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    Russian Sextants
    From: Jean-Philippe Planas
    Date: 2005 Nov 15, 10:32 -0800
    Hello list-members
    I am new in this list and I am a relatively recent owner of an SNO-M and SNO-Ts Russian sextants. Here are the results of some measurements taken last summer in a trial to compare their respective performances.
    I am still a relative beginner at taking sights with sextants. I mostly practice backyard sights with an artificial horizon (plate filled with water). therefore the results are scattered due to wind and operator lack of practice.
    With the SNO-T I took around 150 sights and reduced all of them resulting in a mean value Hc-Hs=0.02'  with a Standard Deviation of 0.35'. I use the on line Almanach provided by the US Naval Obervatory from my known geographical position (N48? 47.1, E02? 10.5). All sights were taken with the 6x Astronomical (inverting) telescope.
    I have practiced less with the SNO-M that I find more tiring ! to handel and less ergonomic. (no thumb rest on the back side of the sextant frame). The drum scale is also more difficult to read when compared with the SNO-T. The SNO-T allows a drum scale reading of 0.1' (do you agree?) when the markings width on the SNO-M allows readings with a precision of 0.2' at best.
    From a series of about 40 sights with the SNO-M, the result is an average of 0.43' with a SD of 0.55'. Of course I took all SNO-M sights using a 6x Astronomical (inverting) telescope.
    For both sextant I did not try to correct the readings with the sextant correction table (only available for the SNO-T and not with the SNO-M).
    I also practised Star-Star distances with both instrument in a try at gathering data to produce a correction table against angle but I had disappointing results so far. Only the Standard Deviations are smaller with both sextants at 0.2' for the SNO-M and less than 0.2' for the SNO-T.
    I practised lunar-distances with the SNO-T in order to find GMT Time and had very widespread results, from 18s to a couple of minutes! I had only one try with the SNO-M and found time within 20s (sheer luck).
    In general I find the SNO-T far easier to handel and to read measurement from than the SNO-M.
    I  would be interested if SNO-Ms  and SNO-Ts users could share their experience at using those instruments.


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