A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2020 Feb 3, 09:58 -0800
Jim, you wrote:
"This is all very interesting. What do you (Paul and/or Frank) use to determine the relative angular velocities of, say, the Moon and Venus? Are you using the prediction software on ReedNavigation and finding the rates in a one or three hour period?"
Yes, it's quite simple. You can just look at tabulated lunar distances. Take the difference in the tabulated distances (convert to minutes of arc if necessary). Determine the number of elapsed seconds of time between the entries (3600 for one hour tables). Then get the rate of seconds of time to minutes of arc:
Rate = 3600sec / Diff.
The rate that you find will be about 120 seconds per minute of arc of distance. Does this sound familiar? It should. It's prominently spelled out on page 2 of the notes from the Lunars class you attended.
"Can Stellarium be used for this purpose?"
Only for very rough estimates, not really relevant for lunars work. There is an angle measuring tool in Stellarium, but it's difficult to use over large angles, and it has no "snap-to" capability that would allow it to measure exact angles from one celestial object to another. It's only as good as your point-and-click skills.