New data with the ASI 6200M and a new processing technique thanks to this site:
pixinsight-dynamic-narrowband-combinations-with-pixelmath.
The basic pixelmath:
R = (Oiii^~Oiii)*Sii + ~(Oiii^~Oiii)*Ha=12.0pt
G = ((Oiii*Ha)^~(Oiii*Ha))*Ha + ~((Oiii*Ha)^~(Oiii*Ha))*Oiii=12.0pt
B = Oiii
Prior Ha effort:
Sh2 236 H-alpha RGBFrom
GalaxyMap:Lying at the core of the
Aur OB2 association, the great HII region
IC 410 (associated with the radio source
W8) surrounds the star cluster
NGC 1893 and is sometimes called the Tadpole nebula because of tadpole like structures (the nebulae
Sim 129 and
Sim 130) visible in
detailed images.
Avedisova lists 5 ionising stars (including 4 O-class stars). The hottest of these is the O5 V star
HD 242908. She places Sh 2-136 in the star formation region
SFR 173.63-1.70 along with the young stellar object [url=
http://simbad.harvard.edu/simbad/sim-id?Ident=[MJD95]%20J052308.30%2B332837.5]IRAS 05198+3325[/url].
A 2002 study states that NGC 1893 contains "at least five O-type stars".
There is an enormous range of distance estimates for NGC 1893. The most recent estimates appear to be converging around 3500 pc, consistent with a location in the Perseus arm.
The very young open cluster NGC 1893 is considered to be the centre of the Aur OB2 association. NGC 1893 can be recognized as an extended region of loosely grouped early-type stars, associated with the Hii region IC 410 and obscured by several conspicuous dust clouds. NGC 1893 contains at least five O-type stars, of which two, HD 242908 and LS V +33 16 are main-sequence O5 stars, and therefore younger than ~ 3 Myr.
GENERAL NOTE ON SHARPLESS2 OBJECTS>>>>>>>>>>>>>
There are 313 Sh2 objects. As of the date of this image I had imaged all 313 (100%).
Some of the challenges with this series are FOV size and low declination:
There are 11 too diffuse/large to image well with my set up (Sh2 111, 117, 122, 131, 132, 145, 178, 218, 230, 268 and 310). I have imaged the first 6 of these mostly in the Nikon Wide angle shot referenced below and 178 and 230 as part of other images.
There are 5 that are never above 14 DEG (Sh2 2-6) but as of 7/12/21 I can get these now with pier upgrades and the images are completed as best as I can.
Many were taken with my old Tak 180 ED, which had a wide field of view, but was replaced with my Stellarvue 130, which is more narrow field. I have also taken two very wide field HA images with my Nikon D800 and a 50mm lens. I transitioned from my CCD SBIG 8300M to a CMOS ZWO ASI6200M Pro in September 2021.
The first one was taken on December 23, 2013 and the series completed October 17, 2019.This is my collection:
Sharpless2
Wide-Angle Hydrogen Alpha Nikon Image Sh2 79-171
Please note there is also a Sharpless2 Group with now more than 1500 examples.
Sharpless2 Group
Other useful links include:
Gary Imm's Collection
GalaxyMap's Collection
The Sharpless Catalog
The MDW H-alpha Sky Survey
Reiner Vogel's detailed observing catalog
Hope you enjoy these obscure but interesting objects...
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