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    Re: Kollsman Aircraft Sextants
    From: David Pike
    Date: 2021 Dec 10, 12:11 -0800

    As it was such a lovely day, I had the 3V Kollsman out of its box this morning to experiment with.  This is what I found:

    1.  The lighting works as soon as power is applied, but it won’t let you see the sky until you prime the averager.

     2.  The sextant normally runs for two minutes, but you can stop it at any time.  To stop it at any time while running, just press and let go of the start trigger.  The sextant stops the moment you release your finger from the trigger. To find the average Hs just centralise the right-hand side of the averager window as for a 2-minute shot and read average Hs from the index window

    3.  The figures in the averager run from 0 to 60 in two minutes, so each division represents 2 seconds of time.  To find mid-time of your observation, add the figure showing in the left-hand side of the averager window to your start time.

    Test.  I set 30° 00’ on the index window. I started the sextant at 11:59.  After 30 seconds, I quickly increased the index setting to 31° 00’ (the averager was reading 15).  I stopped the sextant at 12:00, one minute after I started it.  The averager read 30.  Then I zeroed the right-hand side of the averager; the index window read 30° 30’.  Mid time was start-time plus 30 = 11:59 and 30 seconds, so that was OK.

    4.  With the sextant on the window ledge, I lined up the Sun’s lower limb with the graticule and checked if opening and closing the double-glazed window made any difference to the alignment.  I was unable to detect any difference, which is only to be expected considering the price of the double glazing.

    5.  3 x A Duracell Batteries in the 3v Kollsman Ever Ready torch maintain their umph much longer than the 2 x AA Duracell batteries I use with my Smiths sextants.

    6.  Take care how you undo the power lead.  It’s easy to start undoing the innards of the plug rather than where the plug joins the sextant. 

    7.  Before I put the 3V Kollsman back, I took the 28V Bubble Kollsman out from its hiding place under the bed behind the 3V in case it was feeling neglected.  It must have been under there for at least a year.  Once I’d reminded myself where the bubble hibernates and coaxed it out using a mixture of gentle horse-whispering and tilting left, I was reassured to note that the bubble Kollsman works in the daytime with no voltage applied at all.  Furthermore, upon checking quickly against GPS Anti-Spoof set to: CTR, Bubble, I was pleased to note that that its IE was around 1’ or less.  DaveP

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