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The A-10A has an averager, the A-10 doesn't.

Here is a link to more information.
http://home.earthlink.net/%7Es543t-24dst/airnav/index.html#PERISCOPIC

The frosted glass is called the "sunshade" in the parts list. I have
always used it as a diffuser to make the illumination of the bubble more
uniform. I take all my shots with it in place. With it swung out of the
way you can see the sky through the bubble which is distracting.  Are
the faint lines you mentioned in an arc? Mine has some which are just
scratches from swinging it in and out of position.

Yes, you can use the natural horizon by looking past the left edge of
the horizon prism. If you ever have to dismount the index prism this is
the way to get it back into proper alignment.

To identify an unknown star get a star finder. H.O.  2101-D or 2102-D.

Or look at the star diagrams in the Air Almanac.


Or download for free the Navigator Light program here:

http://www.tecepe.com.br/nav/download.htm

it does celestial computations and one of its displays is the position
of stars visible from you A.P.

Or go to this web site and put in your A.P. and the GMT and it gives you
a list of all the stars visible with their azimuths and altitudes.

http://aa.usno.navy.mil/data/docs/celnavtable.php

Or do it the old fashioned way, work the formulas backwards to derive
declination and LHA, add you assumed longitude to get GHA, subtract GHA
Aries to get SHA and look in the Nautical Almanac for a star with the
derived declination and SHA.

gl







bruce hamilton wrote:

>I just received an A-10 that I got for cheap on E-bay. Well, most of one
>as is is missing the averaging mechanism, but as I plan to use it with
>my feet firmly planted on the ground, I don't need that bit. I also
>managed to coax a bubble out of it too.  I must say that it is the best
>thing for us urban dwellers with no horizon handy. I might get a
>calibrated A-12 next as I love the concept. Put the body in the center
>of the bubble and I have a reading. Very nice! I am a bubble sextant fan
>now.
>
>I have one question for someone who has used one (A-10) before. What is
>the use of the frosted glass that swings over the top of the bubble
>column? Mine has some faint lines on it, but it seems to me that if the
>body is in the bubble, no other reference is needed.  As well, it seems
>to me if I peek to the left of the view, I could see a natural horizon,
>if I had one. Is this possible or a pipe dream?
>
>Another question. Last night, I could get a reading from a single star
>through a single whole in the clouds.  My star identification skills are
>still poor, and those circumstances were beyond me. Is there a quick and
>dirty way to take that single observation and find what star I was
>looking at using the observation, an Almanac a watch and calculator?  I
>think I found the star in the site plan section of Celest Nav on my palm
>pilot, but I would like to be able to do it without.
>
>Thank You
>
>Bruce Hamilton
>Vancouver, BC
>
>
>
>>
>
>
>


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