L-RGB combination - blue cast

rleighton

New member
Jun 5, 2020
4
1
Hi All!

Hoping someone may be able to provide some insight in how to improve the LRGB combination of this image of M51!

Prior to this point, in PixInsight I’ve used DBE, Deconvolution, initial noise reduction, Linear fit, stretched to non-linear, rgb combined, then used background neutralisation, PhotometicColorCombination, and ColourCalibration.

The following image is the RGB a combined.

View attachment rgb.jpg

I’m quite happy with the rgb combination, however when I combine with luminance, I get a deep blue cast - which I guess is amplifying the glow from the RGB. I’ve tried range masks and DBE to remove some of the glow before the combination (to try and neutralise it post LRGB) but the result isn’t great!

View attachment lrgb.jpg

To rectify this, I also tried rerunning ColourCalibration on the RGB and instead of using M51 as the white reference used a couple of stars, then combined with L

View attachment lrgb2.jpg

I’m keen to keep my original RGB colours and balance but with the luminance data added, or even better to try and resolve something similar to the images you see of M51 where its a nice shade of blue, and the glow / luminence surrounding more yellow in colour…

Any pointers or tips, would be sincerely appreciated!

Incidentally, I’m using 6x300s for each RGB channel, and 10x300s for L.

Thanks in advance
Richard
 

Bobinius

Well-known member
Jan 11, 2019
51
1
Hi Richard,

First, you should use background neutralization and photometric color calibration on the linear image, before stretching. Second, please provide tiff files at least not jpeg.

You have a glow on the RGB image already which looks to me similar to condensation or haze on the B channel during acquisition, so it is a bad start. I would suggest you try BN and PCC on the linear image, stretch and then SCNR to see what you got.

CS,
Bogdan
 

rleighton

New member
Jun 5, 2020
4
1
Hi Richard,

First, you should use background neutralization and photometric color calibration on the linear image, before stretching. Second, please provide tiff files at least not jpeg.

You have a glow on the RGB image already which looks to me similar to condensation or haze on the B channel during acquisition, so it is a bad start. I would suggest you try BN and PCC on the linear image, stretch and then SCNR to see what you got.

CS,
Bogdan
Thanks Bogdan for the advice, I'll give this a go.

I did try adding the TIFFs but was rejected due to file sizes.

Many thanks
Richard