NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Venus with Earth Oblateness
From: Michael Dorl
Date: 2004 Oct 13, 14:24 -0500
From: Michael Dorl
Date: 2004 Oct 13, 14:24 -0500
Don't know what I might have done but George says I sent some html.
So here's another try.
Here are the bloody details on the calculation of TPC for Geocentric coordinates from Mosier's
routines for Venus and the Moon
11/9/2004
11:13:05
dt = 64.4 seconds
temp = 5Cpressure 1010 MB
elevation 294M
Venus Moon
geocentric RA 10h34m45.1022s 9h37m13.8949s
diurnal aberration 0.0076s 0.0113s
dirunal parallax 0.3498s 2m7.3158s
refraction -5.6126s -3.2805s
tpc RA 10h34m39.8470s 9h39m17.9415s
geocentric DECL 9d40'04.3470'" 19d29'00.7421"
diurnal aberration -0.0346" -0.0573"
diurnal parallax -4.8748" -26'23.5639"
refraction 1'18.7829s 41.3482"
tpc DECL 9d41'18.2205" 19d3'18.4692"
I can supply the details on the J2000 to Geocentric transformation if that would help but I think we all three agreed on the Geocentric position.
Calculating Venus/Moon Ctr/Ctr distance from TPC coordinates, one gets 16d20'22.16". Assuming Moon semi-diameter of 15'3.876" gives distance from venus to Moon limb of 16d05'18.284" = 16d05.3"; half way between your two estimates.
As far as I can tell there is nothing in the routines to allow for oblateness of the earth. One can specify a elevation. Looks like the earth is assumed to have a radius of 6378137 Meters, same as equatorial radius in my 1988 AA page K6.
If I include an elevation of -9600 meters, I get a ctr/ctr distance of 16d20'25.88". Taking off a moon semi-diameter of 15'3.88" gives a ctr to limb distance of 16d5'22" or 16d5.37' which is close to Frank's 16d5.5'. I got the -9600 meters by considering the earth to be an oblate spheroid. I think Mosier considers the earth to have an equatorial radius so setting the elevation negative should compensate for the oblateness.
Michael
Here are the bloody details on the calculation of TPC for Geocentric coordinates from Mosier's
routines for Venus and the Moon
11/9/2004
11:13:05
dt = 64.4 seconds
temp = 5Cpressure 1010 MB
elevation 294M
Venus Moon
geocentric RA 10h34m45.1022s 9h37m13.8949s
diurnal aberration 0.0076s 0.0113s
dirunal parallax 0.3498s 2m7.3158s
refraction -5.6126s -3.2805s
tpc RA 10h34m39.8470s 9h39m17.9415s
geocentric DECL 9d40'04.3470'" 19d29'00.7421"
diurnal aberration -0.0346" -0.0573"
diurnal parallax -4.8748" -26'23.5639"
refraction 1'18.7829s 41.3482"
tpc DECL 9d41'18.2205" 19d3'18.4692"
I can supply the details on the J2000 to Geocentric transformation if that would help but I think we all three agreed on the Geocentric position.
Calculating Venus/Moon Ctr/Ctr distance from TPC coordinates, one gets 16d20'22.16". Assuming Moon semi-diameter of 15'3.876" gives distance from venus to Moon limb of 16d05'18.284" = 16d05.3"; half way between your two estimates.
As far as I can tell there is nothing in the routines to allow for oblateness of the earth. One can specify a elevation. Looks like the earth is assumed to have a radius of 6378137 Meters, same as equatorial radius in my 1988 AA page K6.
If I include an elevation of -9600 meters, I get a ctr/ctr distance of 16d20'25.88". Taking off a moon semi-diameter of 15'3.88" gives a ctr to limb distance of 16d5'22" or 16d5.37' which is close to Frank's 16d5.5'. I got the -9600 meters by considering the earth to be an oblate spheroid. I think Mosier considers the earth to have an equatorial radius so setting the elevation negative should compensate for the oblateness.
Michael