[time-nuts] Why not TAI?

Brooke Clarke brooke at pacific.net
Wed Aug 10 17:38:29 UTC 2011


A friend has an observatory and needs very precise time.  It turns out 
that the best way is to command the system to point to some star then 
manually move the scope to put the star on the cross hairs.  Doing this 
a half dozen times and then fitting the data results in the system 
knowing the time to maybe a millisecond.

Doing an NTP sync or having a fancy time base in the control computer 
can only get within hundreds of a second.  Remember that all the 
broadcast time signals are to the nearest second but WWV and WWVB send 
the tenths of a second offset for astronomical time but using that he 
could get to the nearest tenth of a second.  But the above procedure 
gets him to maybe a millisecond.  I say "maybe" because how well the 
scope points in terms of arc seconds of angle depends on many factors.

So, maybe if you really want precision time you also need a very good 

Have Fun,

Brooke Clarke

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