Are Cheap Replica Sextants Any Good?

[Fore and Aft]

This is a great video of using a sextant, if Hadley can sand and antifoul, I think I have found my dream woman!
Cheers
https://fb.watch/gZ3D-VQ8C-/

[SeanPatrick]

As El Pinguino concisely wrote: NO!

As he and others have written, get a Davis or a used Astra, Plath, etc.

Another GPS is never a bad idea. But the thought of abandoning the idea of celestial navigation just because it's "old fashioned" and/or requires one to maintain a certain skill set seems odd to me ... especially on a forum like this. I mean, if that's your mindset, why even go sailing? It's much faster, easier, cheaper and probably safer to fly wherever you want to go. But where's the romance and adventure in that?

Besides that, another GPS isn't going to give you an independent check on your position. Many people like to point out how reliable the GNSS systems are - and that's absolutely true. But it's also true that spoofing and jamming are becoming a more frequent occurrence. And just because a solar flare hasn't taken out a few satellites yet, that certainly doesn't mean that it will never happen.

Anyway, if you want to practice CN, I say "Go for it!" I have found it to be a richly satisfying hobby. To be able to find where you are - anywhere on Earth - just by observing the sky and doing some simple arithmetic ... well, I think it's nothing short of magical.

And - as always - if you [or anyone] have any questions, I'd be more than happy to help you out!

Cheers!

[Adelie]

Originally Posted by goboatingnow

Just use GPS or anyone of THE four GNSSS up there.

I don’t agree it’s “ fragile technology. “ no evidence of that at all.

Given the increasing prospect of war between various of the GNSSS owners and the fact that 3 of them openly have anti-satellite weapons, I no longer consider that fact that there are 4 such systems will prevent an extended outage let alone a guarantee of reliability.

The fact that there has not been an extended outage does not mean that there won't be one in the future.

The USNavy has begun teaching midshipmen CelNav again. Not because there ever stopped using it, the enlisted ranks continued to do so, but the Navy has realized that the system is vulnerable to hacking as well as direct destruction of on-orbit equipment and they want the officers to have the basics to understand what info the enlisted ranks are providing, what its limitations are and to be able to effectively manage the enlisted.

[Lepke]

Used quality sextants are often on ebay from ships scrapped in India, etc.

[goboatingnow]

Originally Posted by Adelie

Given the increasing prospect of war between various of the GNSSS owners and the fact that 3 of them openly have anti-satellite weapons, I no longer consider that fact that there are 4 such systems will prevent an extended outage let alone a guarantee of reliability.



The fact that there has not been an extended outage does not mean that there won't be one in the future.



The USNavy has begun teaching midshipmen CelNav again. Not because there ever stopped using it, the enlisted ranks continued to do so, but the Navy has realized that the system is vulnerable to hacking as well as direct destruction of on-orbit equipment and they want the officers to have the basics to understand what info the enlisted ranks are providing, what its limitations are and to be able to effectively manage the enlisted.

A navy is expected nay designed to operate in war times.

Leisure sailors have no such compunction.

Use the best tools available at present that’s gnsss

Anything else is a hobby. I like hobbies. But that’s all they are.

[Franziska]

Originally Posted by goboatingnow

A navy is expected nay designed to operate in war times.

Leisure sailors have no such compunction.

Use the best tools available at present that’s gnsss

Anything else is a hobby. I like hobbies. But that’s all they are.

That's until you decide to use your vessel to get the hell out of there.
Than a cheap plastic sextant can help when making landfall in the southern hemisphere.

Not everyone will move and that's OK, but many will.
Folks from those countries which are so strongly anti migration right now may be the refugees of the future.

[ChrisJHC]

Originally Posted by SeanPatrick

Besides that, another GPS isn't going to give you an independent check on your position.

Unless, of course, you set each device to a separate GNSS system.
I might give that a try next time I’m on the water and see if I get significant differences.

[goboatingnow]

Originally Posted by Franziska

That's until you decide to use your vessel to get the hell out of there.
Than a cheap plastic sextant can help when making landfall in the southern hemisphere.

Not everyone will move and that's OK, but many will.
Folks from those countries which are so strongly anti migration right now may be the refugees of the future.

Let’s not decend into a discussion about post apocalyptic leisure sailing absolute BS stuff. Let’s just deal with the here and now. In the here and now GNSS is reliable, accurate and easily accessible

Learn anything you’d like as a hobby. CN is a hobby.

[goboatingnow]

Originally Posted by Franziska

That's until you decide to use your vessel to get the hell out of there.
Than a cheap plastic sextant can help when making landfall in the southern hemisphere.

Not everyone will move and that's OK, but many will.
Folks from those countries which are so strongly anti migration right now may be the refugees of the future.

I found a huge leap in precision when I switched to the Astra B so the quality does count

[goboatingnow]

Originally Posted by Jammer

GNSS is an inherently fragile technology. I believe it is wise to consider the possibility of outages.

Dead reckoning, pilotage, radar, and radionavigation using terrestrial beacons and commercial transmitters were the basis of navigation prior to the GPS era. Of these, radionavigation is no longer practicable because of the decommissioning of beacons and unavailability of DF navigation equipment (unless you want to refurbish antique electronics). Celestial nav isn't useful unless you can do all the basic stuff. But you probably know all that.

The cheap Davis sextants are the way to go. In reality you would be doing sun sights to confirm your DR latitude so that you don't, for example, miss the Marquesas. Doing a round of star sights before dawn and after dusk isn't realistic, for someone without considerable celestial nav experience, on a shorthanded sailboat.

I actually always like star sights as it gives you a three point fix and the “ cocked hat “ tends to betray your application errors.

The key with Cn is to practice it repeatedly. But you can practice in your back garden.

[Franziska]

Originally Posted by goboatingnow

Let’s not decend into a discussion about post apocalyptic leisure sailing absolute BS stuff. Let’s just deal with the here and now. In the here and now GNSS is reliable, accurate and easily accessible

Learn anything you’d like as a hobby. CN is a hobby.

Noone talks of the Apocalypse. That's ******** I agree.

I'm merely saying the GPS may get disabled should the war spill over into Nato territory.
In my view it's highly unlikely that this will be a nuclear scenario.

So, enough time to sail away from it for some of us, I certainly would, I'm on the boat and can leave very quickly.

This is NOT the reason I am on a boat though, should that idea come up.

[CarlF]

Originally Posted by goboatingnow

A navy is expected nay designed to operate in war times.

Leisure sailors have no such compunction.

Use the best tools available at present that’s gnsss

Anything else is a hobby. I like hobbies. But that’s all they are.

Yes. If the OP is on a tight budget as he says, he shouldn't be wasting limited funds on a sextant. His shopping list should include things that he might actually need - storm sails, Jordan drogue, InReach, liferaft, spare autopilot, and so on.

[Jim Cate]

In a small boat at sea, except in unusually benign conditions the limits on accuracy are more associated with the low height of eye and erratic boat motion than the quality of the instrument.

My first offshore voyages (SF-Oahu-Kauai-SF) were made using only a Davis plastic sextant. Our landfalls were adequately accurate every time and when I upgraded to a Frieberg sextant they did not improve all that much. It was much easier to use for star sights due to better optics (by far) and that is a useful improvement IMO.

But I would not consider the replica as a substitute for use in real navigation.

Jim

[Jammer]

Originally Posted by ChrisJHC

Unless, of course, you set each device to a separate GNSS system.
I might give that a try next time I’m on the water and see if I get significant differences.

See now, these discrepancies are caused by external factors. They are due to the fact that GPS uses Imperial degrees, while Galileo uses metric degrees. BDS uses whatever units are cheapest that day, and GLONASS reports whatever the Kremlin wants you to believe.

[valhalla360]

Originally Posted by goboatingnow

Could we really leave the issue of gps or more correctly GNSS disrupted. It’s brought up every time someone talk about GNSS

it’s utterly BS. There are 4 GNSS systems active the day they ALL GO offline you’ll be the least bit unconcerned as people in dust form tend not to need their position fixed.

I think that was his point.

Without even trying we have 6 separate GPS units onboard. Every phone and tablet built now has GPS.

Then add in the likelihood of pulling the practice sextant out of a hatch and using it with any degree of accuracy, is highly unlikely.

If you are really concerned, keep an old cell phone in a metal box along with a portable battery pack. This should cover you in case of lightning strike.

As mentioned, if all the GPS satellites go down, good luck because it's likely the end of the world...plus on a boat that cruises at 6kt, you can simply slow down and point towards known open water while you figure out what to do.

In the modern world, sextants might be a fun hobby but not practical (yes they work but no real point).