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Sh2-091 SNR in Cygnus

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#1 JayinUT

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Posted 12 July 2013 - 12:27 AM

On Tuesday I was out with a couple of friends observing and what should have been great conditions were hampered by the smoke. Zenith was good and as the night went on, it got better. I actually had a pretty good night hunting down a few galaxies in Hercules and some planetary nebula. One item I am trying to chase down this summer is SH2-091, the SNR about 2 degrees above Albireo. Anyway, I know I had the field correct, but felt I had hints of pseudo-nebulosity, which equally could have been averted imagination, so I can't count it as a hit.

I was using my 14" dob with Zambuto mirror, Protostar secondary. A 30mm ES 82 degree and a 27mm Panoptic as my finders. I also was using an OIII filter. The SQM was 21.55, as this site is not our main dark site (for conditions we didn't want to drive out that far, but it may take the mag. 7.0 skies at our dark site for this one). I believe that the conditions, transparency, due to the smoke from Las Vegas just were not good enough to bring out the SNR.

Anyone else with success with this object? What were your conditions and SQM if possible. What scope, eyepiece and filter? Thanks!

Oh, I do know about the follow sites with this object:
Adv in Deep Space Link.

Reiner Vogels Site where he has the Sharpless HII Catalog which includes a finder for this object at this link

.I also have a book and a print out chart for so I think I am pretty good there.

So will this have to be something I wait until I get the 20" I am going to order this fall or can my 14 with the quality optics it has pull this in?

#2 David Knisely

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Posted 12 July 2013 - 01:02 AM

We ran into this one (Sh2-91) by accident at the Nebraska Star Party while hunting for Minkowski's footprint (Mink 1-92) using Dragan Niken's 25 inch Obsession and an OIII filter. It was fairly faint but fairly easy to see in that scope. I may have to try for it again with my 14 inch, but it is bound to be harder to notice in that aperture. Clear skies to you.

#3 JayinUT

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Posted 12 July 2013 - 11:23 PM

Thanks David. Steve G hooked me up with some very helpful links. In one of them a 15 inch Obsession is able to pull in the brighter parts and some of the fainter parts of this SNR. I'll share the links.

This is the post Steve G. shared (and he has seen it in a 14 inch Starmaster with CZ optics so both our 14 in the right conditions should pull this in I would think). The post is by Reiner Vogel and Matthias Kronberger (he uses a 15" Obsession if I remember correctly) that includes multiple sections of this supernova

Link 1

This link is from Reiner V.'s webpage and shares a lot of information.
Link 2

This link is from the Cornell University Library and is called Deep optical observations of G 65.3+5.7. I think its fun to read up on items you want to observe, especially somewhat challenging ones.

Link 3

Hope a few others find this information helpful.

#4 GlennLeDrew

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Posted 13 July 2013 - 07:32 AM

If this is a very low surface brightness object (and I'm certain it is), one need not have a 1/10 wave system to see it. Due to the very poor resolving power of the eye at such low brightness and contrast, a 1/2 or even 1 wave scope will do (at least if having a reasonably smooth surface, and not with pronounced/sharp zonal errors.). On the nebulosity (certainly not the stars, which have very much higher surface brightness), the on-axis aberrations will be fully below the ability to resolve. That is, the minimum size for detection, at the moderate exit pupil most likely used (even small-ish, probably) has the wisps of nebulosity much wider/larger than the scale of aberration. The latter is too small in relative scale to be of import.

Many a risible Coulter from days of yore can do well enough on the quite dim stuff, if well enough baffled. Even the coatings need not necessarily be better than the good ol' standard aluminum, due to the eye being primarily a contrast detector. But if one wanted to compensate for reduced transmission efficiency, an exit pupil 10-15% larger should get image surface brightness up to that of the modern high-reflectance coatings.

I can already hear howls of protest at my heresy. But such reactions are borne of an incomplete appreciation of just how very *awful* is our resolving power at these low levels of brightness/contrast. Sure, the stars will look less sharp, but the nebulosity will be perceived just well as seen through a same-aperture, equally-baffled top-end scope.

#5 sgottlieb

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Posted 13 July 2013 - 11:58 AM

Many a risible Coulter from days of yore can do well enough on the quite dim stuff, if well enough baffled. Even the coatings need not necessarily be better than the good ol' standard aluminum, due to the eye being primarily a contrast detector. But if one wanted to compensate for reduced transmission efficiency, an exit pupil 10-15% larger should get image surface brightness up to that of the modern high-reflectance coatings.

I can already hear howls of protest at my heresy. But such reactions are borne of an incomplete appreciation of just how very *awful* is our resolving power at these low levels of brightness/contrast. Sure, the stars will look less sharp, but the nebulosity will be perceived just well as seen through a same-aperture, equally-baffled top-end scope.



No protest here, Glenn. Though I'd prefer to describe the mirror as "mediocre" rather than "risible", my first observation of Sh 2-91 described here was made with a Coulter 17.5-inch mirror from the mid-80's -- and it was easily up to the task of picking up this low surface supernova remnant!

#6 nytecam

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Posted 13 July 2013 - 01:09 PM

That's interesting ! I had one of the first order 17.5" Coulters that I collected in Daytona and brought home to UK. Images were a bit soft and I got it refigured but not much improvement. It proved perhaps too big an aperture for suburbia so I went back to a 12" go to SCT and have stuck with it since to very good effect:-)

#7 GlennLeDrew

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Posted 13 July 2013 - 02:47 PM

Steve,
My descriptor was likely in line with what many might think nowadays, what with so many 1/4 wave and better dobs on offer. I mean, these days what is one's first reaction when encountering a 3/4 or 1wave P-V error? Most would run screaming into the hills! :grin:

#8 sgottlieb

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Posted 13 July 2013 - 10:39 PM

That's interesting ! I had one of the first order 17.5" Coulters that I collected in Daytona and brought home to UK. Images were a bit soft and I got it refigured but not much improvement. It proved perhaps too big an aperture for suburbia so I went back to a 12" go to SCT and have stuck with it since to very good effect:-)


Same here, Maurice, though I went one step further and had my Coulter refigured twice. :lol:

Still there weren't too many other options in the mid-80's and I ended up observing thousands of faint fuzzies with it!

#9 David Knisely

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Posted 14 July 2013 - 01:24 AM

Steve,
My descriptor was likely in line with what many might think nowadays, what with so many 1/4 wave and better dobs on offer. I mean, these days what is one's first reaction when encountering a 3/4 or 1wave P-V error? Most would run screaming into the hills! :grin:


Yup, and on some of the smaller deep-sky objects, the mirror quality can indeed be a really important factor in seeing detail. I do know that I am enjoying the custom refigured primary in my Orion XX14i a lot more now than I did before Lockwood gave it the once-over. I regularly use far higher powers and see far more fine detail in small galaxies, globular clusters, and planetary nebulae than I did before the mirror was fixed properly. Some people may be happy with the simple "light buckets" that don't even meet the Rayleigh criterion, but as for me, its "1/4 Wave Or Bust" when it comes to acceptable mirror p-v wavefront quality. Clear skies to you.

#10 GlennLeDrew

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Posted 14 July 2013 - 02:23 AM

David,
As I keep pointing out, the subject surface brightness (and contrast) is critical. Little globulars and galaxies typically have SB in their brighter parts *several* magnitudes brighter than the low surface brightness nebulosities such as discussed here. The resulting difference in the eye's resolving power is very considerable.

On something like the Cave nebula (Sh2-155), do you suppose a 1 wave error will make any difference in the view of the nebula? I posit that it most certainly will not. Or how about a more filamentary nebulosity, like Semeis 147, whose structures are of arcminute width. I still feel a 1 wave error will result in no real impact on the view.

To put this into perspective, imagine viewing Jupiter (which is at largest 45 arcseconds in width) through a pair of large scopes, one perfect, and the other having a 1 wave error. At full brightness the differences will be alarming. Now gradually interpose neutral density filters of increasing density while continuing to compare views...

At what level of dimming do you suppose the views would become indistinguishable? I would say well before dimming to that of any moderately dim nebula, let alone that of something like the Cave.

This would make for a very instructive experiment. Along the lines of viewing the Moon through a solar filter (which still results in a surface brightness brighter than that of a rather dim nebula.)

Note: I'm not advocating the promulgation of bad optics! :grin:

#11 reiner

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Posted 16 July 2013 - 02:42 PM

Hi Jay,

the notes for this object are widely different for different observers. I don't know why.

I find the SNR not overly difficult, at least not the part around phi Cygni and the part around 9 Cygni. These are labeled filament 01 and 02 in my finder chart here

http://www.reinervog...1_finderbig.jpg

Other, definitely not less experienced observers, have had, same night, same location, a hard time to see anything at all. I have no explanation for this difference in perception, and it does not apply to other objects.

#12 JayinUT

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Posted 16 July 2013 - 08:10 PM

Reiner,

Thanks. I really thought I saw parts of it but the transparency that night just wasn't good at all. I'll be trying again in August from a very dark site here in Utah. Using your charts and a few others I printed a finder chart off that is a little closer with more stars in Starry Night Pro. Let me know if you'd like me to email you a copy, or anyone for that matter.

Jay

#13 JayinUT

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Posted 24 July 2013 - 07:29 PM

If anyone is interested here is a chart from Starry Night Pro show Sh2-091. I have roughly drawn in the SN remenant with a pencil so it will not be exact, but close. Please feel free to take it, modify or redo as you want. Here is the link from my Google Docs.

#14 JayinUT

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Posted 30 July 2013 - 03:29 AM

Bagged it tonight at around 11:30pm at 8500 ft using my OIII filter in my 27mm Panoptic and Type 1 Paracorr in my 14" dob. The ribbon is indeed slim but easy to see. Averted vision right off of it enhanced it in a view places. My 30mm ES 82 degrees showed a slight hint but it was so much better in my 27mm Pan. I am heading out Thursday and Friday and will sketch it.

#15 FJA

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Posted 30 July 2013 - 06:36 AM

That's interesting ! I had one of the first order 17.5" Coulters that I collected in Daytona and brought home to UK. Images were a bit soft and I got it refigured but not much improvement. It proved perhaps too big an aperture for suburbia so I went back to a 12" go to SCT and have stuck with it since to very good effect:-)


Same here, Maurice, though I went one step further and had my Coulter refigured twice. :lol:

Still there weren't too many other options in the mid-80's and I ended up observing thousands of faint fuzzies with it!


I remember lusting after the big Coulters and Meade Starfinder Dobs in the S&T and Astronomy magazine ads, when I was a beginner and caught a very early bad case of aperture fever. It was probably just as well I couldn't afford one, because I'd never have been able to move it.

This SNR is one of my targets for when the storms move out of the way.

#16 reiner

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Posted 31 July 2013 - 07:56 AM

Bagged it tonight ...


Congratulations! The second time is always easier. Now you can tackle the other filaments ;)

Filament 02 is in the same ballpark as 01, the one you observed. 33 in the northern loop is somewhat more difficult, but not much, the same for filament 04, which is very thin, or 31 (UHC). The others require very transparent skies, but most are feasible even with a 15".






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