The Helix Nebula (NGC 7293)
Characteristics:
Magnitude: 7.3
Size: 16' x 28'
Distance: 450 light years
RA: 22h 29m 36s
Dec: 20 degrees 48' 00"
Description:
The Helix Nebula is one of the closest and largest planetary nebula,
with a total span equivalent to the diameter of the full moon.
Planetary nebulae are beautiful objects that represent dying stars in
the process of shedding their outer layers of gas into space.
Although it has a magnitude of 7.3, the surface brightness of the
Helix is low due to its large size. The Helix is low in the
south for me and can only be photographed for about an hour at my
imaging location before it is obscured by trees. Although the
above Ha photograph could benefit from more exposure (and higher
elevation), a surprising amoung of internal detail can still be
observed (but nothing in comparison to the view from the Hubble Space
Telescope).
Photographic
Details:
Date: September 2, 2004
Scope: Takahashi
Sky 90 at f4.5 with field flattener/focal reducer, on the G11 Losmandy
Mount.
Autoguider: SBIG STV with
e-finder.
Camera: SXV-H9
Filter: Astronomik
Ha filter (13 nm bandpass).
Exposures: 14 x 5' each, binned
1 x 1, 70
minutes total.
Conditions: Temperature 55 degrees F; average
transparency; average seeing; calm.
Post-processing: Dark and
bias frame calibrated (dark frames consisted of 10, 2 minute
subexposures). Two-star aligned
in ImagesPlus; Sigma combined using RC Sigma Reject in MaximDL,
followed by DDP
in ImagesPlus. Subsequent
levels and curves adjustments in Photoshop CS (16 bit format).
Please
note: Graphics on this website
may not be reproduced without author permission.
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