M20 Trifid Nebula

DotDotDotZ · Post by **DotDotDotZ** » Mon May 28, 2007 10:34 pm

wow....beautiful photo

cataclysm · Post by **cataclysm** » Mon May 28, 2007 10:35 pm

A modified camera shouldn't affect the blue channel... May be you are too aggressive with your processing??

Could be. I forgot to mention that IDAS light pollution filter was employed. That may be the cause of it. Will try without the filter next time. Too kia su la!

The reason why cataclysm's photo is poor in blue is simple. Because his H-alpha photos (which doesn't have blue and green spectrum) have exposure that is longer that his colour photos. So when you stack them together, you see very poor blue.

This may not be the case. The H-alpha frames were grey scaled and were only used as luminance for the final image. My best guess is the Mewlon is inherently slow and coupled with the higher sensitivity to Red of the modified camera may be the cause. To get the rest of the colours, i would probably have to tripple or quadruple the total exposures.
Anyone has other ideas?

Post by **VinSnr** » Mon May 28, 2007 11:52 pm

This may not be the case. The H-alpha frames were grey scaled and were only used as luminance for the final image

why do you grey scaled the H-alpha? You are not taking RGB are you?

Maybe you should explain exactly what you did, if not it will be hard to deduce why the blue is lacking.

Post by **Airconvent** » Tue May 29, 2007 12:01 am

wow weixing...
This seems to be your best effort ever! The image is so rich in colours they are awesome....Hope to see more of this expecially from Singapore skies.
Cataclysm is not doing too bad either...The master and the disciple! heh heh

Post by **rcj** » Tue May 29, 2007 9:35 am

excellent image weixing! you might like to try www.1111mb.com to host the images, no pop-ups and 5G of space. I am using that for my personal website

Post by **rcj** » Tue May 29, 2007 9:37 am

kelvin,

you might like to take longer RGB data for the modified DSLR. Also when you are in PS, perhaps you could check that the histogram profiles for each colour channel has roughly the same spread, nevertheless it is a good try!

Post by **VinSnr** » Tue May 29, 2007 10:27 am

In the first place, need to also know what is being "modified" in that 350D. There are three kinds of modification that people usually do

1) Totally remove camera filter. For this, you get all the spectrum but you can't autofocus or use the viewfinder

2) Replace camera filter with clear glass. All the spectrum will be there and you can autofocus and use viewfinder

3) Replace camera filter with a different UV/IR filter or deep sky filter. Now this one is tricky. You need to find out first the properties of this filter before using any other external filters.

So which one of the above is the modified camera? It will have impact on the images.