1566 I've at last ended up with something better than I have here.
There just seems to be no significant variation between the colour exposures to generate any reasonable amount of contrast between the colours. Yet I look at other shots of this galaxy on the web and there's some nice variation.
I've set the image background to a neutral colour using levels, and used levels and curves to brighten the image, but other than that not done any processing on the stacked (average) files.
I realise my RGB exposure times are short, 40mins max per channel, but surely there should still b some variation apparent, just noisy?
I'm happy to send anyone the 4 stacked LRGB fits if they want to help (all the FITS if you like, but doubt that's necessary).
Full details:
L= 125 mins (100mins of 10 min subs, 25 mins of 5 min subs, two sets averaged then added/summed two sets together)
R,G= 40 mins each
B= 30 mins (one blue was trailed so excluded)
Individual exposures of 10 minutes in all but the 5 luminance at 5min, Luminance all at 1x1, RGB at 2x2 and resized to 1x1 for processing. Approx F/7.5.
Attached is my best effort, which is essentially a yellow grayscale image :(
Thanks for any assistance :thumbsup:
Roger.