Telescope Reviews: Some success with the H-beta filter

This is an excerpt from an observing report I posted here and on another couple forums. Not sure why the search function isn't finding it. Background information is that this observation took place from 10 miles WSW of Fort Davis, TX, under pristine, unpolluted skies at 6000' of elevation. Telescope was an 18" Obsession. The date was 12/21/06.

"Sh2-245 (Eridanus Bubble)- 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/photo.cgi?Image=images/Eridanus_Bubble_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."

As far as IC 59 and 63 goes, you may need a bigger scope to help them stand out more. Since they aren't exactly huge objects, more aperture helps, up to perhaps a 10" after which you'll get some diminishing returns (just estimating here). Their filter response is just about tied between UHC and H-beta, but perhaps under more light pollution (but not too much, they are very faint objects), the H-beta might have an edge as it has a narrower bandpass. The point is, since they are reflection and emission nebula hybrids, the fact that they have a just about equal response in H-beta and UHC means that their H-beta emission component is very strong, as the H-beta blocks more of the reflection nebulosity than the UHC does.

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John T.
Austin, TX
25" f/4.2 Dob
18" Obsession #701
4" Stellar Vue Achromat
8X56 Binos

Edited by tatarjj (10/31/09 04:37 PM)