Thread: formula for astronomical midnight at Greenwich, in UT?
View Single Post
  #3  
Old September 22nd 10, 03:05 AM posted to sci.astro.amateur,uk.sci.astronomy
William Hamblen[_2_]
external usenet poster
  
Posts: 236
Default formula for astronomical midnight at Greenwich, in UT?
On Tue, 21 Sep 2010 09:00:24 -0700 (PDT),
wrote:

Hi, I mentioned this in another thread but thought I'd give it a
thread of its own.

Can someone help with a formula for astronomical midnight at
Greenwich, in UT, given the Julian Day Number? I.e. the UT of the
first astronomical midnight (lower culmination of the apparent Sun)
following JDN = x.

Ideally I need an accuracy of a few seconds.

You want to get Jean Meeus' book on Astronomical Algorthims. The
answer is from chapter 11.

T = (JD - 2452545.0)/36525

mean sidereal time in seconds = 24110.64841 + 8640184.812866*T +
0.093104*T^2 - 0.0000062 * T^3.

This works only for 0 h UT.

Bud