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Sextant mirrors


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not sure about blurred

 

but the sextant that came with my boat, (1987 east german freiberger yacht compass) is in very good condition except for the silver at the edges of the mirror being attacked by moisture

 

mirror.jpg

 

same thing happens to mirrors in bathrooms

 

my understanding is that this is really only cosmetic as it is the centre of the mirror where all the action happens

 

 

Mirrors - Sextant mirrors have a limited lifetime before needing resilvering or replacement. Estimates range from 2 to 6 years in marine service. While resilvering is an option, good quality is hard to achieve. New mirrors are not much more expensive, and are shown below.

Horizon Mirrors
Astra IIIB - 51mm diameter with mirror frame
Traditional (half silvered) #0504R
Whole Horizon #0503R

Other sextants (Cassens & Plath, C. Plath, Tamaya,Freiberger) 57mm, frame not included
Traditional (half silvered) #0703

Index Mirrors (56 x 42mm)
Astra IIIB no frame #0517D $80
Astra IIIB with frame #0516D $95

Other sextants no frame #0517D $80

 

https://www.celestaire.com/marine-sextants/replacement-parts.html

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Yep, the silvering on the mirrors eventually fails, rendering the sextant useless. I checked mine last year (30 odd years old) and it was unusable. Replaced the mirrors...should be a good backup for another 30 years.I might be near swallowing the anchor by then :-( 

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Sextant what on earth is that.

I have a friend who commissions commercial jets for introduction to service.

Has not seen a sextant nor a chart on a aircraft since the war.

I recently gained my NZ Coastguard Ocean Yachtmaster cert and half of the course (in terms of effort) was the use of a sextant for plotting courses. Further, in developing the position, NZ Coastguard requires the use of trigonometry (sight reduction tables aren't allowed). See syllabus here.

 

I found too, that in order to get a Cat. 1 certificate then at least one of the crew had to have this qualification.

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I found too, that in order to get a Cat. 1 certificate then at least one of the crew had to have this qualification.

 

No, that's not correct.  There is no such stipulation that in order to get Cat 1 clearance that you (if your solo) or one of you (if you have a crew) must have a Yachmaster Cert.

 

I know this because I have read the current Cat 1 safety rules cover to cover while I decide whether to register my boat here in NZ, or in 'Outer Mongolia' for a flag of covenience.

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No, that's not correct.  There is no such stipulation that in order to get Cat 1 clearance that you (if your solo) or one of you (if you have a crew) must have a Yachmaster Cert.

 

The requirement can be found here under section 21 on page 84. This sections covers the competency of the crew.

 

And Partisan you are technically correct. The NZ regulations don't actually say that at least the navigator has to have done the actual course to which I referred. But the inspector I dealt with 18 months ago interpreted section 21 to mean this. He wanted proof that we had the knowledge and experience to go offshore. We were first time offshore. As an aside he also required Survival at Sea and Marine Medic courses be attended.

 

In the previous edition of the cat 1 rules it was under SR Appendix 3. 

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Speaking of using a sextant, I tried for quite a few days on the bouncy waves during an ocean crossing a few years ago. But I couldn't quite get good consistent readings I was happy with. Am I a slow learner, does my heavy spectacles prescription make it hard? How long does it take most people to become proficient on the bouncy waves?

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When I did yachtmaster way back in the late 80's, it was purely classroom based. IMO it is (or was) more of an academic thing than a practical cert of competence. Has this changed??

To some degree you're correct Matt. But to be fair we did have to demonstrate sea miles/time and also do a trip where we were out of sight of land for 3 days (I did a Welly to Gisborne trip).  

 

A criticism I have always had of all four Coastguard courses (Day Skipper, Boat Master, Coastal and Ocean Skipper) is that they are all classroom based courses. Practical experience on the water is, I feel, more useful. 

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Speaking of using a sextant, I tried for quite a few days on the bouncy waves during an ocean crossing a few years ago. But I couldn't quite get good consistent readings I was happy with. Am I a slow learner, does my heavy spectacles prescription make it hard? How long does it take most people to become proficient on the bouncy waves?

I use to take about 5 or 6 shots and plot them on graph paper and draw a line thru the average and use use the shot and time closest to the line. You can soon pick up the bad shots.

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The requirement can be found here under section 21 on page 84. This sections covers the competency of the crew.

 

And Partisan you are technically correct. The NZ regulations don't actually say that at least the navigator has to have done the actual course to which I referred. But the inspector I dealt with 18 months ago interpreted section 21 to mean this. He wanted proof that we had the knowledge and experience to go offshore. We were first time offshore. As an aside he also required Survival at Sea and Marine Medic courses be attended.

 

In the previous edition of the cat 1 rules it was under SR Appendix 3. 

 

"He wanted proof that we had knowledge and experience to go offhsore"

 

How long is a piece of string?  If the above is going to be interpreted that this means producing a Yachmaster Certificate, then why don't they just state that in the Cat 1 rules?

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tuffyluffy, have you ever seen electrics fail out on the ocean?

 

Yup, but last weekend when Miss Italy and I were away on the boat I counted 6 gismos with GPS's on board. Chartplotter, tablet, handheld GPS and 3 phones.

 

You'll loose your sextant overboard long before all 6 of my gismos die simultaneously.

 

Have you ever seem a swimming sextant?

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tuffyluffy, after a few days at sea perhaps your gismos will run out of power? Do the Davis plastic sextants float? Maybe. But you'd be pretty silly to rely on it. If your sextant is on a lanyard around your neck and you are tethered on, as you should be at sea taking readings, it's pretty unlikely to go overboard. Whereas I can see electrics failing as much more likely.

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