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Bubble sextant

Old 9th Oct 2009, 03:45
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Bubble sextant

I'm looking for a good bubble sextant - anybody know of a good one I might be able to borrow/purchase?
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Old 9th Oct 2009, 05:19
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what, have they taken the IRS out of your aircraft.........?
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Old 9th Oct 2009, 05:19
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Not quite a bubble sextant, but I picked up a WW2 astrocompass (complete with service stamp from Duxford in 1944) off ebay for 29 quid.

And here it is in use a couple of years ago...


Last edited by compressor stall; 9th Oct 2009 at 08:02.
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Old 9th Oct 2009, 06:40
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bubble sextant!

you'll have to visit an adult shop for one of those mate.

good luck
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Old 9th Oct 2009, 15:13
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Folks,
Kollsman bubble sextants come up on eBay USA frequently, usually in the proper storage container. Prices vary, US$50 to $100.
Tootle pip!!
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Old 9th Oct 2009, 22:53
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Lightbulb

However, ensure that the Kollsman is not a periscopic because it sure ain't easy to hand hold and then there's the power supply!?

Ideally, a WWII Mk.IX would suit, but heaven knows where you'd get one. Most are in museums or collections.

There are marine sextants which have a bubble attachment and a google search would bring one up. Just remember that aviation sextants usually have a two minute averager [I think the Mk IX had a 1/2 minute option switch] to counter aircraft movement. I haven't heard of recent marine sextant use in the air.

G'day
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Old 9th Oct 2009, 23:08
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Is that what they used to navigate with in the days when they had navigators as flight crew? I've often wondered how aircraft like the 707 and DC8 flew across the Indian and Pacific oceans in the 1960's when there was no INS systems onboard (let alone IRS and GPS).
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Old 9th Oct 2009, 23:27
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LORAN (plus a navigator in some aircraft)
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Old 10th Oct 2009, 02:23
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Air Pacific used Ded(for deduced) Reckoning and a Doppler Driftsight, which gave drift in real time on their BAC 111 's for years on their longer (for a BAC 111)legs. Know the track required, know the actual drift, apply it accurately, read the groundspeed, and you end up where you should. With a full load of pax (albeit not many by todays numbers) they didn't have much fuel left over to muck around on arrival either sometimes. They had to turn back now and then to top up with fuel if they ran into unforecast headwinds. And if there was a thunderstorm hailing cricket ball sized ice sitting over Brisbane on arrival, the divert to Rocky required attention as observed from the only seat left, the jumpseat, on one occasion. First into Rocky and first out again, just as the diverted Melbourne and Sydney 72's were arriving. That was the technology of the time.
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Old 10th Oct 2009, 03:00
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What about this one?
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Old 10th Oct 2009, 04:16
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Thumbs up

HH, just what the doctor ordered. You just have to ensure that you can form a bubble as the bags tend to dry out and won't hold liquid.

SARMC; I'd suggest that if you look at the World, LORAN had pretty limited coverage.

G'day
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Old 10th Oct 2009, 09:01
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These are apparantly a little better....

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Old 11th Oct 2009, 11:47
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HH, love the bubble sextant - just have to factor in the extra 100 quid for P&H in the bid!
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Old 12th Oct 2009, 07:43
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Bubble Sextant:

A Mr P Millward, has /had a Sperry (I think) model, its speed calibration range was from Zero to 620kts,.(from memory)

He use to be in Fijian CAA circa 1990's and I drawled over it then, I think he is around the Auckland Area.

H/Snort
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Old 12th Oct 2009, 14:58
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Feather#3,
The USAF Kollsmans or Eastman are periscopic, but come with their own power supply --usually.
Then all you need is the mount out of the roof of a 707/Herc/C141 etc, or the one out of the roof of the 12th floor of Bu----t One at the Arthur Baird Jetbase, and you are all set. Too easy. Worked for me --- but the mount cost as much as the sextant.
Tootle pip!!
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Old 12th Oct 2009, 16:33
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Had a conversation with a guy from WW2 one time and he mentioned how they were flying between Pacific islands in a Beaufighter (I think?) squadron and after a bombing run they were trying to get back home on min fuel. The navigator was uncharacteristically way off course. The bubble dome had been shot out and the navigator had been breathing some drawn in exhaust fumes.
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Old 13th Oct 2009, 01:20
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You can buy them from a company called Celestaire in the US. AFAIK their website is:-

Celestaire, Inc. - Navigation Equipment

A few comments, if I may?

For low-level work (seaplanes & airships, blimps etc) a marine sextant can be used if there is a visible horizon (with appropriate corrections from the Nautical Almanc for Dip, refraction etc), or a marine sextant artificial horizon attachment (such as the Weems & Plath unit or the hard-to-find C. Plath units) can be used with a marine sextant, although with reduced accuracy due to the motion of the aircraft making it very difficult to centre the bubble and celestial body at the same time. The sextant errors (error-of-perpendicularity and side-error, as well as any index-error) would have to be deteremined and reduced as much as possible, although some marine navigators feel a little bit of side-error isn't necessarily a bad thing when doing stars.

The two preferred marine sextants would be the Tamaya Jupiter (or more expensive Spica) models, or any of the Plath, C. Plath or Weems & Plath full-size marine sextants. These can be bought new, or from reputable second-hand sextant dealers (such as Joel Jacobs in the US; his website is Land and Sea Collection Nautical Antiques,). Tamaya Jupiters are standard on the bridge of thousands of merchant ships and are a fine sextant at a much more realistic price than the no-longer-made C. Plath units. (I have owned and used both.) Cassens & Plath sextants are still available new but are likely to be significantly more expensive than the Tamaya for no discernable increase in practically-achievable accuracy.

However, for work in a high-flying aircraft the purpose-designed and built aircraft bubble-sextants, taking 60 readings in a minute and averaging them, would be a far better choice. You will also need to get the "Sight Reduction Tables For Air Navigation", and "Selected Stars Epoch 2010", unless you are working your sights using a calculator.
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