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    Re: Bubble horizon
    From: Paul Hirose
    Date: 2002 Dec 16, 20:42 -0800

    Robert Eno wrote:
    > This bubble attachment did not have a provision for adjusting the size of
    > the bubble. In my estimation, it was not worth the price. It appears to me,
    Come on, don't be coy. Who made that poorly designed bubble horizon?
    Cassens & Plath?
    > Contrast this to a C.Plath bubble attachment which does have a provision for
    > adjusting the size of the bubble. One can obtain very accurate positioning
    > data when using this device. Unfortunately, they are relics of the past. I
    > don't think that they have been manufactured since the early 1960's but are
    > still available from time to time, from antique and used sextant dealers.
    The 2003 Celestaire catalog has C. Plath bubble horizons for $950.
    They are German military surplus, never issued.
    > best, the most accurate and the easiest to use, ever, is the RAE Mark IX
    > aircraft sextant. It wins hands down in all categories.
    I would like to hear about the good and bad points of the bubble
    sextants you've tried. Recently I won a Kollsman periscopic on eBay
    for about $100. Hasn't arrived yet. Back when I was in the USAF I
    played with these a couple times but never dreamed I'd own one.
    Thinking about buying an AN-5851 (Navy Mark V) bubble sextant as well.
    There are plenty on eBay and the prices are good.
    I've seen British Mark IXs from time to time but know little about
    them. If they are the cat's meow like you say, maybe I ought to get
    one too.
    In an article I saw on the Web, one old air navigator said he found
    the Kollsman periscopic sextants a real breakthrough. No more
    scratched, dirty astrodomes with their refraction corrections and
    blowout hazard in pressurized planes. The periscopic sextant tube
    slipped into a mount in the top of the cockpit and was held securely
    and conveniently for the navigator. The mount had an azimuth scale
    which was visible through the sextant. You could use that to help find
    stars, or get an accurate true heading.
    Unfortunately I won't have the luxury of a mount, so I'll have to get
    used to freehand use or set it on a support. At least I've handled
    these sextants before, so I know what to expect.
    KC-135s used to have flat windows on top of the plane near the bubble
    sextant port. I heard they were replaced with metal plates after an
    accident in the 80s (?) in which a nav got sucked out to his death.
    Such stories are often apocryphal, but there may be some truth to this
    one. The one -135 I worked on in my career, in the 1990s, did have the
    window openings plated over. In fact, I heard the story of the nav
    from one of the crew chiefs on that bird, after he noticed me playing
    with the periscopic sextant. What a way to die.

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