[time-nuts] Information on the Danjon Astrolab

[Geoff Powell]

In article <fJo2gIAsON2EFwIu at g8kbz.demon.co.uk>, Geoff Powell
<geoff at g8kbz.demon.co.uk> writes
>
>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.

"Geodesy" wasn't on the shelves when I checked yesterday, but I did find
a copy of "Plane and Geodetic Surveying for Engineers" by the late David
Clarke, Vol. 2, 6th Edition, Constable Press, London 1973, reprinted
1986, ISBN 0 09 459120 2, which has a description of a "Prismatic
Astrolabe", a device which is similar to the Danjon instrument.

I've put a PDF (200 dpi, 2.6MB) of the relevant pages on my website at 

http://www.g8kbz.demon.co.uk/images/PrismaticAstrolabe.pdf

including the discussion of errors in the observations.

It's not linked from anywhere else, so no search engine will see it
except via the list archive, and it won't be there long, either, since I
only have 20MB of space. Get it while it's hot!

"Geodesy" is on order, but from the date, it's the 1st Edition.

-- 
Geoff Powell