NGC 7023 (Iris Nebula)

NGC 7023
All Images Copyright Steve Cannistra

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Magnitude:  7.1
Size: about 18'
Distance: 1,300 light years
RA: 21h 00m 30s
Dec: 68 degrees 10' 00"

The Iris Nebula (NGC 7023) is located in the constellation Cepheus and is a beautiful example of a reflection nebula.  The young, central star (designated HD 200775) is only about 5,000 years old, and its blue light is preferentially scattered by the surrounding dust (resulting in the characteristic blue color of the reflection nebula).  However, on higher magnification, areas of red emission can be observed flanking the central star, a result of ultraviolet radiation that excites Ha emission within this region.  Finally, the entire region is filled with a dense, chocolate-brown dust that obscures light from stars behind the nebula.   Therefore, this region is comprised of all three main nebulosities:  reflection, emission, and dark, much like the Cocoon Nebula.

Photographic Details:

Date:  September 10, 2005
Scope:  Takahashi FS-102 at f6 with TOA-130 focal reducer, on the G11 Losmandy Mount.
Autoguider:  SBIG STV with e-finder.
Camera:  Maxcam CM10.

Astronomiks Type II  RGB filter set; IDAS-LPS filter).
Exposures:  Luminance filter, 24 x 8'; Red filter, 7 x 8'; Green filter, 5 x 8'; Blue filter, 10 x 8' (all unbinned).  Total exposure: 6.1 hours.
Conditions:  Temperature 75 degrees F, dropping to 50 degrees; average transparency, average seeing; calm; clear. 
Post-processing:  This is an LRGB image (192:56:40:80 minutes).  Subs were debloomed with Ron Wodaski's Debloomer software, calibrated in Maxim and aligned in Registar.  Sigma combined using RC Sigma Reject, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format).
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