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    Metal versus plastic or better telescope?
    From: Randall Morrow
    Date: 2012 Mar 27, 07:35 -0700

       I recently acquired an Astra IIIB on eBay.  The results with my Davis Mark 15 were good for stars but sun and moon sights as well as index correction sights were less "stellar".   (pun intended, sorry)   Inferior optics may have contributed to this difficulty.
    Here are the first results with a metal sextant and a mirror AH, index correction of (+) 0.2:                                                          (GPS 35*19.5 N, 119*05.5W)

    The Davis sextant would change angles if you squeezed the handle too tight and I could never get two sun-index correction sights that were the same.   Seeing the point of tangency of the sun and the moon was always difficult due to what I described as optical distortion/lack of resolution of the shapes or the brightness  of one image washing out the other.   This Astra moon sight is the best I have ever done and I attribute this to a better telescope with more resolution.   The extra weight of the metal instrument will take getting used to but I think I can officially retire my Davis.    I hope sun sight have improved as well as the moon but I have wait to do manual sight reductions as the USNO web page does not include the sun.  

    Randall F Morrow PT
    Ergonomics Safety Consultant

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