Something truly weird happened tonight - we had clouds that actually went away. Perhaps I am overstating the case but it has been weeks since we have had a good night at FDO. It was cold and windy but the viewing was better than average although not rock steady.

The heavy hitter of the evening was Comet Holmes - and yes I did manage to fit in a bad pun involving "Elementary my dear Watson". Actually, this "quote" never appears in any work by Arthur Conan Doyle about the words foremost fictional detective. It was something that first appeared in a movie starring Basil Rathbone. Rather a shame too, because the Rathbone version of Holmes cases always made Dr. Watson an idiot when in fact he was an astute observer and bright mind up against a totally brilliant polymath. Oddly enough while Sherlock Holmes was a fictional character, Watson was a very thinly disguised version of a real person - Conan Doyle's teacher.

Well so much for my diversionary escapade into the 1890's London and back to the comet which has caused so much excitement. Basically, Comet Holmes was a small nearly invisible comet (17th magnitude) which suddenly "exploded" into an object which had a total brightness equivalent to one of the stars in the Big Dipper (2nd magnitude). Actually while the total light reflected from the comet is second magnitude, the comet is much dimmer to the eye because this light is spread all over a wide area. The comet is about 1.2 astronomical units from the Earth (roughly 112 million miles). The gas ball expanding from the comet is nearly a million miles across - a volume that is the size of the Sun but the gas is so very thin and rarified that it constitutes an extreme vacuum and the whole shebang weighs less than a good size mountain on Earth.

Visually Comet Holmes is a startlingly broad circle very near Mirfak (Alpha Perseus). I am including a map of the comet's track between early October and the middle of January. It is at the end of this log entry.

One of the things that I love about astronomy is that old friends return again and again more regularly than clockwork (unless of course you just happen to have a repeater for the atomic clock in Colorado Springs). A month of rainouts causes the sky to shift by roughly 30 degrees and things which were just on the horizon when we opened in early October now ride nicely high for viewing. In addition to Comet Holmes (the unexpected but welcome new face) Mars has returned and so have mighty Orion and the twins (Castor and Pollox). The Pleiades, the Hyades, Taurus and the brightest star of all, Sirius dominate the sky shortly after opening. About the only problem is that the kids' favorite constellation (the Big Dipper part of Ursa Major) is inconveniently close to the northern horizon.

We looked at Mars after many of the kids, including scouts camping in Ninigret Park were tucked into sleeping bags. It was actually a lot better than I expected. There was some instability due to the turbulent atmosphere but we could make out all sorts of things on the surface. We tried a deep red, a yellow-green, and a medium yellow filter on our 12mm Angler eyepiece (more than 300x magnification). With the deep red, the rough terrain (or perhaps the ariane[!?] if you wish to be pedantic) of Syrtis Major was quite easily visible.

Ernie Evans suggested we try a yellow filter to see if we could spot the so called "blue clouds" that form above Syrtis Major on occasion. I had never seen them but was game to try. The trick is that yellow filters convert these blue clouds to the color green. Syrtis Major appears brown if the clouds are missing and green when they are present. Bright green they were! The clouds were up while we watched.

Ernie had also converted an old Criterion eyepiece to an "occulting bar eyepiece" in the hope that it would block out the brilliant image of Mars so we could see its moons, Deimos and Phobos. Ernie had made the occulting bar about 99% opaque but allows just enough light through so that we could easily place Mars on the edge of the bar. Well the occulting bar worked fine but frankly the old Criterion filter simply isn't in the same class as the Nagler. What it gained in blocking brilliant Mars it lost to lowered contrast. Neither moon was certain although both Ernie and I suspect that we saw the outer moon.

We also got a fine view of M42 for the first time this season.

We will be closed on Thanksgiving Friday.

-Les Coleman

Author:

Leslie Coleman

Entry Date:

Nov 16, 2007

Published Under:

Leslie Coleman's Log