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    Re: Space sextants
    From: Frank Reed
    Date: 2010 Oct 24, 19:50 -0700

    I wrote yesterday:
    "The Apollo spacecraft also had an instrument called a "telescope" mounted right next to the sextant. This was actually just a unit power viewer with a computer-readable orientation, useful for gross alignment of the sextant. The astronauts enjoyed joking about the fact that only a government project could pay good money for a telescope with no magnification. This telescope was used occasionally in experiments and at least once in actual practice. In 1968 on Apollo 8, returning from their historic lunar orbit mission, Jim Lovell accidentally entered a key sequence that told the computer it was back on the ground in pre-launch mode potentially wiping out the inertial platform's alignment. Just to be safe they ran "P51" which re-aligned the platform starting from scratch with gross alignment provided by the so-called telescope. This was a case where the astronaut had to identify the bright stars visually based on his knowledge of the constellations. It was a rare moment in manned space flight."

    I found the quotation on the unit power telescope. It's from Neil Armstrong who said, "NASA is probably the only organization in history that's been sold a one-power telescope." Of course, it was the computer-driven telescope mount that made it so useful. You could tell the computer "Point at Betelgeuse" and it would do just that. The view through the eyepiece would be centered on Betelgeuse with the stars of Orion around it at exactly the scale seen with the unaided eye. The computer-driven sextant could then slew to the same spot.

    It's funny. It's taken almost fifty years, but we can now do that (the computer-driven, unit-power telescope part) with pocket devices. The other day I was outside in front of a restaurant with some friends along with some other people who had popped out for a smoke. I said, "There's Jupiter" and pointed at it in the sky. Then I took out my phone/computer, started up "Google SkyMap" and showed them that it pointed right at it. Over my shoulder I heard, "oh yeah, it is Jupiter" and when I turned around I was amazed to see three other people holding their phones up. They ALL were running Google SkyMap. We had a couple of minutes of fun identifying a few more of the two or three dozen stars visible from downtown Chicago.


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