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The 2004 Transit of Venus

No one alive, until this day, had ever seen a transit of Venus. Since the first transit was observed by the Lancastrian amateur astronomer, Jeremiah Horrocks in 1639, only four other transits had ever been observed, the last being in 1882. So this was number six in recorded history.

To make sure we didn't oversleep, and had a good easterly horizon, we headed off after a meeting of the Abingdon Astronomical Society to camp on White Horse Hill at Uffington in Oxfordshire.

We rose around 5:30am (04:30UT) and set up our equipment - a 6" reflector (borrowed from the society), an SLR with a 1000mm lens, and a video camcorder - all equipped with home-made solar filters (made from card and Baader Astrosolar film).

Slight haze greeted us during the ingress of Venus' disk onto the solar disk. However, we were still able to observe well, though we did not see the black drop effect, and were not sure whether this was simply due to poor viewing from the haze. The thin clouds all but disappeared soon after and we had a great view until Venus was mid-disk. Several passers by, mainly dog-walkers stopped to gaze at this historic event through the 'scope. One couple talked of the magic of total solar eclipses, and with memories of Romania in 1999 still as fresh as ever in my mind, I had to agree that that was probably the most amazing thing I have ever seen.

Around 10:30am, we headed back to East Hagbourne for a late breakfast, and to prepare to observe egress. The seeing was perfect and this time I distinctly saw the black drop effect as possibly an extra short horizontal line between Venus and the solar limb. It only lasted a few seconds. I also thought I saw two streaks of sunlight reaching out from the solar limb up the side of the half-on, half-off Venusian disk. This only lasted about two seconds. Or did I imagine it? Well, my friend Jon in Oxford also thought he saw the same phenomenon, so maybe I didn't.

So, having waited 122 years to witness this event, I was well pleased. The Venusian disk was larger than I thought it was going to be - much larger than Mercury last year.

We entered our observations of the times of first, second, third and fourth contacts into the European Space Observatory's web site, and were satisfied that from them was calculated four estimates of the mean astronomical unit, all of which were within 0.3% of the known value (see below). Not bad for a couple of amateurs!

    Instants (UTC)  AU(km)     PI(")   Delta(AU)(km) Delta(PI)(")  Error

1   05h 20m 47.00s  149990653  8.7711  392783        0.0230        0.263%
2   05h 39m  0.00s  149251517  8.8146  346353        0.0204        0.232%
3   11h 05m  4.00s  149176424  8.8190  421446        0.0249        0.282%
4   11h 22m 48.00s  149960509  8.7729  362639        0.0213        0.242%

Average AU = 149594776 km 
Average PI = 8.7944"
Average error = 0.002% 

See how our results fitted in with all those submitted.

Here are some images I took using an Olympus C220 digital 2MPixel camera down the 19mm eyepiece of the 6" reflecting telescope. I used a special adaptor to hold the camera steady - my right finger and thumb! Apologies for the random rotation introduced.

Sunrise Moon over tent Our setup
Ingress Mid-transit (or thereabouts) Egress

Some notes from the Institute of Physics: