A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Bill Morris
Date: 2008 Jul 10, 22:40 -0700
The British Mk IX is about 200 grams lighter. and is my favourite because all the controls come readily to hand, it is easy to use and read and you have a reasonable chance of getting one that works. With the exception of the averager on the Mk IX A, the works of the Mk IX series are accesible and usually easy to fix. The bubble assembly is also easy to refill. My A7 has a vapour pressure bubble chamber which, if empty when you get it is very difficult for the non-specialist to refill. Many of the WW II US instruments suffered from "complification" and some used 4 prisms, heavy and expensive to produce. The AN 5854-1's averager(strictly, a median device)is temperamental and hard to fix if it has suffered corrosion in storage. The AN 5851(Navy Mk 5)is heavy and clunky and initial setting of its averager needs care. The A10-A is perhaps the handiest instrument to use, provided the electrical marking system is in good order. It is not impossible for a reasonably handy person to fix the system, once it has been understood. The A10 uses the Mark I finger to operate the marking pencil. That leaves rarer instruments, like the A8-A and the Navy Mk IV. The latter was plainly not a success and if you find one, the averaging system will tax the average person to fix. The A12 is a favourite of many people and was designed to be cheap to produce(some of the others cost almost the price of a small home to produce). The arc and vernier on mine are poorly cut, but if you can get one free from corrosion and in working order it would be a good one to start with. The Achilles heel of nearly all the bubble sextants is the bubble chamber. For practical purposes, you cannot refill a vapour pressure chamber. Happily, most of the later bubble sextant produced used a different system with an air reservoir; and these are fairly easy to refill. The MA series are, alas, expensive and do not often come on to the market. Bill Morris On Jul 11, 1:54�pm, "Gary J. LaPook"
wrote: > My fravorite is my MA-1 which isn't a bubble sextant but a pendulous > mirror type and my second favorite is the MA-2 with a bubble. If you > want a light, simple sextant get a Bendix A-7, it is the lightest bubble > sextant I have. > > gl > > > > glap...---.net wrote: > >Here is a link to a site with discriptions of many types of bubble > >sextants: > > >http://home.earthlink.net/%7Es543t-24dst/airnav/index.html > > >gl > > >On Jul 5, 3:19 am, glap...---.net wrote: > > >>You should also check the files section of the Yahoo sextant group for > >>more information on sextants. > > >>http://groups.yahoo.com/group/Sextants/files/ > > >>gl > > >>On Jul 3, 5:14 pm, bubi352 wrote: > > >>>I am new to this group and new to celestial navigation. I currently > >>>work as an airline pilot and fly extensively over water at night. I > >>>have developed a keen interest in determining my position the old > >>>fashion way. > > >>>Could someone tell me which bubble sextant I should buy? > >>>What should I be looking on a bubble sextant? > >>>Where can I buy one? > > >>>Thank you in advance. > > >>>Bubi- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To unsubscribe, email NavListemail@example.com -~----------~----~----~----~------~----~------~--~---