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Re: Accuracy of delta T

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  • prafulla Vaman Mendki
    Dear Laren Following are values of delta T which I have calculated: 3008BC : 23 Hours 46 min 5502BC : 2 days 9 hours,17 min 9102BC : 5 days 11 hours 9 min
    Message 1 of 26 , Apr 4, 2008
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      Dear Laren
      Following are values of delta T which I have calculated:
      3008BC : 23 Hours 46 min
      5502BC : 2 days 9 hours,17 min
      9102BC : 5 days 11 hours 9 min
      13902BC : 11 days 12 hours 51 min
      These match with Indian history.
      Prafulla

      --- In skymap@yahoogroups.com, Laren Dart <sandman@...> wrote:
      >
      > Thanks Chris,
      >
      > I know different programs use different formulas for dT. There
      isn't
      > really any way to be accurate, anyway. The Difference of Time is
      > basically an o-c residual in lunar theory. For all the talk about
      > "the tidal term," I've never seen any calculated values for what
      the
      > tidal coupling between Moon and Earth should be. There's no way I
      > could calculate it, but the Earth-Moon parameters should be known
      > well enough to at least get a reasonable estimate from some expert
      on
      > the subject. I got hooked on delta T back in the mid-70s, and
      have
      > turned into a real dT addict! :-)
      >
      > Have you ever seen a table of approximate calculated values for
      the
      > tidal coupling?
      >
      > Regards,
      > Laren
      >
      > At 12:37 PM 3/18/2008, you wrote:
      >
      >
      > >----- Original Message -----
      > >From: "Laren Dart" <<mailto:sandman%40got.net>sandman@...>
      > >To: <<mailto:skymap%40yahoogroups.com>skymap@yahoogroups.com>
      > >Sent: Monday, March 17, 2008 6:44 PM
      > >Subject: Re: [skymap] Re: Accuracy of delta T
      > >
      > >Hi Laren,
      > >
      > >To answer your question about deltaT:
      > >
      > >Before 948AD the formula used is:
      > >
      > >B = (dJE - 948.0)/100.0;
      > >ans = (46.5 * B - 405.0) * B + 1830.0;
      > >
      > >Between 948 and 1620, the formula is:
      > >
      > >B = (dJE - 1850.0)/100.0;
      > >ans = 22.5 * B * B;
      > >
      > >where:
      > >
      > >dJE = 2000.0 + (dJD - J2000)/365.25;
      > >
      > >(dJD is the current Julian day number)
      > >
      > >In both these cases, a correction is applied:
      > >
      > >T = (dJD - J2000)/36525.0;
      > >ans += 0.6 - 0.6*T - 2*T*T;
      > >
      > >to avvount for the difference in the Moon's secular acceleration
      assumed by
      > >Stephenson and Houlden and that used by the ELP2000 lunar
      ephemeris, which
      > >SkyMap uses.
      > >
      > >After 1620, the tabulated values from the AA are used.
      > >
      > >Regards,
      > >
      > >Chris
      > >
      > >
      >
      >
      > Laren Dart
      > http://ldart.got.net
      >
      >
      > [Non-text portions of this message have been removed]
      >
    • Chris Marriott
      ... From: prafulla Vaman Mendki To: Sent: Friday, April 04, 2008 12:36 PM Subject: [skymap] Re:
      Message 2 of 26 , Apr 4, 2008
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        ----- Original Message -----
        From: "prafulla Vaman Mendki" <prafulla_mendki@...>
        To: <skymap@yahoogroups.com>
        Sent: Friday, April 04, 2008 12:36 PM
        Subject: [skymap] Re: Accuracy of delta T


        > Dear Laren
        > Following are values of delta T which I have calculated:
        > 3008BC : 23 Hours 46 min
        > 5502BC : 2 days 9 hours,17 min
        > 9102BC : 5 days 11 hours 9 min
        > 13902BC : 11 days 12 hours 51 min
        > These match with Indian history.
        > Prafulla

        Prafulla,

        I don't mean to offend your religious beliefs, but in fairness to the
        members of this group, I have to warn people that, in my considered opinion,
        your treatment of the Indian epics such as the "Mahabharata" as literal
        historical documents, describing real events which can be precisely dated,
        is of extremely dubious veracity. The view of "mainstream" historians is
        that these are "oral" epics, very like those traditionally attributed to
        Homer, and were composed at approximately the same sort of time (somewhere
        between about the 8th and 6th centuries, BC).

        To regard their descriptions of events dating back to 13,000 BC as anything
        other than myth is, I think, unsupportable, especially in light of
        archeological evidence placing the oldest human civilizations as those of
        southern Iraq (around what is now the Shatt-al-arab waterway) in around 5000
        BC (the Sumarian civilization of cities such as Ur), while the oldest known
        cities in India are those of the Indus Valley civilization in modern day
        Pakistan, which flourished from around 3300-1700 BC.

        You are welcome to your views, of course, but I cannot allow them to be put
        forward on this mailing list as "scientific" calculations without a "health
        warning" such as this.

        I do not wish to discuss this matter further - it is way off topic for this
        group. Anyone interested should consult appropriate historical references.

        Thank you,

        Chris
      • Laren Dart
        Chris, As someone who has been researching Delta T for many years, I thank you for this responce. I received email from this person on the same subject and
        Message 3 of 26 , Apr 4, 2008
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          Chris,

          As someone who has been researching Delta T for many years, I thank
          you for this responce. I received email from this person on the
          same subject and promptly trashed it. I try to keep an open mind,
          but there is a limit!

          Laren

          At 01:22 PM 4/4/2008, you wrote:


          >----- Original Message -----
          >From: "prafulla Vaman Mendki"
          ><<mailto:prafulla_mendki%40yahoo.co.in>prafulla_mendki@...>
          >To: <<mailto:skymap%40yahoogroups.com>skymap@yahoogroups.com>
          >Sent: Friday, April 04, 2008 12:36 PM
          >Subject: [skymap] Re: Accuracy of delta T
          >
          > > Dear Laren
          > > Following are values of delta T which I have calculated:
          > > 3008BC : 23 Hours 46 min
          > > 5502BC : 2 days 9 hours,17 min
          > > 9102BC : 5 days 11 hours 9 min
          > > 13902BC : 11 days 12 hours 51 min
          > > These match with Indian history.
          > > Prafulla
          >
          >Prafulla,
          >
          >I don't mean to offend your religious beliefs, but in fairness to the
          >members of this group, I have to warn people that, in my considered opinion,
          >your treatment of the Indian epics such as the "Mahabharata" as literal
          >historical documents, describing real events which can be precisely dated,
          >is of extremely dubious veracity. The view of "mainstream" historians is
          >that these are "oral" epics, very like those traditionally attributed to
          >Homer, and were composed at approximately the same sort of time (somewhere
          >between about the 8th and 6th centuries, BC).
          >
          >To regard their descriptions of events dating back to 13,000 BC as anything
          >other than myth is, I think, unsupportable, especially in light of
          >archeological evidence placing the oldest human civilizations as those of
          >southern Iraq (around what is now the Shatt-al-arab waterway) in around 5000
          >BC (the Sumarian civilization of cities such as Ur), while the oldest known
          >cities in India are those of the Indus Valley civilization in modern day
          >Pakistan, which flourished from around 3300-1700 BC.
          >
          >You are welcome to your views, of course, but I cannot allow them to be put
          >forward on this mailing list as "scientific" calculations without a "health
          >warning" such as this.
          >
          >I do not wish to discuss this matter further - it is way off topic for this
          >group. Anyone interested should consult appropriate historical references.
          >
          >Thank you,
          >
          >Chris
          >
          >
          >No virus found in this incoming message.
          >Checked by AVG.
          >Version: 7.5.519 / Virus Database: 269.22.5/1359 - Release Date:
          >4/4/2008 8:23 AM


          Laren Dart
          http://ldart.got.net


          [Non-text portions of this message have been removed]
        • prafulla Vaman Mendki
          Dear Chris I have calculated delta T using mathematical formulae. There is no relegious matter. If you have calculated any values of delta T ,pl. let me know.
          Message 4 of 26 , Apr 6, 2008
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            Dear Chris
            I have calculated delta T using mathematical formulae.
            There is no relegious matter.
            If you have calculated any values of delta T ,pl. let me know.
            Archeology has already found old city of Dwarka and also river
            Sarswati which had disappeared 5000 years ago.
            However the question under discussion was not Mahabharata or
            archeology Indian history.
            If you have calculated any figures of delta T for this period
            pl.let me know.

            --- In skymap@yahoogroups.com, "Chris Marriott" <chris@...> wrote:
            >
            >
            > ----- Original Message -----
            > From: "prafulla Vaman Mendki" <prafulla_mendki@...>
            > To: <skymap@yahoogroups.com>
            > Sent: Friday, April 04, 2008 12:36 PM
            > Subject: [skymap] Re: Accuracy of delta T
            >
            >
            > > Dear Laren
            > > Following are values of delta T which I have calculated:
            > > 3008BC : 23 Hours 46 min
            > > 5502BC : 2 days 9 hours,17 min
            > > 9102BC : 5 days 11 hours 9 min
            > > 13902BC : 11 days 12 hours 51 min
            > > These match with Indian history.
            > > Prafulla
            >
            > Prafulla,
            >
            > I don't mean to offend your religious beliefs, but in fairness to
            the
            > members of this group, I have to warn people that, in my
            considered opinion,
            > your treatment of the Indian epics such as the "Mahabharata" as
            literal
            > historical documents, describing real events which can be
            precisely dated,
            > is of extremely dubious veracity. The view of "mainstream"
            historians is
            > that these are "oral" epics, very like those traditionally
            attributed to
            > Homer, and were composed at approximately the same sort of time
            (somewhere
            > between about the 8th and 6th centuries, BC).
            >
            > To regard their descriptions of events dating back to 13,000 BC as
            anything
            > other than myth is, I think, unsupportable, especially in light of
            > archeological evidence placing the oldest human civilizations as
            those of
            > southern Iraq (around what is now the Shatt-al-arab waterway) in
            around 5000
            > BC (the Sumarian civilization of cities such as Ur), while the
            oldest known
            > cities in India are those of the Indus Valley civilization in
            modern day
            > Pakistan, which flourished from around 3300-1700 BC.
            >
            > You are welcome to your views, of course, but I cannot allow them
            to be put
            > forward on this mailing list as "scientific" calculations without
            a "health
            > warning" such as this.
            >
            > I do not wish to discuss this matter further - it is way off topic
            for this
            > group. Anyone interested should consult appropriate historical
            references.
            >
            > Thank you,
            >
            > Chris
            >
          • David Webber
            From: prafulla Vaman Mendki ... In mathematical terms the problem is one of *extrapolation*. If you have a formula y=f(t)
            Message 5 of 26 , Apr 7, 2008
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              From: "prafulla Vaman Mendki" <prafulla_mendki@...>

              > I have calculated delta T using mathematical formulae.
              > There is no relegious matter...

              In mathematical terms the problem is one of *extrapolation*. If you have a
              formula y=f(t) which fits data giving good values of y for some range of t,
              but know nothing outside that range, then you must *never* use the formula
              outside that range.

              The reason is that there is an infinite number of formulae which will fit
              data within a range, but diverge (sometimes spectacularly) outside that
              range. And the one which fits "best" within the range will not turn out
              to be the best outside the known range.

              [If you know something about the expected form of f(t) outside the range,
              then you can cautiously relax the "never", but in that case it becomes an
              "untested prediction" instead of a "random guess"- it still isn't fact or
              even a "calculation".]

              Extrapolation of mathematical correlations therefore becomes a matter of
              faith, rather than of science. And any "data" you refer to at the dates
              you mention (and certainly to the accuracy you want) is also a matter of
              faith rather than of science.

              SkyMap's success is based on it being firmly rooted in science, not faith.
              It has to be. Science is based on tests which anyone can do, and get the
              same answer. Faith is something which is different for everyone, so a
              single computer program cannot cover it.

              Dave
              David Webber
              Author of 'Mozart the Music Processor'
              http://www.mozart.co.uk
              For discussion/support see
              http://www.mozart.co.uk/mozartists/mailinglist.htm
            • Richard Mallett
              Reply to : Laren Dart ... Where did you find that ? I can t find it in Skymap Pro 10, and it s not in the list of new features for Skymap Pro 11. -- Richard
              Message 6 of 26 , Apr 10, 2008
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                Reply to : Laren Dart
                >
                > Got it! I thought I found it once, but couldn't find it again. I'll
                > try entering the delta T from Guide and see what happens. Guide
                > allows entering different formulas for different periods of time,
                > but doesn't allow entering individual values the way SM does. Both
                > ways are very useful to me.
                >
                Where did you find that ? I can't find it in Skymap Pro 10, and it's
                not in the list of new features for Skymap Pro 11.

                --
                Richard Mallett
                Eaton Bray, Dunstable
                South Beds. UK
              • Laren Dart
                Richard, I spent ten minutes trying to find it again. Help | Eclipse settings has a great image of the dialogue panel, but doesn t give a clue where to find
                Message 7 of 26 , Apr 10, 2008
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                  Richard,

                  I spent ten minutes trying to find it again. Help | Eclipse settings
                  has a great image of the dialogue panel, but doesn't give a clue
                  where to find it. I found it, you have to have a map showing. Then
                  click Map | Eclipse settings. But any program that makes an
                  experienced user have trouble finding a feature is not terribly
                  impressive. I've used Guide since 2000, strictly for eclipses, and
                  still had trouble.

                  Laren

                  At 11:05 AM 4/10/2008, you wrote:

                  >Reply to : Laren Dart
                  > >
                  > > Got it! I thought I found it once, but couldn't find it again. I'll
                  > > try entering the delta T from Guide and see what happens. Guide
                  > > allows entering different formulas for different periods of time,
                  > > but doesn't allow entering individual values the way SM does. Both
                  > > ways are very useful to me.
                  > >
                  >Where did you find that ? I can't find it in Skymap Pro 10, and it's
                  >not in the list of new features for Skymap Pro 11.
                  >
                  >--
                  >Richard Mallett
                  >Eaton Bray, Dunstable
                  >South Beds. UK
                  >
                  >
                  >No virus found in this incoming message.
                  >Checked by AVG.
                  >Version: 7.5.519 / Virus Database: 269.22.11/1371 - Release Date:
                  >4/10/2008 12:23 PM


                  Laren Dart
                  http://ldart.got.net


                  [Non-text portions of this message have been removed]
                • chris@chrism.demon.co.uk
                  ... It s not a new feature - it s been there for a number of versions. Display a solar eclipse map. On the map window, go to the Map menu and select the
                  Message 8 of 26 , Apr 10, 2008
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                    Quoting Richard Mallett <100114.573@...>:

                    > Where did you find that ? I can't find it in Skymap Pro 10, and it's
                    > not in the list of new features for Skymap Pro 11.

                    It's not a new feature - it's been there for a number of versions.

                    Display a solar eclipse map. On the map window, go to the "Map" menu
                    and select the "Eclipse Settings" dialog.

                    Regards,

                    Chris
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