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Steve,

Very nice site with great pictures.  Your learning curve on position
accuracy seems at least comparable to mine using the Bendix Navy Mk V with
about the same level of practice.  I agree with you assessment that in
aircraft at several hundred Knots this accuracy is probably sufficient....I
don't expect to get much better than the 2-3 nm

Since I know my AP using GPS very accurately and not needing to use a moving
fix I used multiple sites throughout the day trying out stars, planets, moon
and sun.  I achieved the following

Day 1:  Sun lower limb, Rigel, Betelgeuse ---   4.45 nm
Day 2:  Sun lower limb, moon lower limb, Rigel  3.86 nm
Day 3:  Sun and moon lower limb and Polaris     4.91 nm
Day 4:  Sun and moon lower limb and Jupiter     8.61 nm (poorly dispersed in
azimuth for a good position, all within 90 degrees)

Use all 12 LOP's  2.84 nm

From the plot it appears I have better plots using stars and planet than
with the moon and sun which makes me want to consider how

Jim Dullea


-----Original Message-----
From: Navigation Mailing List [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]
On Behalf Of Grobler, Steven
Sent: Monday, February 10, 2003 10:47 PM
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Bubble Sextant

A few weeks ago I posted a message requesting help with my WW2 bubble
sextant. I received very useful replies and I have now got my sextant
working and taken my first sights - many thanks those on the group that
have responded.

I have taken a few photo's and written up some of things I had to do to
get the sextant working, which I have posted at
www.users.bigpond.com/bgrobler/sextant/sextant.html

Unlike most of the others on the group, I don't know the first thing
about sailing, and only very little about celestial navigation, at least
at this stage. Unfortunately I tend to get seasick, even on the 18km
crossing on the ferry between Fremantle and Rottnest Island here in
Perth, Australia. I also get airsick in light aircraft, so I probably
wouldn't have made a good aircraft navigator either! :)

I am relying on computers to do all the number crunching to plot lines
of position and get fixes. I get my satisfaction from the engineering
and historical interest in my bubble sextant, and the fascination at
being able to generate a fix from a few angle measurements...

--
Steve

   

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