Telescope: Celestron 9.25"
Schmidt-Cassegrain at f/6.3
Focus: Prime focus
Filter: Astronomik Hydrogen Alpha
Mount: Vixen GPD with Skysensor2000
Camera: Modified Canon EOS 300D, at
Guiding: 700mm refractor guidescope,
SAC7 camera, autoguided with Guidedog software
Exposure: Total 117 mins L (39 x 180s),
46 mins RGB (23 x 120s)
Date: 17th May, 4th June 2005
Processing: Reused the H alpha image
from 17th May. For RGB, RAW file conversion,
Offset and Dark subtraction, flat fielding, registering and stacking done in
IRIS. Used the ASINH function to enhance colours. Curve stretching and a
little unsharp masking in Photoshop CS. Colour saturation enhancement
with Luminance Layering, the RGB was composited with the Luminance image using a
technique described by Rob Gendler
(Method 2). Noise reduction
in Neat Image.
Star ovality reduced through making a
duplicate layer and offsetting that by half a pixel using the 'darken'
blending mode in Photoshop.
This was a hard one to get right. I
had good luminosity and RGB data, with nearly 2 hrs exposure on the L, but
colour balance was difficult. Took great care to calibrate the colours
the the white balance indicated by my flats (produced using my white LEB
lightbox - which gives a very neutral white light) and finally managed to
get good representation of colours.