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    Re: Neat video about LEM stellar alignment scope
    From: Brad Morris
    Date: 2016 Jun 9, 12:07 -0400

    In my experience as a engineer, the resolution should be about 10 times finer than the desired measurement.  Which implies a measurement good to +/-0.2°.

    One could argue that 5 times is sufficient resolution.  Certainly, it's practical if the measurement is taken with care.  Nothing like life and death survival to stir the measurement juices!  But IMO that's as far as you should push it.  Which implies a measurement good to +/-0.1°.

    Very likely that the intent was just to get the vehicle back near Earth and then use ground based radar for final adjustment.


    On Jun 9, 2016 11:10 AM, "Don Seltzer" <NoReply_Seltzer@fer3.com> wrote:
    Yes, I also think that those are likely typos, but I wanted to copy exactly what was published.

    Don Seltzer

    Sent from my iPad

    On Jun 9, 2016, at 1:38 AM, Brad Morris <NoReply_Morris@fer3.com> wrote:


    There appear to be typographical errors in that text. 

    The counter reads in degrees to within ±0.02" or ±72 seconds. 
    Shouldn't it read to ±0.02°, not ±0.02"?

    The maximum reading is 359.88 degrees.
    Shouldn't it read to 359.98 degrees?

    Obviously, this takes nothing away from the intent or data of the paragraph.  I just puzzled over it for a moment or two until it made sense. 


    On Jun 8, 2016 7:55 PM, "Don Seltzer" <NoReply_Seltzer@fer3.com> wrote:

    On Wed, Jun 8, 2016 at 5:08 AM, Gary LaPook <NoReply_LaPook@fer3.com> wrote:
    I wonder what what level of precision they achieved (needed) for this method of measuring angles to celestial objects.

    It doesn't exactly answer the intent of your question, but I did dig up the following:

    A reticle control enables manual rotation of the reticle for use in lunar surface alignments. A counter on the left side of the unit, provides angular readout of the reticle rotation. The counter reads in degrees to within ±0.02" or ±72 seconds. The maximum reading is 359.88 degrees, then the Counter returns to 0 degrees. Interpolation is possible to within ±0.01 degrees. 

    Don Seltzer

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