Ascendant (Astrology)

Schematic representation of the position of the ascendant in 5 views with a day curve, meridian / longitude, center of the sky, horizon, equator and ecliptic (excerpt).

The ascendant ( Latin for 'the ascending') is a term from astrology . It is the intersection of the eastern horizon with the ecliptic and denotes the degree of the zodiac rising at the given time and geographical location on the eastern horizon . The opposite degree on the western horizon is called the descendant (Latin descendere , to descend).

Astrological definition

The ascendant is the beginning or the tip of the 1st house of the twelve-part astrological house circle and is considered a very important factor in the horoscope . In general, according to many astrologers, the ascendant (including other elements of interpretation) also describes the personality or at least a decisive part of it. From the ascendant as a starting point, it should be possible to determine the basic motivation with which the horoscope owner comes into life. It should, for example, show the instinctive temperament and initially unconscious 'vital forces' with which the born is essentially endowed. More traditional perspectives connect the ascendant with the physique and vitality. In astrological directions, which work with the so-called half sums , the ascendant is supposed to depict how the person affects his fellow world, how he is seen and perceived by it. It symbolizes the influence of others on one's own behavior as well as one's own reaction to the environment.

Calculation of the ascendant

Relationship between the ascendant, horizon and celestial equator

In order to be able to determine the zodiac sign of the intersection of the horizon and the ecliptic with a given local sidereal time θ, geographical latitude Φ and the inclination of the ecliptic ε = 23 ° 26 ′ 21.45 ″ ( J2000.0 ), its ecliptical longitude λ must be determined. From the triangle of the great circles horizon (in the astronomical sense), celestial equator and ecliptic on the celestial sphere (see graphic), the following relationship results according to the cotangent theorem :

{\ displaystyle \ sin \ epsilon \ cdot \ cot \ left ({\ pi / 2 + \ phi} \ right) = \ sin \ left ({\ pi / 2 + \ theta} \ right) \ cdot \ cot \ left (\ lambda \ right) - \ cos \ left ({\ pi / 2 + \ theta} \ right) \ cdot \ cos \ epsilon}

From it follows: ${\ displaystyle \ cot (\ pi / 2 + \ phi) = - \ tan \ phi \ ,, \, \, \ sin (\ pi / 2 + \ theta) = \ cos \ theta \ ,, \, \, \ cos (\ pi / 2 + \ phi) = - \ sin \ phi}$

{\ displaystyle \ tan \ lambda = {\ frac {- \ cos \ theta} {\ sin \ theta \ cos \ epsilon + \ tan \ phi \ sin \ epsilon}}}

Since most implementations of the arctangent function have the value range , the returned value has to be converted by λ mod 180 ° . There are also two points of intersection between the horizon and the ecliptic. To see which point is returning arctangent, consider the quadrant of θ. Applies the Descendant is returned, otherwise the ascendant. ${\ displaystyle (- \ pi / 2; \ pi / 2)}$ ${\ displaystyle \ pi / 2 <\ theta <3 \ pi / 2}$

To convert between ascendant and descendant, add 180 ° and, if necessary, bring the result back into the value range - for example with (λ + 180 °) mod 360 . ${\ displaystyle (0; 2 \ pi)}$

Determine the zodiac sign

The twelve signs of the zodiac used in astrology divide the ecliptic in 30 ° steps. Using the calculated ecliptical length λ, the corresponding sign of the zodiac can be determined from the table of signs of the zodiac.

Due to the precession effect, the base of the ecliptical coordinate system - the vernal equinox - continues to move on the ecliptic. This changes the position of all fixed stars and thus also of the constellations in the tropical zodiac . In this respect, today's astronomical constellation of the Ascendant differs from the astrological one.

Declination and right ascension of the ascendant

Since β = 0 ° ( ecliptical latitude ), the conversion of ecliptical and equatorial coordinates is particularly easy: sin ε · sin λ = sin δ and tan λ · cos ε = tan α .

Special cases

At the poles, the spring equinox always cuts the horizon. The ascendant therefore always has the ecliptical longitude 0 ° or 180 °, depending on the time of day.
On the polar circles, the horizon plane is parallel to the ecliptic plane once a day (at θ = 90 ° on the southern and θ = 270 ° on the northern polar circle). The two great circles then coincide and no ascendant can be defined.

Assess the error

Since θ, Φ and ε are always error-prone quantities, the error can be estimated using the total differential . The maximum error can be calculated by maximizing the partial derivatives; however, this does not make sense because the function has a pole at the Arctic Circle, as mentioned in the special cases, and the error there would theoretically be infinite. ${\ displaystyle \ Delta \ lambda = \ left | {\ frac {\ partial \ lambda} {\ partial \ theta}} \ right | \ Delta \ theta + \ left | {\ frac {\ partial \ lambda} {\ partial \ phi}} \ right | \ Delta \ phi + \ left | {\ frac {\ partial \ lambda} {\ partial \ varepsilon}} \ right | \ Delta \ varepsilon}$

A statistical method makes more sense: the error is better than for 99% of all values ${\ displaystyle \ Delta \ lambda = 2.77 \ Delta \ theta +6.42 \ Delta \ phi +6.25 \ Delta \ epsilon}$

This means that for 99% of all possible values for θ, Φ and ε the partial derivatives are smaller than the numbers shown. Since the local sidereal time is calculated by adding the geographical longitude to the sidereal time at the prime meridian, you can also write. ${\ displaystyle \ Delta \ theta = \ Delta \ Theta + \ Delta l}$

From this it can be seen that for a determination of λ with an accuracy of 1 ° the geographical latitude of the place of birth must be known at least to an accuracy of 9 ', this corresponds to around 17 km for the 50th degree of latitude. The time of birth is added to the sidereal time, the permitted error is 1 ° / 2.77, this corresponds to a period of approx. 1.5 minutes and is the required accuracy of the time of birth.

To determine the respective zodiac sign, a significantly greater inaccuracy is permitted (depending on the place and time). For the whole of Germany on February 18, 1983, the ascendant Gemini is from 11:00 a.m. to 11:40 a.m., in some places in Germany the ascendant begins between 10:00 a.m. (in the northeast) and 11:00 a.m. and ends after 1.5 hours to 2 hours between 11:40 a.m. and 12:45 p.m. (in the southwest).

Examples

Latitude [°]	Length [°]	Date (UT)	JD	T	Θ [°]	θ [°]	tan (λ)	S ₁ [°]	S ₂ [°]	Ascendant	Position [°]
48	16	11/10/1983 13:04	2445649,04444	-0.161422466	-2128074.8724	261.1276	-0.331882633	161.6399	341.6399	fishes	11.6399
-61	-27	12/10/1986 11:12 PM	2446775,46667	-0.130582706	-1721452.6173	40.3827	6.183809507	80.8141	260.8141	Twins	20.8141
78	17th	07.08.2007 13:08	2454320,04722	0.075976652	1002032,6786	169.6786	0.483263665	25.7928	205.7928	Libra	25.7928
-30	161	12/16/2002 11:32 PM	2452625,48056	0.029581945	390318,4334	239.4334	-0.498741575	153.4927	333.4927	fishes	3.4927
17th	57	05/17/1987 6:18 PM	2446933,26250	-0.126262491	-1664490.5863	206.4137	-3.125708396	107.7409	287.7409	Capricorn	17.7409
-1	-58	09/18/1979 3:35 AM	2444134,64931	-0.202884345	-2674749.7820	352.2180	7.553238471	82.4583	262.4583	Twins	22.4583
63	-17	09/17/1987 1:24 AM	2447055,55833	-0.122914214	-1620343.5457	359.4543	-1.295373592	127.6674	307.6674	lion	7.6674
-14	-6	12/6/2020 12:27 AM	2459189,51875	0.209295517	2759842,0104	76.0104	-0.305584898	163.0076	343.0076	Virgin	13.0076
-17	-61	10/28/1976 2:19 PM	2443080.09653	-0.231756426	-3055428.1992	190.8008	-3.346284094	106.6382	286.6382	Capricorn	16.6382
-27	51	03.09.2010 02:04	2455442,58611	0.106710092	1407253.1061	64.1061	-0.701318031	144.9573	324,9573	lion	24.9573
45	-93	08/03/2008 09:41 AM	2454681.90347	0.085883736	1132657,5913	4.5913	-2.115346746	115.3018	295,3018	cancer	25.3018
-90	-21	05/25/2015 7:15 am	2457167,80208	0.153943931	2030031,3107	330.3107	0.000000000	0.0000	180.0000	Aries	0.0000
-36	20th	11/21/1987 12:15	2447121,01042	-0.121122234	-1596716.2831	263.7169	-0.091126331	174.7932	354.7932	fishes	24.7932
-3	-178	07/12/2016 7:13 PM	2457582,30069	0.165292285	2179659.3601	41.3601	-1.282114641	127.9529	307.9529	lion	7.9529

Legend : Latitude / Longitude : Latitude or longitude, negative to the south or west; JD: Julian date; T: Julian centuries since J2000.0; Θ: sidereal time at the prime meridian; θ: local sidereal time; S ₁ and S ₂ : points of intersection of the ecliptic with the horizon; Position: difference in length at the beginning of the zodiac sign

Web links

Wiktionary: Ascendant - explanations of meanings, word origins, synonyms, translations

Individual evidence

↑ Nicolaus Klein: workbook on astrology . Heinrich Hugendubel Verlag, Munich 1993. P. 39f.
^ William Lilly : Christian Astrology. Book 1 and Book 2 . Chiron Verlag, Tübingen 2007. P. 70f.
↑ Reinhold Ebertin : The combination of the celestial influences . Ebertin Verlag, Freiburg / Breisgau 1983. P. 76f.

[1] Nicolaus Klein: workbook on astrology . Heinrich Hugendubel Verlag, Munich 1993. P. 39f.

[2] William Lilly : Christian Astrology. Book 1 and Book 2 . Chiron Verlag, Tübingen 2007. P. 70f.

[3] Reinhold Ebertin : The combination of the celestial influences . Ebertin Verlag, Freiburg / Breisgau 1983. P. 76f.