The Ascendant in Polar Latitudes - Reverse and Direct

The ascendant seems to behave unpredictably in polar regions, i.e., in areas above the arctic circle and below the antarctic circle. The ascendant seems to leap around, from one edge of the horizon to the other, and is sometimes direct and sometimes 'retrograde'. Some degrees never rise, and consequently can never set; some degrees never set, and consequently can never rise. However, the behaviour of the ascendant in polar latitudes is quite predictable and follows an understandable course.

The following description applies to all polar latitudes. However, as one travels north (in the northern arctic circle) fewer and fewer degrees rise and set in the conventional sense (i.e., in the manner that is observable in sub-polar latitudes). I will look at the situation at 70 North, which is around 3 1/2 degrees north of the arctic circle. At this latitude the two signs around the summer and winter solstices don't rise and set. The summer signs, Gemini and Cancer, remain above the horizon (i.e. are circumpolar and never set). The winter signs, Sagittarius and Capricorn, remain below the horizon and never rise.

It is worth bearing in mind that the phenomena associated with circumpolar and sub-horizon signs in the polar regions are related to the astrological concept of antiscia. Antiscia are pairs of degrees that fall equidistant from the winter and summer solstices. So the first circumpolar degree at any particular latitude (i.e., the first degree that doesn't set at the latitude), is the antiscion of the final circumpolar degree at that latitude. Degrees between the two antisicia are ones that remain above the horizon. A similar explanation may be given for sub-horizon signs in polar regions.

The following data is taken from a table of RAMC (right ascension of the MC) in Alan Leo's Casting the Horoscope. This book forms one part of Alan Leo's classic instructional textbooks for astrologers. Leo's tables give the RAMC for every latitude from the equator to 70 North. The ascendant for each latitude and RAMC can be read from the table. The RAMC for a given latitude also shows the MC.

The tables show that when the RAMC is 237 degs 03 mins (15 hours 48 mins and 12 secs) 29 Scorpio 15 is on the midheaven. This degree in Scorpio is the last degree to join the meridian before the phenomenon of sub-horizon midheavens occurs. At this time 29 Scorpio 15 also forms the ascendant. At polar latitudes, twice a day, the ascendant and MC will conjunct on the horizon due south of the observer. This is the first instance of the ascendant and MC conjoining. (See 1. in the image below.)

Leo's tables also show that the last degree to rise at 70 North (i.e., before the circumpolar zone of the zodiac) is 29 Taurus 15 - at RAMC 237 degs 03 mins (sidereal - 15 hours 48 mins and 12 secs). What is to be made of this? What the tables are illustrating is that at the moment the ascendant conjoins the MC due south at RAMC 237 degs 03 mins, the opposite degree in Taurus immediately begins to rise due north. At the same time the last degree of Scorpio becomes the descendant and begins to set. It is often said that the ascendant has 'flipped'. However, it is more accurate to say that the rising degree has passed from the final degree of Scorpio to the final degree of Taurus. This 'handover' occurs because of the way that the ecliptic moves in relation to the horizon in polar latitudes. (See 2. in the image below.)

What happens now is even more unusual, at least when compared to the principles of astrology in tropical and temperate regions. The ascendant degree begins to move along the eastern half of the horizon in a 'retrograde' fashion, with the later degrees in a sign rising before the earlier degrees. So, for example, 25 Taurus, in polar latitudes above 70 north, will rise before 20 Taurus, and this degree rises before 10 Taurus and so on. However, the degrees will rise in an orderly fashion, with each degree rising in sequence, but in reverse order to that observed in sub-polar latitudes. Notice that signs will also follow each other over the horizon in reverse order, with Taurus rising before Aries, Aries before Pisces and so on. To clarify this point, consider that in tropical and temperate zones the degree to rise after 29 Taurus would be 00 Gemini. However, in this example from the polar zone, 28 Taurus rises after 29 Taurus, and this is followed by 27 Taurus.

This phenomenon occurs because the ecliptic lies close to the plane of the horizon in polar latitudes. This means that rather than rising at a large angle to the horizon, the ecliptic appears to be 'peeled away' from the horizon, from the north point of the horizon to its south point. This is most noticeable when the ascendant is in reverse in the sense that I have described it here. The other notable feature of this retrograde ascendant is that the 'twelfth house' is below the horizon and the 'first house' is above the horizon. This is quite different to most astrological house systems in tropical and temperate regions where the twelfth house is above the horizon and the first is yet to rise (in the sense that is it has appeared above the horizon). The implications of this will be considered in a later article, looking at house systems in polar regions.

The ascendant now moves rapidly along the eastern half of the horizon towards the point due south of the observer. At times, around ten degrees of the ecliptic can rise in less than eight minutes (the first decan of Aries at 70 North). When the rising degree reaches the antisicion of 29 Scorpio 15 - 00 Aquarius 45 - the ascendant is again conjunct the MC. The midheaven, in the time that it has taken the ascendant to travel backwards from 29 Taurus 15 to 00 Aquarius 45, has travelled from 29 Scorpio 15 to 00 Aquarius 45. (See 3. in the image below.) This occurs at RAMC 302 degs 57 mins (sidereal - 20 hours 11 mins and 48 secs). In total the ascendant has been rising in reverse for 4 hours 23 mins 36 secs and has covered nearly half the zodiac.

At this point, the rising degree is immediately handed to 00 Leo 45 - due north of the observer. (See 4. in the image below.) From this point, until 29 Scorpio 15 again becomes the ascendant and MC conjointly due south of the observer, the ascendant will rise in the way that it does in sub-polar regions, with earlier degrees in a sign rising before later degrees. The order of the signs will also be preserved, with Leo rising before Virgo, etc. During the time that the ascendant moves from 00 Leo 45 to 29 Scorpio 15 the midheaven moves methodically (at the rate of one degree every four minutes) through the rest of the zodiac from 00 Aquarius 45 to 29 Scorpio 15. It 'chases' the slowly rising ascendant, eventually 'catching' the rising degree in the last degree of Scorpio. The movement of the ascendant from 00 Leo 45 to 29 Scorpio 15 takes 19 hours 36 mins 24 secs. The polar ascendant cycle then repeats during the next diurnal phase. All midheavens between 00 Aquarius 45 and 29 Scorpio 15 will be formed above the horizon, in the way that the MC is observed in tropical and temperate latitudes.

The following diagram summaries the movement of the ascendant and midheaven at the polar latitude of 70 degrees north. The cycle begins at 1. and concludes at 4. before returning to 1. for a further diurnal cycle.

Figure 1. The Ascendant and Midheaven at 70 Degrees North

In short, the minimum zenith distances of midheavens formed in Sagittarius and Capricorn at this latitude will be greater than ninety degrees (sub-horizon), whilst the minimum zenith distances of midheavens formed in the rest of the zodiac will be less than ninety degrees (above horizon). There are two midheavens at this latitude - 29 Scorpio 15 and 00 Aquarius 45 - where the zenith distance will be precisely ninety degrees (on the horizon) when the ascendant conjoins the MC at the sidereal times identified above.

Please note that the combined rising times for the retrograde and direct ascendants at 70 north is 24 hours, even though around 120 degrees of the zodiac (Sagittarius, Capricorn, Gemini and Cancer) will not rise (i.e., have a zenith distance of precisely ninety degrees) during the course of a day. A midheaven will be formed at all 360 degrees of the zodiac over the course of 24 hours. However, just over sixty degrees of the zodiac (Sagittarius, Capricorn) will form an MC below the horizon.

This article is the third part of a series of pieces exploring the ascendant, midheaven and houses in polar regions. Readers are directed to preliminary blog entries on the definition of the midheaven and ascendant using the concept of zenith distance.

The Definition of the Midheaven

The Definition of the Ascendant

The Definition of the Midheaven

The midheaven, or MC (from Medium Coeli), is one of the angles of the horoscope. The other principal angle is the ascendant. The identification of the angles seems unproblematic, and astrologers are often able to cite some sort of definition for each one. However, a technically correct definition for the ascendant or midheaven can be elusive.

For example astrologers will often say that the midheaven is the highest point in the chart. This is a disarmingly simple statement, but once considered in detail, turns out be a crude and problematic definition of the MC. Firstly, which point in the chart is being identified. To say the midheaven is the highest point in the chart doesn't really clarify the issue of what, exactly, this point is in the horoscope. Secondly, and most problematically, 'highest' in relation to what? Terms like 'highest' and 'higher' are relative and need to be defined in terms of some sort of absolute position.

Robert Hand provides two useful and more precise definitions in his essay on the ascendant, midheaven and vertex in extreme latitudes (for reference see below). Hand's first definition is that the midheaven may be the point of intersection of the meridian and ecliptic in the south. His second definition is that the midheaven may be the point of intersection of the ecliptic and meridian above the horizon. (p. 132)

These definitions do advance our understanding because we now know that the midheaven or MC is the point where the ecliptic meets the meridian. The meridian is the great circle through the running north and south points of the observer's horizon, and through the zenith, the point exactly overhead on the celestial sphere, and the nadir, the point on the celestial sphere opposite the zenith. 

The following diagram illustrates the points made in the previous paragraph. Note that the midheaven is shown crossing the ecliptic above the horizon and due south. This is a fair representation of the midheaven for a northern hemisphere observer at mid-latitudes. The diagram is for illustrative purposes and the situation will vary for observers at other latitudes.

Figure 1: The Celestial Sphere (Horizontal Frame of Reference)

But how do we decide between the definitions of the midheaven that Hand has offered? By direction? Or by altitude above the horizon? This is critical because in polar regions and at the equator both definitions become ambiguous for different reasons.

Let's consider the definition by direction. Firstly, to be accurate, the definition by direction must be made relative to the hemisphere of the observer. For those in the southern hemisphere, the midheaven is generally to the north. So for more precision, the definition of the midheaven must be extended to refer to the hemisphere of the observer. However, a problem immediately arises for observers in the tropics (those living close to the equator). For an observer who lives just north of the equator, the midheaven will be to their north when signs of northern declination (those north of the equator) are culminating.

So our definition by direction and hemisphere has already broken down. To correct this problem, we have had to qualify the directional definition further, by reference to the latitude of the observer. What seemed to be a straightforward description of the midheaven has now become complex and unwieldy.

What about the definition with relation to the horizon. In this definition the midheaven is always above the horizon, irrespective of its direction. This, on the face of it, seems quite reasonable. After all, it is true for anybody living in the tropics and temperate regions. However, when we get to the polar regions (beyond on the arctic or antarctic circles), we find that the midheaven so defined may again be to the north for northern observers. Others also claim that the MC is always to the south in polar regions even when it is below the horizon.

I think there are good reasons why we should be critical of both definitions of the midheaven - by direction (south/north) and by position relative to the horizon (above/below). Neither seems to have offered an unambiguous definition of the concept we are examining.

The definition of above and below the horizon refers to altitude above the horizontal plane. So, in the case of Hand's second definition of the midheaven, the point of intersection of the ecliptic and meridian will have an altitude above the horizon. But let's consider the phenomenon of the midnight sun. In northern polar regions, the sun in summer (at its most northerly declination) will spend 24 hours above the horizon - it neither rises nor sets in the sense of being above or below the horizon.

Now when the northern winter solstice (00 Capricorn 00 in the tropical zodiac), the point on the ecliptic with the most southerly declination, is due south of the observer in polar regions it will be below the horizon. At this time, the Sun at the northern summer solstice will be due north of a northern polar observer but above the horizon.

If we accept the definition of the midheaven as being the point of intersection between the ecliptic and the meridian above the horizon, then the Sun at 00 Cancer 00, the northern summer solstice (in the tropical zodiac), will be on the MC. However, consider the situation twelve hours later: the Sun at the summer solstice will be on the meridian again, this time in the south, but at a point much higher in the sky with relation to the horizon. The winter solstice will still be below the horizon, but also on the meridian due north.

What should we make of this? The summer solstice Sun seems to be on the MC again. It is crossing the meridian and clearly above the horizon. The other point of the ecliptic crossing the meridian, the northern winter solstice, is still below the horizon in the north. So the sun seems to have been on the MC twice in one day if we use the above/below definition of the midheaven in polar regions.

It's my view that it is the second instance of the Sun crossing the meridian that we want to call Sun-MC. This is because it is both on the meridian and at its highest point in the sky in a single diurnal cycle. In short the Sun is at its closest approach to the zenith, the point immediately above the observer. Of course, in polar regions it won't actually be immediately above the observer, but it has attained its minimum zenith distance. It is this observation that finally provides us with an unambiguous definition of the midheaven or MC.

The midheaven or MC is the degree of the ecliptic which, at the time and place of casting the horoscope, has its minimum zenith distance (MZD) measured on the meridian; that is, it is the point at which that particular degree makes its closest approach to the zenith in any single diurnal (24 hour) cycle. This definition does not mess up in the tropics, where directional definitions become unclear, and it means that being above or below the horizon is not relevant, which has been shown to be a problem in polar regions.

The definition of zenith distance is taken from Mitton's Dictionary of Astronomy. Zenith distance is "the angular distance from the zenith to a point on the celestial sphere, measured along a great circle." (p. 416) In our case the great circle of interest is the meridian because in any one diurnal cycle, the minimum zenith distance for any particular point on the ecliptic will occur along this circle.

What about the tropical northern winter solstice? This point never comes above the horizon in northern polar regions. It will still be on the MC according to this definition because when it is due south of a northern observer the particular degree associated with the northern winter solstice – 00 Capricorn 00 in the tropical zodiac - will have reached its minimum zenith distance (MZD) in that diurnal cycle. That is, at that particular time and place, it will be at its closest approach to the zenith despite being below the horizon.

This may seem quite counter-intuitive at first. After all the Sun will still be higher in relation to the horizon in the north than the winter solstice degree below the horizon in the south. But the critical point is that the Sun at this time is not at the closest point to the zenith that it can be during the course of the day. This point will come when it attains its MZD on the meridian twelve hours later.

And consider the midwinter Sun at these latitudes - say, just above the arctic circle. It will rise to a point just below the southern horizon at  noon when it attains its MZD. Although the Sun in midwinter will be below the horizon, a glimmer of noon-day light will come over the horizon. Is this not what we would want for a Sun-MC conjunction, even one below the horizon. It's as light as it is going to get for a midwinter Sun on or just above the arctic circle. Twelve hours later, with the Sun on the IC defined by MZD, it will be midnight and deep dark. 

The following diagram illustrates these points. The summer solstice Sun (identified by CN for Cancer) is shown just above the northern horizon (the midnight sun). In the course of 12 hours it will move along the dashed orange line to the point on the meridian due south of the observer. It is moved there by the rotation of the earth on its pole (marked NCP-SCP). The purple line from the zenith to the highpoint of the Sun shows the MZD (minimum zenith distance) at noon - the Sun-MC. Note that the Sun in the course of those 12 hours has moved to a position much higher in the sky than the midnight Sun - the Sun-IC.

The winter solstice Sun (identified by CP for Capricorn) is shown deep below the northern horizon at midnight. In the course of 12 hours it will move along its dashed orange line to the point on the meridian due south of the observer, just below the horizon. However, note that it has still moved towards the zenith, the point at the top of the sphere. The MC defined by MZD is marked. The difference in zenith distances at both points is shown by the light blue line.

  Figure 2: Illustrating the Concept of Minimum Zenith Distance Marking the Midheaven

At any particular time in the day there may be points on the ecliptic that have less zenith distance (i.e. are closer to the zenith) than the point on the MC. An example is the nonagesimal point, the degree on the ecliptic with the maximum altitude above the horizon at a particular time and place. In general the nonagesimal degree won't be the MC at the time for which the horoscope is cast because it will have had its minimum zenith distance (it's closest approach to the zenith) at some other time during the diurnal cycle.

For example, a nonagesimal degree west of the meridian will have attained its MZD (i.e. been on the midheaven) at some time earlier in the day. A nonagesimal degree east of the meridian it will attain its MZD some time later in the day when it will be the degree of the ecliptic on the meridian.

In fact, the nonagesimal can be precisely defined as the degree on the ecliptic with the minimum zenith distance measured on any great circle running through the zenith and nadir at a particular time and place. 

It is worth noting that exactly at the poles all definitions of the MC become problematic, partly because all directions from the north pole lead south (towards the southern pole) and vice versa in the southern hemisphere. This makes the definition of the meridian itself difficult. However, this is not really a serious issue because as soon as one moves away from the pole, the definition of the meridian becomes possible once again.

So: the MC cannot be defined by direction (fails at the tropics) nor by its being above the horizon (problematic in the polar circles - the 'double midheaven' issue). The definition is unambiguously made using the concept of minimum zenith distance. The midheaven or MC is the point of intersection between the ecliptic and the meridian where that particular degree attains its minimum zenith distance during its diurnal cycle, irrespective of its direction in relation to an observer or its height in relation to the horizon.

Perhaps we should rename the MC the MMZD - minimum meridional zenith distance!

Postscript

Since posting this blog the author has discovered an article in the Astrological Association Journal by Norman Blunsdon that covers this issue. Members of the Astrological Association may wish to explore this piece online (as a benefit of their membership) or at the AA Library. 

The reference is:

N Blunsdon (1967) Low Thoughts on High Latitudes. Astrological Association Journal: Vol. 8, No. 3, p. 30.

It is reprinted in the AA's compendium of early classic articles from the Journal - An Astrological Anthology: Vol. 1 (1959-1970). Selected and arranged by Zach Matthews.

In this piece, Blunsdon points out that the midheaven is the same at all latitudes, and changing the midheaven to conform to a definition (always above the horizon) transgresses this principle. 

Blunsdon writes: "Let us first consider the MC and its derivation. As this is formed by the Meridian for the subject's birthtime, it is both personal and constant. We use the Local Sidereal Time and usually find the corresponding MC in our house tables: this is the same for all latitudes."

References:

Robert Hand (1982) Essays on Astrology: The Ascendant, Midheaven and Vertex in Extreme Latitudes. Whitford Press.

Jaqueline Mitton (1993) The Penguin Dictionary of Astronomy. Penguin Books.