Hello Louise and my friends on the sundial mailing list,
At the NASS Conference in Banff this summer, Tony Moss gave us a preview of your very high latitude sundial project. It is a great design. We were pleased to see how you and Tony have solved many of the design problems and incorporated local themes to create a remarkable sundial, unique to your location. The concept of using this sundial as a moondial is an excellent one for your polar latitude as the full moon will be high in the sky during the winter months when the sun remains below the horizon. However bringing together solar and lunar time is a very complex problem that has perplexed time keepers and calendar makers since time was first measured. It is very difficult to go beyond the average correction with a graph on a sundial. The orbital dynamics of the sun and moon are just too complex, except for days like today. At the time of a lunar eclipse, a sundial works as an accurate moon dial with lunar time being exactly 12 hours different from solar time. Rather than providing useful advice, let me repeat a whimsical solution to this serious design problem. Several years ago this topic of moon dial corrections was reviewed on this list in response to John Carmichael's good question . My contribution at that time was a note "Moon Madness" which reviewed the complexity of the relationship between the solar and lunar orbits and proposed a correction device driven by ocean tides. Unfortunately the astro archives http://www.astroarchive.com/ are down and my files still packed so I cannot retrieve a copy of the original note. But I am pleased to report that I am now able to act on the moon dial tidal corrector proposal and reduce the invention to practice. I have moved from the mountains to the sea, from the Rockies to the Pacific Coast. As I write this note I can now view the ocean 75 meters due east from my home office window. This lunar correction device would sense the height of sea level to adjust an equant corrector on the moon dial. It would have to be tuned to the monthly lunar cycle of spring and neap tides and dampened to ignore the diurnal rhythm and even higher frequency wave action. The yearly cycle of perigean and apogean tides may also have to be considered. This is going to take a lot of research and I will need assistance from creative inventors like Rube Goldberg, Heath Robinson or Gyro Gearloose but I believe that they have passed away. Perhaps Paul Nibley could help. He demonstrated some remarkable sundial alarm devices at the recent NASS conference in Banff. I will also need help with the mathematics. I can handle the harmonic functions with epicycles but need assistance on string theory. There will an opportunity to establish the initial data point tomorrow night, a boundary condition as the moon rises in the umbral phase of the lunar eclipse. At sunset and moonrise, I plan to walk down the driveway, across the road to the shore. Here I hope to mark the height of the tide and simultaneously observe the eclipsed moon rising across the Juan de Fuca Strait, above the San Juan Islands and the distant snow capped volcanic peak of Mt. Baker. Please treat this whimsical note as my official change of address to all on the sundial mailing list. I have missed this correspondence for the last several months as I have been in transit. Cheers, Roger Bailey Walking Shadow Designs 3-9494 Lochside Drive Sidney, British Columbia Canada, V8L-1N8 (250) 656-1577 [EMAIL PROTECTED] N 48.6, W 123.4 Louise Rigozzi <[EMAIL PROTECTED]> wrote: Dear Sundial Mailing List members, I have just joined the list and have quite a tricky question to ask already! I am working with Tony from Lindisfarne Sundials in England to create a sundial at a very high latitude (78 degrees) and I am including a correction graph for reading from the moon's shadow. This is because for three to four months of the year there will be little or no sun. I have made the graph illustrate the principle that the moon is 48 minutes 'fast' each day before the full moon and 48 minutes 'slow' each day after it. The graph hopefully gives the idea that the more precise you can be with the number of days (and even half or quarter days) you are from the full moon, the more accurate your reading will be. If anyone is interested in seeing it, I can JPEG it to you. My main question is, after adding/subtracting the hours and minutes from the reading of the moon's shadow, whether you then need to add/subtract the minutes according to the Equation of Time (! ! which will also be shown on the dial face) for that day of the year. Thanks! Louise Rigozzi -
