Fremont Peak 1/6/03

by David Kingsley

Highlights for me during eight solid hours or so of observing:

1. Some wonderful detail on the moon as we were waiting for it to get dark. Taruntius showed great relief on the edge of Mare Fecunditatis. The entire central 2/3 or so of the crater floor has been raised up higher than the rest of the floor near the crater rim, like a giant piston pushing up inside an oversized cylinder. A central peak sits atop the center of the piston, giving lots of different heights, shadows, and highlights in a very 3 dimensional view.

   Further from the terminator, the eastern edge of the beautiful crater Langrenus showed an interesting feature I had never seen before. Although most of the crater was fully illuminated, there was an obvious inky black spot on the inner side of the eastern wall that looked just like a black cave entrance. I had recently read about a similar cave illusion that shows up in Copernicus when the sun hits the terraced walls just right (O'Meara article in Jan or Feb Sky and Tel). It was very interesting to see a similar apparent cave opening show up in a completely different crater.

2. Despite a bit of moon in the west, I spent a lot of time hunting down new extragalactic globulars in M31. I think transparency last night was better than it had been on several other nights of the project, but the seeing was somewhat softer. I ended up working at a magnification of about 400x (barlowed 9 mm Nagler with 14.5 inch Starmaster scope), which gave good views even though I would often have to wait a few seconds for the image to stabilize. Under these conditions, my limiting magnitude turned out to be very similar to what it had been at LSA in October and Fremont Peak on Thanksgiving day (faintest extragalactic glob about visual magnitude 16.1). With last nights new glob catches, and some others from various observing sessions in December, I finally crossed the half century mark on the extragalactic globular project. I have now logged 52 total globular clusters found around M31 (not counting three or four other candidates that I had previously logged, but which are now thought not to be globs based on additional studies since the Hodge atlas was prepared). I have a handful of M31 candidates left, and a smaller list of possible targets in other galaxies. And as spring and summer comes, I am looking forward to logging some remaining globs from our own Galaxy too.

3. There was a lot of beautiful action on Jupiter last night! Every 6 years, the orbital plane of Jupiter is lined up with Earths in such a way that Jupiter's moons show mutual eclipses and occultations,. Bob Cz. alerted me to a mutual shadow eclipse that was supposed to take place about 1:15 am. I checked the usual chart of mutual events in the recent Sky and Telescope article and saw that there was also going to be an occultation of Io by Europa starting about 10:30 pm. We swung the scopes over periodically during the night, and had some great views when the seeing would momentarily stabilize. Io and Europa hung together off the following edge of Jupiter around 10:15 pm, first looking like a tight double star, than coming into elongated apparent contact. The superimposed moons obviously could not be visually split during during the occultation, but their different colors were apparent at high power in the superimposed image. (Io slightly yellow-reddish, and Europa whitish, the two colors reflecting their different cell surfaces of sulfur volcanoes on Io and cracked ice on Europa). The contrasting colors made a joined object that was yellow/red at one end and white at the other. Shortly after the moons had moved together, Europa's shadow showed up on Jupiter, a beautiful black dot almost perfectly centered between the two main belts of Jupiter. Io's shadow then joined the scene, initially trailing Europa's shadow but gradually overtaking it during the transit because of the faster orbital time of Io. It was very interesting to see the difference in the shadows marching down the central lane of Jupiter at high magnification. Io is both larger and closer to Jupiter than Europa, and its shadow was obviously larger, blacker and sharper looking than Europas during the double shadow transit. I checked the scene again around 1:15 and 1:30 am, the time during which the shadow of Europa was supposed to eclipse Io against the face of Jupiter (second "mutual event" of the night). Unfortunately, the seeing had softened during the night, and this second mutual event took place when the moons themselves were transiting the face of Jupiter. Although the moons were visible when transiting at the edge of Jupiter, I could not seem them well enough on the face of Jupiter to view the eclipse of Io's disc by Europa's shadow. The shadows themselves were still very obvious however, and the bigger blacker dot of Io's shadow had obviously outraced the smaller shadow of Europa, now leading instead of trailing because of the faster orbital time of Io. What a great combination of events, and a beautiful demonstration of surfaces, sizes, and orbits around the King of Planets.

4. I chased down three separate comets during the night using finder charts taken from the Skyhound observing site (see http://www.skyhound.com/sh/comets.html). C/2002 V1 (NEAT) in Pisces was the brightest and biggest, currently estimated at mag 7.3. C2001 HT50 (LINEAR-NEAT) in Hydra and C/2001 RX14 (LINEAR) were much dimmer and smaller (around mag 10 or 11). HT50 was an asymmetric, chevron-shaped nebulosity, and obviously changed position during the time between an initial sketch and when I checked back about an hour later. Getting to C/2001 RX14 (LINEAR ) turned out to be much more interesting than the comet itself. The starting point for my star hop was the M106 galaxy in Ursa Major, a beautiful sight that I had never seen before with 14.5 inches of aperture. In traveling from M106 to the comet, I chanced on at least 3 or 4 other pretty NGC galaxies hiding here and there among the star fields. When the eyepiece is full of UMa galaxies, you know spring can't be too far away.

I enjoyed lots of other objects during the night, including some nice views at various galaxies Jamie Dillon was tracking down. Thanks to everyone for the shared views, Jamie for the calendar, and Bob Cz. for inviting me to come over and observe near the observatory instead of at Coulter. After lots of rainy weather, and then recently being blown out of Coe on New Year's day, and fogged out of Dino Point on Sunday, it was wonderful to be under clear skies again with the 14.5 inch scope.

Definitely my best night since LSA, and a very satisfying mix of both shallow and deep sky objects.

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