OR: Lake Sonoma, Hewett 1

I traveled up to Lake Sonoma to meet up with Muriel to help with the ServoCAT on one of her scopes, and to observe with her, Steve, and Randy and a couple others.  It was clear, with very good transparency, but a bit windy to start, not fully calming down until midnight.  Steve had a SQM reading of 21.4 around that time. 

I travelled light, bringing only my NP101.  I really only had one target in mind, planetary nebula Hewett 1 in Sextans, and had only the hour after astronomical dark to observe it before it set.  It's a large object, so a good small refractor was all that was required.  And a PVS-14 night vision device and filters, naturally.

According to the scientific literature, Hewett 1 is the largest known planetary nebula on the sky with an apparent diameter of about 2° in its brightest portion, corresponding to a linear diameter of 3.5-7.0 pc at the likely distance of 100-200 pc. It is surrounded by an elliptical emission shell with an apparent diameter of 6° × 9°.  A further emission structure, detected northeast of the central star, indicates another shell with a size of 10° × 16° (which is validated by contemporary imagers).  Based on the derived Galactic orbit for the central star PG 1034+001, its thin disk orbit and the morphology of the first halo suggest that the nebula is in an advanced stage of interaction with the interstellar medium.  PG 1034+001 is an extremely hot, helium-rich DO-type star that excites the planetary nebula Hewett 1 and large parts of the surrounding interstellar medium.  It's very unassuming 13th magnitude and is highlighted in the purple box in the below image.  Hewett 1 vies for the "closest" planetary nebula to earth along with SH2-216, at around 425 light-years distant.

As was reported in Astronomy magazine at the time of discovery in 2005, "Most planetary nebulae were discovered in images sensitive to the strong emission lines coming from the nebula’s excited hydrogen. By contrast, Hewett 1 was identified by emission lines from oxygen in the spectra of many background galaxies and quasars observed as part of the Sloan Digital Sky Survey. The nebula’s large size caused many spectra to show oxygen’s characteristic emission-line signature."  

Having aligned my DSC I pointed my scope at NGC 3325, one of these background galaxies, which was slightly offset from the center of the nebula.  The NP101 with a 67mm Plossl+ has a 5-degree TFOV, and a magnification of 8x.  Flipping through the filters on my filter wheel, I immediately noticed a fairly faint elongated glow in a loose trapezium asterism with direct vision, no trouble at all. I flipped through various filters and could see it in Ha+OIII dual band, but 3nm Ha was best.  I was shocked I would find it so easily and called Steve over to have a look.  I asked him to look at the trapezium asterism and flipped the filter wheel to Ha while he was viewing through the eyepiece, and he too could easily see the nebula.  I remembered there was to be a larger outer shell to the northeast of the brightest central region, so I moved the scope in that direction.  With the brighter central region along one side of the field stop, I noticed a wide, long, curved, very faint contrast change with an obvious cut-off along the outer (northeastern) part of the arc.  It was quite difficult, and I moved the scope side-to-side to confirm it moved with the sky and wasn't an aberration.  I sketched what I saw intending to confirm it later.

Today, using Roman Perah's Hewett 1 - AstroBin, I matched the loose trapezium of stars the extent of the relatively brighter glow we saw, and also the gently curving ridge to the northeast:

North is to the lower left corner, east to the lower right corner; green outline of the portions I saw.

Bray Falls' image Hewett 1 - The Giant in Sextans - AstroBin (north down) shows the entire extent including the large outer shell (not seen by me) and greater detail of the bright areas, including what appear to be shadows cast by nebulous pillars on a sheet of nebula behind them -- in line with what would be PG 1034+001's glow:  

I was exhilarated and very happy to have achieved that night's mission.  I spent the rest of the time scanning with the NP101 both visually and with the PVS-14, not taking notes but revisiting old favorites.  A very nice night out.