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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Modern Lunars
From: Paul Hirose
Date: 2016 Sep 23, 20:53 -0700
From: Paul Hirose
Date: 2016 Sep 23, 20:53 -0700
On 2016-09-23 16:58, I wrote: > HORIZONS delta T is .203 s less than Antoine, so it thinks Earth has > rotated further east. To get compatible azimuth and altitude you must > move the observer west to compensate. Convert .203 s to arc and get a > longitude correction of 0.00085° west. That works if the time scale is TT. But HORIZONS also takes input in UT1. You could simply use 08h04m52.32 per Antoine's document. TT will be off by .203 s, equivalent to about a tenth second of arc for the Moon, much less for other bodies. That's close enough. In cases where the TT error is not tolerable, input time in UT1, adjusted to get the correct TT. Now UT1 is wrong, but you correct that with an offset in longitude.
