I am a new member to this group. I found this group while searching
the math of astrology.
Basically my curiosity to know 'how astrology works' took me here. I
am trying to calculate a simple birth chart so that I can understand
what happens in the background.
I've been able to successfully calculate the MidHeaven(MC) but am
totally clueless to the Ascendant calculations.
I'm interested in calculating the birth chart for a person born
midnight GMT, 6 December 1970. So the following details are obtained -
Local Sidereal Time - 4 hours 57 min
RAMC = 74.25
Inclination = 23.44
Latitude at GMT = 51.5
MC = 74.68 (Hence Gemini)
how to calculate Ascendant?
I tried this formula (read this in the great article An Astrological
House Formulary by Michael P. Munkasey and the same formula has been
used in Astrolog Software)
ASC = ARCCOT (- ( (TAN f x SIN e) + (SIN RAMC x COS e) ) ÷ COS RAMC)
its not possible to get ARCCOT directly in MS Excel, also all values
have to be in Radians not degrees so I used following instead -
temp = - ( (TAN f x SIN e) + (SIN RAMC x COS e) ) ÷ COS RAMC
ASC(in radians) = ARCTAN(1/temp)
Here, f = latitude = 0.898844565 (in radians)
e = Inclination = 0.409105177 (in radians)
RAMC = 1.29590697 (in radians)
So putting values into the formula
temp = -( (TAN.89 x SIN .41) + (SIN1.296 x COS .41) ) ÷ COS 1.30
temp = -5.095479952
Asc = -0.193789483
So Ascendant in Degrees = -11.1
Now add 360 degree = Ascendant = 348.9 (hence, Pisces)
but the Ascendant should be VIRGO
Please help me with this, I am clueless, what's the mistake I am
doing ?
in the Astrolog Software they have this extra line -
DegreeFromRadian(Asc)+is.rSid
but I have no idea what is.rSid is. Please suggest me a way through
this...
Thanks
Arpit
I was making a terrible mistake in conversions of inverse
trigonometric functions. So if anyone wishes to calculate ascendant on
MS Excel, use the following conversion -
arccot(x) = pi() + arctan(1/x), where x<0
so,
temp = - ( (TAN f x SIN e) + (SIN RAMC x COS e) ) ÷ COS RAMC
ASC(in radians) = pi() + ARCTAN(1/temp)
But now I'm facing another problem -
In this article http://www.chrismitchell.bristolastrology.net/ascendant_calculation.html
by Chris Mitchell, its mentioned that the if it's a Southern latitude,
swap the signs round
But when I use above formula it automatically gives me the correct
ascendant and I don't need to swap the opposite signs. So is it normal
or am I making a calculation mistake again? Please help.