Beyond Barnard's Loop

Having discovered the Finkbeiner sky map last year, I've been fascinated to make observations of the many filaments which appear to connect the brighter nebula in the sky.  Of particular interest to me is the Orion-Eridanus super bubble, of which Barnard's Loop is only a part.  The super bubble is a series of nested shells of supernova remnants and resulting ionizing of the gas; it appears large on the sky because it is relatively nearby.  While I had visually observed small bits and pieces of Barnard's Loop, the brightest section of Eridanus A, and the Lambda Orionis nebula, it is only with night vision that I hoped to see not just these relatively brighter structures better, but also the faint connecting filaments.

Friday night was my chance, so I headed out to a location on the central coast, which has no light domes south or west.  Transparency was average and seeing poor.  I feared for heavy dew, but it turned out to be light and froze to frost by 11pm.  SQML was 21.3.  While I waited for Orion to culminate, I busied myself with some large planetary nebula (more of which in a different report).  I used the PVS-14 at 1x with a 7nm Ha filter, though the nebula were rather weak.  I had the best views with a 3nm Ha filter front-mounted to a 3x magnifier screwed to the PVS-14's objective.  I used a mirror mount for a steadier (but flipped) view, and also a monopod.  The 3x's field of view captured all of the Lambda Orionis nebula with room to spare.

I found it easiest to navigate by finding a bright and familiar nebula, then following any filaments I noticed coming off it.  Using the below image as reference (I didn't have it in front of me but have memorized it): Barnard's Loop was bright, thick, and heavily knotted.  The northern fork, which flows to Betelgeuse, was easy.  The bright & mottled eastern part of the "C" had a haze of nebula coming off it to the east, like a fog evaporating from ice.  I could not see individual filaments, but by panning the device north-to-south, I could easily distinguish the faint, subtly mottled nebula from the darker sky background -- it had a soft but distinct edge.  Following the trail to the east led me just north of the Seagull (which showed not just the bright body and wings, but the wider, fainter extensions which form a complete bubble in themselves).  I then panned to the north following the diffuse knots of Sivan 5 & 7, then three bright Sharpless nebula leading to the Rosette and the Fox Fur.  The Rosette was very bright, shot through with dark lanes, numerous inner and outer ring crenelations, and had bowed extensions forming a twisted path to the large and diffuse Fox Fur.  I could make out the Christmas Tree cluster and the bright star forming the tip of the Cone Nebula, and with some concentration could see a hint of the dark nebula itself (at small scale).

Back to the Lambda Orionis, or Angelfish nebula: I could see its dark eye, and the dark lanes which separate the dorsal and pectoral fins.  There was a small round bright nebula (Sh2-63) near its mouth like a piece of bait.  From the dorsal fin I followed a moderately bright fission of nebula which hooked west and -- to my amazement -- went through the southern half of the Hyades!  Continuing east the nebula stream thickened and brightened and then turned sharply south -- this was the eastern arm of the Eridanus nebula, Eri A.  It dimmed somewhat further south, but I distinguished where it forks with the western arm, Eri B, and followed that until it petered out.  Moving back to the fork, I followed the dim diffuse nebula fog as it made its broken way back toward the southwest end of Barnard's Loop below Rigel.

Back to Lambda Orionis, on the southeast side there is a faint haze which organizes into a flow to the west, barely detected.  I did not see this clearly, but the haze flows (what appears to be) behind Eri A and connects to the tip and body of Eri B.  To my eye, this forms one large, quarter section of a unified bubble, though the paper I referenced labels these as merely "high latitude clouds."

The whole thing is enormous and engrossing, and probably the most satisfying observation I've ever made.

But wait, there's more!

After making the Orion-Eridanus observation, I moved on to finish up my Sharpless Catalog observations (I'm happy to say I've now made observations of all the Sharpless Catalog!).  The last item was Sh2-312, which was in Pyxis (09 25 00 -28 00 00).  Once it had risen sufficiently, I made my observation, again with the 3x and Ha.  OMG what a beautiful nebula!  It filled more than 2 fields (roughly 15-degrees long and 5-degrees wide) and looks like a comet: starting from a bright point in the southeast, it fans out to the northwest and forks into two relatively bright filaments, which then fade and fan out slowly.  Here's what it looks like in the Finkbeiner all-sky map (a little brighter and more detailed than as I saw it):

Well, that got me panning around the area and it turns out I could see the upper loops of the Gum Nebula (Gum 12)!  The bright claw-like body in the upper right is Sh2-310, which lies behind the "feet" of Canis Major.  I saw the two bright N-S mottled loops below it, along with the bright patches to the east (RCW-19, -20, 27, & -33).  

The entirety of Gum 12 is now on my bucket-list.  I need to head south and get a view of this enormous structure, which is as large as the Orion-Eridanus super bubble, but much brighter, at least as Finkbeiner illustrates: