NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Removing/Replacing Sextant Mirrors?
From: Greg R_
Date: 2006 Jun 6, 10:26 -0700
From: Greg R_
Date: 2006 Jun 6, 10:26 -0700
JPP wrote:
> I don't know what the correct procedure is
for the ASTRA
> but for the SNO-T/SNO-M and similar designs,
it is necessary
> to completely remove (completely unscrew the
fitting screw)
> at least for 1of the 3 spring clips and to
release pressure on
> the 2 others (partially unscrew the fitting
screw) to remove
> and replace the index mirror.
I just got an e-mail from Celestaire (who import
the Astra sextants) and they concur with this - thanks for the info, and it's
good to know that my instincts were also correct. :-)
> It is advisable to protect the coated face
of the mirror to be
> installed with paper (sulfurized paper) so
that the clips do not
> scratch the mirror face during the
installation procedure as they
> are pushing hard for some designs
(Freiberger). That's about all
> there is to do.
Don't know if it's true for other sextants, but
the Astra index mirror has 3 small rectangular "pads" (i.e. non-silvered
areas) that sit under the springs when the mirror is in place - no
doubt for that exact purpose. I'm curious about why you recommend sulfurized
paper for the process.
Thanks again for the info, appreciate it.
:-)
--
GregR
----- Original Message -----From: jean-philippe planasSent: Saturday, June 03, 2006 12:53 PMSubject: Re: Removing/Replacing Sextant Mirrors?I don't know what the correct procedure is for the ASTRA but for the SNO-T/SNO-M and similar designs, it is necessary to completely remove (completely unscrew the fitting screw) at least for 1of the 3 spring clips and to release pressure on the 2 others (partially unscrew the fitting screw) to remove and replace the index mirror. It is advisable to protect the coated face of the mirror to be installed with paper (sulfurized paper) so that the clips do not scratch the mirror face during the installation procedure as they are pushing hard for some designs (Freiberger). That's about all there is to do.JPP
"Greg R." <gregr_ingest@YAHOO.COM> wrote:What's the right way to remove and replace sextant mirrors? The Astra that I won on EBay arrived (finally...) yesterday, with the index mirror removed and packed separately (not sure if I asked the seller to ship it that way or not, but maybe that was a safer way to ship it).Couldn't find any instructions for how to replace the mirrors in the manuals that came with it, and since it didn't look like the spring-clips would bend enough to insert the mirror without either breaking or deforming, I just unscrewed one of them and replaced the mirror that way. That seemed to work OK (index error has now been adjusted to zero on that particular setup, and it seems to sight OK), but just for future reference what's the right way to do this?--Thanks,GregR
JPP__________________________________________________
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