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Old 09-04-2011, 02:10 PM
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JohnH
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Join Date: Feb 2005
Location: NSW
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Centaurus A - LRGB attempt - help needed!

Hi, This is quite literally my 2nd attempt at LRGB imaging - light pollution and moonlight normally drive me to narrowband plus my targets are more often bright nebulae so nb is a good option, but....last night was clear and dark so I tried LRGB again....

First I should apologise for the processing - I did not have good flats and darks and lost signal as a result of approximated calibration and then I pushed to hard to compensate, I will re-do the image but the result does illustrate the challenge I have with RGB and LRGB processing.

The image is 30 mins each of LRGB using Astronomic filters and an Opticstar 145m CCD connected to a 127mm refractor. I find that even when I refocus the blue images are always softer than R and G. I think this is normal - blue light is scattered more by the atmosphere than the R and G. I understand you can minimise the imapct by getting blue lights when your target is at its highest but this only gets you part way - what is the best way to reduce the impact of the blue bloat?

I have re-processed the image - and have a bit more light data but still face the same issue...
Attached Thumbnails
Click for full-size image (CentA_LRGB.jpg)
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Click for full-size image (rgb_subs.JPG)
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Click for full-size image (CentA_LRGB2.jpg)
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Last edited by JohnH; 10-04-2011 at 04:07 PM. Reason: added reprocess
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