I practiced some good social distancing and went out for a solo observing session on Sunday night. I got to the site (a pullout on the Mauna Loa access road at about 8600 ft elevation) right at sunset and set up quickly. The original plan from months ago was to attempt a Messier Marathon around this time in March with a bunch of other people, but with the COVID-19 crisis gatherings were not recommended and with a crazy week at work leading up to this, I didn’t want to attempt an all nighter. I figure if there can be such a thing as a “half marathon” for runners, I could try a Half Messier Marathon.
Conditions were beautiful with very light winds. At sunset I could see the clouds of the inversion layer below. One disadvantage of the Mauna Loa Access Road area is that the clouds tend to be pushed up the northeastern slope of Mauna Loa by the prevailing winds, so as you drive up the access road going east on the north slope of the mountain, the clouds tend to rise along with you. This meant I went a bit further up than I’d planned, hence the arrival right at sunset. I set up the scope, an SVX152 on a Losmandy G-11 and started trying to spot the constellations setting in the West, so I could begin with my first objects of the night: the M31 group (M31, M32, M110).
I found Mirach by eye and star hopped over to the area where M31 should be, still too bright. I wanted a while and the core of M31 slowly emerged from the sunset glow. M32 followed soon after. M110 was a bit harder and I was beginning to wonder if I’d miss it, but it also emerged about 10 or so minutes later. I moved on to M33 which is a bit higher in the sky, but larger and more diffuse. Fortunately the galaxy was bright enough to punch through. I was even able to find it without star hopping, just pointing to the right region and scanning, then verifying its position against the star patterns on my star chart.
Next was M74, the biggest challenge of the night. I reasonably quickly found the position based on the star patterns in the eyepiece, but would the sky get dark enough while the galaxy was still high enough to be seen? It took almost 20 minutes, but I did just get it. At about 6 degrees elevation I declared victory. I could not hold the galaxy with direct vision, but by nudging the scope a bit, I could see the faintest glow moving against the fading twilight.
Cetus A (M77) followed and it was easy in comparison. It was now dark enough and the objects I was looking at were not as low in the twilight. The Little Dumbbell (M76) and M103 followed quickly. While I was up North in Cassiopeia, I stopped to look at Comet PanSTARRS (C/2017 T2) which I had not looked at during previous observing sessions. It was a lopsided fuzzball affected a bit by the low elevation.
From there, the rush of catching things in twilight was mostly over. I hit the M34 cluster, then stopped to look at asteroid Vesta which was easily recognizable as a medium bright star which was not there in the star chart. I then moved from south to north through the winter Milky Way, hitting objects in Lepus, Orion, Taurus, and Auriga (along with a few non-Messier objects which were on the way).
I worked my was through the objects in rough RA order. When I neared the meridian, I jumped across to the east to avoid the neck strain of trying to find things near the zenith. This was now galaxy country, well away from the winter Milky Way. Galaxies in Leo and Ursa Major were next on the list. Then I took a short beak before tackling the Virgo cluster, which is always a landmark in any Messier Marathon. The Virgo cluster of galaxies is fun, but also a bit challenging as it is easy to find galaxies there, but not always easy to positively identify them, so working through in a systematic manner helps. I started with Markarian’s Chain, catching both Messier objects and some non-Messier as well.
After Virgo, I picked up a few objects I’d skipped earlier that were now a bit lower in the West and easier to access, then flipped back to the East to work my way down toward the horizon for all the objects over there which were not in Virgo. I wrapped up by finding objects in the very top of Scorpius (M80 and M4) which was just rising. M4 was just 7.5 degrees above the horizon when I got there.
There were a few Messier objects that were technically up at this point, but too low to reasonably observe, so I took a quick look at the Jewel Box in Crux (the Southern Cross) which was now up and declared this to be a complete Half Messier Marathon. I’d started with objects setting in the west and worked my way eastward until there was nothing left that was at a reasonable elevation. To continue the marathon properly, I’d have to take a few hours break to let things rise. My first Messier entry was M31 at 7:19 PM, my last was M4 at midnight on the dot. I observed 69 Messier objects in total (out of 110) and 98 objects were in my log in total including non-Messier objects.
Conditions were great. I did not really get a sense of the seeing as I spent most of my time at low to medium power (21mm = 57x, 13mm = 92x, and a bit of 8mm = 150x) and was focusing on DSOs rather than objects with lots of fine detail. Winds were very light (an unusual occurrence on Mauna Loa) with a whisper of down slope catabatic winds. The inversion was well behaved down below, occasionally filling in the saddle from the east up to Pohakuloa Training Area. I could see a little vehicle activity on Maunakea across the way: a few cars going up or down, but not the large crowds that are usually visible as chains of headlights coming down the mountain. I took a number of SQM measurements of the sky background brightness and once the Milky Way got away from the Zenith, the SQM values improved to about 21.85 on average, an excellent night. My initial impression was that it was a bit hazy or with low transparency, but I think it was just that I was at such a nice dark site that the sky was considerably brighter than the surrounding landforms which are dark lava on Mauna Loa.