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Igor,

Perhaps a slight tangent to your AH/safety question. I have built several AHs (fer3.com/arc/m2.aspx/Tripod-Mirror-Artificial-Horizon-EdPopko-apr-2015-g31098). The 'safest' and the one I use a lot is the common Davis plastic unit with two slanted glass wind shades.  Instead of using water as the reflection medium, I use old motor oil.  Yes, dirty old motor oil!

Why? It is free, self leveling, dark thus I dont need any sextant horizon shades, viscous does not ripple in the wind, does not attract bugs (like molasses), only a high wind causes any ripples and, unlike water, the oil will not fog the glass as the unit heats up in the direct sun.

Clean up is super simple and it's total reuse.  Before putting the dirty oil in the tray, I line the Davis tray with a small piece of kitchen thin-plastic wrap, the kind you wrap up left-overs and store back in the refrigerator.  Thus, the dirty motor oil never actually comes in contact with any of the Davis components. Other trays are possible, I just happened to have a Davis.

When the shooting session is done, I pour the oil back into the original plastic storage soda bottle (the one I filled at the local garage). Only a small oil film remains on the plastic wrap and I fold the wrap inwards and throw it away after shooting.  My hands never actually touch the oil. If I think I'll come back later in the day or a day later, I just leave the oil in the tray, it does't evaporate.

There is one down side to using oil. You can only shoot the sun or moon at night. It is not relective enough to shoot stars. For this, I use the AH in the link above.

Ed