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    Re: Centring Error Detector
    From: Brad Morris
    Date: 2014 Jan 23, 14:26 -0500

    Correct Örjan.  Its a Hirth radial interface.  From any one position to any other whole degree is accurate (for mine) to 0.5".   The repeatability (for mine) is 1/20".   Mine is divided into 360 parts (degrees).  Its traceable to NIST (National Institute of Standards and Technology) and is calibrated within the last year.  It is a spectacular piece of kit.

    Bill, I've gone through your post.  Yes, the Ultradex can take the place of the SNO-T and make short work of the motion from angle A to angle B.  The motion takes just a few seconds of time (5-10, we want to treat the Ultradex with respect).  In doing so, we have the accuracy and repeatability detailed above.

    I'll make a sketch of the optical path I'm thinking of.  Whilst I do have simultaneous access to a Nikon 6D Autocollimator, I would like to try to replicate the original patent.  There is a fundamental reason.  Last I checked, to purchase the Autocollimator and the Ultradex would cost > $40K.   That puts the solution Örjan specified well out of the reach of many. 

    Patience, the sketch is coming!


    On Jan 23, 2014 1:22 PM, "Örjan Sandström" <pokerbacken@yahoo.com> wrote:

    Uhm, i think you are both talking what I have been taught is Hirth Rings, accurate to better than 2 arcseconds and repeatable to 0.5 arcseconds.
    A set of 720 tooth rings (two for each indexing platform) should do well as sextant test platform, add a autocollimator and you are set
    should make short work of testing each degree to VERY accurate value, better than the readout of the sextant at any rate.
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