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Re: Sun sights during an eclipse: "bad limb" calculation
From: Geoff Hitchcox
Date: 2023 Oct 7, 03:17 -0700
From: Geoff Hitchcox
Date: 2023 Oct 7, 03:17 -0700
In my last post, I gave the following output of the JPL Horizons Ephemeris.
Date__(UT)__HR:MN:SC.fff, , ,Azi_(a-app), Elev_(a-app), Ang-diam (arc seconds),
2023-Oct-14 18:20:40.000,*,m, 193.862553, 52.525591, 1828.926, MOON position
2023-Oct-14 18:20:40.000,*,m, 194.280049, 52.793284, 1924.160, SUN position
I then just happened to use Frank's USNO clone ephemeris to check the above numbers, and suddenly found that the SUN was OK, but the Elev of the Moon was out by more than half a degree. A quick check using other sites, showed that Frank's ephemeris was correct, and so it was Horizons that was giving inaccurate elevations for the Moon. As a clue that some parameter was wrong at Horizons, the "declination" of the Moon was out by a similar amount.
Pasadena we have a problem !
A few quick checks at other times and places on the Horizons site (for the Moon) showed a consistent more than a half degree error in generating the Elevation (Azimuth appears OK). In the meantime, I guess I have to wait, to see if the problem is resolved overnight, or does someone on Monday have to "Turn it OFF and turn it ON again".
So my playing with lots of number crunching - will have to wait a while.
Regards, Geoff Hitchcox, Christchurch, New Zealand.
