Not So Clear

If Tuesday night was clear, I intended to take some photos of the moon’s passing in front of the Pleiades star cluster. I checked the predicted altitude (about 70 degrees, seven fists’ height) and orientation (starting in the southeast, moving in a westerly direction), and found a good spot on the front yard.

That afternoon I immersed myself in some writing and did not emerge until about 5:10 p.m. The first star of the cluster would go behind the moon around 6 and the sky was beautifully clear.

My telescope “Baby” weighs 73 pounds and attaches to a 29-pound wedge, which goes on a tripod weighing 50 pounds. The gear must be aimed at true north so it can track the stars with precision. To avoid making too many adjustments when I take a long exposure, the base must be level. A small finder ‘scope is mounted on the main telescope. For photography I need to attach a reducer lens and a CCD camera, plug the camera into a power strip and laptop, and focus. The telescope’s movements are powered by a rechargeable 12-volt battery. This is my minimum for an easy target like stars at the edge of the moon.

Normally I need at least an hour to set up. Since this was our front yard and I could use an outdoor power cord instead of a generator, I thought it wouldn’t take that long. But once the main telescope was on the wedge, I could not get two secondary bolts to tighten properly. They are crucial to keep the telescope on the wedge. I battled the cranky bolts for a long time; at last, loosening the third bolt and knocking the base, I was able to tighten all three. I struggled to level the telescope by adjusting the length of the tripod legs. Our lawn is so hilly that this job proved nastier than usual. Even though the tripod wasn’t level, I was running out of time, so I switched on the power and began the alignment procedure.

Close to 6 p.m., when the show was to start, I still had not connected the camera. The sky was irritatingly bright — too bright to see any stars disappearing behind the moon, I decided. So I would try to photograph them when they exited from the moon’s dark limb an hour later.

At nearly 7 p.m., I still fiddled with leveling the tripod. I checked the scene through the finder: moonlight shone so fiercely that I thought I could never see stars in the glare.

I gave up on the occultation, took a break and rested indoors. Later in the evening I’d show views through the telescope. Afterward I would make some more photos of the Orion Nebula to add to my mosaic. Maybe I could photograph a galaxy.

A little after 10:30 I went outside, clicking on my flashlight, whose light is red to preserve night vision. Small red flashes glittered across the lawn as if reflecting from broken glass. The grass was frosty. My equipment bags were soggy. Cables were stiff with cold, lens caps were coated with rime. Worst, the telescope’s corrector plate — the large lens at the front — was covered with a solid, hard-looking frost, rendering it opaque.

Daytime had been unseasonably warm and some of the snow cover had sublimated into the atmosphere. But the humidity could not remain airborne once the night grew cold — and now it was bitterly cold. Freezing moisture had condensed everywhere, coating trees, lawn and equipment.

Not quite ready to give up, I plugged in an electric space heater and held it in front of the corrector plate. Just then a neighbor drove past; I wonder what she thought was going on.

The heater melted the frost, turning it into sheets of gritty water and scattered droplets, but did not evaporate it. The upshot was no photos, another hour and a half of taking down equipment and hauling the ‘scope up to my second-story study, and a lens that was filthy with particulate matter. The grime came from either gunk in the air inversion or my electric heater. Or both.

The night remained clear but the lens did not.

Ironically, had I been prudent enough to set up earlier I could have photographed the occultation before intense cold set in. Kurt Fisher told the Utah Astronomy discussion list, “Although I did not expect to be able to see the Pleiades just a few minutes after civil sunset, at 6:00 p.m. I put a small 60 mm. refractor [telescope] on the Moon and was rewarded with a nice view of a shadow ray in Clavius [crater] and 5 Pleiadan stars shining from a steel blue-gray sky.”

At 6:03 p.m. the star Taygeta “winked off during ingress behind the dark limb.” At 6:55 p.m. Fisher set up the small telescope again to watch two of the stars emerge from the bright side of the moon.

“At about 7:00 p.m., I took a break from the eyepiece, looked up, and there was a great pass by the ISS,” the International Space Station. Around 7:05 p.m., Taygeta “popped out from behind the moon.”

Dan Hanks, an Orem resident, told the discussion group he watched from his backyard using his Dobsonian telescope. “Temperature was actually quite nice to begin with, but got colder as the evening progressed,” he wrote. He had “some very pleasing views of the dark limb and some of the Pleiades in the background.”

By keeping the brilliant part of the moon out of view, “I could see a number of the stars in the cluster next to the dark limb. … I was able to watch the dark limb swallow up a couple of the members of the cluster. That was fun to watch.”

Patrick Wiggins, NASA solar system ambassador to Utah, and the experienced observer Chuck Hards offered me advice on frost prevention. It had not been a problem before since I almost always do astronomy at a dark — and dry — site in the desert.

I carefully cleaned the glass Wednesday and it seems fine.

Win or lose, I suppose we can learn.

***
Here’s a view of the frost attack.

For more of the grim details CLICK HERE.

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