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I will be posting about the bygrave in the next couple of days,

gl
bruce hamilton wrote:

>Well, I just received my second bubble sextant in the mail. It was an
>A-12 and it looks new.  I suspect it might be a Celestaire re-build as
>it looks so new, and regular batteries fit. I was all ready to take it
>to work and trim the battery holders down a bit on the lathe, but I
>won't have to.  It came with 2 working bubble sets, and the only thing
>I  might improve is the bubble size, so I will order some Xylene later
>this week. Any recommendations on the perfect bubble size to shoot for?
>
>It was overcast tonight, but I took it out and tried it a bit and peeked
>a a few stars. I have a lot of light pollution where I live,but the
>superimposed bubble is great.  I spent a few years being taught how to
>line up one small round object in a bigger round object, but this
>process doesn't leave me with ringing ears and a sore shoulder. Ah, the
>joys of a steel butt plate.
>
>
>I can see why I was cautioned about getting a bubble sextant by list
>members. They are brilliant machines and you can't buy just one. I can
>also make sure my apartment has not moved, just by stepping out on the
>balcony. I did a LOP with the A10 the other evening with a sun shot a
>half hour before sunset and was 0.87 NM from my AP, which was my actual
>position taken from Google earth. (More luck than skill).  I figured out
>its index error using a distant bridge.  I hope to take both of the
>sextants down to my local surveying shop and pop them in front of the
>horizontal collimator. The fellow in the shop seems to like madmen like
>myself who insist on using antiques to get around in this GPS age. I was
>fascinated to hear that they get accuracies of 2 cm with a proprietary
>GPS system they use now.
>
>I would like to try a bubble sextant on a ship some day. The biggest
>ship I ever worked on would hardly roll at all on a calm day, and even
>less with a load of iron ore!  I used to practice sun shots on my first
>ship, a salty little 315 foot coastal freighter, and always wondered how
>people managed to do it on a sailboat in weather.I used to work out
>distance off by verticle angle with any handy lighthouse, or other
>object of known height, and found that to be quite accurate. I never did
>much horizontal angle work, but an old classmate who is a coast guard
>officer says they still double check all buoy positions that way.
>
>I had asked where Radio Direction finders went as they were the cheap
>backup when I last pleasure sailed in the mid seventies.  I see that the
>technology has been dropped by pleasure boaters, and can only find old
>sets. The modern commercial sets look great and give you an instant
>readout calculated from 4, or more antennas. No more seeking the null.
>Hams use them too. I used the Marconi RDF on the first ship I was a
>cadet on, and it was pretty handy when the loran-c chains were acting
>up, and there was nothing on the radar close enough to give a good range
>and bearing.  I have dim memories of applying some sort of corrections
>for far away stations. The correction sheet looked like sine wave. I'll
>have to look it up in Bowditch. It was great as you would find a strong
>station get a bearing and there you were with a bearing and something to
>listen to as well as it picked up many bands.  Aircraft still have ADF,
>but like all avionics, they are pricey. The Grampion 30 that I sailed
>from Thunder Bay Ont to Georgian Island had nice portable RDF on it. I
>think it was the Gladding Cyclone pictured on the page below.
>
>
>
>Here's a page of old RDFs.
>
>http://www.angelfire.com/space/proto57/rdf.html
>
>
>Here's a great article on Celestial from an airbus pilot.
>
>http://www.airspacemag.com/flight-today/celestial.html
>
>Thanks again for all the information. I enjoy reading everyone's posts.
>
>Other projects I have in mind. I just got 3 microscope slides so if
>anyone has some good pages on the Briss sextant, please send it to me.
>
>Once Gary has recovered from his trip, I look forward to his posting the
>information on the Byrave sextant as constructing one is going to be a
>winter project for me. Here in Vancouver BC, we might not see the sky
>for months on end so I need something to do other than work through
>celestial nav examples.
>
>
>Bruce Hamilton
>Vancouver, BC
>
>>
>
>
>


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