"Short Form" Observing Report
by Brian Davis
Date: 8 Jun 2004
Location: Penn High School, Mishawaka, IN, USA (41.68 Lat,
-86.11 Lon)
Equipment: XT8 (8" dobsonian reflector), 25mm &
9mm plossl, ultrascopic 2x barlow, Thousand Oaks solar filter
Predicted sunrise: 5:10 AM local time (10:10 UTC), at 59°
azimuth
Predicted 3rd contact: around 6:03 AM local time, 8°
altitude
Predicted 4th contact: around 6:24 AM local time, 11°
altitude
Wonderful
event! I observed at a public event that a bunch of us with equipment were recruited
for. While I showed the transit to 100+ folks (a lot of kids, nice to see), I
had exclusive use for third & fourth contact to *try* to time them. Before
that morning I had never used a solar filter - one was provided by the
organizers of the event. The result was almost comic: perhaps a dozen 'scopes
started franticly trying to locate the Sun as soon as it crested the trees near
the horizon around 5:30, almost none with filter-equiped finders and with the
Sun too dim (low & in clouds) too be seen in the eyepiece. Minimize the
shadow cast by the OTA I hear you say? With the Sun so low & dim, there were
no shadows, and we dared not look with the filters off. Eventually everybody
located it, and the viewing began.
Venus
was a wonderfully inky black perfect disk on the Sun, unmistakable. As others
have noted, it seemed larger than I had expected, nice at 48x, with 3rd &
4th contact observed at 96x. The blackness was really noticeable compared to the
two small sunspots centrally located. As 3rd contact approached, I started to
see what looked like a thin thread connected the black disk of Venus to the limb
of the Sun. It was hair-fine, and slightly "wrinkly", not razor
straight but slightly slack and wriggly. I saw it at least three times, when
Venus was perhaps 1/5th of a Venusian diameter or less from the solar limb (did
anyone else see this?). As the bridge thinned, it seemed to thin on both sides,
as if being drawn apart like a piece of taffy. This was subtle, but it soon
formed a wavery bridge of light, trembling to hold Venus within the glowing disk
of the Sun. This very quickly gave way to the "black drop": instead of
a razor-thin line of light, Venus merged with the edge in a non-uniform way, one
instant still within the solar disk, the next breaking the limb of the Sun with
a wider-than-it-should-be black gap. I was unprepared for how difficult this
made timing the moment of contact (I got 11:05:02 UT - the guy next to me was
something like 7 *seconds* earlier, clearly unacceptable... and I'm not sure
either of us trusted our own observations on this). As it pushed through the
limb, I thought I saw a partial ring of light around it when it was perhaps a
quarter of the way out - the guy next to me clearly saw it (not sure what
magnification he was using, but he was on a 4" apo), and was very excited.
He described it as "horns" to a complete arc (it was never that
distinct to me). I *did* notice that from a quarter of the way out to perhaps
halfway or even more, the disk of Venus seemed very slightly darker than the sky
behind it. I could picture the complete disk of Venus even with half of it off
the face of the Sun (perhaps this was my imagination, but it was something I
thought I observed... and after all, that's what this is, an observing report
:-). 4th contact actually seemed easier to judge (note, this doesn't mean I was
any more accurate, just more confident); as Venus departed from the Sun, it
formed a rapidly-diminishing very shallow dimple, and I timed 4th contact as the
moment when this dimple was lost in the seeing variations in the solar limb.
All in
all, we had a fantastic time. Plenty of folks helped out, running 'scopes for
the general public, while others MCed the event. The general public was
wonderful, really enthusiastic... it was also nice, I must admit, getting to
peek through others equipment: I had the XT8 and a TV85 plus a pair of
tripod-mounted binoculars, and I suspect I was the bottom end of the equipment
list. One guy had a 6" refractor, there were a couple of 10"
reflectors, an LX200, several APOs (at least one other TV85), and two 'scopes
with H-alpha filters (a coronado & something else). The night before we had
a mini-starfest, tagging various (mostly bright) objects in the hazy,
light-polluted (but steady!) skies until midnight, then gathering in a tent to
watch a webcast of 1st & 2nd contact. Even on TV it was a spellbinding
event, and picturing the true three-dimensional situation (the Sun being more
than twice as far from Venus as Venus is from us at that moment) made it even
more amazing. The dimmest object I managed to find that night was M82 (!!), but
Jupiter was nice (well-defined features in the NEB), and M13 and colorful
doubles were the public showpieces of the night.
Oh, and
somewhere in there I did land 2 hours of sleep in a tent nearby. Didn't hit me
at all until the next day, late, when I fell asleep waiting for the shower to
warm up. Oops.
Afterthoughts
(for the next transit): (1) I need to have some way to photograph through the
eyepiece, as well as remembering to take a few "naked eye"
(unmagnified) shots of the Sun (I didn't think of it - now *that's* dumb). (2)
Observe on higher power (I really could have gone up from 96x, and seeing would
have probably supported my next option at 133x with the 9mm). (3) Run a tape
recorded to record verbal observations during the event. And maybe, not do the
public thing - although it was FANTASTIC, and I wouldn't have missed it for the
world, I really want to be isolationist for the critical moments of the next
one.
OK,
anybody else want to report? Please?
--
Brian Davis
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