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    Kollsman Periscopic Bubble Adjust
    From: Jeff Gagnon
    Date: 2019 Aug 5, 08:42 -0700

    Let me introduce myself.  My name is Jeff.  I was a C130 navigator for 28 years retiring in 2013.  I received celestial training in the Air Force on the T43 using the Kollsman periscopic sextant.  I'm pretty sure we used the MA-2 when we did some traing on the ground.  I mention this since I found a MA-2 manual and have been using this to solve my problem.  After a search on Ebay I finally came across a Kollsman periscopic that seems to work, ie., the mechanical averager, altitude adjustment, filters and bubble.  I'm not sure if the altitude adjustment will be accurate given years of neglect in a warehouse but I figure an adjustment to the height observed after a shot.  The problem is that I cannot get the bubble to a small enough size for a sun shot.  It seems to fil the whole field of view.  I've followed the steps in the MA-2 manual (attached) but when I return to vertical and turn the knob to full increase the bubble does get bigger before I tilt the sextant to the left and decrease the bubble size.  The bubble does in fact decrease only to increase again when returned to verticle and adjusted to increase.   This is supposed to be a process back and forth to get the bubble small enough to capture the sun accurately.

    While I like having a sextant that I actually used during my career I'm thinking I may just find an MA-2 (lighter and familiar with) or an A10 or A12.  My goal is to teach my wife, daughter and a good friend of mine how to do celestial navigation.  I know I don't need an averager on land or a particularly heavy sextant.  I may go that route in the end but I'm inclined to tackle this bubble issue on the periscopic given that I have it in hand.  

    Could it be a lack of fluid in the sextant?  The sextant is a bit sticky on the case.  Maybe some leak out years ago.  I was never sure where the sextant drew air to form a bubble.  Were these sextants prone to leaks?  I never really considered the maintenance and mechanics of the sextants as they always worked and were cared for by someone else.  

    Thank you for any information you have regarding this.


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