NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunars Calculator (ver. 4)
From: Frank Reed
Date: 2008 Dec 4, 07:32 -0800
From: Frank Reed
Date: 2008 Dec 4, 07:32 -0800
Dave W., you asked: "In the calculator, are the planet distances to center, COI, near, or far?" In keeping with traditional practice, the distances are to the planet's geometric center. So when you shoot a lunar using Jupiter, bring the planet to the Moon's limb and split it. Venus is a problem. When Venus is near the Earth, it has a large apparent diameter and also a significant phase. The best approach that I can think of here is to find out the phase of Venus in advance, and attempt to "visualize" the planet's center in the tiny crescent visible with the sextant telescope. Alternatively, you could attempt to make the limbs match and then subtract or add the semi-diameter of Venus from the sight (for Venus the semi-diameter is very nearly equal to the horizontal parallax on the given date since Venus has nearly the same physical diameter as the Earth). Either approach is extra work. It saves a lot of trouble if you just ignore Venus when it's a crescent. That's what I do. -FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---