Hello all: If we use a lunar sundial to determine the length of a lunar day (27 earth days), and we are already familiar with the terms full, half and quarter moons, then it would be convenient if there were 100 tics in a lunar day.
If 100 tics equal 27 earth days then 1 tic = .27days = 6.48 hours = 388.8 minutes. On the moon, the sun moves across the 180 degrees of sky in half a lunar day: 27/2 = 13.5 earth days (50 tics). So, 50 tics = 180 degrees or 1 tic = 50/180 = .28 degrees. If a good Tony Moss sundial has 1 minute accuracy on the earth, this means it is accurate to 15deg./60 min. = .25 deg./minute. By coincidence, a high quality lunar sundial will be accurate down to the nearest tic! (6.48 earth hours). For lack of a working camera at any of the lunar landing sites, you might be able to use one of the moon's tall mountain peaks as a perpendicular gnomon with the mountain peak serving as the nodus. These mountains are usualy located at the center of large craters. Using a computer and a telescopic earth cam, you could digitally superimpose an image of the sundial face onto an image of the mountain's shadow on the crater's flat floor. john John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "John Schilke" <[EMAIL PROTECTED]> To: "The Shaws" <[EMAIL PROTECTED]>; "Sundial, List" <[email protected]> Cc: <[EMAIL PROTECTED]> Sent: Thursday, June 28, 2001 7:26 AM Subject: Re: A sundial on the Moon > > Patrick Moore then asked if we could design a sundial, to be placed on the > > moon at "Tranquility Base" - Joe Allen to be responsible for getting it > > there!! > > So, we have a challenge > Indeed! This is worth thinking over. > > > > I regret that I don't know much about the Moon. > > I guess with a day of 27 days or so, we won't be able to use Earth time. > > Tony has suggested a "Luna", subdivided, naturally, into "tics". > This sounds like Tony, and is a delight! Lunar tics indeed! > > John > >
