View Full Version here: : How to reduce over exposing stars in nebula images?
Still very new at imaging. Here is a reprocess of the other night's image of NGC 3372 (Eta Carina). It is a stack of 60 second exposures through an 80mm f/5 refractor. How do I reduce exposing stars, but still bring out the nebula? Do I need more but shorter exposures? :question:
26-04-2012, 04:51 PM
what are you doing the processing in Grant?
26-04-2012, 05:37 PM
I'm also interested in the answer to this as well. :question:
26-04-2012, 07:10 PM
me 3 :D
Just got myself a new (2nd hand ) 8" Newt:D
You need to do a non-linear stretch Grant, such that fainter areas are stretched more than the bright areas. I'm guessing you may have just pulled the white point slider down which has comressed the entire dynamic range of the image. Another solution is to mask the stars and then do gently non-lineaer stretches on the rest of the image.
If you Google "non-linear stretching" you should find plenty of references.
27-04-2012, 10:17 AM
:) Thats it rob, its a careful balance of Levels and Curves, Linear and non linear streching! Use your Levels to balance the histogram and strech your data over the whole 16 bit range, use your curves to Boost your data and bring out the faint stuff.!
If your really careful you will even keep star colour.
27-04-2012, 05:02 PM
It does appear that the image was taken with a lot of moisture in the air.
It is like thin fog was present whilst imaging.
That is just a guess, but it sure looks that way.
Thanks all! Much appreciated. :)
Still new to imaging, despite doing a far amount of visual observing over the years.
The scope is a really cheap refractor and there has always been moisture around this year!
I'll put your advice to the test. Thanks!
27-04-2012, 09:12 PM
I found this youtube video http://www.youtube.com/watch?v=BBQQ_Gs6YHM a great introduction on how to properly stretch and process astro images when I was first starting out. Hope it helps you as much as it did me.
08-05-2012, 10:30 AM
Levels , curves, levels, curves, levels , curves, in ever decreasing increments. All the time keeping an eagle eye on your histogram.
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