The solar analemma is the shape described by the sun when photographed over the course of a year at the exact same time of day and same location.* Because the Earth's axis is tilted and its orbit is elliptical rather than circular, it generates an asymmetrical figure of eight. And a beautiful one! So I decided to make an LED chandelier with 365 LEDs, which mimicked the solar analemma and therefore acted as both a stylistic astronomical calendar and a source of illumination for our dining room. I decided to stretch the analemma in such a way that it could be cut out of a 4' × 8' piece of plywood and the LEDs could be placed accurately. This last requirement was really important to me... and made the project vastly more challenging, because every. single. last. LED. needed to be uniquely located and was uniquely spaced.
* this is a famously hard photographic challenge - the first example was recorded by Dennis di Cicco in 1978-9. Check out some of the others. My favorite has to be Tunc Tezel's "Tutulemma": an analemma photograph that includes a total solar eclipse!
Earth's orbit took care of all the pesky details of creating the beautiful shape, and Larry McNish of the Calgary Centre of the Royal Astronomical Society of Canada did all the hard work of creating the spreadsheet that computes the layout. I used his spreadsheet to calculate the solar analemma for the exact latitude and longitude of my house for the calendar year 2016, did some manipulation to convert it into the right aspect ratio to fit it comfortably on to a 4' × 8' sheet of plywood, and imported it into Fusion360 using Add-Ins > Scripts > ImportSplineCSV. That created all the points I needed. I created offset lines 50 mm out from this line on both sides, and extruded the resulting shape 18 mm (I planned to cut it out of 3/4" plywood). I then bored 364 holes (yes, 364; two of the holes at the "X" of the figure 8 almost overlapped, so I averaged their position and just made one hole there) 8 mm in diameter all the way through the material. Another 364 holes 14 mm in diameter were bored in the same position but only 15 mm deep.