celestical navigation

[myshelf]

i'm not sure this is the right place for it, but i thought CN can be considered history, so here it is.

at a second hand shop i stumbled over a WW II aircraft sextant the other day. the item was way to expensive to buy just to find out how it works, but i got to read a bit of the manual, not that i understood it.

so, is anyone around here who could explain it?
i know how to use a marine sextant, but it seems to me that is a different world.

[H]

If you know how to use one, you should be able to use the other. The term is Celestial Navigation, navigating by the stars, and was done long before there were sextants.

[myshelf]

well, i know how to take a sight with a marine sextant, reduce it, how to read pup 229 and 249 to arrive at lines of position and so on.

that aircraft sextant doesn't even look like a sextant.

[H]

My assumption was that you were speaking of an aircraft observer's sextant, which predates WW2 as well as later. Perhaps you are speaking of the gyroscopic sextant, something a bit different?

[EDIT]I just did a little checking. I don't know if the following will help or not...
http://www.mat.uc.pt/~helios/Mestre/Nov ... 61if_2.htm

[myshelf]

the type i'm speaking about looks more like a short periskope.
it has to have some sort of artifical horizon and an averager.
now i know a bubble sextant, but how should the averager work for example?

[expat]

I have a bubble sextant that my grandfather "acquired" during/after the WWII. Anyone know how it works, or where I could get instructions for it. It appears to be in working order. Battery compartment has no corrosion and the clockworks still function.

Matt

[myshelf]

if it's a regular marine bubble sextant i can tell you how it works. if it's one similar to the one i described above i'm lost myself.

[expat]

Well, it has periscope affair in it.

Matt

[myshelf]

guess in that case wehave both the same problem

[Woodlouse2002]

As sextant sights depend heavily on the altitude of the instrument from the earths surface to get an accurate sight (the lower the better) it stands to reason that an aircraft sextant would require an artificial horizon to be anything like accurate. So I should assume that the periscope affair is for sticking up through the astrodome to look at the sun while you line it up with a horizon thats part of the rest of the device. The principle should be the same as a marine sextant.

[myshelf]

as i said, the problem is how to take sights, i'm aware that once i have the measured angle the procedure is tha same.

and ex-pat, i can tell you how get to a position from starsights, either using the publications i metioned above, or a calculator.
there's also a bunch of applets on the net that do the calculations.

the basic principle is to calculate the angle above the horizon the sun or other celestial body you want to use would have from an assumed position, then compare that angle with the measured angle and correct the position accordingly.
each sight gives a line of possible positions, after taking severall sights, where the lines cross is your positon.