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I shot Jupiter

Started: 2010-09-23 22:05:00

Submitted: 2010-09-23 22:22:30

Visibility: World-readable

When I went out running Monday morning, before sunrise, I saw a bright star in the western sky and concluded it was probably Jupiter or Saturn, given its relative position (opposite the sun) and apparent magnitude (the brightest object in the sky, but the pre-dawn sunlight was drowning out most stars). It turns out it was, in fact, Jupiter, at its closest approach to Earth in my lifetime. A quick consultation of the Internet this evening revealed photos of Jupiter taken with digital SLRs, so I took my Nikon D50, 55-200mm lens,and tripod out to my front porch to see what I could do.

I started out with an (overexposed) establishing shot of the moon and Jupiter:

The moon and Jupiter
The moon and Jupiter

I focused first on the moon in an attempt to figure out an appropriate focal length and exposure:

The Moon
The Moon

Finally, I zoomed in on Jupiter for the money shot:

Uranus, Callisto, Ganymede, Europa, Jupiter
Uranus, Callisto, Ganymede, Europa, Jupiter

That's a two-second exposure at f/5.6. I tried longer exposures but they served mostly to motion-blur, even on my tripod using a remote control, and I think I've overexposed Jupiter (apparent magnitude -2.5) anyway.

(I later realized that the motion-blur was not the tripod shaking but the Earth's rotation. At maximum zoom, the moon is about 218 pixels. The moon subtends half a degree, so one degree on maximum zoom is 436 pixels. The Earth rotates 360 degrees per day, or (360/86400) 4 millidegrees per second. My camera resolves that at 1.8 pixels. In my two-second exposure, Jupiter is 17 pixels wide, and rotation-of-Earth motion-blur is 3.6 pixels. I saw noticeable streaking in anything longer than two seconds.)

Look carefully for a little gray speck in the top-left corner: Uranus (apparent magnitude 5.9).

Clearly visible (if a bit blurred) are Jupiter's moons: Callisto stands on its own, and Ganymede and Europa[1] blur together. Io appears to be totally hidden by Jupiter.

Jovian system: Callisto, Ganymede and Europa, Jupiter
Jovian system: Callisto, Ganymede and Europa, Jupiter
[1] All worlds are yours, except Europa. Attempt no landings there.
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