Comments for The Nautical Sextant

Comment on A Box Sextant by engineernz

engineernz — Tue, 31 Jan 2012 19:21:39 +0000

The safety of shades comes up periodically, in the context of worries about ultra-violet rays penetrating to and damaging the retina. In the 1960’s there were people who gazed at the sun under the influence of drugs and whose retinas on the whole came to remarkably little harm, and of course, there was their famous predecessor, Isaac Newton. Ultra-violet rays are quite well absorbed by ordinary glass and I would take the pragmatic view that if one can view the sun comfortably, the filters are satisfactory. Polaroid had not been invented in 1916 and, though older books write about a Nicol prism being used to reduce horizon glare, I have yet to see one. From about 1938 onwards, sextants were occasionally fitted with crossed Polaroids as shades, notably the US Navy Mark II, and I have an instrument from 1967 that has them, but I find that the view of the sun is just on the edge of being too bright for comfort.

Bill

Comment on A Box Sextant by Martin Hoskins

Martin Hoskins — Tue, 31 Jan 2012 10:26:33 +0000

Bill

Really facinating webpage, I have a 1916 Box Sextant by Frankham, it looks exactly like yours. I have been using a book by Jack Case as a guide, and am producing a small notebook of his rules for taking noon readings. I was interested to see the previous message about surveying as mine unit was used by the RAF, possibly for mapping airfields ?? so I would really appreciate a glimpse at it as well please.
I was wondering about your thoughts on the safety and effectivness of the filters for a unit of this age, it has the red and green, and in addition to the peep hole it has a minute dark filter, presumably pre polorizing?

Comment on Faking it. Is it a SNO-M or is it a C Plath? by engineernz

engineernz — Tue, 10 Jan 2012 19:26:02 +0000

Yes, Greg, The number at the zero end of the limb is Plath’s serial number. I don’t know exactly what the naval number indicates, but assume it is the unique identifier for naval stores purposes. Googling “Kriegsmarine” may help – and will certainly keep you occipied for many hours.
Bill

Comment on Faking it. Is it a SNO-M or is it a C Plath? by Greg

Greg — Tue, 10 Jan 2012 18:48:25 +0000

Bill,

I have one more question about my sextant. I noticed on the spreadsheet you sent (thank you by the way) You have in some cases a serial number and a Navy/Ship/Boat Number. I gather that the serial number is the number on the frame near the radius at the right hand end (“0″ end) of the scale and the Navy Number is on the Arm, under the “M”.

Any indication what the Navy number means? Or what it was used for?

Thanks again, you have been an awesome resource.

Greg

Comment on A Drowned Husun Three Circle Sextant by engineernz

engineernz — Fri, 06 Jan 2012 23:34:36 +0000

I will send you a picture to your e-mail address, Fabio.
My book does cover adjustment of the sextant and the principles of how they are calibrated.

Bill

Comment on USN BuShips Mark II sextant: some design oddities. by engineernz

engineernz — Fri, 06 Jan 2012 23:22:16 +0000

I have added some pictures of the cases by the various makers.

Bill

Comment on USN BuShips Mark II sextant: some design oddities. by Fabio Bram

Fabio Bram — Fri, 06 Jan 2012 07:32:41 +0000

Hi there.

Any pictures of the wood box and its contents (including key and locks)?

Thank you in advance.

Comment on A Drowned Husun Three Circle Sextant by curiososolharesFabio Bram

curiososolharesFabio Bram — Fri, 06 Jan 2012 06:47:57 +0000

Greetings from Brazil.

Terrific work… Specially interested in the wood & key mechanism part. If you could add some other pictures, I’d appreciate it.

Another Q: Does your book cover adjustments and calibration?

PS: Send my best to your friends… They really are GOLD

Comment on Faking it. Is it a SNO-M or is it a C Plath? by engineernz

engineernz — Wed, 04 Jan 2012 21:50:40 +0000

I and a friend have compiled a data base of serial numbers linked to the date of the inspection certificate, which of course is not necessarily the date of manufacture. It is not in a form suitable for posting on the blog, but I would be happy to send a copy to you (and anyone else) if you use the “Contact me” tab on the home page (rather than as a “Comment”) or direct to engineer@clear.net.nz. C Plath may still have the original books. I would be happy to see pictures of your instrument and with your permission add one or two to the blog post if appropriate. While the Nazi era markings add value to the instrument for a certain type of collector, your sextant still had monetary value, but in view of its provenance, you would probably not want to sell it anyway.

Bill

Comment on Faking it. Is it a SNO-M or is it a C Plath? by Greg

Greg — Wed, 04 Jan 2012 18:56:54 +0000

Bill,

You note that your Plath is a 1943 and is newer than mine. I take it that is based on the serial number. Is there a data base of Plath Serial numbers somewhere? Can you decode the actual year of manufacture from the serial number? or even better which ship or officer used it?

If it helps with your research I would be happy to send pictures of my sextant curiosity. As I noted, sometime early in its life, much of the “Hamburg” and other German markings have been machined off of my Sextant, which I can only suspect completely devastates any collectable value. I can only imagine that in 1947 the British and Canadian’s were still a little “cool” to all things German.