I bought a M25 off Ebay and really like the beam converger mirror......recently I got a tamaya sextant with the split mirror......and I prefer the M25. Thanks for the video
My Mark 25 needed to recalibrated before each site. The plastic would bend slightly with small temperature changes causing it to go out of calibration by about 5 arc minutes. I found this very frustrating. I bought an eBay barely used metal Chinese sextant off of an Indian ship salvager for $300 (looks exactly like an Astra IIIb with different branding). Never needs recalibration. It’s a pleasure to use. Thanks.
I find that with the mark 15, I have about 5-7 arc minutes of backlash. I need to always turn the micrometer in the same direction when taking a reading, or I miss by that much. Also, I check my index error before & after each reading, then take the average. I sometimes see a minute or two of difference between the two error checks. The vernier scale adds precision, but not accuracy. I really don't bother with it. Thanks for posting. Your descriptions of the differences were spot on.
I had a bad experience with DAVIS. I bought a new M15 sextant (on eBay) and the lens came loose from the 3X telescope. There was no way to fix it. I sent an email to Davis, including photos, and got no response. I sent it again and was told that customer service would respond. The answer came after I insisted, once again, and was "we don't have stock of this part. I asked for more information and no answer. They totally ignored me. So, a serious company is one that cares about the customer and this was not the Davis case with me.
Extensively, yes. The light on the Mk25 makes it a bit quicker taking down readings, but I've also used the Mk15 a lot, and have a small torch around my neck. I'm old-school and generally prefer a split screen to the 'all-view' but for someone starting out and getting comfortable with the 'all-view' it's fine.
Regarding the Mk3, I would think that the lack of a telescope is more of a problem with sun and moon sights where you need to see the touching surfaces more precisely. A star is still a point of light even with a telescope. The main disadvantage of the Mk3 is the windage. Great for young students though. Thank you!
You don’t need telescope for the sun because it’s large. Moon works either way; not as big as sun but bigger than stars. Stars you defo need the telescope. Been doing it 40 years. It’s only my view, but it is backed by experience. Cheers.
@@boatingequipmentreviews9478 A star or planet still looks like a star through a 3x telescope. Yes, the sun and moon are large but to see the point where they touch the horizon, a telescope makes this easier than with the naked eye. Perhaps you have exceptionally good eyesight. Incidentally, the moon and sun are almost the same size and your comment about them is puzzling.
I've always viewed the Davis plastic "Sextants" as mere TOYS. Personally I would never depend on on at sea! Unless I'm stranded in the vastness of the South Pacific Ocean with nothing better. My first choice is a good German instrument. And maybe the metal Chinese tool. It is claimed to be accurate to 20 arc seconds. That's a third of a nautical mile. So, for practical purposes in a smallish sailboat, good enough.
That of course is your prerogative. Many people - me included - have used Davis sextants to cross oceans. The benefit of light weight is important. Long before Satnav, I used a Mk15 to cross the Atlantic and Pacific oceans. On days with 7/8 cloud cover I would sometimes wait for ages with my arms wrapped around the shrouds, waiting for a momentary break in the cloud to get a sight. To use a metal sextant in those circumstances would be lead to very achy shoulders.
Robin Jacobs On a small craft with a low height of eye you are unlikely to get better than 3-4nm accuracy from any sextant. I’ve used the Davis Mk15 sextant as the primary nav equipment for quite a few ocean crossings. I’ve also used in coastal nav for horizontal angles, long before the advent of GPS. They ain’t toys. I recent viewed a Chinese metal sextant that claimed it was so accurate it didn’t need a correction card. That’s just rubbish. Every device has errors in it.
My eyeballs can't see 2 arc minutes of angle. The Davis 15 & 25 are more accurate than this operator when they are used properly. For the money, they are a great value. ...and along with my compass, they still work after the boat gets hit by a lightening strike, unlike my chart plotter, depth finder, EPIRB, etc.
I bought a M25 off Ebay and really like the beam converger mirror......recently I got a tamaya sextant with the split mirror......and I prefer the M25. Thanks for the video
My Mark 25 needed to recalibrated before each site. The plastic would bend slightly with small temperature changes causing it to go out of calibration by about 5 arc minutes. I found this very frustrating. I bought an eBay barely used metal Chinese sextant off of an Indian ship salvager for $300 (looks exactly like an Astra IIIb with different branding). Never needs recalibration. It’s a pleasure to use. Thanks.
I find that with the mark 15, I have about 5-7 arc minutes of backlash. I need to always turn the micrometer in the same direction when taking a reading, or I miss by that much. Also, I check my index error before & after each reading, then take the average. I sometimes see a minute or two of difference between the two error checks. The vernier scale adds precision, but not accuracy. I really don't bother with it. Thanks for posting. Your descriptions of the differences were spot on.
I had a bad experience with DAVIS. I bought a new M15 sextant (on eBay) and the lens came loose from the 3X telescope. There was no way to fix it. I sent an email to Davis, including photos, and got no response. I sent it again and was told that customer service would respond. The answer came after I insisted, once again, and was "we don't have stock of this part. I asked for more information and no answer. They totally ignored me. So, a serious company is one that cares about the customer and this was not the Davis case with me.
Thank you for posting. Have you used the Mk 25 for star and planet shots?
Extensively, yes. The light on the Mk25 makes it a bit quicker taking down readings, but I've also used the Mk15 a lot, and have a small torch around my neck. I'm old-school and generally prefer a split screen to the 'all-view' but for someone starting out and getting comfortable with the 'all-view' it's fine.
Just what I was looking for. Thanks!
First-class explanation of three great sextants.
Regarding the Mk3, I would think that the lack of a telescope is more of a problem with sun and moon sights where you need to see the touching surfaces more precisely. A star is still a point of light even with a telescope. The main disadvantage of the Mk3 is the windage. Great for young students though. Thank you!
You don’t need telescope for the sun because it’s large. Moon works either way; not as big as sun but bigger than stars. Stars you defo need the telescope. Been doing it 40 years. It’s only my view, but it is backed by experience. Cheers.
@@boatingequipmentreviews9478 A star or planet still looks like a star through a 3x telescope. Yes, the sun and moon are large but to see the point where they touch the horizon, a telescope makes this easier than with the naked eye. Perhaps you have exceptionally good eyesight. Incidentally, the moon and sun are almost the same size and your comment about them is puzzling.
I've always viewed the Davis plastic "Sextants" as mere TOYS. Personally I would never depend on on at sea! Unless I'm stranded in the vastness of the South Pacific Ocean with nothing better. My first choice is a good German instrument. And maybe the metal Chinese tool. It is claimed to be accurate to 20 arc seconds. That's a third of a nautical mile. So, for practical purposes in a smallish sailboat, good enough.
That of course is your prerogative. Many people - me included - have used Davis sextants to cross oceans. The benefit of light weight is important. Long before Satnav, I used a Mk15 to cross the Atlantic and Pacific oceans. On days with 7/8 cloud cover I would sometimes wait for ages with my arms wrapped around the shrouds, waiting for a momentary break in the cloud to get a sight. To use a metal sextant in those circumstances would be lead to very achy shoulders.
Robin Jacobs On a small craft with a low height of eye you are unlikely to get better than 3-4nm accuracy from any sextant. I’ve used the Davis Mk15 sextant as the primary nav equipment for quite a few ocean crossings. I’ve also used in coastal nav for horizontal angles, long before the advent of GPS. They ain’t toys. I recent viewed a Chinese metal sextant that claimed it was so accurate it didn’t need a correction card. That’s just rubbish. Every device has errors in it.
My eyeballs can't see 2 arc minutes of angle. The Davis 15 & 25 are more accurate than this operator when they are used properly. For the money, they are a great value. ...and along with my compass, they still work after the boat gets hit by a lightening strike, unlike my chart plotter, depth finder, EPIRB, etc.