Cheap and Reliable Altazimuth Mount

Astronomy is an incredible field which connects our consciousness to Universe. Understanding the way our world moves in relation with Sun and stars, allows to grasp the source of day and night succession, of seasons, of many beautiful phenomena. With this simple tool, students from seventh grade can measure ascension and declination of many stars during all the night, and so compile a map from which deducing many fundamental astronomical laws.

To build this set of four sextants you only need cheap and affordable supplies:

• four mid-size plastic plant saucers
• a set of plastic pipes for hydraulics, about 40mm diameter, to be assembled like in picture
• twelve iron square section short pipes and wood rods for optional tripods
• screws and some other simple metal hardware
• the attached psd file contains drawings of vertical and horizontal goniometers with wind rose, so that you can print it but also modify it as you wish
• cement, sand, glue, and some tool

Make a hole in exact centre of the plant saucers, so that small pipes fit in it. Also make some little holes in the lower part of the plastic pipes.

Close with a tape the top extremity of any pipe and push it in place. Optionally make a little hole in the tape and put a pipe in it, it will help to keep the pointer in place with a cord.

Turn plant saucers upside-down, insert some metal rebar in the pipes and all around, and pour cement mixed with sand. Usually you can use a proportion of 1 part cement and 2 parts sand. Let it dry, a few days at least. It will take two or three weeks to reach a good strength. Try to keep it covered and wet.

To add optional tripods you need to follow instructions at step 12.

After a few days you can extract the concrete disk from the plant saucers, and scratch it with sand-paper to finish the surface.

Print the wind-rose with goniometer and glue it on the cement. Under the base glue some rubber feet.

Since concrete could be annoying to move and could scratch other objects, I made a collar with a bike tube.

Print the vertical goniometer, coat it with transparent plastic sheet, and glue it on the side of a pipe. You can try now to assemble the full structure with all five pipes.

Pin a needle to make a pivot for a metal wire. This metal wire stands vertical because of gravity and indicates the vertical ascension of the stars.

To obtain a better loook you can add some rubber disks on both extremities of the pipes.

We need of course also a needle to indicate horizontal declination. I made it with a simple cardboard stripe coated with plastic.

Make same work on all four sextants, and you'll have a complete set, one for each cardinal point. If you assign a cardinal point to every group of students, they will share their results the next morning.

If you want to make cheap and reliable tripods, you have to insert three metal feet under each base. Find a square section metal pipe and cut twelve pieces about 8-10 cm long. Make two holes on opposite sides, to insert screws for tripod legs. Bend some sides to make a better rebar.

Build a set of four jigs to place feet exactly at 120 degrees one each other. The pour concrete and keep it covered and wet for some days.

Meanwhile build all twelve tripod legs as described in pictures. The tringle structure is the only effective solution for a sextant which needs to turn around vertical axes without losing the alignment.

Place also am L shaped metal bar so that it will hold metal rods as in step 19.

When concrete is dry you can extract bases out of plant saucers and place plastic caps on any metal feet.

I coated tripods feet in a dense black protective paint, something like bitumen, so that they will resist water and moisture during the use.

With tapping screws connect tripod legs to metal pipes.

I painted lower parts of any tripod with different colours.

To avoid tripod legs to open and sextant to fall, bend each extremity of metal bars for 1 cm, the place it in holes. It will be sturdy and easy to assemble.

You can now enjoy the experience with your students, they will observe stars every two hours or so, take note of ascension and declination for brighter stars, and draw on a blackboard the course of constellations.

The next morning each group will have interesting experience and results to share with entire class, and they will discover some of the principles of Universe.