The Sun Solar System: the Moon Planets observing logs

The Planets

May 7, 2003: Mercury transit

Last night Bruce "The Boss" Springsteen & E-Street Band kicked off their European tour in Rotterdam. We had a great night and got home around 03.00 hours this morning.

I totally forgot the Mercury transit. However when I got up this morning, with "Born to Run" still stuck in my head, I looked out of the window. It was a blue sky with nothing but the sun, and I suddenly realized: The Mercury transit; and running I did!

I rushed into my garage, hauled out all the equipment, and within ten minutes I sat at the eyepiece.

The photo to the right shows it all!

It was 8.30 UT. Of course I missed the first and second contact, but there was plenty of time to make a sketch and to observe third and fourth contact.

Explanation: first contact is when due to Mercury the first appearance of a notch at the (eastern) edge of the sun becomes visible. Second contact is when Mercury moves on the solar disc, and a first thread of light is separating Mercury from the Sun's disk. Then Mercury starts moving from east to west across the Sun, until it reaches the western edge of the solar disc. Third contact is the moment when the last thread of light breaks between Mercury and the Sun. Mercury starts moving off the Sun, making a notch in the Sun's limb. This notch gets shallower and shallower, until it finally disappears. The instant it disappears is the fourth contact.

The basic sketch (please don't shoot me, it's the first time I am sketching an event like this) was completed at 09 hours and 10 minutes UT. Mercury is positioned at (1). At 10 hours and 18 minutes UT I made the second mark (2) for mercury on the solar disk. The third mark (3) is made after third contact and before fourth contact. It was at 10 hours, 30 minutes and 30 seconds universal time.

During the transit Mercury really looked like a black circle perforated into the Sun's disk. In the drawing I added the sunspots that where visible at 9 hours and 10 minutes UT. I used my 8 inch TAL 200K Klevtzov-cassegrain with a full aperture Baader solar screen (see picture) and a yellow filter threaded into the eyepiece. While making the sketch I used a 32mm Televue Plossl.

For the timing of third and fourth contact I used a 20mm Vixen Lanthanum. I timed the contact points with a stopwatch, which I standarized with the U.S.N.O. master clock (internet). I clocked the third contact at 10 hours, 28 minutes and 38 seconds UT and the fourth contact at 10 hours 32 minutes and 31 seconds UT. The location I observed from is 50° 54' 52" NORTH, 6° 3' 30" EAST. (Data from There were no disturbing clouds that could have affected my timing, but I have to admit that the three hour party with the Boss and the long drive home might be of some influence on my observations. Anyway, this was my first Mercury transit, and I tried my best. I'm looking forward to next year's Venus transit!