NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Parallactic retardation - don't give up so easily.
From: Bruce Stark
Date: 2004 Jan 9, 18:29 EST
From: Bruce Stark
Date: 2004 Jan 9, 18:29 EST
Frank, I believe the reason altitude seems to make a difference is that the moon is highest when near the meridian. It is also apt to be higher when the observer is in lower latitudes. The two things that matter are the observer's latitude and the moon's closeness to the meridian. Latitude determines how far the earth's rotation moves the observer in an hour's time. Closeness to the meridian determines the angle between that line of motion and the line from the observer to the moon. The greater the angle, the greater the parallactic retardation. The angle is 90 degrees when the moon is on the meridian, regardless of the moon's altitude. Bruce
