Sextant, what to buy?

[hellosailor]

snowpetrel-
I cheat and use Dupont Krytox. (Oil, not the more common grease.)
In the bigger picture is it only cheap compared to genuine vintage sperm whale oil. You will be shocked at the prices, but.
Krytox never will migrate. Never will become gummy. Never run or thicken. Never degrade in any environment that you or your sextant can survive in.
It is totally inert in pure oxygen, chlorine, or sulfur environments, and maintains original viscosity from -70F to +700F, so you will only need to use it once, for the lifetime of the instrument. (Or until you take it apart to clean & relubricate.)


Overkill, perhaps, but after I once had to fight congealed grease on an old pass of Zeiss binoculars (and I lost)...I decided it was cheap to use the damned expensive stuff and only have to use it once.

[barnakiel]

Originally Posted by El Pinguino

Freiberger quite light

Now c'mon Sir.

I think F is a brick!

I found it way too heavy to comfortably handle for anything more than a quick and easy sight.

I did hope other sextants were much lighter - I misjudged by looking at how many cutouts they have ... some look like crochet compared to F.

Looks like I must rethink my older idea of fabricating prepreg carbon autoclaved sextants?

b.

[barnakiel]

On the second thought, why not make a better sextant by keeping the tant out of it?

Sex alone could be as good a tool of sight taking, especially if we think of sighting Venus.

NO?

Funny that we have a navigation tool that took its name from sex. I wonder what the other half of the word derives from. ;-) TUNTE?

b.

[SeeLevel]

Originally Posted by hellosailor

snowpetrel-
I cheat and use Dupont Krytox. (Oil, not the more common grease.)
In the bigger picture is it only cheap compared to genuine vintage sperm whale oil. You will be shocked at the prices, but.
Krytox never will migrate. Never will become gummy. Never run or thicken. Never degrade in any environment that you or your sextant can survive in.
It is totally inert in pure oxygen, chlorine, or sulfur environments, and maintains original viscosity from -70F to +700F, so you will only need to use it once, for the lifetime of the instrument. (Or until you take it apart to clean & relubricate.) (...snip).

Best Krytox price here, $11.95/oz: GPL 106 Pfpe Oil 14g Auto Roof Door Weatherstripping Rubber Lubricant Krytox 105 | eBay

[lesterbutch]

Originally Posted by Snowpetrel

Ha ping damn near snorted my coffee out my nose in outrage, what are you implying about those of us that own (and cherish) Freibergers?

Thanks for the vote for sewing machine oil. Our ships issue Kelvin Hughs sextants had little bottles of oil in the case, so never had to buy any!

I have also had good luck with fishing reel oil, though I think any light machine oil will be sufficiant! I always keep dry packs in with my instruments to remove any moisture as well.

[gjorgensen]

Celestaire sells an expensive oil called Nye Clock oil that they recommend. When I bought my Astra IIIb used off EBay a few years ago there was a bottle in the case, which I've used. It's definitely good stuff for the purpose, but I think sewing machine oil is probably just as good.

[bletso]

A #7 welding shade wrks great for a Bris sextant. Really neat. Now I have to take the time and calibrated it. Took all of 1/2 hour to construct a working model. I used microscope slides and a # 7 welding shade. Glued together with super glue.

[Snowpetrel]

Very nice. How did you cut the welding shade? Just a normal glass cutter? Thanks for posting.

Sent from my SM-G930F using Cruisers Sailing Forum mobile app

[bletso]

Yes, just a normal glass cutter. Another thing not readily apparent in the articles is that it is for low altitude sights, (dependent on the angles between glass sheets). Also, it appears to be un-important as regards alignment of the glass so each sun is directly vertical, one under the other, as each one is treated separately. He mentioned that no corrections are needed, but don't forget height of eye as that changes your apparent horizon, as well as dip short if applicable.

It was interesting to see the effects of various angles and the number of glass sheets. I have tried three and four sheets as well as single microscope slide separation and double. My biggest problem is that this year we get a day of intermittent sun followed by two or more days rain and clouds, most frustrating.

The first pic is with 4 layers, second with three, (counting the welding glass) Taken with my iPhone just held up the to the Bris sextant