NavList:

I have gotten interested in celestial navigation, and would like some
advice in choosing a sextant. 

I would like to be able to take sightings from my New Hampshire home,
which is some distance from the water.  That pretty much rules out a
regular sextant.

We are also surrounded on most sides by tall trees, which would make
it hard to use an artificial horizon (limited to 60 degrees
elevation).  Besides, I want to make star sightings, which seem pretty
difficult with reflections off water.  (I could try to get hold of
enough mercury to fill an artificial horizon, but it would probably
not be worth the hassle.) [1]

My first feasible alternative would be a bubble horizon for a regular sextant:

http://www.celestaire.com/catalog/Marine_Sextants/Cheap_Sextant/ $27
http://www.celestaire.com/catalog/products/0511.html  practice bubble horizon $49
http://www.celestaire.com/catalog/Marine_Sextants/Cassens_and_Plath/ $900

The last one is definitely out of my price range. 

I have a couple of questions:

1) I'd like to know if these levels are coordinated, in the following
sense: suppose I start with both a star and the bubble centered in
the image, then I lower the sextant so the star rises half way to the
top of the image.  Does the bubble rise to the same height?  That
would greatly simplify the measurement.  Of course, the bubble would
still be sensitive to linear acceleration, which would make no
difference to a regular sextant.

2) Does Celestaire's "practice" bubble horizon fit on any of the Davis
sextants?


My other alternative is a bubble sextant, e.g. one of those at eBay
designed for aircraft:

Kollsman MS28011-S
Kollsman 1471-01
Bendix AN-5851-1
Link A-12

3) Are these set up for star sights, as well as sun and moon?

4) At least some of these call for 28 VDC.  Is that only required for
the averager, or also to illuminate the bubble or for some other
function?

5) I can't judge size very well from the pictures.  Are these sextants
too heavy or bulky to be hand held?  (Although I think it would be
cool to mount one in a sun roof :-)


I'd appreciate any pointers.

         - Jim Van Zandt


[1] I see Lewis and Clark sometimes used a carefully leveled mirror
  http://www.davidcortner.com/2822/mandan_moon.html
I suppose I could try that.


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