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Re: Using any star for a lunar
From: George Huxtable
Date: 2005 Mar 12, 23:38 +0000
From: George Huxtable
Date: 2005 Mar 12, 23:38 +0000
Bill wrote- >I have yet to try lunars, but am slowly moving in that direction. If I >understand the basic concept, we are looking at two bodies that cross the >sky at different rates; Sun 15d/hr, Moon 14d 19', stars 15d 02'.5, and >planets. Perhaps a question born from ignorance, but could the Sun (close >to ecliptic) and Moon be used as well? ============= from George: Certainly, Bill. In fact, Sun-Moon lunar observations have always far outnumbered planet lunars or star lunars. With the Sun and the Moon, there's no problem in identifying which two bodies are being observed. This is always the observation that the beginner should start with, and many never even get round to trying lunars to another body. But there are certain times in the lunar month when the angle between Sun and Moon makes Sun-Moon lunars difficult or impossible, and sometimes a star or planet lunar can be used instead. The Sun is always exactly on the ecliptic (as near as dammit) and the Moon is always within 5 degrees or so of the ecliptic, so the Sun is always close enough to the direction of the Moon's motion. I am puzzled about the value Bill has quoted for the angular speed of the Moon across the sky, at 14d 19'. Where did it come from? The Moon's motion fluctuates a lot, but I would have thought a more representative value would be about 14 degrees 30'. George. ================================================================ contact George Huxtable by email at george@huxtable.u-net.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================
