Observing at Bonny Doon
By Jay Reynolds Freeman

A brief break in the El Nino storms on the evening of February 28, 1998, allowed photon-deprived amateur astronomers of the central California coast a crack at their hobby. Several of us assembled on a gravel aircraft parking area of the Bonny Doon Airport, in the hills north of Santa Cruz, California, for a few hours' observing.

It was moderately dewy: Even with a nearly foot-long dewcap, the outer corrector surface of my six-inch Intes Maksutov was beginning to mist lightly before the evening was over. intermittent high clouds came and went, so that seeking faint galaxies met alternately with success and failure. Yet I managed to bag another eighteen objects on the "big" Herschel list, all in Ursa Major.

I took a break from faint stuff to look at the Owl Nebula and at nearby M108. At 97x, both showed a hint of detail -- the owl's low-contrast surface did not quite reveal the "eyes", and M108's long streak seemed slightly mottled. Some of my companions were bemused that I considered the Owl to be "bright", but I had been looking for galaxies down to fourteenth magnitude...

One observer had an eleven-year-old six-inch f/8 Astro-Physics refractor. I star-tested it and checked for residual color, in this relatively early Roland Christen design, on Capella. The star test was as good as the not-quite-perfect seeing would allow me to determine, but the lens did show a trace of chromatic aberration: The out-of-focus diffraction pattern at 207x was tinged purple on the outside and green at the center on one side of focus, and the colors were reversed on the other side. I could not detect any colored haze near the focused image of the star.

One observer was practicing for a Messier Marathon: We helped her unravel some areas of the winter and spring sky, where her 10-inch Dobson-mounted Newtonian will show more galaxies than Messier dreamed of. The field of M105 was a case in point: Nearly adjacent are two NGC galaxies, one of almost the same brightness as the Messier object. Hee, hee, hee, wait till she gets into the heart of the Virgo cloud.

As onrushing cirrus thickened, I struck camp, and was home in Palo Alto by midnight. I hope for some more breaks in the weather before summer, but with El Nino, who knows?