[time-nuts] Information on the Danjon Astrolab

[Brooke Clarke]

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?

The PZT used a large pool of Mercury to define "Up".  The source of many 
errors was considered in the design and as far as I know were all 
eliminated.  The PZT worked by exposing a glass plate at 4 known times.  
I think it was reversed for two of the exposures and then after 
development read on what amounted to a coordinate measuring machine.  
Then a number of corrections could be made depending on the geometric 
relation between the 4 points.

The Dent Meridian Instrument or as he called it the Dipleidscope uses a 
couple of mirrors behind a clear glass and when the two reflections 
coincide the star is on the meridian.  The manual gives a number of ways 
of aligning it, one of which depends on already knowing the time.  See:
http://www.pacificsites.com/~brooke/Dent.shtml  But it's intended for 
visual use, not automated.

Have Fun,

Brooke Clarke

Geoff Powell wrote:

>In article <7ntf7JA6qD2EFwuF at g8kbz.demon.co.uk>, Geoff Powell
><geoff at g8kbz.demon.co.uk> writes
>  
>
>>>Does anyone know how a "Danjon Astrolabe" works?
>>>      
>>>
><snip>
>
>  
>
>>Source for this - the book "Geodesy" by Bomford. Sorry, no ISBN or
>>publisher (I'm typing from memory)
>>    
>>
>Geodesy
>
>Bomford, Guy
>
>Clarendon Press, Oxford
>
>2nd Edition (1965) (Out of Print)
>
>3rd Edition (1971) ISBN 0198519192 (Out of Print)
>
>4th edition, from 1980. ISBN 0-19-851946-X
>
>Or you can try this Biblioquest search
>
>http://www.biblioz.com/main.php?action=5&u=24b729e881416a4d4feb2da5a9d34
>ed3&author=Bomford&title=Geodesy
>
>It is considered one of the primary references for geodetic surveying,
>albeit somewhat dated.
>  
>

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