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| I've been trying to get a photo of a satellite transiting
(crossing in front of) the crescent moon for quite a while.
It's the image in the Turkish and Pakistani flags, except with
a star, it's obviously impossible since the moon is nearer than
all stars. But it should be possible with a satellite. After
many months of practice, I got pretty good at figuring out where
satellites would be and taking pictures of them and the moon.
One problem is that the moon is much brighter than most satellites.
A bright satellite is needed. The brightest thing up in low earth
orbit is Mir, but it won't be up there for long and there won't be
any convenient transits from Stagecoach Observatory. So I hit the
road. The first really good transit happened on New Year's morning
at 5:38 AM, just north of Pueblo, CO. So I trucked out there,
wandered around the ranches in the dark at 3 AM, found what I thought
was a pretty good place (thanks, GPS) and set up. Mir showed up on
time but missed the moon's limb by 0.1 degree, drat!! I hadn't
realized how critical it was to be in the exact position ... nor
how much barbed wire there was in S. Colorado!
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| The next chance was in the evening of 9 January, near the Mexican
border around Las Cruces, NM.
Here's the prediction of the Mir-moon appulse for that evening,
at a location near Las Cruces.
We actually ended up near small town named Dona Ana.
Estimated magnitude was pretty bright, +0.4, not nearly as bright as when
it passes overhead (mag -1.7 from that location that evening) but the
crescent moon always means a low-altitude shot (12.59 degrees).
Unfortunately, my calculations didn't account for atmospheric extinction,
so Mir was dimmer than calculated. Anyway, I exposed for the moon.
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| The Pueblo experience provided a lot of lessons.
For one thing, when the time comes, things happen fast and the
workload is too high for a single person using mobile gear.
(Not a problem in an observatory, but Mir didn't cooperate that
much ;-) Aaron Gilbert agreed to come along and help, he's almost
as crazy as I am, I guess.
Another thing that became obvious from the Pueblo experience was that
5 frames-per-second or so that the Nikon F3/MD4 can manage with fresh
batteries is not nearly fast enough for this purpose.
Neither is normal film.
So for the Dona Ana trip, we went "loaded for bear".
I obtained a 35mm movie camera and some special-purpose film which
is superfast (can be pushed to 3200 ASA!), super fine grain, and
(most important for high speed cinematography in the cold) really,
really, strong. This film is designed for shooting movie special
effects. Great stuff, it's Kodak 5289 "Vision 800T".
So this is a photo of the setup we used.
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| Here it comes!
It's the speck in the lower-left corner.
This is frame 44 from a print of the movie.
The moon was exposed properly, and since it was a pretty thin
crescent, it wasn't that bright.
But even so, with Mir at 1000 km range,
the moon was much brigher than Mir.
So I had to overexpose the moon when digitizing these pictures.
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| There's the transit!
Frame 107. It's the speck in the upper middle of the moon.
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| Inverting the images and superimposing them, one can see the trajectory
of Mir against the moon.
Just about the same trajectory (next time I'll level the telescope!)
and exactly on time according to the GPS, very satisfying.
We were a bit out of position (about 1600') due to local constraints
but that was mostly made up by the altitude difference (380').
Also, the orbital elements used in the calculation were about 0.6 days
old.
So for one reason or another, Mir didn't cross quite smack in front
of the middle of the moon from where we were. But it did transit....
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| It's hard to describe what a kick it is to get this sort of thing right.
The photos and text here seem pretty dry and lifeless, but the real thing
is a tremendous thrill. Here's a picture of Aaron and me just after the
transit. We're jazzed. Which was a good thing because we had 5+ hours
of driving back to Santa Fe ahead of us. Which went like a flash.
This is also a pretty nice photo of the photographic setup I used to
record this transit. Eyemo 35mm camera which manages 48 fps without
tearing up Estar-based film (turret modified for Nikon lens mount),
a TeleVue-85 700mm f/7 Apo, operated here at f/5.6 with a 0.8x
compressor/flattener, a Bogen "versatile/pro" style tripod with a
simple heavy-duty head and custom bracket (cobbled together out of
maple, the big block is slotted to allow focusing). Not absolutely
perfect (the observatory is perfect), but it works well for road
trips. It's also an interesting blend of technology: a telescope
designed just a few years ago (that Al Nagler is really good),
a movie camera designed in the 20's (it's wind-up!) and film which
just hit the pro market a few years ago. What fun.
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