Re: [LEAPSECS] The opportunity of leap seconds

From: Tom Van Baak <tvb_at_LEAPSECOND.COM>
Date: Sun, 8 Jan 2006 13:56:42 -0800

> Research-quality telescopes, in particular all the ones built in the last
> few decades on alt-azimuth mounts, do of course use UT1; a 0.9s error
> would be a complex ~10 arcsec error in both axes and give a quite useless
> pointing performance. However, UTC is often used as a UT1 delivery
> system; because it's an international standard, and is widely available,
> and DUT1 is guarenteed to be less than 0.9s, it's a natural choice for
> supplier of time. Interestingly, because control algorithms tend to be
> rigorous, a large DUT1 probably would be ok in itself (there would be a
> cost involved in checking that this would be so) but certainly in the case
> of a couple of telescope control systems of which I have the required
> knowledge, the DUT1 input method does a 0.9 second range check.
>
> Peter.

Peter,

So where do these modern telescope get UT1? Do you or
any other astronomers on the list know if they pick off bits
from WWV (or equivalent SW or LF broadcast)? Or is there
a nice thumbwheel switch in a control room that someone
gets to advance anytime they get an IERS Bulletin by FAX
or email? Or is it a software interface to the IERS website?

I guess in all the years this list has operated, and with
all the detailed anecdotes about leap seconds I've never
heard details of how an observatory anywhere actually
obtains, and uses, DUT1; and to what level of precision.

/tvb
Received on Sun Jan 08 2006 - 13:58:39 PST