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    Re: Web on-line CelNav sights reduction
    From: Antoine Couëtte
    Date: 2010 Nov 11, 08:48 -0800

    Nov 11, 2010

    Dear Gary and David,

    Better late than never !

    Thanks to both of you for your kind and quick replies in [NavList 14297 & NavList 14299].

    Actually, my (no longer now ...) secret aim was to try identifying Celnav Sites and preferably Government Celnav Sites who deal with the Planets phase correction.


    A few remarks remarks about the USNO site :

    The USNO site which you mentionned to me Gary specifically indicates that it does NOT take PLanetary S-D's in account. This is a bit surprising since the same USNO probably (still ??? ) keeps publishing Nautical Almanacs which incorporate data about such correction, and

    The USNO apparently would give ... Lower Limb planetary heights, whether Lower Limbs are visible or even NOT VISIBLE due to local circumstances. That would be QUITE impressive !!! even for any sharp eye sextant observer ... , and

    The USNO simply publishes what looks like being both :
    - geocentric coordinates of the various bodies center apparent coordinates, and
    - topocentric local coordinates of the same bodies (i.e. erath radius effect parallax duly taken in account) with no refraction. At first I was a bit disappointed that they do not include refraction - although they offer a value for it - but I am now realizing that it enables one to use his own refraction values, "just" as in other circumstances one would feel more comfortable to use his own chosen "TT-UT" value. Still - for the purists only - the USNO tabulated data would be best corrected with the 'reverse' refraction tables, or with Saemundson's Formula. It is my understanding that the USNO proposed refraction values might be based on the plain and usual "direct" tables. This approximation should be sufficiently accurate most of the time. The USNO also rightly points out the possible importance of any (big) error in DR position which might have a bigger effect on Refraction that their proposed use of the "direct" tables. And

    The USNO does not compute intercepts. This is a direct consequence of the choice here above.

    As a summary, I was highly expecting that the USNO Web site would definitely take in account the Planetary phase corrections effects. Alas, no !!! they do not not ... I now feel (miserably) disappointed ! If USNO does not (no longer ???) do it, who will on Earth ?

    Any info here ?


    Anyway, Thanks and Best Regards to both of you :-)))


    Antoine M. "Kermit" Couëtte

    [NavList 14299] Re: Web on-line CelNav sights reduction
    From: waldendand---com
    Date: 8 Nov 2010 15:55

    USNO links to:




    [NavList 14297] Re: Web on-line CelNav sights reduction
    From: glapook---net
    Date: 8 Nov 2010 09:38

    They changed their URL a while ago. Try http://www.usno.navy.mil/USNO/astronomical-applications/data-services/cel-nav-data

    it worked for me a second ago.

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