Hello David: My suggestion would be to make an typical vertical east sundial and add a simple moonlight time conversion chart with simple instructions.
I often make horizontal dials with these charts carved into the dial face. Perhaps the most famous of these sundials with moonlight time conversion charts is the big blue wall dial at Queens College in Cambridge. http://www.quns.cam.ac.uk/queens/images/sundial.html Here is a copy of the moonlight conversion chart- "Telling Time by Moon Shadows" that appears in my Sundial Owner's Manual. (see attachment). Feel free to use it or modify it as needed for your project. Here is the text from the Manual that I wrote to explain how to read sundials by moon shadows. You may copy or use any of this if you want: MOONLIGHT READINGS If you look at the movement of the moon during the course of a night and its position in the sky, you will see that it pretty much follows the same path as the sun. We all have seen that on a full moon, the moon is opposite the sun near the horizon at sunrise or sunset. We see the full moon rise as the sun sets. Therefore, when there is a full moon, it will act like the sun at night, casting a shadow and showing sundial time. Since the moon's orbital plane is tilted 5 degrees with respect to the earth-sun plane, a good reading can be off by as much as 45 minutes. Every night, we see that the moon has moved east in the sky and that the phases change. The phase that the moon is in is proportional to its age. We can find out the exact age of the moon in almost any calendar or we can estimate its age by looking at the phase. The easterly distance which the moon moves away from the sun each night decreases the time shown on the sundial by about two minutes an hour, or 48 minutes a day. This means that on a full moon, no corrections will have to be made, but the night after a full moon, you must add 48 minutes to sundial time. If your "moondial" says it is 12 midnight, it is actually 12:48. The moon time on your sundial runs "fast" before a full moon, and "slow" after a full moon. In order to use the chart (Fig. 6) to make a moonlight reading, first determine the number of days the moon is from being full, using either a calendar or by looking at the moon phase. If the date is within two weeks before a full moon, the moon is fast and you subtract the correction. If the date is after the full moon, then moon time is slow and you must add the correction. Finally, for more accuracy, correct for the Equation of Time and use the EXACT age of the moon in the calculation. Interesting note: The sundial will show perfect time on the nights on or near a partial or total lunar eclipse because the earth, the sun and the moon are in perfect alignment! Note: You can't tell time by moonlight on analemmatic sundials. Good Question, John -----Original Message----- From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of David Sent: Tuesday, May 13, 2014 11:30 PM To: Sundial list Subject: Moon dial. Dear All, I have had a request to construct a moon dial for a vertical east-facing wall. This is new territory for me. Can anyone point me in the direction of sources/computer programmes that would give me guidance? David Brown Somerton, Somerset, UK --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
MOONLIGHT SUNDIALTIME CONVERSION INSTRUCTIONS.pdf
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