March 27, 2012

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Four Moons Over Arkansas

image by Richard Ulrich, Springdale, Arkansas

I went through a lot of combinations of shutter speed and ISO tonight and this was about the best I could do. First, there is no exposure setting that will give detail on the illuminated side of our Moon and, at the same time, show the moons of Jupiter. Second, I was limited by not being on a tracking mount. Any shutter speed slower than 1/8 second gave me smear at 300 mm so I had to jack up the ISO instead. The Jovian moons are, top to bottom, Io, Ganymede and Callisto. Europa is right in front of the planet casting a shadow, but no way to see it here. The top moon, Io, is almost exactly the same size as our Moon, but tonight is about 2200 times further away. It’s almost completely on the other side of the Sun from us right now, which is why we can get this cool effect of the old Moon in the arms of the new and can see Jupiter at the same time.

If I live long enough to see this sort of thing again, I'll use a tracking mount!

Richard Ulrich

Technical Details
March 25, 2012. 300 mm Canon L lens, 1/8 sec, f/5.6, ISO 6400 into a Canon 7D

Yesterday's LPOD: Kepler Rayology

Tomorrow's LPOD: If At First You Don't Succeed


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