This "artificial horizon" can be used in cunjunction with a sextant to practise celestial navigation at home. Just print the parts and get hold of a pair of plain window glasses with a thickness of 2 mm and 125 mm * 125 mm length and width (I paid 4 € for both of them at the local glazier).

Stick the two sides (they are identical) in the respective holes in the bottom part and fill the bottom with 1 to 2 cm of some fluid. A viscous fluid (motor oil, molasses) might work better, but even water will do if it is not windy. Then insert the two glasses into the guides on the two sides. These windows will stop the wind from messing up the fluid. You can improve wind protection by applying some adhesive tape to cover the remaining gaps.

Before you start working with your sextant please ensure that you have the appropriate filters in place, especially if you want to measure the sun. You MUST also take care that there is a filter towards the horizon as you will be looking at the reflection of the object! If your sextant does not provide a filter in the horizon line of sight one possibility is to darken the window glasses of this artificial horizon with appropriate filters. Please be careful!

Look for the reflection of the celestial body you want to measure on the fluid and then point your sextant to that reflection. Then bring your object down to this reflection. For a star or planet (which are very, very hard to measure with an artificial horizon) bring the two images on top of each other. For the more realistic readings of sun and moon move the two images to just touch each other, the image which is brought down from the sky defines whether you measure lower or upper limb. Now read the angle from the sextant and apply the index correction. Next, DIVIDE THE ANGLE BY 2 as you measured between object and reflection and not object and horizon. Afterwards the corrections are applied as usual, however, there is no correction for dip.

Once you are finished, just take out the glasses and the two sides and store all parts in the bottom part. They fit in quite nicely.

I did some experiments to find out which fluid works best (see relevant picture) and found that plain water is perfect, but only if there is absolutely no wind. You can try and cover remaining slits on the artificial horizon to protect from wind, but this will bring you only so far. With moderate wind present, I found motor oil performing quite well, whereas at temperatures between 10°C and 20°C I was not happy with molasses or syrup. These might do their job at higher temperatures, however.

Enjoy and help keeping this wonderful art of navigation alive!