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    Re: Lunar longitudes, not by lunar distance.
    From: Brad Morris
    Date: 2009 Aug 8, 22:44 -0400
    Hi Hanno
     
    I do not possess a transit, but that will be the instrument you will require.  I believe that the instrument that you have found is for equal altitudes. 
     
    Firstly, the altitude of the objects as they cross your meridian will be at different altitudes as a function of their declination.  You will likely be forced to adjust the elevation of the observation telescope to see the moon and the other celestial object.  You may get lucky and have both objects within the scope without change, but the moon's declination changes constantly.
     
    You may obtain the expected meridian passage of the sun and moon at Greenwich directly from the Nautical Almanac to the nearest second.  It is a simple matter to convert your longitude to time and predict when the objects will cross your meridian.  Alternatively, you can obtain more exact data from the Astronomical Almanac for the these objects.  If you choose to use stars, then it is simple to calculate the meridian crossing. 
     
    The procedure for aligning your transit to the meridian is given in Bowditch.  In my 1856 copy, there is a wonderful exposition on this procedure.  Any earlier edition will have this, 1856 is not important.
     
    -------------
    Ah, sight reduction.  For meridian crossings, you will only get a Line of Positon (LOP) that is equal to your latitude.  May I recommend Dutton's Piloting and Navigation, 1973 or earlier.  That is the textbook used by the US Navy at Annapolis, to train cadets in celestial navigation.  This is a wonderful learning tool and will explain the entire process to you, in gory detail.  You can generally get a copy of Dutton on eBay for less than $20.
     
    However, there will be no exposition of the experiment you have proposed in Dutton.  If you wish guidance on transits and how to align to the meridian, you will need an older resource.  Norie's, Bowditch, Moore, etc will serve your purpose.
     
    Best Regards
    Brad
     
     
     

    From: NavList@fer3.com [NavList@fer3.com] On Behalf Of Hanno Ix [hannoix---.net]
    Sent: Saturday, August 08, 2009 1:15 PM
    To: NavList@fer3.com
    Subject: [NavList 9416] Re: Lunar longitudes, not by lunar distance.


    Gentlemen:

    Thanks for agreeing so graciously.

    Would you, too, like to proceed to more technical issues?

    1. The transit.

    Searching for a suitable instrument I found an old invention on the net. Would you please take the effort of loading down from Google Patent the US patent 239,315.  It carries the title: Altitude Instrument, and was issued to S.C.Chandler of Boston on March 29, 1881.

    The instrument is of  simple construction, and it is not out of he question for a hobbyist to reconstruct it .The drawings show an instrument a microscope.resembling in size and shape and are clear enough to understand its mechanics and optics.

    BTW: Who was S. C. Chandler?

    J. Palisa, at that time Director of the Observatory in Vienna, Austria, reported on its practical use. Thanks to the present officers there, I have now in hand two reports by Palisa on his experiments - one in German, the other in French. I have yet to find out the exact citations. According to the reports, Palisa made experimental observations  in 1888 at Vienna.

    The instrument he used had been built by Hartmann & Braun. According to Wikipedia, the Co existed independently from 1882 until 1999.It was located around Frankfurt, Germany.  It's records are said to be kept at the Historical Institute of the City of Frankfurt Palisa says the actual implemetation included several improvements suggested by his Institute.

    Palisa refers to the instrument as a  Chronodeik. I am still studying the reports. Perhaps you can assist in locating reports about the Chronodeik in the English language? I am eager to find out what accuracy he might have achieved. Would it be sufficient for a practical test of our concept?

    If you have other idea re: a suitable astonomicals transit taht van be taken along please inform us.


    2. The sight reduction.

    I am a novice. So, if you kow how meridian transits is properly reduced please let me know, too. Palisa gave some hints.


    3. DT.

    I reckon, Chauvette's methods are too cumbersome today when my PC can calculate accurate epherimides.  I assume there are fancy programs on the market that could calculate ephemerides. However, I have MATLAB, a rather complete technical system, and would love to calculate and tabulate DT myself.


    Best regards, and a happy weekend!

    H



    --- On Sat, 8/8/09, George Huxtable <george{at}hux.me.uk> wrote:

    From: George Huxtable <george{at}hux.me.uk>
    Subject: [NavList 9411] Re: Lunar longitudes, not by lunar distance.
    To: NavList@fer3.com
    Date: Saturday, August 8, 2009, 6:12 AM


    Hanno Ix wrote, in [9382],

    If I see things right, there must be a LOP which connects all locations
    on Earth with a given, fixed difference DT between the meridian
    passages of sun and moon.

    What I meant is:

    If I see things right, there must be a LOP which connects all those
    locations
    on Earth that have a given, fixed difference DT between the meridian
    passages of sun and moon.

    ================

    and I replied, in [9402]-

    Is there woolly thinking here, I wonder?

    Wherever on Earth the Moon is seen from, it's phase is the same except for
    the effects of parallax, which can be corrected for. At Full Moon, it's
    always very nearly 180 º from the Sun. So that's the Sun's lunar distance,
    which is the same wherever on Earth it's observed from. And then the time
    difference between meridian passages of Sun and Moon is 12 hours, the whole
    World over. The phase of the Moon, the lunar distance, and the time
    difference between meridian passages, change in step, going through a whole
    cycle in a month, and at any moment in the month all are the same wherever
    on Earth they are observed from. Measuring a lunar distance, or the time
    between meridian passage (or even the phase, if it was possible to do that
    precisely), all provide the same message: the time of the month. From that
    time of the month, from the nautical tables, we could deduce the day (if
    that was needed) or, more importantly, the time-of-day, in terms of GMT. It
    by comparing that GMT with the local time that we deduce the longitude.

    There's no "LOP which connects all those locations on Earth that have a
    given, fixed difference DT between the meridian passages of sun and moon."
    At any moment that DT is the same everywhere.

    ===================


    To which Brad Morris has responded in [9403]-

    Hang on George,


    Hanno has required that the moon and the other object be ON the meridian at
    different times, and that the delta time between those meridian passages be
    the key component.

    I agree with your statement that it is the same for everybody on earth,
    should that delta time not include the meridian passage.

    Once the meridian passage is included however, then only ONE meridian has
    that precise delta time, the meridian of observation.  As the earth rotates
    and the moon changes position, then the delta time will change.

    At your meridian in the UK, the delta time will be X.  By the time those
    same objects individually CROSS MY MERIDIAN in the US, about 5 hours later,
    the position of the moon will change by about 2.5 degrees.  Thus the delta
    time between those objects on my meridian will be different!

    Anyone on your meridian, independent of latitude and under the assumption
    that they can see them, will get the same delta time.

    ===================

    Response from George-

    It's making my head hurt a bit, this question, but I now think Brad, and
    Hanno also, have it right.

    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.








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