Purpose

To determine a fairly accurate elevation i.e. altitude (vertical angle above the horizontal: full range, i.e. 0 degrees to 90 degrees) of a star or the Moon (or a landscape object), when it's not too windy, on land.

DO NOT USE FOR THE SUN, for the Sun use the HangDial.

For a faster-to-use but less-accurate 3D print which does the same thing, see the StarSquare.

You can also use this to measure the angular distance between any two things (as long as that is less than 15 degrees, or 20 if using the 'universal' ring), e.g. the horizontal angular distance between two mountains, or the diagonal angular distance between two stars to ensure you have the right stars.

Model Files

There are two set of model files, the standard set, and a set for people with shorter arms (or who want smaller prints)- this smaller set will be slightly less accurate. You can also scale these files. Each set contains 6 files, one for measuring altitudes 0 to 15 degrees, one for 15 to 30 degrees, one for 30 to 45 degrees, one for 45 to 60 degrees, one for 60 to 75 degrees, and one for 75 to 90 degrees. You can scale them to suit your arm-length or e.g. produce a nested (concentric) set you can print in one go.
There is also a 'universal' file which covers -90 to +90 degrees, but is less accurate due to a lack of symmetry: you'll have to come up with your own 'calibrations' (e.g. 'if I use this hole, I need to subtract 0.75 degrees') for it, by e.g. comparing your readings using it to 'true' values from a quality source.

Accuracy

Better than 0.25 degree

How to print it

Print flat (rotate it 90)
0.3 or 0.2mm layer height
NO brim or raft (skirt ok), as want print to be symmetrical
NO supports
Infill: doesn't matter, say 15%
White (or glow in the dark?) filament might be best for night-time visibility
'Random' Z seam location (to stop blobs forming down one side of holes).

After printing

Remove any stringing in the holes using e.g. a small screwdriver.
You can write numbers on the ring to help you using a permanent marker, e.g. on the 45 to 60 ring you might write '45' against the bottom (note: the two pyramids are the 'top' of the ring) large hole on the outside of the StarRing, '50' against the next large hole as you ascend the ring, '55' against the next, and then finally '60' against the top large hole; and then spin the StarRing 180 and do the same for the other set of holes.

Caveat

This thing and the associated PDFs are not intended for life-critical or indeed any applications other than educational only! Use for navigation etc. at your own risk!

Care of the print

Don't twist or squash it, don't leave it in the sun for a long time- you want it to stay a circle else it will lose accuracy.

Using it

If using at night, have a gentle light-source to your side.
Suspend the chosen StarRing from a string, through the hole between the two 'pyramids'. You can tie a loop in the string on the far side (outside the ring) to fit a couple of fingers through. Dental floss, cut at a sharp angle to get it into the hole, works well. Alternatively, you can rest the ring on a smooth cylinder (e.g. a pencil or pen, if cylindrical) in-between the two pyramids, or balance it on e.g. an opened keyring or bent wire.
Let the ring dangle free from the string between you and the star/Moon, and place a finger on each side of the ring. Then grip the ring with those fingers and move it and/or your head until the bottom large cut-out hole on the front face aligns exactly with the bottom large cut-out hole on the back face, and then so-on for all the other holes, making sure you align larger holes with larger holes and not with smaller holes. Release the ring and move it and/or your head until the star/Moon is next to the LEFT (your left) of the ring, moving your head to keep the holes aligned, using the fingers on each side of the ring to gently spin the holes into alignment. Then read off the altitude of the star: each large hole represents an increment of 5 degrees, each medium hole an increment of 1 degree, and each tiny hole 0.5 degrees.
Then, spin the StarRing180 degrees and do it again; average the readings to get your result. By doing this any error from the ring not hanging perfectly vertical is cancelled out. If you are using the 'universal' ring, the pyramids with their holes are 20 degrees apart, and the ring when suspended from a given hole spans a 20 degree range; and for the second reading instead of spinning it 180 you instead ROLL it 180 and take the second reading off the other side of the StarRing: this will cancel out some but not all the errors from the print not hanging perfectly vertically.
Once you have your averaged reading, apply the Refraction correction (and if it is the Moon, also the Parallax correction), and that's the star's/Moon's current altitude: see attached PDF.
You can also use (any!) StarRing to measure angular distances between any two objects- just hold the StarRing using your fingers (ignore the string) and line up the holes and the first object with the 'bottom' hole (which is your '0 degree' mark, then read off the angular distance to second object.

Using measurements of the star's altitude to establish your latitude

Refer to the attached PDFs.

Using measurements of the Moon's altitude to determine the Moon's declination and from that establish your approximate LONGITUDE(!!) and UTC date/time. No clocks required!

Refer to the attached PDFs.

Using measurements of the star's altitude to tell the time

Correct for Refraction, then refer to the PDFs of the StarSquare (altitude->stellar time->'wall clock' time)

Getting the bearing (azimuth) of a star using it

Correct for Refraction, then refer to the PDFs of the StarSquare (altitude->stellar time->(altitude->stellar time, stellar time->bearing)

Using the bearing (azimuth) to a star to tell the time

Correct for Refraction, then refer to the PDFs of the StarSquare (altitude->stellar time->, reversing things as appropriate (bearing->stellar time, stellar time->'wall clock' time)

Note

You can use Long Addition/Subtraction to help you do the calculations in the PDFs, if you don't want to use a pen and paper.