Winters Coming - Barnard's Loop

[scarp15]

Only on here when during a mid September period, could the notion of Winter become a focus for discussion, perhaps for some a sense of expectation.

Accounting for recent past winters, expectation is just maybe a bit inaccurate a notion, yet another excuse for conversing upon this subject right now might be accounting for the present full moon.

Consisting of part of the vast Orion Cloud complex, Sh2-276, Barnard's Loop was considered to have been discovered by William Herschel, re-discovered and named as the Orion Loop by E.E Barnard. This immense diffuse emission nebula is suspected to be a Supernova Remnant, associated from an even larger Hydrogen cloud. The nebula has an apparent diameter of over 30 degrees.

Barnard's Loop is a very tricky subject to observe. The 'brighter' northern section, is possible by drifting across starting at reflection nebula M78 to the open cluster NGC 2112. The southern arc section near to Rigel is also considered to be possible. A good quality 2" H-beta filter is necessary, observations are feasible with wide field binoculars, wide field refractor and even naked eye, whilst holding the filter into the line of vision. Conversely, larger dobsonians are also a good tool for attempting this observation. 

There have been interesting and intriguing accounts posted on SGL in past seasons. These have included Gavsters enhanced observing principle, employing a night Vision device into the optical path, this technology providing views even in suburban skies. There had been past accounts by a keen eyed observer in darkest Norfolk through her large aperture dobsonian of this and even aspects of the Eridanus Loop and Gerry's (Jetstream) successful observations of certain parts and features that constitute the long curving profile of this expansive object. Perhaps most notably (not featured directly on SGL) are the observation accounts and sketches of Mel Bartel using his very fast 6" F2.8 newtonian. 

To observe the northern portion, Barnard's Loop requires a dark, transparent sky and complete dark adaption. It is not so easy, yet tracing along a faint haze or 'ghost' like impression where the background stars are blotted out is possible with some determination and patience. A topic that I am guilty of highlighting at least once before, it is in a way one of those slightly irrational seasonal obsessions and I look forward again to the challenge. This season I plan on another stargazing wild camping adventure close to the Scottish Border and taking along a wide field refractor, where hopefully Barnard's Loop will receive some attention. 

Here is a Mel Bartel sketch,

 

 

[Littleguy80]

Looking forward to trying for this over the winter. I managed a maybe last winter but have another years experience behind me now. 

[scarp15]

For interest, here is another sketch by Mel Bartels of the Southern arc. I do not ever anticipate seeing anything resembling this feature, although I did attempt last year.

 

[Littleguy80]

Would the widefield frac be the better choice for this over the dob? 

[jetstream]

5 minutes ago, Littleguy80 said:

Would the widefield frac be the better choice for this over the dob? 

It depends... in my experience the refractor used matters, for some unknown reason. My 90mm SV triplet shows it but the SW120ED is much better eventhough a smaller FOV.My VX10 does a nice job on it and the TSA120 is good on everything.

Try them all Neil!

ps the f7ish fracs love the 42mm LVW on Barnards Loop..exit pupil deal.

[Littleguy80]

12 minutes ago, jetstream said:

It depends... in my experience the refractor used matters, for some unknown reason. My 90mm SV triplet shows it but the SW120ED is much better eventhough a smaller FOV.My VX10 does a nice job on it and the TSA120 is good on everything.

Try them all Neil!

ps the f7ish fracs love the 42mm LVW on Barnards Loop..exit pupil deal.

I haven’t tried anything at that focal length. Big exit pupil makes sense though. It’s worked well for me with the dob. The Equinox 80 is a little faster than F7 though. Would that be an issue?

[scarp15]

I would definitely as Gerry has said Neil, try both approaches. Large exit pupil is a must, faster than F7 could be an advantage. My 31T5 works Ok with the VX14 on the brighter portion, big 6.7mm exit pupil combining with the H-beta filter, the contrast, considering how diffuse this is responds quite well. The same eyepiece with my 85mm F7 refractor will give 4.4mm exit pupil and 4.24mm field of view, the 42mm LVW would be very interesting.   

[jetstream]

21 minutes ago, Littleguy80 said:

I haven’t tried anything at that focal length. Big exit pupil makes sense though. It’s worked well for me with the dob. The Equinox 80 is a little faster than F7 though. Would that be an issue?

Whats your f ratio? What the highest fl eyepiece you have?

Forget all what youve heard about too big exit pupil Neil IMHO...I was stuck on that for years until a member here told how he had used very large ones with success. These days I just try everything on objects to see what works. The 30ES 82 works good for me at f3.8 for instance.

[Littleguy80]

10 minutes ago, jetstream said:

Whats your f ratio? What the highest fl eyepiece you have?

Forget all what youve heard about too big exit pupil Neil IMHO...I was stuck on that for years until a member here told how he had used very large ones with success. These days I just try everything on objects to see what works. The 30ES 82 works good for me at f3.8 for instance.

The frac is F6.2. The ES82 30mm is the longest FL eyepiece I have. Works great on the Veil with the Lumicon OIII in the frac. I used the same eyepiece with the dob for the Horsehead. FOV is a bit big bit got the job done. I now have a 25mm TV Plossl which should be better suited for the HH. I’m certainly happy to spend some pennies on a LV 42mm or similar to get at the loop. When I did looked at the numbers on an eyepiece around 40mm I was put off by the low mag but I guess that’s probably what you want for something as big as the loop? 

[Littleguy80]

Isn’t funny how your preconceptions can be turned around. They say aperture is king and yet it’s the 80mm frac rather than the 10” dob that is coming out as the tool of choice for this faint target. 

[scarp15]

It can sometimes become a bit of a conundrum, through experience my understanding for experimenting with exit pupil is increasingly relevant, sometimes much more so than aperture considerations. For example, with my 85mm refractor, I cannot gain the Merope Nebula with a 31mm eyepiece. The exit pupil is simply not big enough. It is no problem in both my other scopes with respective 5.1mm and 6.7mm (equally 5.84 with paracorr). Gerry's suggestion for a yet longer focal length is quite logical.

[jetstream]

1 hour ago, Littleguy80 said:

When I did looked at the numbers on an eyepiece around 40mm I was put off by the low mag but I guess that’s probably what you want for something as big as the loop? 

The Loop is huge!

I can follow it from top to bottom under my best skies. The first thing to look for is the shade edge just off M78, the brightest section, one side brighter than the other. The 30ES in the f7 kills the Loop, the 42mm brings it out (for me). The 42mm not only gives more eye illumination but more FOV which is also needed. Before buying the 42mm LVW ask around- some don't like it, but I find it meets my needs. The big Pan might be better,not sure.

[Littleguy80]

Thank you both! Apologies Iain for filling your thread with questions. Hopefully it will prove useful to others too. 

[scarp15]

No that's fine Neil it is quite valid and I am open to the same questions. Picking Gerry's mind on these things is always good. My TV-85 has a maximum true field of 4.4 degrees, the 31T5 is a good match at 4.2 degrees. Will have to do the calculations. The contrast on these objects is so subtle that a 'brighter' image will pick out this subtlety. More to think about as always. Quite some time ago I use to have a Pan 35mm, I have never seen a Panoptic 41, assume its even chunkier than the 31T5. Would also like to emphasis more use of my 8" F6 dob for this nebula, quite possibly some vignetting using a 31T5, but gaining a 5.1mm exit pupil. In comparison, the California nebula is relatively bright and in conjunction with a H-beta filter, quite achievable with a smaller aperture refractor and employing an exit pupil ranging between 3.0mm and 4.4mm.

Edit: Checked the Televue 85 eyepiece calculator chart, Pan 41 = 5.8mm exit pupil, 4.4 degree true field, x14.6 mag.

Edited September 14, 2019 by scarp15

[estwing]

One for me this year deffo. 

[PeterW]

Good luck, it really is “good sized” Nebula. Makes a change from the usual Horse obsession. As mentioned @GavStar provided us a good picture (with house roof included for scale), https://stargazerslounge.com/topic/325834-using-two-night-vision-monoculars-as-a-binocular/

The meissa/angelfish Nebula is on Orions shoulders. Wait for the most transparent skies and check easier nebulae like the monkeyhead or Pac-Man. Sometimes it’s dark, but the nebulae don’t want to play. You night also want to swing down to the seagull in  CMaj, be interesting to hear how people do!

Peter