Image Colour - post processing or lack of data

[malc-c]

I've recently moddified my Canon D400 to full spectrum (ie removed all the internal filters) and use a CCD-CLS clip filter to cut IR and UV.

Whilst conditions last night were not brilliant, with the sky quite light I took 25 x 300s subs of M81.  These were then stacked with 15 x 300s darks of the same ISO (800) in DSS and the final Tiff tweeked in photoshop CS2 using curves and some of Noels astro tool filters, the best result has been attached.  However I still can't pick out colour in the stars in the spiral arms that is seen in other images.

I'm not sure if the issue is caused by the sky conditions, lack of data, or not being stretched enough in post processing, or the data wasn't stacked right in DSS

Any ideas

[rfdesigner]

I've found some stretching kills colour, some doesn't it's down to the maths.

With IRIS which I use, I stretch the Luminance, then balance the luminance background with the linear RGBs and then combine.. then I get sensible colours.  If I stretch a RGB I lose my colour...  If I combine a stretched  luminace with a linear RGB but get the background of the luminance much brighter than the RGB I end up with horrible over strong colours and weird backgrounds.

Derek

[lensman57]

I've recently moddified my Canon D400 to full spectrum (ie removed all the internal filters) and use a CCD-CLS clip filter to cut IR and UV.

Whilst conditions last night were not brilliant, with the sky quite light I took 25 x 300s subs of M81.  These were then stacked with 15 x 300s darks of the same ISO (800) in DSS and the final Tiff tweeked in photoshop CS2 using curves and some of Noels astro tool filters, the best result has been attached.  However I still can't pick out colour in the stars in the spiral arms that is seen in other images.

I'm not sure if the issue is caused by the sky conditions, lack of data, or not being stretched enough in post processing, or the data wasn't stacked right in DSS

Any ideas

M81 is quite difficult for an OSC capture with short data. Perhaps from a true dark site 300s subs will be long enough. I  favour doing the galaxies in LRGB now if the weather permits or do a lot of long subs in OSC and then do masked stretching to preserve the star colours and galaxies,

A.G