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Steve Gillion
Hang onto that sextant.  It might be quite valuable.  Hughes made thousands of MkIX aircraft bubble sextants of which a few were modified by enthusiasts for marine use.  However, you appear to have a genuine Hughes produced Marine Bubble Sextant which must be very rare as its serial number suggests.  Before doing any serious mending, check that it isn’t just asleep after 80 years inactivity.  Don’t worry, you don’t have to kiss it to wake it up although it sometimes helps. 

Do you know how to make a bubble in a Hughes sextant?  First screw the bubble chamber back onto your sextant; it’ll be easier.  Then hold your sextant normally.  If you look at the photograph I’ve attached.  Ignore the shadow on the right-hand side.  That’s just the hanging up hook.  Ignore the large speck at 10 o’clock.  That’s just my mucky sextant.  However, also at 10 o'clock is a tiny mark in the circumference of the bubble chamber.  That’s the air/fluid inlet port.  Next, twist your sextant 60 degree clockwise so the inlet port is now at the top.  Whilst still looking through your sextant gently turn the bubble adjusting knob fully one way and the other a few times.  If it was just lack of use, you’ll see great spurts of bubbles coming through and then disappearing again.  If that starts to happen adjust the size of the bubble with the knob, and when you get to the desired size bubble (about 1/3 of the width of the tramlines) twist the sextant 60 degrees anticlockwise so that the bubble is then trapped in the chamber.  You should now be able to back the knob off to ease the tension on the diaphragm without losing your bubble.  You need to practice this for a while until it becomes second nature.  Some people say remove the bubble when finished shooting, but I’ve never bothered.  If this doesn’t work, you’ll need to come back to us.  DaveP

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