March Last Quarter

Posted by Josh Walawender on Thu 04 March 2021

I got out for a short, mid-week observing session to take advantage of the last quarter moon last night. I drove up to one the the pullouts on the Mauna Loa access road at about the 7,300 foot elevation level. I stayed out for less than two hours of full darkness, but it was a lovely night anyway. It was quiet (at first) with no wind. At sunset there was a haze layer above me, possibly vog, which I could see as very thin, patchy "clouds" and the sunset colors were a bit washed out due to the scattering. Once it was dark though, the effects were minimal and there were no thick clouds from the inversion layer.

I started the night early, just after the end of civil twilight by looking at Zeta Cancri. This had been described in a recent Cosmic Challenge article by Phil Harrington on Cloudy Nights. The timing was good as the seeing was excellent to start the night. My notes describe Zeta Cancri as:

A lovely trio in my 5mm Pentax XW eyepiece. The close pair is nicely surrounded by airy rings. Moving to the 2-4mm Nagler Zoom eyepiece at 3mm reveals the dark gap between the close pair.

Later on, I tried to look for Sirius B (since the seeing seemed to be good on Zeta Cancri), but it was tough in the glare of Sirius A. I actually was able to see it far better in the lower power 5mm XW eyepiece than in the 2-4mm Nagler Zoom eyepiece. Sirius B was a small, faint star following Sirius A almost hidden in the glare of the brighter star.

I spent most of the remainder of the night finishing out my observing list for the constellation of Eridanus. Almost all targets were faint galaxies and some were quite challenging because they were low on the horizon.

One highlight was NGC 1532, an edge on galaxy. It was hurt a bit by the low elevation I was observing it at (about 22 degrees). It was large in my 8mm Ethos eyepiece with a bight core a large elongated halo. Clearly an edge on galaxy.

I also re-discovered NGC 1535, a planetary nebula I'd observed before as part of another observing list dedicated to planetary nebulae. Unfiltered, the 5mm XW eyepiece revealed the central star, a round nebula with hints of a multiple shell structure visible. The shell structure was not visible as full shells, but more of arc segments around the core. In looking up the object this morning, I note that it is sometimes referred to as "Cleopatra's Eye" and that Phil Harrington recently featured it in another of his Cosmic Challenge series.

The night was somewhat memorable because it alternated in character. There was no wind, so at first the night was totally silent and quite peaceful. I spent some time just enjoying the naked eye sky. The haze in the air made the brightness contrast between the local horizon and the distant shape of Maunakea quite noticeable. Maunakea was silhouetted against the nighttime sky, but it was brighter than the nearby horizon defined by the lava rocks of Mauna Loa. This is presumably due, at least in part, to scattered light from human activities in the saddle area: cars on the highway and lights at Pohakuloa Training Area.

The military at Pohakuloa Training Area made itself known in other ways though. They were apparently doing live fire night exercises and my observing was occasionally interrupted by flares sent up to illuminate the area. They were low on my horizon, but if you were looking at them when they lit up, it would reset your night vision adaptation. In addition, there were occasional bursts of heavy machine gun fire and the flashes and booms of distant exposions. At one point, I tried counting the seconds between the flash and the sound as one does with lightning. I figured that the explosions were about 5-6 miles away.

The military activities, while dramatic, did not take away from a lovely night. Having not planned on a long observing session, I started packing around 9:30PM after a quick look at the Orion Nebula. Conditions were still good: six stars were visible in the trapezium even at the moderate magnification of my 13mm Ethos eyepiece.