[time-nuts] Re Danjon Astrolabe

Poul-Henning Kamp phk at phk.freebsd.dk
Tue Sep 26 15:24:47 EDT 2006

In message <451976CA.1000602 at pacific.net>, Brooke Clarke writes:

>A telescope and PIN diode might be the best way to get precise timings.  
>If a fixed scope is used with a reticule where the star crosses twice or 
>more then a plot of brightness vs. time will have a flat top pulse for 
>each line crossed.  The leading and trailing edges of these pulses can 
>be measured to hopefully milliseconds.

If you want to seriously play with this, study the Hipparcos
astrometry missions telescope design carefully.

You can probably find the docs if you start here:


Historical tidbit:  The Hipparcos main catalogue contains only 100k
stars, but Erik Høg (Copenhagen University) proposed some minor
changes to the navigation sensors and have used the resulting data
to make first the Tycho-1 catalogue of 1M stars at slightly lower
precision, than the Hipparcos catalogue, and then reprocessing the
data he subsequently generated the Tycho-2 with 2.5M stars.


Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

More information about the time-nuts mailing list