Re: Field rotation rate formula

Bill J Gray Sep 21, 2003

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