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Jupiter and moons

August 30th, 2008

I was driving home this evening and noticed that Jupiter was particularly bright in the sky.  After a few moments of marveling, I thought, “Hey, it would be fun to see the Galilean moons!”

My 10×25 binoculars didn’t quite cut it.  I could see the planet, of course, but I couldn’t make out any of the moons.  Time for a bigger hammer.

I got out the 400/2.8, a 1.4x TC, a 40D, and a wholly inadequate tripod.  How inadequate?  The camera, lens, and extender together weigh something like 15 pounds.  I normally use that combination with a very sturdy monopod, but a monopod isn’t good for astrophotography.  That meant putting the 15-pound load on a tripod that’s rated for about 3 pounds.  Needless to say, I kept a firm grip on the lens at all times.

I went to one of the outdoor stairways in my apartment building, set everything up, and pointed the lens towards the heavens.  I wasn’t really sure what exposure to use, so I started with 1/200@f/4 and ISO 800.  Not even close.  More fiddling: 1/100@f/4 and ISO 1600.  Better, not there yet.   Finally, I hit on something that worked:

Jupiter and its moons
Jupiter and the Galilean moons: (l to r) Ganymede, Callisto, Io, Jupiter, Europa

For those of you playing along at home, the magic settings were 1/25@f/4, ISO800, and a 560mm focal length (ignoring FOV crop).

To get more detail, I’d need darker skies, a much better tripod, a motor-driven tracking system, and, of course, a longer lens.  For materials on hand, I think it turned out all right.

  1. Halfcent
    August 31st, 2008 at 00:06 | #1
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    Holy crap I didn’t know that was viewable so easily while earthbound. I thought you needed at least a heavy duty amateur telescope. My Concept of distance and relative size must be all off.

  2. keacher
    August 31st, 2008 at 00:59 | #2
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    Yeah, I think that it would have been a lot easier to see with a true telescope. I went out with my 10x binoculars again and was just barely able to make out Ganymede. With a bunch of hand waving, the image above is roughly equivalent to that of a 140x telescope.

    Jupiter is overexposed, but a more stable mount would have allowed a proper exposure for all five of the bodies — somewhere around 1/2000 s.

    Here’s an amateur photo that I think is particularly good:

    http://forums.dpreview.com/forums/read.asp?forum=1022&message=28786863

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