Nebula, NGC 7293, In Aquarius
The Helix nebula
is another planetary nebula, and consists largely of hydrogen gas and other
substances thrown off by an exploding star. Although quite large, it is rather
dim and low on the southern horizon at my site in California so it is one of the
more difficult nebulas to image. For some reason, I chose two nights with an
almost full moon, which compounded the difficulty. By imaging the luminance
layer in hydrogen-alpha light, I was able to reduce the effect of the moon.
2003 October 10, 11
with two A-P reducers: 0.75x and 0.67x for a final focal ratio of
approximately 4.5. All
mounted on an A-P 1200GTO mount. Guiding with separate 900 mm
guidescope and SBIG ST-4 guider. Camera: SBIG ST-10XME
and CFW color
wheel, controlled with MaxIm
DL/CCD, v 3.1.
R, G, and B exposures 5
x 5 min, 1x1 binning plus 5 x 5 min, 2x2 binning. Six x 5 min H-alpha
frames, binned 1x1,
were used as the luminance layer.
Frames flat- and dark-calibrated and
RGB combined in MaxIm. The luminance layer was
registered with the
RGB composite in RegiStar and then combined in Photoshop. Final
processing with Levels
and Curves in Photoshop.
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