My Observing Log: September/October 2007

10:45 p.m. 4 September 2007 PDT (2007–09–05–0545 UT)

I spent an hour or so this evening wandering around some northern constellations. Lacerta, the darting lizard, is small in name and in area, but it has a decent number of objects in it, given that size. My first target was NGC 7209, an open cluster along the western edge of the constellation, a few degrees to the west of 2 Lacertae. About 3,000 light-years away, at 32x in the C5+, it showed very nicely, with about 30 stars of magnitude 11 or brighter arranged in a C, open to the west, with the whole encased in a cage of several magnitude 8 or 9 stars. The inner cloud of 11th magnitude stars had an appealing fuzziness about them, and was about 15 arcminutes across.

A few degrees to the northeast of NGC 7209 (and a few hundred light-years further on) is NGC 7243, another open cluster. This one did not show as nicely as the first, but it still revealed about 20 stars, perhaps magnitude 9 and 10, arranged in a kind of cardioid shape, like Corona Borealis, open to the northeast and with the nub of the heart to the southwest. Unlike CrB, though, this crown is only about 20 arcminutes across. The somewhat brighter stars gave this cluster a distinctly coarser and sparser feel than NGC 7209.

Along the southern edge of Lacerta, a few degrees to the east of 1 Lacertae, is Struve 2906, a cozy uneven double. A pair of white stars with magnitudes 6.5 and 10.1, and separated by only 4.4 arcseconds, it could only be sporadically seen in the C5+, and I wasn't sure about the split. I estimated a position angle (PA) of about 20 degrees, but my atlas (the Collins Atlas of the Night Sky) says it's actually 1 degree. The atlas says its binary status is unknown, suggesting it's not moving fast enough for that PA figure to be significantly out of date.

I didn't have much better luck with Struve 2942, another double a few degrees to the northeast of NGC 2906. This one is a pair of orange class K stars—magnitudes 6.1 and 8.3, and separated by 2.8 arcseconds, so closer, but with the magnitudes not as different as in NGC 2906, judged easier. I didn't find it so, and the seeing was getting worse at this point. I estimated a PA of 290, but it is actually 279. Both doubles were attempted at a magnification of 125x.

Cepheus is actually pretty well-known, thanks in part to delta Cephei, the namesake of one of the most famous variable star classes. But I wasn't looking for variable stars, but more open clusters. My target in Cepheus was NGC 7380, not at all like the first two in Lacerta. It is at the southeast corner, about 5 degrees to the east of delta Cephei. The atlas calls it fairly bright, but I was only able to detect a dozen or so stars in an elongated oval, about 10 arcminutes along its long (east-west) axis. Perhaps, like some other clusters, it has a couple of what I call "layers" of stars—different populations of disparate brightnesses sharing the same angular wedge of space.

Cassiopeia is home to my one repeat customer this evening, NGC 7789, also known sometimes as Caroline's Cluster, after Caroline Herschel, William Herschel's younger sister who accompanied him to England, and who led some of her own celestial voyages. It is about halfway between rho and sigma Cassiopeiae, near the brighter end of the W, and in dark skies, it is an amazing sight, round and rich. Under bright suburban skies, it is much more subdued. I had trouble seeing it at all in the magnitude 4.3 soup. Only the southern half was visible, but even so, this cluster was still detectably rich, with still 25 stars visible in a faint, powdery arc.

My last target of the night was Collinder 464, which must surely be a neglected cluster, lying as it does within the confines of Camelopardalis. I know Camelopardalis primarily as the home of Kemble's Cascade, a startling linear asterism, and NGC 1502, the open cluster lucky enough to lie at one end of the Cascade, but Collinder 464 may make me rethink this constellation's pedigree. I observed it at 32x, but this cluster probably prefers binoculars. It is very large, about 2 degrees across, and it is sparse, looking like nothing so much as a somewhat dimmer version of the Pleiades. There are perhaps a dozen stars of magnitude 6 or so, and a second layer of magnitude 8 or 9 stars "beneath."

Incidentally, this cluster has a declination of about +73, and I was expecting significant problems pointing the C5+, which rests on a polar-aligned wedge. No such issue arose. Collinder 464 was low enough in the sky (about 20 to 25 degrees in altitude) that the finder was right on top of the tube, and I actually found it easier to train the scope properly at it than at any other object on my list. That's something to keep in mind when I look for circumpolar objects—because with objects that are high in declination but descending in the northwest, the finder would be on the underside, rather than on the top as it was with Collinder 464 ascending in the northeast. Right now, I'm still in reasonable shape physically and can kneel down and crane my neck upward to get at objects, but there will come a time when that's not so much fun anymore, and I'll need as much help as I can get.

Copyright (c) 2007 Brian Tung