> > In article <44D8C0BB.1030608 at pacific.net > <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>>, Brooke Clarke > <brooke at pacific.net > <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>> writes > >/Hi Geoff: > />/ > />/Thanks for the reference to "Geodesy". Do you know if the first edition > />/has the Danjon information? > />/I ask because the second editions are rather pricey and the 3rd and 4th > />/are not available at all. > />/Could someone on this list make a copy of the Danjon section? > />/ > /I'm quoting from memory about the workings of the Danjon Astrolabe - the > book was borrowed from my local library, and I don't remember which > edition it was. > > Nor can I quote chapter and verse, I fear - although I will attempt to > re-borrow the book, and copy the relevant section. Later this week, I > hope. > > AFAIR, the discussion was of the workings of various instruments for > determination of time from the stars, together with ways to mitigate the > systematic errors in each instrument. "Personal equation" figured large > in all this, which is why the PZT was preferred. > -- > Geoff Powell
The explanation of the operation of the Danjon Astrolabe is somewhat oversimplified. There was a motor driven optical mechanism that was used to keep the 2 stellar images superimposed for some time so that a sequence of observations could be taken on a single star. This significantly reduced the personal equation on the measurements obtained with this impersonal version of the astrolabe. I remember a book on Astrometry (sorry cant remember the title) that had detailed cross sections of the astrolabe together with a very detailed description of how it worked. A modified version of the Dajon Astrolabe is currently in use at Santiago Chile for Solar astrometry. Bruce _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
