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(IAAC) Obj: Sh2-245 - Inst: 18" f/4.5 Obsession



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Observation Poster: John Tatarchuk <tatarjj@auburn.edu>

Observer: John Tatarchuk
Your skills: Advanced (many years)
Date/time of observation: 12/21/07 (time unknown)
Location of site: Davis Moutians, 10 miles outside Fort Davis, TX (Lat , Elev 6000 feet)
Site classification: Rural
Sky darkness: 10 <1-10 Scale (10 best)>
Seeing:  <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: 18" f/4.5 Obsession
Magnification: 75X
Filter(s): UHC, OIII, H-beta
Object(s): Sh2-245
Category: Emission nebula.
Class: 
Constellation: Eridanus
Data: mag --  size Many Degrees 
Position: RA 4h:03m  DEC +3:00'
Description:
Supernovae and fierce stellar winds from the Orion Stellar Association have
blown large quantities of gas and dust out of the region surrounding the
Orion, Horsehead, and other nebulae. Half of the gas headed toward the
galactic plane where it slowed down as it collided with the interstellar
medium. This is Sh2-276, better known as Barnard’s Loop. However, the other
half of the gas was blown out, away from the galactic plain where the
interstellar medium is less dense. Thus it did not slow down as much and is
located much farther from the Orion Association than Barnard’s Loop is. This
half is known as the Eridanus Bubble, and it is cataloged as Sh2-245. A good
website that with images of the Eridanus bubble can be found at:
http://canopus.physik.uni-potsdam.de/~axm/...bble_Halpha_600.
However, how observable is this Eridanus Bubble? I had failed every time I had
tried to see this very faint emission region from Alabama. However, on the
night of 12/21 I was at last able to bag it. Starting with OIII filtration and
75X, I followed a tip of where to start the search, and may have detected a
slight increase in sky background brightness as I swept the scope in an E-W
direction at the coordinates 4h 02m +3 30’. Popping in the UHC got me more
excited. I definitely was beginning to pick something up! Inserting the H-beta
filter sealed the case. Using the H-beta, I was able to follow an EXTREMELY
faint strip of nebulosity about 15’-20’ wide from 4h 2m +3 45’ south-southeast
to about 4h 3m +2 10’ at which point the nebulosity slowly faded from view.
When I got back from Texas, I was able to finally find images of this nebular
complex to see that this is just the brightest section of a huge, ~10 degree
object. Chalk yet another object up as an H-beta target.

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