Observing report: Deep and dark in Big BearOctober 12, 2015
This past weekend I was up in Big Bear for a few days’ vacation. The proximate reason was the PVAA tour of the Big Bear Solar Observatory on Friday, Oct. 9 – more on that in another post. London and I went up Thursday evening with Steve Sittig, who runs the Hefner Observatory at the Webb Schools here in Claremont. Thursday evening Steve took us out to one of his favorite dark-sky observing sites a few miles east of Big Bear. (I didn’t get any pictures from the observing site, so you’re getting pictures of London and me hiking instead.)
We had hoped to get an early start but a succession of minor things kept us from getting set up and going until about 10:15 PM. By that time astronomical twilight was long over. There was a noticeable light dome from the LA metro area but it only badly affected the last 15-20 degrees above the local horizon, and only in the southwest.
Oh, speaking of the ‘local horizon’ – the site is in a shallow bowl with low hills fairly close on three sides and a bit more distant on the fourth. We could occasionally see lights from vehicles on a bend in the road about a mile off, but other than that, no artificial lights were visible from the site. None. The altitude is around 6700 feet.
The combined effect of this was that the sky was dark right down to the horizon. There was none of the usual near-horizon crud that obscures objects for the first 10 or so degrees after they rise. The seeing was worse near the horizon but the transparency was still excellent. We looked at Orion virtually as soon as it was up, and although we really had to pour on the magnification to split the Trapezium, the nebulosity was already very extensive.
A word about gear. Steve had his ETX 125, a 5-inch f/15 Mak on a motorized base with a hand controller. London had his Orion 20×50 compact spotting scope – I have been regularly kicking myself for not snapping up one of those for myself while they were still available. I had my C80ED refractor on the SkyWatcher AZ4 mount (= Orion VersaGo II), as well as my trusty old Celestron UpClose 10×50 binos. The choice of the C80ED was driven by two things: my space on the drive up was limited, so it was either the C80ED or the Apex 127 (which would have basically duplicated Steve’s rig), and I knew I’d want to do some wide field, low power observing, which is the one thing the Apex 127 can’t do.
For eyepieces, I spent most of the night using the 24mm ES68, which in the C80ED gives 25x and a sprawling 2.7-degree field. When I needed more power – which is much less often than I had anticipated – I bumped up to the 14mm and 8.8mm ES82s (43x, 1.9-degree field, and 68x, 1.2-degree field), and on a couple of tough double stars, the 6mm Expanse and 2x Shorty barlow. Unusually for me, I didn’t even mount a finder. With a 2.7-degree field, I can usually get the scope on target just by sighting down the tube. On those occasions when I needed more accuracy, I could lay my green laser pointer into a couple of shallow v-shaped notches on the tube ring and just move the scope until the laser was pointing where I wanted to go.
Within moments of hopping out of the car, we could see loads of detail in the Milky Way with our naked eyes. The Double Cluster and the Andromeda Galaxy were both easy as well. Later on, we also spotted the excellent open clusters M35 and NGC 752 without optical aid. I logged the seeing as 4/5 and transparency as 5/5.
Our first few observations were “best in class” objects – the Pleiades, the Double Cluster and Stock 2. At low magnification under dark skies, the Double Cluster looks not so much like a pair of isolated objects, but rather a couple of thickenings or condensations in an incredibly rich Milky Way starfield. So it was that evening. Seeing that far above the horizon was rock steady and even at low mag, the C80 focused the stars down to tiny pinpoints of brilliant light. One of the clusters has a pair of red giants near its center – these were visibly brighter and more yellow than the rest of the cluster stars, even at 25x.
After that I turned west to catch M13 before it got too low. Going up to 68x revealed tantalizing hints of resolution – not bad for an 80mm scope.
M57, the Ring Nebula, was an arresting sight. At 25x, I could get both of the ‘corner’ stars that mark that end of the Lyra parallelogram, with M57 as a small but crisp circle of nebulosity floating in inky dark space. Although we also looked at the nebula with more magnification, I found that lowest-power view delightful. It reminded me of spotting the Ring at 12.5x in the TravelScope 70 three years ago – the view that first infected me with refractoritis.
We didn’t try to split Epsilon Lyrae until a bit later, when it was lower in the sky. The seeing there was only so-so and I had to push the scope to 200x, using the barlowed 6mm Expanse, to get a clean split, although both pairs were visible elongated at much lower magnification.
We stayed out long enough to catch the leading edge of the Big Dipper rising. One of the best views in that part of the sky is the galaxies M81 and M82 in the same field of view. They are close enough to be nicely framed in the same field even in the 8.8mm ES82. At that magnification (68x), M82 was starting to show tantalizing hints of structure.
The most memorable observations of the night were of the Auriga Messier clusters and the other Local Group spiral galaxies. Auriga clusters first – M38, M36, and M37 (from west to east, in the order that they rise) are seasonal favorites and fun to compare. We swept them up easily in binoculars and then scrutinized them in the scopes at progressively higher powers. I had a good laugh at M36 – at the orientation we saw it in this weekend, it looked like a short, fat stick figure, the bobble-head version of the Stock 2 stick-man. But M37 was my favorite, just an incredibly dense swarm of tiny pinpoint stars.
Fairly early in the evening we had a look at the Triangulum galaxy, M33. I was tracing out the constellation Triangulum with the GLP when we noticed a naked-eye glow that turned out to be the fine open cluster NGC 752. Neither of us could make out M33 with our naked eyes but it was dead easy in binoculars, and at 25x in the C80ED it showed considerable structure in averted vision, including what both of us independently took to be one of the spiral arms. Incredible.
We closed the session with another great view of a local galaxy. All through the three-hour session we’d been saying that we’d look at Andromeda, and then one thing or another would capture our attention and we’d get sucked into some other part of the sky. We finally got around to M31 and its companion galaxies a little after 1:00 AM. By that point they were basically at the zenith. Even with the tripod extended as high as it would go, we had to kneel to look in the eyepiece. But when we did, the view was astounding. M31 stretched all the way across the field, with only the very outer edges clipped by the eyepiece’s field stop. The little companion galaxies M32 and M110 were dead easy, of course, but what amazed me was that we could both see structure and detail with the main galaxy. I’d never seen those dust lanes in anything smaller than a 5-inch scope.
We knocked off after three solid hours of observing, exhausted but giddy. It was one of those transcendent nights that makes my heart sing, and also makes it really hard to go back to observing from suburbia. The most surprising thing for me was how much observing I got done with the 24mm ES68. “Small telescope at low power” does not scream satisfying deep sky observing, but under sufficiently dark, clear skies, I rarely needed anything else. I’m already looking forward to the next run.