A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Paul Hirose
Date: 2019 Jan 10, 20:24 -0800
On 2019-01-08 14:45, Robin Stuart wrote: > Maybe the software available on the sight can produce a list local circumstances of stars down to magnitude 6.5 but I wasn't interesting in digging around in it. I also thought it was pretty unlikely to compute longitude and GMT given latitude and local mean time, No, the IOTA site doesn't do any of those things. But it does provide occultation predictions for sites in its database. These can be used as test problems. For instance, see the January 18 occultation of zeta Tauri. http://www.lunar-occultations.com/iota/bstar/0118zc847.htm The first site on the list is Benguela, where disappearance occurs at 18 14 36 UT. Further down the page we see that re-appearance is at 19 19 20. Still further down we see the coordinates of site Benguela: S 12 36.5 E 013 24.2. (On the web page the format is east longitude first, latitude second.) If your software is accurate it should closely match that prediction. My Lunar program has zeta Tauri .02′ outside the limb at the disappearance time given at the IOTA site, .01′ inside the limb at the re-appearance time. If I apply the conventional offset for center of figure, the re-appearance improves a tiny bit to .00′, but there's no change at disappearance.