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"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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