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    Re: Freiberger sextant
    From: Ridge White
    Date: 2012 Aug 13, 17:08 -0400
    Hi Jeremy,

    You mentioned wishing your Freiberger could be read to .1', a tenth of a minute. 

    In our many years of selling and servicing sextants of many types, we are often asked about the desirability of a vernier scale - instead of just an index mark - opposite the micrometer. A number of times I have pulled from our display a sextant without a vernier scale and have arbitrarily turned the micrometer drum to some position, at which time I ask the customer to read the micrometer drum against the index mark. Three times out of four the customer and I agree. When we don't, we differ by one tenth of a minute. Interpolating is something we do all the time.

    Given the likelihood that no sextant can repeat a reading down to one tenth of a minute because of tiny amounts of "slop" between the tangent screw and the limb, vernier scales strike us as maybe desirable - but by no means necessary - for accuracy. 

    Just one man's opinion. Anyone else have thoughts on this?

    Ridge White
      
    Robert E. White Instruments
    PO Box 775
    Medfield, MA 02052

    Tel: 617-482-8460
    Fax: 617-482-8304


    On Mon, Aug 13, 2012 at 11:33 AM, Jeremy C <jcaoy@yahoo.com> wrote:

    Hi All,

    I just took a ship from Anchorage Alaska to Singapore. She had onboard a Freiberger sextant, the first I had seen or used.

    Here's a photo: http://www.flickr.com/photos/37977699@N00/7774059416/

    I can't say that I was too impressed to be honest. It was fairly light, being all Aluminum, and the shades were nice. The unit was also well constructed and the movement of the arm and micrometer drum were silky smooth. Still the non-standard fork precluded the use of my 7x35 scope which was unfortunate.

    The biggest thing that bothered me was that the micrometer drum had me interpolate within 1' incriments. For a Lunarian, this is quite unacceptable. I want to interpolate at 0.1' or 0.2'.

    The weather on the 21 day trip was terrible for stars and shooting in general for my whole trip. I did manage a few sun lines which worked out well, but no stars. I will say that shooting at 60 deg N made this the closest to the pole I've ever shot. It's just too bad there was no chance to shoot a round of stars up there.

    Sadly the ship, MV VIRGINIAN, along with the sextant, will be on the beach being turned into razor blades in a few weeks, as the owners decided to sell it for scrap. So much for my second command. I guess that's the way of the shipping world.

    Jeremy
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