Last weekend I had the pleasure of taking an “insider’s” tour of the Large Binocular Telescope (LBT), currently the largest telescope in the world based on baseline (22M) and I believe collecting aperture (although it’s hard to keep track), at 2X8.2M. It was a very nice afternoon and the trees at the peak (10,200’) had turned a brilliant fall yellow.
Since one of my first experiences in optics was to star test one of the last of the six original mirrors in the Multiple Mirror Telescope (MMT) on Mt. Hopkins south of Tucson, it was quite a reset to view how massive the LBT building is compared to the original MMT building, which can be seen from the LBT. At one point we trekked all the way to the roof (OK, a lot of the trek involved a series of elevators), which is over 200 feet off the ground, to an unseen tiny cement escarpment that provides an amazing view back to Tucson and beyond. In that we are recently applying nodal aberration theory to these telescopes, it is an interesting perspective to look at an 8.2M mirror and then contemplate the question, what does a 10-micron decenter actually mean? With these mirrors, there is no absolutely smooth edge circular aperture to measure from. These are spin-cast mirrors made at Roger Angel’s lab in Tucson and as such the edge is good, but is not a micron-level reference surface. The experience reminds me of when I worked on an Air Force conformal optics project. We kept asking for the wing profiles to a number like 10 microns. The Air Force finally decided the best response was to put us on a plane to St. Louis, where we learned airplanes are made pretty much the same way as a Grumman canoe, containing over three miles of wire. They do not work well as an optical reference surface.
Additional LBT informational websites are shown below:
http://medusa.as.arizona.edu/lbto/
http://en.wikipedia.org/wiki/Large_Binocular_Telescope
http://www.aip.de/groups/lbt/
http://planetquest.jpl.nasa.gov/lbti/lbti_index.cfm (very short)
YouTube video:
http://www.youtube.com/watch?v=rtOyCcJtzcw
I came across a website titled, “100 Hours of Astronomy,” which was created in the spring of this year as part of the global celebration of the 400th anniversary of the first use of an astronomical telescope. I did not spend much time there, but it appears to be a tremendous series of on-site interviews with astronomers at telescopes around the world. I look forward to taking some time to explore the website – enjoy!
100 Hours of Astronomy main page:
http://www.100hoursofastronomy.org/
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