It’s been a few years since we had a substantive thread on sundials. I’ve always found them fascinating and last year I discovered NASS, the North American Sundial Society. After poking around there a few months, I joined. I’ve made a correction and update to the registry and DB.
Here are Google image searches of some of the different types of sundials (I created these shortened URLs and they are safe) —
That is interesting. I have set up a couple of sundials, but was not aware that I was supposed to register them…
There are various programs (eg ShadowsPro - sundial and astrolabes) that automate things by letting you select from a list of common types of sundials, input your location and other parameters, and quickly calculate what the plate would look like corresponding to your design.
This is a famous such design
, unfortunately, I have not had the chance to visit it in person.
I suppose I have always appreciated sundials that let you read mean time directly. These sorts
look cool, but I do not like the fact that you have to manually adjust them according to the Equation of Time. I would rather have a planar dial with analemmas plotted out on it but no mechanical adjustment necessary after the initial installation.
Well, that precisionsundials.com site, an image from which I linked to above, advertises ready as well as custom designs and materials like granite, silicon bronze, and aluminium-magnesium, at prices of several grand. But that is really a boutique/custom sundial business.
ETA not for your relative, but one sundial I actually made once, is Isaac Newton’s method of a mirror on a window sill casting a spot of light onto the bedroom ceiling.
I’ve been working recently on analemmas. I thought that I had found an ancient analemma marked by large rocks at an American site, but after performing the calculations I realized that it wasn’t really the correct shape or proportion. (In fact, none of the suspected ancient analemmas around the world actually are analemmas. It’s just similarity of shape and, in some cases, orientation).
However, in recent years there have been several modern ground analemmas. There’s one in France thought to date back centuries, and one in Italy that over 150 years old.
And there are several in Australia made recently, for some reason.
Nice and accurate, and corrects for the equation of time/time zones, but this style of dial is more like an instrument you actively use than a purely decorative object standing in the garden. You adjust the vernier every day to keep it correctly reading mean time.
@CalMeacham, about the analemma traced by the sun, years ago at Stanford Hospital, in the main corridor by the main entrance, they had a nice, framed time lapse photo of the sun above the Stanford campus, and the analemma was very clear.
Have you seen the article about all the mission churches in California where the church was built and statuary positions so that the statue of the patron saint is illuminated on the saint’s day, or the altar is illuminated on the solstice.
Which one is that? It does not have any curved hour lines or require you to rotate the dial manually?
ETA I have not yet considered all the possibilities, but, ignoring the potential difficulties in precisely shaping and mounting the wires, with a bifilar sundial you have the freedom to use arbitrarily shaped and positioned curves for the gnomon, therefore letting you control the resulting dial in exotic ways.
The wiki is not as good as it should be, but the pix in the OP’s link lead to some other reading on point.
As best I can put it together (and no guarantees expressed or implied) … if you correctly arranging the two straight wires in 3D space versus the plane of the dial and the latitude and orientation of the dial then the point of intersection of the shadows as projected onto the dial deals with EOT. Depending on other details you may need curved hour lines inscribed on your dial but not necessarily.