Solar Eclipse (2-D method)
--------------------------

The following QBASIC program will perform the calculations needed for
the 2-D method in conncetion with the solar eclipse observations,
performed by Astronomy On-Line participants.

It may be used freely and copied if the source is indicated.

Author: Mogens Winther, Soenderborg Amtsgymnasium, Soenderborg, Denmark 
Date:   October 24, 1996


SCREEN 11
DEFDBL A-H
DEFDBL J-Z
CLS
PRINT "Astronomy On Line , Solar Eclipse ."
PRINT "This Software makes all the calculations needed to the 2D method"
PRINT ""; ""
PRINT "First of all - it interpolates the correct declinations during
your observations"
PRINT " "
PRINT "Any data e.g. 14h18m should be entered in format 14 comma 18 "

'simple software, calculating the Sun and Moon declination
'as a function of time :  MET = Mean European Winter Time.
declsun = -(7 + 37 / 60 + 39.77 / 3600)
declmoon = -(6 + 32 / 60 + 2.59 / 3600)
rm = 15 / 60 + 18 / 3600
rs = 16 / 60 + 1.7 / 3600


'PRINT "declsun ", declsun
'PRINT "declmoon", declmoon
'hourly motion of the Sun :
hourmoSU = -(0 / 60 + 56.18 / 3600)
'hourly motion of the Moon :
hourmoMO = -(9 / 60 + 23.77 / 3600)
PRINT " "
PRINT "Now enter the UT time for your observed Maximum "
PRINT "Separation between hours minutes and seconds ; write a comma"
PRINT "Please observe, Universal time UT = ordinary European CEST  - 2 "
INPUT "UT TIME for MAXIMUM : ", iih, iim

time = iih + iim / 60
PRINT "UT - time entered by you : ", iih, iim
timetab = 13 + 23 / 60 + 50.198 / 3600

timediff = time - timetab

diffsun = hourmoSU * timediff
diffmoon = hourmoMO * timediff

declsun2 = declsun + diffsun
declmoo2 = declmoon + diffmoon
PRINT "Solar Geocentric Declination during your observations", declsun2
PRINT "Moon Geocentric Declination during your observations", declmoo2
PRINT " "

PRINT "Now, enter the accurate fraction between h and w "
INPUT "as observed by YOU during the eclipse maximum ", hdivW

PRINT " "
PRINT "H-W Fraction entered by you : ", hdivW


pi = 4 * ATN(1)
radfac = pi / 180
PRINT "Now enter your Geographical Latitude in Deg - comma - minutes"
INPUT idg, idm
geolat = idg + (idm / 60)
diff = (geolat - declmoo2)

xc = hdivW * 2 * rs + rm - rs


PRINT "Distance in Degrees from Lunar - center to Solar- center ", xc
PRINT " "
PRINT "Comparing with the Geocentric declinations above, this
separation"
PRINT "has decreased by an angle alfa (see the AOL Chapter on the 2D
Method)"
alfa = declmoo2 - declsun2 - xc
PRINT "this parallax angle alfa is equal to ", alfa
PRINT " "
PRINT "In addition - the difference between GL and LD (see text)", diff
distmoon = 6378 * SIN(diff * radfac) / SIN(alfa * radfac)
idistmon = INT(distmoon)
PRINT
"***********************************************************************"
PRINT "Finally the distance from us to the Moon is equal to",
idistmon, "  km"
PRINT
"***********************************************************************"