NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: sextant for use on land
From: Michael Dorl
Date: 2006 Aug 12, 08:41 -0500
At 07:10 PM 8/11/2006, you wrote:
>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
I bought a an-5851 on ebay for about $120. My instrument was in pristine
condition. Everything works including the bubble adjustment averager, and
and lights. It requires power only if you want to run the lights. The
averager is mechanical. As I understand it, the averager is of little
value for land sights but is needed for air bourne sights since planes tend
to wobble with the gravity vector changing direction. It's kind of neat to
hear two minutes of whirring clockwork when you trip off the averager. It
is fairly heavy and has a ring to suspend it from a hook in the observation
bubble in your B-17. I've used it for star, sun, and moon sights. Don't
know how it would do for lunars. Precision is not great. One revolution
of the drum is 5 degrees and the drum is marked off in 2 minutes
increments. You are not going to be doing second level measurements with
it. Mine has a turret of filters for Sun observation, a astigmatizer to
smear the Sun into a line, a control to add/remove the horizon, and a place
to put a stop watch that can be triggered with the averager. I also got a
flash light like power supply for the lights, spare lights, and a Bakelite
carrying case.
It does the trick for the playing I do in my back yard. You need to make
the bubble fairly large (Sun sized) to overcome frictional drag so you
kind of guess where the center of the bubble is. Mine is about 8 inches high.
Let me know if you need more info on this thing.
>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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To , send email to NavList-@fer3.com
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From: Michael Dorl
Date: 2006 Aug 12, 08:41 -0500
At 07:10 PM 8/11/2006, you wrote:
>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
I bought a an-5851 on ebay for about $120. My instrument was in pristine
condition. Everything works including the bubble adjustment averager, and
and lights. It requires power only if you want to run the lights. The
averager is mechanical. As I understand it, the averager is of little
value for land sights but is needed for air bourne sights since planes tend
to wobble with the gravity vector changing direction. It's kind of neat to
hear two minutes of whirring clockwork when you trip off the averager. It
is fairly heavy and has a ring to suspend it from a hook in the observation
bubble in your B-17. I've used it for star, sun, and moon sights. Don't
know how it would do for lunars. Precision is not great. One revolution
of the drum is 5 degrees and the drum is marked off in 2 minutes
increments. You are not going to be doing second level measurements with
it. Mine has a turret of filters for Sun observation, a astigmatizer to
smear the Sun into a line, a control to add/remove the horizon, and a place
to put a stop watch that can be triggered with the averager. I also got a
flash light like power supply for the lights, spare lights, and a Bakelite
carrying case.
It does the trick for the playing I do in my back yard. You need to make
the bubble fairly large (Sun sized) to overcome frictional drag so you
kind of guess where the center of the bubble is. Mine is about 8 inches high.
Let me know if you need more info on this thing.
>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.
>
>
>
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
