M83 through UHC-S nebula filter

[tornado33]

Hello all.
Though the skies were clear and temperature only around 8 degrees, burning off smoke haze made the sky quite bright and light polluted. I wanted to shoot longer subs and highlight the hydrogen emission areas in M83 so used the UHC-S filter which Id normally only use on emission nebulae, not other galaxies.

Image is 7 x 20 minutes ISO 400. Hand guided as usual with no dec corrections in most of the subs, truly amazing how accurately SharpCap can get polar alignment spot on, even taking atmospheric refraction into account. 10 inch F5.6 scope, Modded 350D camera, Baader MPCC coma corrector.

Full sized version here https://www.astrobin.com/408084/
Scott

[Placidus]

An interesting experiment, worth doing.

Your zero point (dark point) can take some serious adjustment, especially in the blue. Set the zero point sliders separately for each channel until the foothill of the histogram (point where the left hand edge just kicks upward from zero) is almost touching the x-axis. You'll get enormously more contrast without losing one single photon of data.

Hard to know how to handle the colour balance of the brights when using a nebula filter, as you'll be mostly seeing red H-alpha and cyan OIII, but you can't even begin to do so until you've got the black point right.

If you do that, you'll see that you've got much more data there than first meets the eye.

Hope that helps.
Mike

[tornado33]

Thanks for that will give it a go