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    Re: Venus mer-pass for Lat, Sun time sight for Lon.
    From: Antoine Couëtte
    Date: 2020 Apr 11, 12:20 -0700

    Nice to get some numbers crunching opportunities. Thanks to you Tony.

    Please find here-enclosed the results of my computations (check enclosed document).

    From only Venus, I am getting through a LAN method : 

    Transit Time at 12h56m49.4s, yielding Fix at N60°14.2’ E029°45.8’

    Using the here-above Fix as DR position and through processing ALL Venus and Sun observations as LOP's, I am getting as Final Fix :  N60°14.6’ E029°51.3’ .

    This Final Fix is essentially a Longitude Correction to the LAN Fix.

    LAN Fixes are known - "by essence / per se" actually - to yield generally better results in Latitude than in Longitude. Even here at 60°N the Latitude correction is only 0.4 NM while the Longitude correction is 2.2 NM.

    Hence these results seem quite reasonable and consistent between them. They demonstrate that you are a good and reliable observer, Tony.

    Two Questions or Remarks then :

    1 - Tony, how does this Final Fix compare to your GPS Fix ?

    2 - As we are an international group, we do not use the same acronyms throughout. I again experienced difficulties in decyphering the exact meanings of your "Ha" and "Ho" Values. I eventually ended up suspecting your "Ha" values as directly read from the Sextant indexes and corrected for only Instrument Errors. At least this has been my assumption throughout this lengthy many-hour computation, re-checking and proof-reading task.

    Nonetheless, while suspecting your "Ho" values to probably represent the geocentric values, I have failed to entirely reconcile them with their "Ha" counterparts. For the Sun Ha's and Ho's seem to differ by one half diameter (i.e. approximately 15') , but unfortunately this does not occur for every single case. Hence it is a bit annoying to accept that - in spite of a sizeable 3+ hour effort - I might have based my computations one some false initial assumption.

    File:
    200411-Tony-Oz-Venus-Sun-Data-computed-by-AMC-.pdf
       
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