NavList:

I have received inquiries re the various Kollsman artificial horizon sextants. From examining and servicing them, I note the following:

1) The Kollsman periscopic bubble sextant must be used with the mount to be an effective instrument. Mounts are few and far between. This instrument has an internal combining pellicle which can wrinkle due to moisture over time. There is a desiccant capsule inside which must be opened and heated to renew the desiccant and absorb moisture. Field of view is limited and necessitates precomputation of star sights. The Air Almanac has star pattern diagrams to help orient the navigator. A 28V power source is required. The bubble chamber is filled with the correct viscosity Dow Corning silicone fluid which doesn't evaporate (an advantage). The averager is an integrating 2 min. clock mechanism.

2) Kollsman MA-1 pendulous mirror sextant is an instrument designed to be hung in a plane's astrodome. It is heavy, has a limited field of view and again, a combining pellicle with desiccant. The artificial horizon is a mirror suspended in a silicone fluid reservoir (which must be totally filled with the correct viscosity silicone oil). Again, a 28V power source is required. The averager is the same as on the periscopic.

3) Kollsman MA-2 is basically the periscopic bubble sextant without the periscope. it is heavy and was designed to hang in a plane's astrodome. Same issues as with the periscopic. Advantage is the silicone fluid filled bubble chamber. Repairing and servicing these instruments requires specialty tools and optical collimators. Index error can be determined, however, by the Polaris - latitude method or by working a series of sights for a fix. These were post WWII instruments issued from the 1950s to the present.

I have limited my instrument work to WWII and earlier bubble sextants as many have been surplused out and I can obtain the instruments and some parts. I have the tooling and an optical collimator to calibrate them. They were designed as hand held or hand held/astrodome hung instruments which make them navigator friendly. I now work on and sell the following instruments only: Link A-12; Bausch and Lomb A8-A; Bausch and Lomb AN5854-1; B&L Bureau of Standards Sextant

Robert Swartz
Ph. 773-330-0860 USA
jujutsu(at)hotmail.com