by Dan Wright
"Let me see", I asked. A small dim satellite was moving slowly out of view. But hey! Another appeared, entering from the west and flying through the northern part of the Duck cluster, following the same track as the first. And here came another! All were about the same magnitude.
"Kevin, what are these things?" I asked. K. Roberts got up to the eyepiece in time to see them exiting the field. The only satellites I could imagine that would move along in a train and be about the same magnitude would be geosynchronous. But I thought, "those wouldn't be moving, they'd be stationary". I didn't give it much thought.
Until later when Bob Jardine said another fellow (Rich N?) had been publicly showing M11 and had seen them. Bob pointed out that my scope had been tracking, that's why the geostationaries appeared to move. This was a slap-yourself-on-the-forehead-and-say-duh! moment.
There was still some doubt they were geo-sats, though. You'd expect geo-sats to be at DEC zero -- the equatorial plane. What's the DEC of the Duck? It's about -6.3. Does that make sense, if we are observing from 40 degrees north latitude? Actually yes, it seems to. The proof they are truly geo-sats, Bob declared, would be to center one and turn off tracking -- it should freeze while the stars drift east to west.
So I watched the Duck for a long time, but I didn't see another one. I began to despair, when suddenly one sailed into view. I followed it with slew keys as it moved steadily away from M11, thinking frantically, "how do you turn off tracking on this LX200?" Several keystrokes deep in the menu, I eventually turned tracking off.
The bird froze in the field of view while stars drifted through. The illusion was that it was sailing through stars. I slewed a bit west and found two others nearby, and eventually I had three in the same field. I ran up and down the Shingletown runway at 3:00 AM bragging and inviting people to see.
The birds often appeared to get on dangerous-looking collision courses with stars. Crilly was funny. He said, "My god! That one just split in two pieces! Yes! And started firing lasers at the others!"
M11 is at the right declination to observe geostationary satellites at Shingletown. If you're at Shingletown, just watch the Wild Duck for awhile, and you'll see them -- simple as that. This is true for past and future Shingletowns (though earth's precession very gradually changes it).
At different latitudes, geo-sats appear at different DECs. That's why we haven't noticed them flying through M11 in the bay area. Here is a link to an Excel spreadsheet with a formula for geo-sat DEC as a function of latitude. I've calculated the precise DEC for observing geo-sats at Montebello, Coe, FP, LSA, and Coyote:
http://home.covad.net/~danwri/geo-sats.html
The spreadsheet uses macros, so you'll have to "allow" the macros. Go ahead; I didn't include any viruses.
Cast around east and west on the correct DEC for your latitude (helps immensely if you have a equatorial mount). You should come across them; they're in a ring all over the sky at this DEC. Perhaps you can find a cluster of three as I did.
For the bay area, the DEC is basically -5 deg 55 min. For LSA it's -5 deg 45 min (still really close to M11). Exercise for the reader: what common objects lie directly on the geo-sat DEC for LSA, or for Coe, the way the Duck does for Shingletown?
It is surprising we saw them so easily during solstice. From what I've read, they appear most readily when "at opposition" -- at the equinoxes. Near equinox, they flare bright enough to be naked-eye. Here is a good link:
http://members.aol.com/_ht_a/hattonjasonp/hasohp/GEO.HTML
Geo-sats were easily my favorite thing to observe at Shingletown!
Posted on sf-bay-tac Jun 24, 2004 17:36:27 PT
Converted by report.pm 1.2 Jan 02, 2005 09:02:11 PT