  The instant of greatest eclipse occurs when the distance between the Moon's shadow axis and Earth's 
geocenter reaches a minimum.  Although greatest eclipse differs slightly from the instants of greatest 
magnitude and greatest duration (for total eclipses), the differences are usually quite small. 
  Minimum distance of the Moon's shadow axis from Earth's center in units of equatorial Earth radii. 
  Eclipse magnitude is defined as the fraction of the Sun's diameter occulted by the Moon.  It is strictly a 
ratio of diameters and should not be confused with eclipse obscuration which is a measure of the Sun's 
surface area occulted by the Moon.  Eclipse magnitude may be expressed as either a percentage or a 
decimal fraction (e.g.: 50% or 0.50).
  T is the difference between Terrestrial Dynamical Time and Universal Time
  Eclipse obscuration is defined as the fraction of the Sun's surface area occulted by the Moon.
  P is defined as the contact angle measured counter-clockwise from the north point of the Sun's disk.
	V is defined as the contact angle measured counter-clockwise from the zenith point of the Sun's disk.
  For partial eclipses, maximum eclipse is the instant when the greatest fraction of the Sun's diameter is 
occulted.  For total eclipses, maximum eclipse is the instant of mid-totality.
  The elevation factor is the product, tan(90-A) * sin(D), where A is the altitude of the Sun and D is the 
difference between the azimuth of the Sun and the azimuth of the limit line, with the sign selected to be 
positive if the path should be shifted north with positive elevations above sea level.
  Minimum distance of the Moon's shadow axis from Earth's center in units of equatorial Earth radii.  
Gamma defines the instant of greatest eclipse and takes on negative values south of the Earth's center.
  In addition to the term transmittance (in percent), the energy transmission of a filter can also be described 
by the term density (unitless) where density 'd' is the common logarithm of the reciprocal of 
transmittance 't'  or  d = log10[1/t]. A density of '0' corresponds to a transmittance of 100%; a density of 
'1' corresponds to a transmittance of 10%; a density of '2' corresponds to a transmittance of 1%, etc....
  Aluminized polyester is popularly known to as mylar. DuPont actually owns the trademark "Mylar" 
and does not manufacture this material for use as a solar filter.
