SUNCLOCK(1)              USER COMMANDS                SUNCLOCK(1)



NAME
     sunclock - show illuminated portion of Earth

SYNOPSIS
     sunclock [ _o_p_t_i_o_n_s ]

DESCRIPTION
     _s_u_n_c_l_o_c_k is an X11 application that displays a  map  of  the
     Earth  and indicates the illuminated portion of the globe by
     drawing sunlit areas dark on light, night areas as light  on
     dark.  It also displays the current date and time.

OPTIONS
     The program does not use the X Toolkit, and hence only those
     options  explicitly  enumerated  below may be used.  Neither
     are any resources used.

     -version
          Show program version and patch level, and then exit.

     -display _d_i_s_p_n_a_m_e
          Give the name of the X server to contact.

     -iconic
          Start iconic.  Usually you will want  to  specify  this
          option.

     -geometry +_x+_y
          Specify the position of the window.  Only the  position
          is used; any size information given is ignored.

     -icongeometry +_x+_y
          Specify the position of the icon.  Only the position is
          used; any size information given is ignored.

HOW IT WORKS
     _s_u_n_c_l_o_c_k calculates the position of the Sun using the  algo-
     rithm in chapter 18 of:

     _A_s_t_r_o_n_o_m_i_c_a_l _F_o_r_m_u_l_a_e _f_o_r _C_a_l_c_u_l_a_t_o_r_s by Jean  Meeus,  Third
     Edition, Richmond: Willmann-Bell, 1985.

     and Mercator projects the illuminated area onto  map  image.
     The  Sun's  position  is  calculated to better than one arc-
     second in accuracy.

BUGS
     The maps are not rescaled if you resize the open  window  or
     icon.   (I don't want to have to store a vector database for
     the map.)  The program  contravenes  section  4.1.9  of  the
     ICCCM  in  that  its  icon  window  is a fixed size, and any
     WM_ICON_SIZE property of the root window is ignored.



Sun Release 4.1           Last change:                          1






SUNCLOCK(1)              USER COMMANDS                SUNCLOCK(1)



     The illuminated area shown is the area which would be sunlit
     if the Earth had no atmosphere.  The actual illuminated area
     is larger because of atmospheric refraction and twilight.

AUTHOR
     John Mackin, Basser Department of Computer Science,  Univer-
     sity   of  Sydney,  Sydney,  Australia;  <john@cs.su.oz.AU>.
     Based on a Suntools program by John Walker, Autodesk,  Inc.;
     <kelvin@acad.uu.NET>.














































Sun Release 4.1           Last change:                          2