Hi Bill,

I am not at all well versed in astronomic calculations...
I do not even know what the parallactic angle is..let alone have a formula.

F1!
F1!
F1!

Siebren Klein
s.s.klein@...
http://www.geocities.com/siebren2001/index.html

----- Original Message -----
From: "Bill J Gray" <pluto@...>
To: <guide-user@yahoogroups.com>
Sent: Sunday, September 21, 2003 11:39 PM
Subject: [guide-user] Re: Field rotation rate formula


Hi Siebren,

I get the field rotation rate by computing the parallactic
angle one second before, then one second after, the current
time. I assume that the difference is the "rate" every two
seconds, and adjust units accordingly.

I suppose I could have done it The Right Way, taking the
derivative of the parallactic angle with respect to time. But
I already had code in there to compute the parallactic angle
(as you probably do, too; please let me know if you don't),
so I just recycled it.

-- Bill