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 42 mins (14 x 180s)
Date: 17th May 2005
Processing: RAW file conversion,
Offset and Dark subtraction, flat fielding, registering and stacking done in
IRIS. Only the Red channel was used. Curve stretching and a
little unsharp masking in Photoshop CS. Star ovality reduced through
making a duplicate layer and offsetting that by 1.5 pixels using the
'darken' blending mode in Photoshop. Noise reduction in Neat Image.
A humid night in between days of rain - 26
deg C, 95-99% humidity and windless. Transparency was very good.
I was surprised that the image is acceptable though a little noisy, given
that exposure time was less than ideal, and that the corrector plate started
to dew up towards the end of the imaging session. The guidescope dewed
up as well, making guiding inaccurate.