Re: "season dial"

[Chris Lusby Taylor]

-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Deamicis-Roberts Sent: Wednesday, 10 October 2001 10:10 PM To: sundial@rrz.uni-koeln.de Subject: "season dial"  Hello, I live on a large piece of property and wanted to build a large "season dial."  I imagined being able to get up at sunrise on any morning and be able to see were in the seasonal cycle we were in: how many days left in spring, summer, fall ( also marking equinoxes, olsitices, even metor showers, and the sort)     I imagined a large sundial-like device. Are there any plans for something like this? Thanks for your help, Best regards,   Mike Deamicis-Roberts  I didn't see this original either. I have designed a sundial that only shows the season. It does not show the time. The sundial is, in essence, an equatorial ring dial with the roles of gnomon and dial reversed. So the ring casts a shadow on the 'gnomon' at a height that depends only on the sun's declination. The 'gnomon', instead of being a thin rod, can be extended to look like the gnomon of a normal horizontal dial. This gives it two faces that are the dial surfaces. Outside the arctic it needn't be thin, as the sun never shines from certain directions, and its two faces can be rotated independently about the central axis, so that it becomes wedge-shaped. The axial edges can be calibrated in any function of the declination, such as the date, Zodiac, length of day, EoT, time of sunset (this could incorporate the EoT if desired)... As you cannot distinguish between spring and autumn merely from the sun's position, you need two scales. The two surfaces of the dial can serve this purpose. Use one for each half of the year. Admittedly, they aren't both illuminated all day long, but the shadow is read where they meet, so it's not difficult. One way to make the dial is to use a cone for the ring. I have attached a Zip file with a Windows bmp of a sketch. The ellipse is the top edge of the cone. It casts a shadow on the cheese-wedge-shaped dial. The shadow is read at the edge of the dial. The original was made by me in ceramics. John Moir created a cardboard version of it, which was included with the Bulletin of the British Sundial Society a few years ago. He proved that it can be made from a single disc of sheet material, with three folds but without cutting, for a range of latitudes that includes England (around 51 degrees). It can be made from two pieces for any other latitude. Please feel free to adopt, adapt and/or improve this design. Hope this helps Regards Chris Newbury, England 51.4N, 1.3W     Attachment converted: Macintosh HD:Conedial.zip (pZIP/pZIP) (000341DB)