The Rosette Nebula (NGC 2237-2239) using Bicolor Technique
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).
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.
Date: December 27 (Ha
data) and December 30 (OIII data),
FS-102 at f6 with TOA-130 focal reducer, on the G11 Losmandy
Autoguider: SBIG STV with
Camera: Maxcam CM10.
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,
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.
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
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.
note: Graphics on this website may not be reproduced without
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