Posted by: Chris Cole | June 6, 2012

Transit of Venus 2012

I thought I’d toss up a few snapshots I took today from my front yard in Canberra, as Venus wandered across the face of the Sun from our point of view, something it does fairly rarely by the standards of a human lifetime. The transits come in pairs, 8 years apart, with the previous one occurring in 2004 and the next not due until 2117 (in December, if you want to leave your great great grandkids a reminder note).

This particular transit was visible during it’s entirety if you happened to be anywhere in roughly the Eastern half of Australia (the sandgropers missed the first bit, as it started before dawn for them) and you were either high enough to be above the cloud layer, or lucky enough to spot the Sun through a few fleeting gaps in the quite pervasive clouds.

I didn’t catch the beginning or ingress part of the transit because… well, I don’t do mornings, really… but I dragged myself from beneath my exceptionally comfy doona and managed to haul my telescope and camera out onto the front lawn by 1030hrs or so in order to see what I could see betwixt the clouds. At great personal peril (it was a toss-up between being frozen, or blown away Wizard of Oz style in the gale force winds) I eeked out a few reasonably clear shots when the clouds deigned to part now and then, with some of the results posted below. These are also on Facebook, but the size reduction involved on FB kind of munted a few of them up, especially the stacked image (the nice red one), so I thought I’d chuck them on here at higher resolution. (Having said that, I have no idea how badly WordPress will squish them, too…)

They were all taken with a Canon 450D at prime focus of a Celestron C8 (8-inch Schmidt-Cassegrain) telescope. This is an f/10 instrument, and some shots were taken “bare” at f/10 and some were taken with a f/6.3 focal length reducer in the light path. Exposures on the camera varied but typically I was using shutter speeds between 1/400 and 1/1,000 seconds and an ISO between 400 and 1600.  Being too impoverished to afford a H-alpha filter big enough to cover the aperture of my telescope, a $15 sheet of near-enough-is-good-enough filter material found on eBay did the trick, sticky-taped over the front end of the OTA. 🙂  Unfortunately, I couldn’t find the right sized T-ring/adapter to mate the camera to the optical back on the OTA, and so an extra degree of dodginess was added by way of me having to manually hold the camera up to the optical back and/or mount it on an independent tripod behind the telescope.

The first image is composited from a stack of 9 separate exposures taken fractions of a second apart, and the rest are all single exposures.


[NOTE:  Okay, so it apparently just chops off the right hand side of each image. Click on them to bring up the full-sized images…]




  1. Good photos Chris

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