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The Moon is not too bright to see with Hubble.
A lot of people claim that some objects are simply too bright to observe with Hubble. For some limited cases this is true — there’s a camera on board Hubble sensitive to ultraviolet light, and at a 2500 Volt potential too many UV photons can fry the instrument.
But that’s not true for most of Hubble’s cameras. Actually, some of the brightest objects in the sky have been observed… including the Moon! The image shown here is of Copernicus, a 90 kilometer wide impact crater on the Moon. It wasn’t actually Hubble’s primary target; another camera (the Space Telescope Imaging Spectrograph, or STIS, a camera I worked on for many years) was observing reflected sunlight off the Moon’s limb, and Hubble was rotated so that Wide Field/Planetary Camera 2 (WFPC2) would be able to take snapshots of the crater.
So while the Moon is not too bright to observe with Hubble, it is moving too rapidly across the sky for the ‘scope to track it. So the observations were made in what’s called “ambush mode”: Hubble is pointed at a spot in the sky where the Moon is going to be, and when the right moment arrives the images are taken. It’s a very difficult operation, which is one the reasons why there are so few observations of our nearest neighbor.
Back in 1999 I took part in a set of lunar observations using Hubble; we were hoping to get spectra of water ice splashed up from the Moon’s south pole when the Lunar Prospector probe impacted there at high speed. Unfortunately, the spectra were screwed up; the pointing was off by a bit and we didn’t see anything (it turns out no one saw anything using any telescope, so we didn’t really miss much). Although it failed, that observation run was incredibly exciting, some of the most fun I’ve had using Hubble.
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Links to this Post
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- SphericalTechnologies.com » Blog Archive » Hubble’s 20th Birthday Pic: “Eagle Nebula on Steroids” | April 24, 2010
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- Science Quiz: Happy Birthday, Hubble! - The Learning Network Blog - NYTimes.com | April 28, 2010
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- Happy 20th Anniversary, NASA! « Little Forest Playschool | May 7, 2010
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