My Transit of Mercury, 7 May 2003
Transits occur when a planet crosses the face of the Sun as seen from Earth. Naturally, a planet has to be between Earth and the Sun for this to happen, and so transits are limited to Mercury and Venus. As the orbits of these planets are tilted with respect to Earths orbit, we will see Mercury and Venus cross the Suns face rarely, as most of the time the planets will cross above or below the Sun. Transits can only be seen when the planet is between the Earth and the Sun at the same time as the planet is crossing the plane of Earths orbit. For Mercury, this occurs roughly 13 to 14 times a century, and for Venus, roughly every 100 years. So transits are relatively rare phenomenon, and quite interesting to watch.
The weather looked a bit uncertain for the May 7 transit of Mercury, and as I returned home from work, the sky was partly covered by thin high clouds, slipping over the suns face at regular intervals. Despite getting home on time, I was delayed in setting up my equipment due to the electrician wanting to discuss why our stove was busted, my spouse thought that this was important for some reason. Once this discussion was over, I feverishly set up my telescope, placed the solar filter on and aligned it.
Disappointingly, I just missed the black drop effect. This is when Mercury is just crossing into the sun, and it looks as if there is a trail or drop joining Mercury to the Suns edge. However, I did see the crisp black circle of Mercury separated from the Suns edge by a hairline filament of light, which was absolutely beautiful. With mounting excitementI then got down to the business of watching Mercury move slowly over the surface of the Sun, using several sunspots as landmarks. I also started taking pictures.
I used two methods to follow the transit. My 4" reflector with a solar aperture filter, and binocular projection. I used the telescope to take the pictures you see below. The binocular projection was less successful, as I used overly floppy cardboard for the sun screen, and didn't have a holder for the projection screen, but you could see Mercury, although not as crisply as in the telescope.
The transit progressed, and the Sun lowered towards the horizon. Clouds came over and obscured the view at intervals, nonetheless I was able to follow the transit for most of the time. I took my last photo at 4:30 pm, the my last hand drawn diagram was at 4:47, I had the scope set up for photos again at 5:00 pm (it takes a few moments to set up as I have to remove the eyepiece, put on the camera assembly and refocus the scope and adjust the image into the best position in the camera), but just after I had set things up the Sun went behind some trees, and I was unable to get my last photo. Nonetheless I saw virtually the whole transit as visible from Adelaide, it was far clearer than I expected (the crispness and size of the circle that was Mercury was quite distinct), and I am looking forward to the Tranist of venus next year, and the Next transit of Mwercury in 2006.
|3:00 pm ACST, Mercury has just cleared the Suns limb 10 minutes before||3:30 pm, Mercury is clearly visible against the Suns disk|
|4:00 pm||4:30 pm, clouds move in front of the Sun|
Technical guff. The eclipse was photographed on Kodak CMAX 400 colour print film via 2x Barlow projection (no-name Barlow lens) and a Pentax KM SLR camera body with T adaptor. The solar filter was a full apature Identi-View SVD 4.5 filter from Astro-Optical Supplies (thanks) fitted to a York Optical Skyrover 114 mm Newtonian reflector. Exposures were 1/125 of a second. Images were scanned at 300 dpi using an Olympic Technology scanner, and sharpened and cropped with Photoshop.
The scans are somewhat dissapointing, and don't show up the detail in the pictures. The pictures have less detail than what I actually saw, due to the high haze over the Sun most of the time messing up exposure levels, and slow exposure speeds leading to some bluring due to atmospheric turbulence. The spot tht is Mercury is fuzzy and sort of grey in the scans, but was crisp and black in the eyepiece.
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Created: Monday, 9 December 2002, 11:22:32
Last Updated: Monday, 9 December 2002, 11:22:32