Nocturnal Celestial Stardials were originally called "horologium nocturnum" (time instrument for night), or nocturlabes. Sundials work great, but only during the day. Nocturnal Stardials tell time at night by measuring the stars. The dials move. It works like a charm. It needn't even be configured to longitude and latitude like a sundial.
This long-forgotten instrument aided a few lucky navigators and charmed romantics of the Renaissance. Earliest references include Cosmographicus Liber in 1530, Arte de Navegar, in 1551, and Horologiographia, The Art Of Dialling in 1626. 'Twas rare then as now.
The outer disc is marked with the months as well as an indicator for each of the 365 days of the year. The inner disc is marked with hours and 5-minute increments. The pointer rotates on the same center axis as the discs. The center axis has a sight hole through which the North Star Polaris can be aligned.
In the northern hemisphere, all stars will appear to rotate about the North Star, aka Polaris. The North Star is very close to the north celestial pole, but about 434 light years away.
The time can be read on my Nocturnal Stardial from any of three reference constellations: Big Dipper (Ursa Major), the Little Dipper (Ursa Minor), or Cassiopeia.
Recommended Materials and Processes:
ï· Computer with internet access
ï· 3d modeling software (or download my 3d model for free)
ï· access to 3d printer (I use Shapeways.com)
Step 1: 3d Modeling(?)
1.) model your own in 3d design software. Rhino costs $995. or $195. for students and teachers (2012 numbers).
2.) Why pay a thousand bucks for modeling software? Several excellent FREE 3d-modeling software can be found at:
3.) Download my model for free. I believe it is the only downloadable 3d Nocturnal Stardial model anywhere in the world. It's available here:
Step 2: Building in Rhino
This downloadable PDF below can be cut apart with scissors and assembled with a rivet or eyelet into a functioning paper Nocturnal Sundial. Instructions for that are to be found in my instructable "2d Nocturnal Celestial Stardial TJT1/6" found at:
However, if you are prepared for some 3d modeling, then this PDF will give you the engineered, basic architecture from which you can create a unique, and functioning 3d model.
Step 3: 3d Modeling Overview
In Rhino, I colored the 3 components differently to visually distinguish them:
Dial A is blue
Dial B is red
the main piece is green
These 3d objects are built of many pieces. For example, the green component has 365 geometric shapes arranged symmetrically around its circumference, just for the days. The overall number of components to the stardial 3d model is about 1,000. It is not as hard to model as one might think. For example, the 365 units around the perimeter are actually just 73 identical sets of 5 units.
Illustrating each step in modeling this object may be too lengthy for an instructable. However, one could model an equally-well-functioning stardial much more quickly. For example, each of the three components could be essentially planar. Printing out and assembling the paper PDF Nocturnal Stardial would help one to see the essential simplicity of design and function. That's a great place to start. My design is a whole lot more sculpturally intricate than necessary, but that's how I roll.
My 2 previous instructables walk through the actual modeling steps of building two different 3d models form beginning to end. Here they are:
Step 5: How to Operate the Nocturnal Celestial Stardial
1.) Find one of the 3 reference constellations, the larger reference star of it in particular.
2.) Align the appropriate constellation dial (Dial B) to the day's date.
3.) Hold instrument in a vertical position whilst facing north.
4.) Sight Polaris, the North Star, through the hole in the center of the instrument.
5.) Rotate the long arm (Dial A) to point to the reference constellation.
6.) The time units on Dial B are in 5-minute increments. The flat edge of Dial B will show the time increment to the nearest 5 minutes.
Note: for greater accuracy one could point directly to specific stars within the chosen constellation:
ï· Schedar within Cassiopeia
ï· Kochab within Ursa Minor (the Little Dipper)
ï· The Pointers within Ursa Major (the Big Dipper)