Cas A observations

[Howard B]

I've observed the Cas A SNR several times under decent to excellent sky conditions and had my best view to date at last years Oregon Star Party. The first time I saw Cas A I was surprised how easy the brightest segment was to see in my 28 inch - heck, I was amazed that Bill Gates had seen it through his 9.25 inch SCT - and after repeated observations I've now started to think that the other half of the loop should be visible on a superb night at altitude. Maybe that's wishful thinking on my part, but I wonder if anyone here has seen both loops? I've attached my current sketch to show what I've seen so far.
9594

[Steve Gottlieb]

Great sketch, Howard. I've observed Cass A a few times with my 18" but had no hint of any additional nebulosity. You didn't mention use of a filter, but did you use an OIII?

[Howard B]

I used an NPB filter - should have mentioned that before! My best view was at x355, and the OIII filter dimmed the image too much while the h-beta blocked it entirely. However, the non-filter view was second best to the NPB, which surprised me, as it was perhaps 80% of the NPB view.

The SQM was 21.71 at the time of the observation and Cas A was more or less around the meridian - so conditions were quite good. Even so, the transparency wasn't as good as it generally is at the OSP which gives me hope that it's possible to see the fainter loop.

[Marko]

This observation doe not say much about the nebulous elongated glow but it's all I have from one viewing at Mt Lasson last summer. I'm kind of embarrased I did not write down if I had used NPB or if it killed it or if OIII worked so I wonder if this is just white light. I forget at this time but it is likely it was NPB and I did not make the note. It was an extremely nice night at 8000 feet and once you knew where it was in my 18" dob it was available when patient.

Cas A Cas SNR 23 23 25 +58 52 30 15.0b 30.0x 2.0' This appears as a faint EW elongated glow of around 1.5' length. Both Carter and I were able to see this coming and going with greater length as seeing allowed. Detailed finder charts required but GSC4011:1069 is 2.2' due north of the west side of the fragment we can see visually. The middle of this segment has some very fine stealler objects that form the south star in a eq triangle of 2.5' side. Then 7' NE of this EQ tri is a more obvious EQ tri that points to this Cas A objects triangle. 07/29/11 02:00 LassenBA 216x 9mmNag 18SMasterPC NELM 6.9 and 21.7 mag/ArcSec

[Uwe Glahn]

Great sketch Howard, very similar to my sketch with 16" (http://www.deepsky-visuell.de/Zeichnungen/CasA.htm) but with much less stars :)

I was also surprised, that we could see the N part with the 10" Dob of my friend. Best view was with an UHC, [OIII] darkened the nebula to much.

With my 27" I tried also the S part but could only see the brightest part as a very small, nearly stellar spot of light. I used an [OIII] with 172x under good but not perfect transparency.