European Helio- and Asteroseismology Network (HELAS)

    Local Helioseismology Network Activity








    Geometry of the Observed Solar Surface



    (L0, B0) is the central longitude and latitude of the apparent solar disc.

    1. Use soho_ephem.c to determine L0, B0 as viewed by SOHO-MDI at a particular time like this, with year.month.day_hour:minute:second 

    STANFORD> soho_ephem 2002.04.14_22:52:56
    which will return 
    OBS_DIST (au L0 (deg  B0 (deg VR (m/s) VN (m/s) VW (m/s) Carr Rot
0.9919838074 150.007  -5.6812   476.97  2363.58 29524.2 1988.5833

    Note: If fastrack.c left the MDI header keywords OBS_L0 and OBS_B0 in the fastracked cube headers, the need for soho_ephem would be redundant.

     

    The solar ephemeris can also be calculated from this tool.

    To calculate the longitude and latitude of each spatial point of a map which has been Postel projected use geom_postel.pro.

    A solar rotation applet good to understand L0 and B0.

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