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Umbral Image

Originally published February 27, 2008
image by Filipe Dias, the Algarve, Portugal. Eclipse prediction graphic by Fred Espenak, NASA/GSFC

I took this picture of the Earth's umbra, during the last eclipse. It's the only one I know of the kind. It is a long exposure on film tracking the umbra, rather than the Moon or the sky. Exposure ranged from 1:30 UT to roughly 4:45 UT. To track it, I sampled the umbra's coordinates every 15 minutes, and calculated an average tracking speed between each position. I then manually and periodically inputted the adequate tracking speed to the equatorial mount to follow it. Unfortunately, there were some high clouds and a lot of humidity in the beginning of the eclipse (top of image), which contributed to the glow before totality. Also unfortunately, the weather forced the exposure to end before the expected time of 5:30 UT, so the Moon trail was not symmetrical. The next chance to do something similar or better from over here will be on the 26th of June 2029!! At least it will be summer :)

Filipe Dias
Note: I encourage people to repeat this mapping of the umbra on the upcoming partial eclipse in August!

Technical Details
Feb 20, 2008, 1:30-4:45 UT. Kodak E200 120 film on a Kiev60 camera, through an FS-102 @ F/6, apertured-down to 50mm and using two polarizing filter rotated ~85 degrees from each other to cut a lot of moon light and prevent saturating the background. Guide-scope was a Bresser 70mm F/10, with an Atik-2HS camera (field of view of: 23 x 17 arc-minutes). I wanted to guide on Regulus, unfortunately the glow was too strong, and I chose the next bright "thing" around, which was Saturn! As Saturn moves in the sky, I did not "guide" on it, I just used it to check if tracking was going OK.

Related Links
Another image of just near totality phase - note the different direction of movement of Regulus - top right.

Yesterday's LPOD: From Orbit?

Tomorrow's LPOD: Sim Pole


(1) The astrophotogrpaher Akira Fujii took a similar photograph of the 30 December 1982 lunar eclipse, which can be seen at:
Images tracking the anti-solar point (the center of the Earth's shadow) are valuable for teaching students that the ancient Greeks understood that the Earth was spherical and was at least 3 times larger than the Moon.

(2) Thanks for this double history lesson! Fujii's image is wonderful but to me doesn't give the same sense of movement as Filipe's.

- tychocrater-lg.jpg tychocrater Feb 27, 2008

(3) Nice new maps of moon’s rugged south polar region here

(4) For some reason, the comment section for the 2-28-08 LPOD is navigating back to this page when I click "here". (??)


(5) Oops - I fixed it. Thanks, Bill!


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