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----- Original Message -----
From: "Alexandre Eremenko" 
To: 
Sent: Thursday, November 11, 2004 3:23 PM
Subject: Re: SNO sextants


>> Speaking of adjustment of SNO-T, this issue was already
> addressed by Lisa: the screw that adjusts the horizon mirror
> perpendicularity is
> a) over-sensitive and
> b) works in a funny way:
> you adjust it and it "plays back". Furthermore, I found that
> sometimes it apparently "plays back" even when I don't touch it.
> So unfortunately this mirror needs frequent adjustment;
> it does not "hold" well its adjusted position.

Hmmm. The adjustment screws on mine are quite "stiff", requiring a
noticeable force to turn, and there is no problem holding adjustment. A
couple of thoughts.

The adjusting screws do not screw directly into the mirror housings, as is
the case with many sextants. There is a steel "housing" screw which screws
into the mirror housing; the centre of the housing screw is drilled out and
threaded, and the adjusting screw is screwed through the housing screw.
(This arrangement hides the adjusting screw from knocks, allows for ready
replacement of the adjusting screw mechanism, and is possibly essential with
alloy construction.) Is it possible that the "housing" screw is not done up
tight?? If it is loose, I would be inclined to reset it with Loctite.

Second thought: the adjusting screw has been assembled with lubricant.
Removing the screw, cleaning it, and reassembling dry may work.

Third thought: as per the comment by Jared.

Lee Martin

   

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