Saturday, March 17, 2007

Hunting comets digitally without a telescope

According to Sky & Telescope magazine's SkyTonight website, Terry Lovejoy of Thornlands, Queensland, Australia, is the happy discoverer of a 9th-magnitude comet (still very dim) in the southern constellation Indus. It's the faint blurry green thing near the top of the frame at right. That's not what caught my eye, though -- comets are discovered regularly, and most don't make much of a splash. What caught my eye was the fact that Terry didn't use a telescope but an off-the-shelf, consumer digital SLR with a zoom lens (granted, one of the pricier telephoto zooms with an f2.8 maximum aperature).
Lovejoy's find opens a new chapter in the long and glorious history of comet hunting. It appears to be the first case of a comet discovered in a systematic survey with an off-the-shelf, consumer digital camera: a Canon 350D with a zoom lens set to 200-mm focal length at f/2.8. Lovejoy spotted the object near the frame edge in 16 exposures of 90 seconds each. He prepared the cropped composite here from eight of these frames. North is toward left, and the field about 0.8° wide.
The body of the 8-megapixel Canon 350D (also known as the Digital Rebel XT) lists at B&H Photo Video for $514.95. A few years ago, digital cameras with sensors like that cost thousands of dollars, but these days, the camera is practically a commodity and the part of the package that is apt to push four figures is a fine lens like the highly regarded Canon Zoom Telephoto EF 70-200mm f/2.8L USM Autofocus Lens, which lists for $1,099.95 at B&H (image stabilization would add another 600 bucks to the cost of the lens, but comet seekers probably wouldn't need that, since they would be using a tripod anyhow).

1 comment:

Anonymous said...

Yes I found the information that the comet was discovered with a camera. I saw on your blog it was a canon XT which is what I just bought.
Your explanation about finding comets with digital pics through a handheld digital camera , might as you say be the first one.
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