More Complicated Than I Thought...

This is a detailed picture of a horoscope and how it is created. So, I didn't realize how complicated the process was, but here is my attempt at explaining it based on my research...
Important terms to know:
There are four angles, or Cardinal points of an astrological chart: the Ascendant, the Midheaven, the Descendant and the Imum Coeli.

"The astrological chart is a schematic representation of the sky at any given moment of time, projected upon the ecliptic--or the apparent path of the Sun as seen from the Earth--which forms the circle in which the chart is enclosed."
Ascendant= exact place where the Sun's path crosses the horizon in the East.
Midheaven=highest point in the sky reached by the Sun, or its culmination, as it crosses from one horizon to the other--the noon point in a chart which is plotted for dawn.
Descendant= where the Sun's path meets the horizon in the West.
Imum Coeli= bottom of the sky


The time and date of birth of a particular individual or the exact time and date must be known to an astrologer in order for them to create an appropriate horoscope. As far as the next steps are concerned, I'm not going to lie, it is extremely confusing to me, so I am going to simply paste my research and hope that it makes sense:
"To create a horoscope, an astrologer first has to ascertain the exact time and place of the subject's birth, or the initiation of an event. The local standard time (adjusting for any daylight saving time or war time) is then converted into Greenwich Mean Time or Universal Time at that same instant. The astrologer then has to convert this into the local sidereal time at birth in order to be able to calculate the ascendant and midheaven. The astrologer will next consult a set of tables called an ephemeris, which lists the location of the sun, moon and planets for a particular year, date and sidereal time, with respect to the northern hemisphere vernal equinox or the fixed stars (depending on which astrological system is being used). The astrologer then adds or subtracts the difference between the longitude of Greenwich and the longitude of the place in question to determine the true local mean time (LMT) at the place of birth to show where planets would be visible above the horizon at the precise time and place in question. Planets hidden from view beneath the earth are also shown in the horoscope".




http://en.wikipedia.org/wiki/Horoscope