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    Re: The new guy on the horizon...
    From: Geoffrey Kolbe
    Date: 2011 Oct 11, 07:13 +0100
    At 20:54 10/10/2011, Randall F Morrow  wrote:

     I have made an aluminum, three screw leveling plate with a 6 ½ inch square first-surface mirror as my a.h..    It is convenient and wind proof but a not very accurate since my Craftsman digital level is only accurate to 1/10 degree.   A hyper accurate level such as a coincidence level costs over $1300.00.   A Freiberger a.h.  runs over $800.00.   Cheaper digital levels run $40.00 and $162.00 for 1/10 degree and 5/100 degree accuracy respectively.

    Randall, small 20" precision machine levels are available brand new for around $170 (see http://www.leveldevelopments.com/acatalog/Precision_Engineers_Block_Levels.html for example). A diligent search on ebay will turn up second hand levels for less - and the vials for these levels for considerably less. You only need one if your setup is reasonably rigid - theodolites only have one level vial in them to level the thing up, for example. The Freiberger AH has two small 30" levels which can (and probably should) be left on the AH after it is levelled and while the sight is taken, so that the act of removing the level does not change the level-ness of the AH.

    As noted before though, the fact that the graduations on the level vials supplied with the Freiberger AH is 30" does not mean that this the best you can do in getting the thing level. It should be easily possible to get the Freiberger AH level to better than 6" of dead level using the levels supplied - which is the precision of most marine sextants - and with care within 3" of dead level should be achievable.

    Geoffrey Kolbe
       
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