Ebbco Sextant

coopec

coopec

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Some years ago I bought an Ebbco Sextant on eBay for £7 but it wasn't working. I fixed the mirrors and think I've got it working but I suspect there is a glass lens missing in the far end of the "telescope". I took it to the optician who said if it was missing it may be just plain glass to keep the dust off the eye piece. As I can read the degree measurement I think maybe he is correct

Does anyone know?

Clive
PS The would be "Captain Cooks" might like to look at the two being auctioned on eBay. I was very tempted until I saw the postage to Australia was £25.
 
Although I have an Ebbco sextant which I bought new in the '70s, unfortunately I have taken the possibly unjustified risk of trying to navigate through Friesland without it and so I don't have it to hand to check.
 
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Bought one off ebay and found that the filters had degraded. Returned it and got my money back but every time I see one I write and ask if the filters are OK and every time the sellers who have 'found' it in a loft or junk shop and have no idea how it works, look at the filters which they hadn't checked and they are not usable.
 
coopec said:
Some years ago I bought an Ebbco Sextant on eBay for £7 but it wasn't working. I fixed the mirrors and think I've got it working but I suspect there is a glass lens missing in the far end of the "telescope". I took it to the optician who said if it was missing it may be just plain glass to keep the dust off the eye piece. As I can read the degree measurement I think maybe he is correct

Does anyone know?
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I'm puzzled. Why would the state of the telescope have anything to do with whether you can read the degree scale?

Pete
 
coopec said:
. As I can read the degree measurement I think maybe he is correct .
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coopec said:
Pete

Maybe I should have called it an "eye piece" or something like that
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I think Pete was puzzled, as I was, that the telescope/ eyepiece had anything to do with reading the degree scales

Do you use it as a magnifier to read the scales in addition to using it as the telescope to take the sight ?

I didn't ask for fear of making a fool of myself. I thought I'd leave that honour to someone else

What ever I would say that if you can focus the telescope on the horizon there is not likely to be a lens missing
 
VicS said:
I think Pete was puzzled, as I was, that the telescope/ eyepiece had anything to do with reading the degree scales

Do you use it as a magnifier to read the scales in addition to using it as the telescope to take the sight ?

I didn't ask for fear of making a fool of myself. I thought I'd leave that honour to someone else

What ever I would say that if you can focus the telescope on the horizon there is not likely to be a lens missing
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Well I had never seen a sextant before and I've only practiced taking a few shots (noon sights?) so I'm not much help. (It is something I'll spend a bit of time in the future)

Yes I can see the horizon and I can bring the reflected image down beside it so I suppose it must working OK as you say

Temp%20Sextant%20parts_zpsqtlloa4q.jpg
 
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VicS said:
What ever I would say that if you can focus the telescope on the horizon there is not likely to be a lens missing
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Seems like the acid test.

For ease, set the reading to zero degrees and look through the eyepiece towards the horizon. Don't expect sharpness of a more expensive instrument but you should see two horizons. A small adjustment of the micrometer barrel should align the two (this should be done at every use and the value written down as it's used in the sight reduction process).

I had an Ebbco and sold it for £20 on ebay to a forumite. He bought a bargain!

Despite their often bad press, they are ok for sun sights. Within limits, of course. I wouldn't recommend trying to take a star or planet sight as the optics aren't up to the task.

Hope you have fun with it. Please keep posting questions about astro because it brings out the salty sea dogs who have lots of knowledge and experience and willing share it for us all to learn more!
 
davidjackson said:
Seems like the acid test.

For ease, set the reading to zero degrees and look through the eyepiece towards the horizon. Don't expect sharpness of a more expensive instrument but you should see two horizons. A small adjustment of the micrometer barrel should align the two (this should be done at every use and the value written down as it's used in the sight reduction process).

I had an Ebbco and sold it for £20 on ebay to a forumite. He bought a bargain!

Despite their often bad press, they are ok for sun sights. Within limits, of course. I wouldn't recommend trying to take a star or planet sight as the optics aren't up to the task.

Hope you have fun with it. Please keep posting questions about astro because it brings out the salty sea dogs who have lots of knowledge and experience and willing share it for us all to learn more!
Click to expand...
In the 1970s I had a basic Ebbco for some years, as long as you took an index error reading every single time it worked well enough, including for brighter stars or planets. Used for genuine offshore navigation, not just practice. As my eyes got older and I got paid a bit more I bought an ex WWII US Navy sextant with better optics. Not much real difference in sight accuracy, just much nicer to use.

In response to the OP - I wouldn't replace the filters with anything not intended for viewing the sun with - too easy to damage your eyes.....
 
davidjackson said:
Seems like the acid test.

For ease, set the reading to zero degrees and look through the eyepiece towards the horizon. Don't expect sharpness of a more expensive instrument but you should see two horizons. A small adjustment of the micrometer barrel should align the two (this should be done at every use and the value written down as it's used in the sight reduction process).

Hope you have fun with it. Please keep posting questions about astro because it brings out the salty sea dogs who have lots of knowledge and experience and willing share it for us all to learn more!
Click to expand...

I have done that exercise of setting it to zero degrees when I replaced the mirrors. Well it looks as though there is nothing wrong with it now.

I am very keen to learn to navigate using a sextant. Some time ago I looked at downloading a nautical almanac for 2016 and from memory I found a link.

Gee getting sights on the stars seems a bit ambitious at this stage!

Clive
 
I took a tongue lashing here about filters:

http://www.ybw.com/forums/showthrea...removing-properties/page3#ojYUX3SjuQuuXEbC.99

Conclusion seemed to be that: glass will filter out UV. So get some plain old glass from a local glass maker, fit it to all filters (and 'viewfinder' thing) and then you have a degree of safety and THEN place plastic colours over the glass filters so you can get a clear image of the sun.

I have an Ebcco somewhere in good nick and a Davis and I can post some photos if it would help you.

One day I will learn how to use the instruments. But at least I have them for now. Oh yes, I'd love an aluminium one, but that will wait for the 5 year circumnavigation adventure.
 
jwilson said:
In response to the OP - I wouldn't replace the filters with anything not intended for viewing the sun with - too easy to damage your eyes.....
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Yes, thanks for that advice but I do a bit of welding so I would be very careful.

Your comments regarding the US Navy sextant are interesting and appreciated.

Clive
 
You also need to ensure that you are not holding the hand grip too tightly, or you will distort the main body and change the reading. They are great value but you get what you pay for.
 
johnalison said:
You also need to ensure that you are not holding the hand grip too tightly, or you will distort the main body and change the reading. They are great value but you get what you pay for.
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Yes, I found that too. If I had time (and in open water you often do) I used to check index error, take 5 sights, check index error again, average them, and calculate and plot. Before GPS the only proof of accuracy of the Ebbco was finding islands or headlands where you expected them to be, but I always did.

Later with my old US Navy sextant I could compare astro position lines with GPS, rarely more than 2 miles out, often much closer.
 
Sailingsaves said:
I took a tongue lashing here about filters:

http://www.ybw.com/forums/showthrea...removing-properties/page3#ojYUX3SjuQuuXEbC.99

Conclusion seemed to be that: glass will filter out UV. So get some plain old glass from a local glass maker, fit it to all filters (and 'viewfinder' thing) and then you have a degree of safety and THEN place plastic colours over the glass filters so you can get a clear image of the sun.

I have an Ebcco somewhere in good nick and a Davis and I can post some photos if it would help you.

One day I will learn how to use the instruments. But at least I have them for now. Oh yes, I'd love an aluminium one, but that will wait for the 5 year circumnavigation adventure.
Click to expand...


Actually the filters on my sextant are usable so I'll leave them at this stage.

What I'd like to know is there a glass lens in the end of the telescope away from the eye-piece. And do you think it is plain flat glass or does it look like a curved magnifying lens.

Clive
 
If the question still hasn't been answered about the lenses in the eye piece or what I call the telescope in the Ebbco sextant, I can confirm that there is a lens in both ends of the eyepiece. the eyepiece is in two parts and if you only had one part you would then have only one lens as there is a lens in each part. And of course the two parts slide out and in to adjust the focus just like a telescope.

I have not used my Ebbco since 2007 when after 10 days of dense cloud I found I was in the Bay of Biscay not 50 miles west of the Scillies which was my dead reckoning. I have use dthe much more reliable GPS system since then.

I also have a Plath sextant but as a single hander I found the Ebbco being considerably lighter was much easier to use as once I had my sight I could drop it on the lanyard around my neck and take my time. When I could get a sight and worked out a position I found that generally in comparison to GPS I would be within 9 to 15 miles which was quite satisfactory to me. Never bothered with star sights as the likelihood of getting a good horizon at twilight was generally affected by haze at least in the North Atlantic.
 
I did the yachtmaster ocean theory course a couple of year's ago which covered astronav, however, ive never used the technique in anger and probably never will. The course though was a great way of filling a winter evening.There are a variety of books on the subject, the best is by Tom Cunliffe and also free online courses. I'd love a proper sextant but can't afford one. They're always on eBay, many from the far east where they are salvaged from scrapped ships. I think all commercial vessels are required to have one aboard but doubt whether the midshipmen are lined up for noon sights these days even in the Royal Navy.[QnUOTE=Sailingsaves;5733817]I took a tongue lashing here about filters:

http://www.ybw.com/forums/showthrea...removing-properties/page3#ojYUX3SjuQuuXEbC.99

Conclusion seemed to be that: glass will filter out UV. So get some plain old glass from a local glass maker, fit it to all filters (and 'viewfinder' thing) and then you have a degree of safety and THEN place plastic colours over the glass filters so you can get a clear image of the sun.

I have an Ebcco somewhere in good nick and a Davis and I can post some photos if it would help you.

One day I will learn how to use the instruments. But at least I have them for now. Oh yes, I'd love an aluminium one, but that will wait for the 5 year circumnavigation adventure.[/QUOTE]
 
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