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Re: Removing/Replacing Sextant Mirrors?
From: Jean-Philippe Planas
Date: 2006 Jun 6, 11:14 -0700
JPP
From: Jean-Philippe Planas
Date: 2006 Jun 6, 11:14 -0700
It's only that sulfurized paper is a little "glassy" or "oily" by nature without being wet. Some "harder" paper type could scratch the first surface of the mirror when this latter is not covered by a special protective coating. I think ASTRA mirrors are protected by such a coating. But better safe than sorry! When sextants are delivered new from factory (at least the Russian sextants) their mirrors are covered and protected by this type of paper.
JPP
"Greg R." <gregr_ingest@YAHOO.COM> wrote:
"Greg R." <gregr_ingest@YAHOO.COM> wrote:
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
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