lake sonoma 20 january 2025

A nice observing window opened up last Monday night.  Clear conditions with good seeing, low possibility of dew, and a 3rd quarter moon.  I drove up to Lake Sonoma where a sizable group, for a work night, gathered, including Bob, Dan, and Steve.  The transparency was not quite perfect, as we noticed a long and persistent contrail to the west during dusk.  But Steve recorded 21.3+ on his SQM, so it was pretty good.  The drive up was 2 hours non-stop, with the usual slowdowns on 880 -- I even used the express lane all the way up 880, and it was still slow.  So much for "holiday light."

Because I planned to drive home at midnight, I kept my set-up simple, with night vision on a NP101 and 60mm ED dual mounted on a Twighlight  II, with Nexus DSC.  I also brought my monopod for 1x and 3x viewing -- though I wish I brought my mirror mount, as my primary goal for the night was at zenith...  I revisited many observations I made previously.  

My main goal was a sweep of very faint nebulosity which comes off of the California nebula NGC 1499 to the south to Sivan 4, then tuns west past Barnard 3 and north in long filamentary streams.  The stringy nebula stream stretches a whopping 20 degrees.  I've wanted to observe this for the 2 years since I first noticed it on Aladin.   I found the existence of this nebula by bringing up the Finkbeiner Ha gas line on Aladin, then using the Pixel Mapping slider to the left, which greatly enhances the view of faint extended nebula.  

Near the center of the Aladin screen shot is a comparatively brighter "H" shape, centered at roughly 03:00h RA, +37:00 Dec.  Using my 60mm refractor which has 5x and a 9-degree field of view, I pushed my scope to the position.  Starting out with a 685 longpass filter, I saw a nice field of stars, and while looking through the eyepiece flipped to a 3nm Ha, and instantly saw a broad, subtly mottled very faint nebula, as thick as half the field but steaming through all of it, orientated N-S.  It was very faint, but not difficult, and looked like a broken up, lingering contrail.  The nebula also showed fairly well with a Ha+OIII dual band, but perhaps because I knew what to look for.  I did not clearly distinguish a "H" shape, but there were some subtly brighter sections in the stream.

I proceeded to pan the telescope to follow the stream, first south-eastward.  The nebula quickly faded and became very difficult to follow until I came to the region near Barnard 3 (aka the "Wreath Nebula"), a large, round dusty cloud about 1.5x2.0 degrees, very faint and turbulent, with a brighter irregular knot in the middle, and three turbulent clouds on the east, south, and southwest periphery of the nebulous circle.  Further northeast is Sivan 4, a broad featureless glow, then NGC 1499, which was very bright and layered with filamentary streaks, especially on its long flanks.  Since NGC 1499 "points" westward toward the "H" shaped nebula, I panned in that direction, losing sight of all nebulae briefly until the filamentary trunk reappeared.  I then panned northward, and the trunk very quickly dissipated.  The nebula became very broken up and intermingled with the sky background, and I lost the trail of it the further north I panned.

I plan to re-observe this steam the next chance I get, probably with my mirror mount at 3x, to make the viewing easier on my neck.

Another highlight was IRAS 22298+6505, which the WISE website describes as a "a hidden star-forming cloud complex of dust and gas located in the constellation of Cepheus."  Observed with the 4-inch with 3nm Ha, I saw a large arc of very faint nebula which took half the field.  The inside arc was deeply crenellated with dark lanes, leaving the clear impression of dust and gas being blown out by stellar winds.  The outside arc was a sheet of mottled nebula which dissipated slowly.  I also noticed a tight round knot of brighter nebula around a star, which can be seen on the WISE image below.  As their website explains, this is the "bright blue giant star, 26 Cephei...[it] is surrounded by a bubble of cool, red dust and dust-enshrouded younger stars that may owe their existence to their older sibling."  

NGC 7380, aka the "Wizard Nebula": With the 4-inch, it appeared as a very faint crinkly arc with the Tr-band, but was transformed when flipping to the 3nm Ha.  The inside arc became very bright and the dark nebula columns were prominent.  The back end of the arc cut-off rather quickly but irregularly.  I had the sense the whole area was a dark, turbulent cloud of smoke, with only a small part of it illuminated by a candle.

Sivan 3: My prior observations were slightly tentative, only picking out a very weak nebula.  This time, with the 60mm, I had a "no doubt about it" experience.  It was still very weak, but it was immediately detected when flipping from the Tri-band (in which I didn't see anything but stars) to the 3nm Ha: a very large, curved mottled cloud, with Alpha Camelopardalis lying inside the arc.  The nebula was 3-degrees in width, which took up half the field of view, and extended a little beyond the field on either side.  I believe I did see the bow shock feature, which is the arc of brighter nebulosity near Alpha (above it, in this image, with Sivan 3 in the background) -- but I really didn't make a careful enough sketch.  I must try better next time!