It's missing long periods in Jan and Feb. I haven't been able to collect data for those dates yet due to lack of sunny weather converging with noon conflicts on both Saturday and Sunday. But other than that, I've been able to fill it in pretty nicely. The figure 8
shape is really clear, and it is easy to see that the sun returns to the same position year after year.
At some point I intend to work out the math formulas that would convert the shadow points to the actual sun declination and right ascension at mean solar noon, but haven't taken the time yet. There are two big complications to this: the grid
lines do not run perfectly north and south, and the board is not perfectly level. If I ever make a new one I will try to correct for those problems. In the meantime I'm happy with just seeing the analemma traced out.
Most people are mildly interested when I show them, but I figured you'd be especially interested!
Wow! Yeah Steve, I'm especially interested! Is that cool or what? This is what I love about Classical Astronomy. It's real and it's easy to observe and experience if you take a little bit of time out of your day to notice. I give Steve a lot of credit for undertaking this and feel kind of dumb in comparison. I have some perfect south-facing windows here in my office where I
could have been doing this for the last 25 years and it never crossed my mind! So like, DUH! And I'm supposed to be the Classical Astronomy guy!
*************ACTIVITY!!!*************
I'd encourage you all to attempt this
yourselves. Any fixed spot of sunlight or any shadow viewed at the same precise clock time each day will trace out an analemma over the span of a year. You can use a hole in a window shade that casts a sunbeam on the floor or whatever you can think of. You can put a colorful window cling on a window or hang a jewel or other ornament that shines a colorful spot on the wall or floor. The main idea is to mark the spot with the date at the precise minute each sunny day over
the span of the year. Once you create the analemma, you have a calendar that can be used to find the date forever more. The sunbeam or shadow will cross the analemma at the same spot on the same date for years to come. This would be a fun activity with homeschool kids, too bad I didn't think of it when our kids were still at home.
There are
old churches in Europe with analemmas, like the Cathedral of St. Alexander of Bergamo in northern Italy. A sunbeam shines through a little hole and shines onto a meridian marker and traces out an analemma. Some pictures are shown in this link and this link, with accompanying text if you can read Italian.
Once again, my family and I wish you and your family a very blessed and Merry Christmas and a prosperous and purposeful New Year in 2026!
Till next time, God bless and clear skies,
- jay
The Ryan Family
Cleveland, Ohio, USA
When I consider thy heavens, the work of thy
fingers,
the moon and the stars, which thou hast ordained,
what is man that thou art mindful of him? and
the son of man, that thou visitest him?
- Psalm 8:3-4, a Psalm of David