NavList:

Showing you age there David, and experience.

I am only an amateur when it comes to this nav business but I can recall doing some basic checks on sextants and drift sights on Super Constellations way back in the late 50s, I was but a mere apprentice at the time.

I have been tempted to purchase an aviation  bubble sextant but find I get into enough trouble with a standard sextant.

Interesting posts all the same.

Frank 33.52 S 121.53 E
Frank

They're OK.  Expect between 1.5 to 3 miles accuracy.  Make sure you get one that works though, because the cost of having a broken one reconditioned will be more than the price difference between a poor one and a good one.  In general, a large number of ex WW2 aircraft sextants are now too dirty, stiff, and have too big a minimum size of bubble to be much practical use.  They can be reconditioned.  Paul Brewer's the man for that.  Later periscopic models are more likely to work, but they need some way of holding and powering them.  If you're after shooting stars, look for one with as clean a light path as possible.  The Smth's RAF Mk2B & C(swivel eyepiece)s are a good easy to use models, but don't ever, not even once, not even just a little try, attempt to change from one minute to two minutes or vice versa whilst the clockwork's running.  Try offering this chap 100GBP http://www.ebay.co.uk/itm/RAF-Aircraft-Vickers-VC10-XV104-Periscope-Navigators-Sextant-Instrument-/131364186441?pt=UK_CPV_Aviation_SM&hash=item1e95ea6949 when it doesn't sell at 199GBP.  It looks as if XV104 is currently being scrapped, so less chance of anyone claiming ownership of sextant http://baeg.blogspot.co.uk/2012/11/sunday-25-november-2012-bruntingthorpe.html .  Dave