Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: A-12 etc.
    From: Gary LaPook
    Date: 2008 Sep 04, 00:32 -0700

    I love my M1A.
    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.
    >Here's a great article on Celestial from an airbus pilot.
    >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
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site