29 people. After a long and discouraging string of rained or clouded out Fridays, the skies finally were clear from start to finish for a whole Friday night at FDO! Some members hadn't been at the dome for two months because of poor conditions, so they were raring to go. And we had visitors from as far away as New Jersey. Unfortunately, it was also the night of full moon, so our viewing options were severely limited. Nonetheless, a respectable crowd gathered to enjoy the developing conjunction of five planets in the western sky after sunset.

Closest to the horizon (as is usually the case) was Mercury. This seldom seen planet was easily visible in the twilight, shining at magnitude -0.5. It's small disk, about 6.6" in diameter, was 60% illuminated, and most observers noted a distinctly pinkish tinge to it, probably caused by dust in our own atmosphere.

To Mercury's upper left, 7 degrees away, was the brilliant Venus, ablaze at magnitude -3.9. It's larger 11" disk was a brilliant but featureless white, about 90% illuminated.

Moving eastward we next observed Mars, now a rather dim object, at least in comparison to the other four planets. Lying 215 million miles from Earth it has faded to magnitude 1.6, and it's tiny disk, just 4" in diameter, revealed no features at all. What a change there will be when Mars makes its next approach to Earth 16 months from now, the closest opposition in history. Mars will then appear over 6 times larger and about 150 times brighter than it did this night!

Moving on we at last observed a planet that showed some detail, wonderful Saturn. Though it has now moved 915 million miles from Earth it still was a grand sight, showing fine detail in its ring system and in the cloud bands. We also observed five moons: Iapetus, Titan, Rhea, Dione and Tethys. Were it not for the bright moonlight we surely would have spotted Enceladus and possibly Hyperion as well.

Last came mighty Jupiter, always an impressive sight, no matter its location in the sky. There were no moon events to watch nor was the great red spot visible at the time, but all enjoyed viewing the many colored bands on the planet, some of which contained obvious storms. Each of the four bright moons revealed crisp little disks, despite Jupiter's growing distance from Earth, now almost 520 million miles.

Joe had set up his 10 x 70 binoculars on a tripod outdoors, and we were able to look at Comet Ikeya-Zhang, lying low near the NNE horizon in Cepheus. A dim tail was visible, but the comet's increasing distance (45 million miles) and low position took its toll. Still we swung the 16" scope over for a look at the bright and not terribly condensed core. Ikeya-Zhang is now climbing higher in the NE sky after midnight, and will be visible for many weeks to come.

The remainder of the night was limited to views of a few a few double stars. Notable were Polaris and Rasalgethi (alpha Herculis). We took the obligatory look at the full moon (nearly blinding ourselves in the process) and pointing out the remarkable ray structures found all over the lunar surface. The variable polarizing filter made viewing much more comfortable! Shortly later, with a change of staffers at the 16", we turned to M13 just for the heck of it. Only about 22 degrees from the full moon we weren't expecting much, and that's what we got. Just a dim hazy spot, which for some reason appeared much dimmer than 5th magnitude Ikeya-Zhang. Odd, we thought, until a bit later when we realized that we'd left the polarizing filter on the 40mm eyepiece!

With the brilliant moon rising higher and higher and the planets setting in the west, we had little else to observe. A few folks asked about the outer flanets, Uranus, Neptune and Pluto. Doug pointed out that this next month or so will be one of those rare times when all of the planets beyond Earth can be observed in one night. This is something that's never been done at FDO, nor have many observers elsewhere tried it. Right now the outer planets are coming into position late at night, and we may try to view all 8 planets on one of the next two Fridays if the weather cooperates and we can hang in for most of the night. The moon will also be moving from view, making for some fine deep sky possibilities to go along with milder temperatures.

At 11:40 Steve and Doug began closing down the dome and were on the way out of the park just before midnight - with a beacon of a moon to guide them on their long rides home.

-Les Coleman

Author:

Leslie Coleman

Entry Date:

Apr 26, 2002

Published Under:

Leslie Coleman's Log