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Re: equinox
From: Fred Hebard
Date: 2004 Mar 21, 15:20 -0500
From: Fred Hebard
Date: 2004 Mar 21, 15:20 -0500
My calculation was based on the Nautical Almanac, which had a 0 degree
declination for the Sun exactly at 6:48:00 UT. The Sun's GHA is
adjusted by up to 1.5' to reduce the error arising from ignoring the v
correction. The GHA of the Sun may be in error by up to 0.25'.
MICA reports:
Sun
Apparent Topocentric Positions
Local Zenith and True North
Location: E 79?51'26", 0?00'00", 0m
(Longitude referred to Greenwich meridian)
Date Time Zenith Azimuth Distance
(UT1) Distance (E of N) to Object
h m s ? ' " ? ' " AU
2004 Mar 20 06:48:00.2 0 00 02.4 111 21 02.9 0.995960666
2004 Mar 20 06:48:00.3 0 00 01.1 141 03 00.3 0.995960666
2004 Mar 20 06:48:00.4 0 00 01.2 223 27 24.7 0.995960666
2004 Mar 20 06:48:00.5 0 00 02.5 249 45 07.1 0.995960667
The Naval Observatory reports 6:49 for the vernal equinox:
2004 2004
Perihelion Jan 4 18 Equinoxes Mar 20 06 49 Sept 22 16 30
Aphelion July 5 11 Solstices June 21 00 57 Dec 21 12 42
Perhaps one of the astronomically literate will explain the discrepancy.
On Mar 21, 2004, at 2:01 PM, Gary Harkins wrote:
> In a message dated 3/21/2004 1:23:55 PM Eastern Standard Time,
> legras@MAD.SCIENTIST.COM writes:
> spring equinox was on earth 20/03/2004 at 06:49 utc according to Jean
> Meeus' sky calender 2004
>
> On which planet does it occur at 6:48 ????
>
> Using the Nautical Almanac and interpolating between .8' South at 0600
> utc and .2' North at 0700 utc the equinox calculates to occur at
> exactly 0648 utc. Are you saying that Jean Meeus' sky calendar is
> more accurate than the nautical almanac? Does he carry his
> calculations out to more precision than .1' of declination? And who
> cares anyway, it's cold as most winter days here regardless of what
> the calendar says.
