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    Re: 60° Pendulum Astrolabe
    From: Peter Monta
    Date: 2016 Jul 20, 14:10 -0700
    I'll bite, though I know only a little of the history.  Since it's WW2-era, it predates the Danjon astrolabes, which contained refinements to reduce some systematic and "personal" errors.

    Also, you say it's a *pendulum* astrolabe.  How does that compare in accuracy to a liquid flat?  Are there any significant uncertainties in the chain-of-vertical-truth from the pendulous mirror?  Just wondering.

    Your students might want to review the error analyses that went into the Danjon design.  A cool project would be to retrofit the instrument with improvements (if possible).

    Since you mention smartphone timing, the stars might be bright enough to simply video them with eyepiece projection using a separate small tripod to isolate the phone from the instrument..  In the same video clip, shoot an accurate clock before and after, and maybe also an LED blinking a PPS signal from an inexpensive GPS receiver module.  Some iPhones can shoot at 240 Hz (~4 ms frames).


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