Seeking an ecliptic monitor

  1. I'm looking for a good source for the day by day (or even smaller graduations would be nice) angle of the sun along the ecliptic. I would like to know exactly when the various "solar terms" begin and end, and their dates and times vary from year to year.

    http://en.wikipedia.org/wiki/Solar_term

    Thanks.
     
  2. jcsd
  3. The JPL Horizons database will give you this information. For example, I set it up as follows:

    Ephemeris Type [change] : OBSERVER
    Target Body [change] : Sun [Sol] [10]
    Observer Location [change] : Geocentric [500]
    Time Span [change] : Start=2014-03-20 21:00, Stop=2014-03-20 22:00, Step=1 m
    Table Settings [change] : QUANTITIES=1,9,15,20,23,24
    Display/Output [change] : default (formatted HTML)

    And I got the output below. This allows you to see that the vernal equinox (Sun's longitude = 0) happens at 2014-Mar-20 21:40 . It's a simple matter to set it up to find whatever longitude you want. For example, the first one (longitude = 315 degrees, which is RA = 21h) happens at 2014-Feb-01 16:23

    Code (Text):

    *******************************************************************************
    Ephemeris / WWW_USER Thu Jan 30 07:11:50 2014 Pasadena, USA      / Horizons    
    *******************************************************************************
    Target body name: Sun (10)                        {source: DE-0431LE-0431}
    Center body name: Earth (399)                     {source: DE-0431LE-0431}
    Center-site name: GEOCENTRIC
    *******************************************************************************
    Start time      : A.D. 2014-Mar-20 21:00:00.0000 UT      
    Stop  time      : A.D. 2014-Mar-20 22:00:00.0000 UT      
    Step-size       : 1 minutes
    *******************************************************************************
    Target pole/equ : IAU_SUN                         {East-longitude +}
    Target radii    : 696000.0 x 696000.0 x 696000.0 k{Equator, meridian, pole}    
    Center geodetic : 0.00000000,0.00000000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)}
    Center cylindric: 0.00000000,0.00000000,0.0000000 {E-lon(deg),Dxy(km),Dz(km)}
    Center pole/equ : High-precision EOP model        {East-longitude +}
    Center radii    : 6378.1 x 6378.1 x 6356.8 km     {Equator, meridian, pole}    
    Target primary  : Sun
    Vis. interferer : MOON (R_eq= 1737.400) km        {source: DE-0431LE-0431}
    Rel. light bend : Sun, EARTH                      {source: DE-0431LE-0431}
    Rel. lght bnd GM: 1.3271E+11, 3.9860E+05 km^3/s^2                              
    Atmos refraction: NO (AIRLESS)
    RA format       : HMS
    Time format     : CAL
    EOP file        : eop.140129.p140422                                          
    EOP coverage    : DATA-BASED 1962-JAN-20 TO 2014-JAN-29. PREDICTS-> 2014-APR-21
    Units conversion: 1 au= 149597870.700 km, c= 299792.458 km/s, 1 day= 86400.0 s
    Table cut-offs 1: Elevation (-90.0deg=NO ),Airmass (>38.000=NO), Daylight (NO )
    Table cut-offs 2: Solar Elongation (  0.0,180.0=NO ),Local Hour Angle( 0.0=NO )
    ****************************************************************************************************************************
     Date__(UT)__HR:MN     R.A._(ICRF/J2000.0)_DEC  APmag  S-brt Sl-lon Sl-lat            delta      deldot    S-O-T /r    S-T-O
    ****************************************************************************************************************************
    $$SOE
     2014-Mar-20 21:00     23 59 53.90 -00 00 40.0 -26.75 -10.59   n.a.   n.a. 0.99596242291714   0.4932997   0.0000 /?   0.0000
     2014-Mar-20 21:01     23 59 54.05 -00 00 39.1 -26.75 -10.59   n.a.   n.a. 0.99596262076792   0.4933022   0.0000 /?   0.0000
     2014-Mar-20 21:02     23 59 54.20 -00 00 38.1 -26.75 -10.59   n.a.   n.a. 0.99596281861970   0.4933046   0.0000 /?   0.0000
     2014-Mar-20 21:03     23 59 54.35 -00 00 37.1 -26.75 -10.59   n.a.   n.a. 0.99596301647246   0.4933071   0.0000 /?   0.0000
     2014-Mar-20 21:04     23 59 54.51 -00 00 36.1 -26.75 -10.59   n.a.   n.a. 0.99596321432621   0.4933096   0.0000 /?   0.0000
     2014-Mar-20 21:05     23 59 54.66 -00 00 35.1 -26.75 -10.59   n.a.   n.a. 0.99596341218094   0.4933120   0.0000 /?   0.0000
     2014-Mar-20 21:06     23 59 54.81 -00 00 34.1 -26.75 -10.59   n.a.   n.a. 0.99596361003666   0.4933145   0.0000 /?   0.0000
     2014-Mar-20 21:07     23 59 54.96 -00 00 33.1 -26.75 -10.59   n.a.   n.a. 0.99596380789337   0.4933170   0.0000 /?   0.0000
     2014-Mar-20 21:08     23 59 55.11 -00 00 32.1 -26.75 -10.59   n.a.   n.a. 0.99596400575107   0.4933194   0.0000 /?   0.0000
     2014-Mar-20 21:09     23 59 55.27 -00 00 31.2 -26.75 -10.59   n.a.   n.a. 0.99596420360975   0.4933219   0.0000 /?   0.0000
     2014-Mar-20 21:10     23 59 55.42 -00 00 30.2 -26.75 -10.59   n.a.   n.a. 0.99596440146942   0.4933243   0.0000 /?   0.0000
     2014-Mar-20 21:11     23 59 55.57 -00 00 29.2 -26.75 -10.59   n.a.   n.a. 0.99596459933007   0.4933268   0.0000 /?   0.0000
     2014-Mar-20 21:12     23 59 55.72 -00 00 28.2 -26.75 -10.59   n.a.   n.a. 0.99596479719171   0.4933292   0.0000 /?   0.0000
     2014-Mar-20 21:13     23 59 55.87 -00 00 27.2 -26.75 -10.59   n.a.   n.a. 0.99596499505434   0.4933317   0.0000 /?   0.0000
     2014-Mar-20 21:14     23 59 56.02 -00 00 26.2 -26.75 -10.59   n.a.   n.a. 0.99596519291795   0.4933342   0.0000 /?   0.0000
     2014-Mar-20 21:15     23 59 56.18 -00 00 25.2 -26.75 -10.59   n.a.   n.a. 0.99596539078255   0.4933366   0.0000 /?   0.0000
     2014-Mar-20 21:16     23 59 56.33 -00 00 24.2 -26.75 -10.59   n.a.   n.a. 0.99596558864814   0.4933391   0.0000 /?   0.0000
     2014-Mar-20 21:17     23 59 56.48 -00 00 23.3 -26.75 -10.59   n.a.   n.a. 0.99596578651471   0.4933415   0.0000 /?   0.0000
     2014-Mar-20 21:18     23 59 56.63 -00 00 22.3 -26.75 -10.59   n.a.   n.a. 0.99596598438226   0.4933440   0.0000 /?   0.0000
     2014-Mar-20 21:19     23 59 56.78 -00 00 21.3 -26.75 -10.59   n.a.   n.a. 0.99596618225081   0.4933465   0.0000 /?   0.0000
     2014-Mar-20 21:20     23 59 56.94 -00 00 20.3 -26.75 -10.59   n.a.   n.a. 0.99596638012033   0.4933489   0.0000 /?   0.0000
     2014-Mar-20 21:21     23 59 57.09 -00 00 19.3 -26.75 -10.59   n.a.   n.a. 0.99596657799084   0.4933514   0.0000 /?   0.0000
     2014-Mar-20 21:22     23 59 57.24 -00 00 18.3 -26.75 -10.59   n.a.   n.a. 0.99596677586234   0.4933538   0.0000 /?   0.0000
     2014-Mar-20 21:23     23 59 57.39 -00 00 17.3 -26.75 -10.59   n.a.   n.a. 0.99596697373483   0.4933563   0.0000 /?   0.0000
     2014-Mar-20 21:24     23 59 57.54 -00 00 16.3 -26.75 -10.59   n.a.   n.a. 0.99596717160829   0.4933587   0.0000 /?   0.0000
     2014-Mar-20 21:25     23 59 57.70 -00 00 15.4 -26.75 -10.59   n.a.   n.a. 0.99596736948275   0.4933612   0.0000 /?   0.0000
     2014-Mar-20 21:26     23 59 57.85 -00 00 14.4 -26.75 -10.59   n.a.   n.a. 0.99596756735818   0.4933636   0.0000 /?   0.0000
     2014-Mar-20 21:27     23 59 58.00 -00 00 13.4 -26.75 -10.59   n.a.   n.a. 0.99596776523460   0.4933661   0.0000 /?   0.0000
     2014-Mar-20 21:28     23 59 58.15 -00 00 12.4 -26.75 -10.59   n.a.   n.a. 0.99596796311201   0.4933686   0.0000 /?   0.0000
     2014-Mar-20 21:29     23 59 58.30 -00 00 11.4 -26.75 -10.59   n.a.   n.a. 0.99596816099040   0.4933710   0.0000 /?   0.0000
     2014-Mar-20 21:30     23 59 58.45 -00 00 10.4 -26.75 -10.59   n.a.   n.a. 0.99596835886978   0.4933735   0.0000 /?   0.0000
     2014-Mar-20 21:31     23 59 58.61 -00 00 09.4 -26.75 -10.59   n.a.   n.a. 0.99596855675014   0.4933759   0.0000 /?   0.0000
     2014-Mar-20 21:32     23 59 58.76 -00 00 08.4 -26.75 -10.59   n.a.   n.a. 0.99596875463148   0.4933784   0.0000 /?   0.0000
     2014-Mar-20 21:33     23 59 58.91 -00 00 07.4 -26.75 -10.59   n.a.   n.a. 0.99596895251381   0.4933808   0.0000 /?   0.0000
     2014-Mar-20 21:34     23 59 59.06 -00 00 06.5 -26.75 -10.59   n.a.   n.a. 0.99596915039712   0.4933833   0.0000 /?   0.0000
     2014-Mar-20 21:35     23 59 59.21 -00 00 05.5 -26.75 -10.59   n.a.   n.a. 0.99596934828142   0.4933857   0.0000 /?   0.0000
     2014-Mar-20 21:36     23 59 59.37 -00 00 04.5 -26.75 -10.59   n.a.   n.a. 0.99596954616670   0.4933882   0.0000 /?   0.0000
     2014-Mar-20 21:37     23 59 59.52 -00 00 03.5 -26.75 -10.59   n.a.   n.a. 0.99596974405296   0.4933906   0.0000 /?   0.0000
     2014-Mar-20 21:38     23 59 59.67 -00 00 02.5 -26.75 -10.59   n.a.   n.a. 0.99596994194021   0.4933931   0.0000 /?   0.0000
     2014-Mar-20 21:39     23 59 59.82 -00 00 01.5 -26.75 -10.59   n.a.   n.a. 0.99597013982844   0.4933955   0.0000 /?   0.0000
     2014-Mar-20 21:40     23 59 59.97 -00 00 00.5 -26.75 -10.59   n.a.   n.a. 0.99597033771766   0.4933980   0.0000 /?   0.0000
     2014-Mar-20 21:41     00 00 00.12 +00 00 00.5 -26.75 -10.59   n.a.   n.a. 0.99597053560786   0.4934004   0.0000 /?   0.0000
     2014-Mar-20 21:42     00 00 00.28 +00 00 01.4 -26.75 -10.59   n.a.   n.a. 0.99597073349904   0.4934029   0.0000 /?   0.0000
     2014-Mar-20 21:43     00 00 00.43 +00 00 02.4 -26.75 -10.59   n.a.   n.a. 0.99597093139120   0.4934053   0.0000 /?   0.0000
     2014-Mar-20 21:44     00 00 00.58 +00 00 03.4 -26.75 -10.59   n.a.   n.a. 0.99597112928435   0.4934078   0.0000 /?   0.0000
     2014-Mar-20 21:45     00 00 00.73 +00 00 04.4 -26.75 -10.59   n.a.   n.a. 0.99597132717848   0.4934102   0.0000 /?   0.0000
     2014-Mar-20 21:46     00 00 00.88 +00 00 05.4 -26.75 -10.59   n.a.   n.a. 0.99597152507359   0.4934127   0.0000 /?   0.0000
     2014-Mar-20 21:47     00 00 01.04 +00 00 06.4 -26.75 -10.59   n.a.   n.a. 0.99597172296969   0.4934151   0.0000 /?   0.0000
     2014-Mar-20 21:48     00 00 01.19 +00 00 07.4 -26.75 -10.59   n.a.   n.a. 0.99597192086676   0.4934176   0.0000 /?   0.0000
     2014-Mar-20 21:49     00 00 01.34 +00 00 08.4 -26.75 -10.59   n.a.   n.a. 0.99597211876483   0.4934200   0.0000 /?   0.0000
     2014-Mar-20 21:50     00 00 01.49 +00 00 09.3 -26.75 -10.59   n.a.   n.a. 0.99597231666387   0.4934225   0.0000 /?   0.0000
     2014-Mar-20 21:51     00 00 01.64 +00 00 10.3 -26.75 -10.59   n.a.   n.a. 0.99597251456389   0.4934249   0.0000 /?   0.0000
     2014-Mar-20 21:52     00 00 01.80 +00 00 11.3 -26.75 -10.59   n.a.   n.a. 0.99597271246490   0.4934274   0.0000 /?   0.0000
     2014-Mar-20 21:53     00 00 01.95 +00 00 12.3 -26.75 -10.59   n.a.   n.a. 0.99597291036689   0.4934298   0.0000 /?   0.0000
     2014-Mar-20 21:54     00 00 02.10 +00 00 13.3 -26.75 -10.59   n.a.   n.a. 0.99597310826986   0.4934323   0.0000 /?   0.0000
     2014-Mar-20 21:55     00 00 02.25 +00 00 14.3 -26.75 -10.59   n.a.   n.a. 0.99597330617382   0.4934347   0.0000 /?   0.0000
     2014-Mar-20 21:56     00 00 02.40 +00 00 15.3 -26.75 -10.59   n.a.   n.a. 0.99597350407875   0.4934372   0.0000 /?   0.0000
     2014-Mar-20 21:57     00 00 02.55 +00 00 16.3 -26.75 -10.59   n.a.   n.a. 0.99597370198467   0.4934396   0.0000 /?   0.0000
     2014-Mar-20 21:58     00 00 02.71 +00 00 17.2 -26.75 -10.59   n.a.   n.a. 0.99597389989157   0.4934421   0.0000 /?   0.0000
     2014-Mar-20 21:59     00 00 02.86 +00 00 18.2 -26.75 -10.59   n.a.   n.a. 0.99597409779945   0.4934445   0.0000 /?   0.0000
     2014-Mar-20 22:00     00 00 03.01 +00 00 19.2 -26.75 -10.59   n.a.   n.a. 0.99597429570831   0.4934470   0.0000 /?   0.0000
    $$EOE
    ****************************************************************************************************************************
    Column meaning:
     
    TIME

      Prior to 1962, times are UT1. Dates thereafter are UTC. Any 'b' symbol in
    the 1st-column denotes a B.C. date. First-column blank (" ") denotes an A.D.
    date. Calendar dates prior to 1582-Oct-15 are in the Julian calendar system.
    Later calendar dates are in the Gregorian system.

      Time tags refer to the same instant throughout the universe, regardless of
    where the observer is located.

      The dynamical Coordinate Time scale is used internally. It is equivalent to
    the current IAU definition of "TDB". Conversion between CT and the selected
    non-uniform UT output scale has not been determined for UTC times after the
    next July or January 1st.  The last known leap-second is used over any future
    interval.

      NOTE: "n.a." in output means quantity "not available" at the print-time.
     
     R.A._(ICRF/J2000.0)_DEC =
       J2000.0 astrometric right ascension and declination of target center.
    Adjusted for light-time. Units: HMS (HH MM SS.ff) and DMS (DD MM SS.f)
     
     APmag S-brt =
       Sun's approximate apparent visual magnitude & surface brightness.
    APmag= M - 5 + 5*log10(d), where M= 4.83 and d= distance from Sun in parsecs.
       Units: MAGNITUDE & VISUAL MAGNITUDES PER SQUARE ARCSECOND
     
     Sl-lon Sl-lat =
       Apparent planetographic ("geodetic") longitude and latitude of the Sun
    (IAU2009) as seen by the observer at print-time. This is NOT exactly the same
    as the "sub-solar" (nearest) point for a non-spherical target shape, but is
    generally very close if not an irregular body shape. Light travel-time from Sun
    to target and from target to observer is taken into account. Latitude is the
    angle between the equatorial plane and the line perpendicular to the reference
    ellipsoid of the body. The reference ellipsoid is an oblate spheroid with a
    single flatness coefficient in which the y-axis body radius is taken to be the
    same value as the x-axis radius.  For the gas giants Jupiter, Saturn, Uranus
    and Neptune, IAU2009 longitude is based on the "System III" prime meridian
    rotation angle of the magnetic field. By contrast, pole direction (thus
    latitude) is relative to the body dynamical equator. There can be an offset
    between the magnetic pole and the dynamical pole of rotation. Positive
    longitude is to the EAST.  Units: DEGREES
     
     delta  deldot =
       Range ("delta") and range-rate ("delta-dot") of target center with respect
    to the observer at the instant light seen by the observer at print-time would
    have left the target center (print-time minus down-leg light-time); the
    distance traveled by a light ray emanating from the center of the target and
    recorded by the observer at print-time. "deldot" is a projection of the
    velocity vector along this ray, the light-time-corrected line-of-sight from the
    coordinate center, and indicates relative motion. A positive "deldot" means the
    target center is moving away from the observer (coordinate center). A negative
    "deldot" means the target center is moving toward the observer.
    Units: AU and KM/S
     
     S-O-T /r =
        Sun-Observer-Target angle; target's apparent solar elongation seen from
    observer location at print-time. If negative, the target center is behind
    the Sun. Angular units: DEGREES.

        The '/r' column is a Sun-relative code, output for observing sites
    with defined rotation models only.

             /T indicates target trails Sun (evening sky)
             /L indicates target leads Sun  (morning sky)

        NOTE: The S-O-T solar elongation angle is the total separation in any
    direction. It does not indicate the angle of Sun leading or trailing.
     
     S-T-O =
       "S-T-O" is the Sun->Target->Observer angle; the interior vertex angle at
    target center formed by a vector to the apparent center of the Sun at
    reflection time on the target and the apparent vector to the observer at
    print-time. Slightly different from true PHASE ANGLE (requestable separately)
    at the few arcsecond level in that it includes stellar aberration on the
    down-leg from target to observer.  Units: DEGREES


     Computations by ...
         Solar System Dynamics Group, Horizons On-Line Ephemeris System
         4800 Oak Grove Drive, Jet Propulsion Laboratory
         Pasadena, CA  91109   USA
         Information: http://ssd.jpl.nasa.gov/
         Connect    : telnet://ssd.jpl.nasa.gov:6775  (via browser)
                      telnet ssd.jpl.nasa.gov 6775    (via command-line)
         Author     : Jon.Giorgini@jpl.nasa.gov

    ****************************************************************************************************************************
     
     
  4. Thanks phyzguy, that was easy. :) If I used it correctly, this year solar spring begins Feburary 1st, 11:23 AM EST. Yay spring!
     
  5. I think you did it right. I don't know what causes the discrepancy. I would tend to believe JPL.
     
  6. What ya doing with the data? Anything fun?

    I went to http://www.imcce.fr/en/ephemerides/formulaire/form_ephepos.php and typed in your data... are you looking for the time when the Sun's ecliptic longitude is exactly 21h00m?
    I got about 11:44 UTC on Feb. 1, which is 7:44 Eastern, I believe.

    Edit... oops, make that the Sun's right ascention is exactly 21h00m.
     
    Last edited: Jan 30, 2014
  7. Thanks for the other source tfr000, I got the same answer. Yup, 21 hours exactly ~ I just wanna know when to celebrate spring!
     
  8. davenn

    davenn 3,811
    Science Advisor
    Gold Member
    2014 Award

    when the daffodils bloom and the lambs are frolicking in the fields :wink:


    Dave
     
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