LRGB quadcolor composit test
LRGB quadcolor composit method is a new technique to make high S/N
color images. Also it will allows us to reduce the total exposure
1. Take R, G, B images and a monochrome image (without filter or with
filter for example DSP filter or H-alpha filter etc).
2. Composit the RGB images in a tricolor image.
3. Load it in PhotoShop, and comvert it to Lab mode.
Note: L-ch is "brightness" channel, a/b-ch include the color
4. Replace the L-ch with the monochrome image.
Note: the position of stars in both images must be adjusted before
This process is LRGB quadcolor composit process, where L means
"Luminance". You do not need high quality RGB images for a/b ch,
if you obtain a good monochrome image for L-ch. Therefore you may
take the RGB images with 2x2 or 3x3 bining.
M74 original images
Gray channel: 31cm F=5 Newtonian + HPC-1 CCD + DSP
RGB channel: 20cm F=4 Newtonian + ST-7 CCD + SBIG filters
(R=G=B=30min, 2x2 bining for B)
LRGB composit result for
M74 by Lab method
NGC253 original images by C5
Gray channel: C5 + ST-7 Nofilter (22 min)
RGB channel: C5 + ST-7 + SBIG RGB filters + Edmund new IR
(R=G=B=20 min, 2x2 bining)
Self guided images
LRGB composit image of NGC253
by Lab method
(proposed by myself)
LRGB composit image of NGC253 by
(proposed by Robert
Note that both results are very similar.
LRGB composit image of
by HLS mode of Picture Publisher 4.0 (MicroGrafx)
(proposed by Oohashi)
HLS mode is somewhat senstive to tone-curve tuning of
The color images are processed by
Digital development and color enhancement
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please go to C5 image gallary
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