NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant Repairs
From: Gary LaPook
Date: 2014 Jan 14, 20:51 -0800
From: Gary LaPook
Date: 2014 Jan 14, 20:51 -0800
There is no reason to send your sextant off to someone just to get the mirrors adjusted, this is normal work for every navigator that has ever handled a sextant. Every navigation book you can find will have a section on how these adjustments are done. I have attached a section from the 1920 edition of Bowditch that explains the process. Here is a link to the manual for the soviet sextant which also describes the same process. For the first adjustment instead of lining up the arc with its reflection the soviets place a "diopter" (maybe a bad translation) which are just equal height metal tabs placed at two points on the arc that you line up in the mirror, it might be easier to see than the arc itself. You can just use two equal stacks of coins instead. I have attached the Tamaya manual that also shows this simple adjustment. Don't
be afraid that you will hurt the instrument, they are designed to be adjusted by the navigator, that is the reason that wrench came with it.
Soviet manual.
http://www.fer3.com/arc/img/103181.cho-t%20sextant%20manual.pdf
Tamaya manual.
http://www.tamaya-technics.com/e_site/images/pdf/manual/sextant_e.pdf
Davis manual.
http://www.suomennavigaatioliitto.com/files/manual/mark15_25.pdf
Good book and site.
http://sextantbook.com/
gl
From: Steve E. Bryant <steveebryant@att.net>
To: garylapook@pacbell.net
Sent: Monday, January 13, 2014 7:52 PM
Subject: [NavList] Sextant Repairs
Soviet manual.
http://www.fer3.com/arc/img/103181.cho-t%20sextant%20manual.pdf
Tamaya manual.
http://www.tamaya-technics.com/e_site/images/pdf/manual/sextant_e.pdf
Davis manual.
http://www.suomennavigaatioliitto.com/files/manual/mark15_25.pdf
Good book and site.
http://sextantbook.com/
gl
From: Steve E. Bryant <steveebryant@att.net>
To: garylapook@pacbell.net
Sent: Monday, January 13, 2014 7:52 PM
Subject: [NavList] Sextant Repairs
Dear Celestial Navigators,
I have a Tamaya sextant model MS-833 dated 19 June, 1981. I’ve owned it for eight years.
I have used it over the past 5 years and have routinely obtained fixes within 3nm from a GPS position. This evening, as I was driving around our local city lake looking for a good position(s) in order to obtain a (running) fix with the moon and Deneb. I slowed down quickly and turned abruptly thus causing my sextant to slide from the seat onto the floorboard. Sorry, an amateurish, disrespectful mistake I know. I knew when I did it that I should not have leave it unattended like I did.
I apologize for not being able to properly converse with you about the various possible mechanical adjustments and other technical aspects of this instrument. I will proceed nevertheless in an attempt to describe what I notice to be an effect of the accident.
As I checked the instrument for index error, I notice that the when I attempt to superimpose the image of a star upon itself, there appears to be some type of misalignment in that the image of the star can only be brought alongside the star as I obtain the measure the index error. My history with regard to index error has been 0.5’ on the arc. Now, the first several attempts at determining index error gave 2.5’ on the arc as I tried to imagine when the star and its image were in alignment with one another.
I don’t know what else may have been affected in the accident. The instrument came with a little square headed wrench that fits the mirrors. I am reluctant to try to make any adjustments by myself.
Could you provide information for reputable sextant service centers that I may contact for repair, please?
Thank you,
Steve
: http://fer3.com/arc/m2.aspx?i=126351
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