Is this a sundial? If so, how does it work?

September 7, 2023 8:45 AM

Link to the image. Or are the markings just decorative? I can't figure it out. It's just a circle of glass otherwise.
posted by Borborygmus to Grab Bag (5 answers total)

If you were to hold it vertically, the markings could correspond to the position of the sun at various parts of the day - though it would only be accurate at certain latitudes and certain times.
posted by dmd at 9:17 AM on September 7, 2023

The way that the PM numbers are mirrored makes me think that the sun is supposed to shine through from one side in the morning and the other side in the afternoon. I think you're supposed to find your latitude and use the angle markings to mount it on its edge, so the lines point north-south and the sun hits it edge-on at noon.

Then it casts a shadow on one side in the morning and the other way in the afternoon. If you draw a line on both sides, the number whose shadow hits the line should be roughly the time.
posted by ectabo at 9:28 AM on September 7, 2023 [5 favorites]

Some form of Stained Glass Sundial?
posted by zamboni at 9:31 AM on September 7, 2023 [1 favorite]

It looks like it's missing a gnomon (the thing that casts the shadow on the dial) but this primer says that with glass sundials the gnomon was traditionally mounted separately so as to avoid stress on the glass. It's also a little weird to me that the numbers for AM and PM are oriented in such a way they'd be read from opposite sides, but maybe it makes sense if you also have the gnomon? I'm also wondering if somehow the edge itself is detailed in a way that it casts the necessary shadow, and maybe the 90º marker on the edge is telling you where to align the disk based on latitude.
posted by fedward at 9:49 AM on September 7, 2023

The copyright reads  © Glassmasters 1984, using a logo with a distinctive curved S that matches the logo on a brochure in this Craigslist post.

That brochure gives the address of Glassmasters as 27 West 23rd St, NYC, matching the address given in this 1984 copy of New York Magazine:

Glassmasters' Guild, which has recently relocated, is holding a sale with reductions of 20-40 percent on selected stained•glass items, including reproductions of medieval, Disney, and Tiffany designs. A few examples: slight seconds of small Tiffany-window reproductions. created by the guild for the Metropolitan Museum of Art, were : $65. here $37.50; slight seconds of Disney scenes from Alice in Wonderland. Bambi. Fantasia. and Pinocchio. were $45. here $25. Lead borders on the above are an additional $5. Other stained-glass pieces are now 20 percent off including: pretty standing sundials to put on vour windowsill

Emphasis added. I suspect it sat in a slot in a stand, so you could adjust angles.
posted by zamboni at 12:14 PM on September 7, 2023 [9 favorites]