The Rosette Nebula (NGC 2237-2239) using Bicolor Technique

Rosette Nebula
All Images Copyright Steve Cannistra

Please click here or on image for a larger size.
Please click here for this image in hydrogen alpha light.

Magnitude:  4.8 (for NGC 2244 star cluster in center)
Size: 80' x 60'
Distance: 5500 light years
RA: 6h 31m
Dec: 4 degrees 57' 00"

This narrowband image shows ionized hydrogen (HII, 656.3 nm) in red and ionized oxygen (OIII, 501 nm) in blue (see below for more details).  The Rosette Nebula is a winter showpiece for astrophotographers, as well as for visual observers at low power.  This large emission nebula is located in Monoceros and can be seen in dark locations with the naked eye, especially if viewed through a UHC filter held up to the sky.  The nebula actually consists of several sections (NGC 2237-2239), with a central ladder like star formation known as NGC 2244.  The Rosette Nebula is a star forming region- its central stars are young and newly-formed, and their radiation is responsible for ionization of elements such as hydrogen, which in turn emits light in the red.  Since hydrogen is the most abundant element in nebulae such as the Rosette, the dominant color of this nebula is red when viewed in a standard broadband image (taken by Wolfgang Promper).  However, other elements such as oxygen are present in the Rosette Nebula as well.  Such elements were actually created in other stars as a result of successive fusion of hydrogen to helium, to oxygen, to carbon, all the way down to iron, and were subsequently released during a supernova explosion.  Along with hydrogen, these other elements eventually coalesced to become part of the Rosette Nebula, which in turn is producing the next generation of stars.  Compared to hydrogen, oxygen requires bombardment by higher energy radiation to become ionized.  As a result, oxygen emission (shown in blue) is concentrated in the central parts of this nebula, where radiation is the greatest due to the proximity of hot, newly-formed stars.

Photographic Details:

Date:  December 27 (Ha data) and December 30 (OIII data), 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 6nm Ha filter and 13nm OIII filter.
Exposures:  Ha: 24 x 10' unbinned (4 hours); OIII 21 x 10' unbinned (3.5 hours); total exposure (Ha plus OIII) 7.5 hours.
Conditions:  December 27- Temperature 30 degrees F, average transparency, average seeing, a slight breeze, clouds invaded early, then cleared later for a good session.  December 30- Temperature 27 degrees F, above average transparency, poor seeing, intermittent breeze, clouds rolled in after 1 AM.
Post-processing:  This is an Ha:sG:OIII image.  Subs were debloomed using Ron Wodaski's Debloomer, and then calibrated and aligned in Maxim.  Combined using RC Sigma Combine, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format) using my bicolor technique.  The bicolor technique requires only Ha and OIII data to create a third channel (synthetic green, sG).  The process of color mapping is described further in a video by Ken Crawford, using the technique developed by Travis Rector.

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