The Helix Nebula (NGC 7293)

Helix Nebula
All Images Copyright Steve Cannistra

Please click here or on image for a higher resolution view.

Magnitude:  7.3
Size:  16' x 28'
Distance: 450 light years
RA: 22h 29m 36s
Dec: 20 degrees 48' 00"

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
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
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.
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).

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