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: Lunar Distances with Alex's SNO-T
    From: Alexandre Eremenko
    Date: 2006 Dec 3, 19:11 -0500

    I made some further testing
    of this SNO-T sextant, following an advise of
    Frank (who tried it for several weeks).
    His advise was to slacken the
    pressure of
    the misterious adjusting screw on the drum
    (this tiny SNO-T screw was discussed several times
    on the old list). As a result, the worm can be rotated now
    with very light effort. The results seem to be satisfactory.
    (Previously, more than a year ago,
    I actually tightened this screw myself,
    that I couldprevent or remove backlash this way).
    Nov 21 IC from Sun -0.4, 4SD exact
    Nov 22 IC from Sun -0.5, 4SD exact
    Using IC=-0.5:
    Deneb-Vega at 24d 3 observations, errors: 0.0, 0.2, 0.1
    Altair-Deneb at 38d 4 observations, errors: 0.3, 0.0, 0.0, 0.3
    Nov. 23 IC=-0.5 from Altair, 6 obs, sigma=0.2
    Using IC=-0.5:
    Deneb-Vega at 24d, 3 observations, errors: 0.1, 0.1, 0.0
    Altair-Deneb at 38d, 4 obs 0.0, 0.2, -0.2, 0.2
    Nov. 24 lunars:
    Sun-Moon at 46 degrees, errors: 0.3, 0.2, 0.2, -0.1, 0.2,
    Average error 0.16, sigma=0.15
    Sun-Moon at 47 degrees, errors: 0.1, 0.1, 0.2, 0.3, 0.1,
    Average error 0.16, sigma=0.09.
    Dec. 2 IC=-0.45 from Sun 4SD exact, 5 obs, sigma=0.15
    Using IC=-0.45
    Dec. 2 lunars:
    Moon-Altair at 99 degrees, errors: -0.1, 0.0, 0.4, -0.2, -0.1,
    average error 0.0, sigma=0.23.
    On Sat, 2 Dec 2006, Bill wrote:
    > Bill, you wrote:
    > > "Point being, I seriously doubt the lasers you refer to meet the standards  of
    > > both monochromatic and collimated light. "
    > Frank replied:
    > > They're real lasers. They produce monochromatic, coherent light --no
    > > cheating on the terminology. All lasers have some beam spread, and you can
    > > counteract it, up to the diffraction limit, using a telescope...
    > Ok. I'm buying into that.  Been shopping.  Found a straight-line laser for
    > $5 after rebate at Ace.  It's nice as the height in relation to the eyepiece
    > doesn't matter much, and very easy to center on eye-side scope lens, but it
    > does not produce the fine spike that a point source produces.
    > Borrowed a friend's "Taiwan Tom" level laser complete with tripod and all
    > the niceties, but the off/on knob is on the front so one cannot center the
    > beam up with the scope.
    > Finally, after realizing batteries for my aging Compaq pen/pointer gimme
    > would be $12 and considering that a poor investment as the dot is more of an
    > ellipse than a circle, I ferreted out a laser pointer/led light/pen at Wal
    > Mart for the princely sum of $2.88!  It works very well, with a fine
    > vertical diffraction line.
    > Refining rigs to mount it now, as well as producing a circle to mount on the
    > eye end of the scope with a tiny hole to be sure I am shooting down the
    > center of the scope.  Centering the spot on the glass/mirror section of the
    > horizon mirror is simple trial and error and can be done satisfactorily by
    > eye.
    > Using George's suggesting on how to determine the distance between the
    > horizon mirror and index mirror working points, I set up the rigs for trial
    > runs. The distance was only 40 ft, but the results were right on (probably
    > beginner�s luck.)
    > Last sun IE check was 0.788' on the arc.  When matching the predetermined
    > mirror distance, the sextant reading was just a hair below 0.8' on the arc.
    > I'm looking forward to more stringent tests as greater distances.
    > Thanks for the idea Frank.
    > Alex
    > You ready to grab some sextants, a pair of FRS radios and go play?
    > Bill
    > >
    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to 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