Skyscript Astrology Forum

This can become a can of worms if you are not careful:

On horizons, there is more than one definition of 'horizon'. Here are some of them:

Visible Horizon: The junction between the sky and the land (or sea)

Celestial horizon: The plane that passes through the centre of the earth normal to (at right angles to) a line from the centre of the eath to the observer's zenith.

Geoidal horizon: The plane that passes tangential to the earth at the observer's position.

Sensible horizon: The plane that passes through the observer's eye parallel to the Celestial/Geoidal horizon.

Normally, in astrological charts, we calculate the celestial horizon. But if we are to figure that the chart becomes diurnal once the Sun is seen to rise above the visible horizon, then are we to consider the moment the upper limb of the Sun is seen? The moment the centre of the Sun is seen to be above the visible horizon? The moment the whole Sun is above the visible horizon?

And let us not forget that the visible horizon depends on the observer's altitude. The higher you are, the earlier the sun appears to rise, so the altitude of the location of the chart would need to be known! But there again, if there is a mountain between you and the Sun....

I asked Robert Hand this question at a workshop and he said that if you can see any light at all in the dawn sky (irrespective of the sun's visible body), it's a diurnal birth.

Hello everyone,

?Tom: when seeking a solution to a problem, the statistical measure of the importance of the problem does not give the answer to the specific question. I asked the question referring to a certain chart but also having in mind the other ones about which I still have some big question marks in my mind. Percentage rates do not help me to solve the problem.
?EA: the possibility of rectifying the chart I mentioned was one of the reasons I asked this question, in fact. Thank you for the link.
?Geoffrey: I hope to fish something with this can of worms :-) Are there answers to the questions you have put (as these are questions I ask myself as well).
?Astraea: I had this kind of idea as well, but how can it be astrologically applied? These are not (or rarely) times when the astrologer is physically present at the birth of a child, and thus the question remains (and this was part of my original intention to ask): seeing a computer-drawn chart, how can one establish if there was some visible light already? (And that is why I thought that maybe the 8?30' of combustion or the 17? degree of under the sunbeams could be applicable.)

Iris

irisalbus wrote: ?Geoffrey: I hope to fish something with this can of worms :-) Are there answers to the questions you have put (as these are questions I ask myself as well)

I think that we can put Robert Hand's comments in a more quantitative form by looking at the definitions of 'twilight'. Once again, there is more than one kind of twilight, but typically they are:

Civil twilight: When the bright stars are still (or become) visible. The sun is 6 degrees below the celestial horizon.

Nautical twilight: The horizon is not visible (yet, or any more). The sun is 12 degrees below the horizon.

Astronomical twilight: Full night, the faintest stars are visible. The sun is 18 degrees below the horizon.

It is possible to see Jupiter, Venus and even Sirius in full daylight. Even Polaris can be seen with a small telescope if you know where to look (and the sky is very clear). So, I would discount civil twilight as being in accord with Robert Hand's comment.

But if you are no longer able to see the horizon, I would say that, "The Sun has set," and night time is upon us. Too, the new Moon only becomes visible once the sun has sunk about 6 degrees below the celestial horizon. This is very important to the Islamic faith as the new month - and typically Ramadan - only starts once the new Moon is sighted. It is apt, I think, that the Moon, a nocturnal body, should only show itself when night time has come. So, to me, nautical twilight is a good benchmark for when the day actually starts and ends.

zoidsoft wrote:

johannes susato wrote: ...
Is not the traditional - astrological - defnition of night and day that by the position of the Sun being below or above the true horizon, signified by the AC-DC Axis?

Did the ancients understand atmospheric refraction?

Irisalbus wrote:I asked the question because I had always thought that the below/above the horizon distinction was clear enough, until I learnt there are certain differences.

The definition of a diurnal/nocturnal chart is clear (and simple), being defined by the Sun, without any consideration of twilight, or whether the Sun's disc/light can be seen. It simply rests on whether the chart is cast in the "daytime" or "nighttime". We know what the ancients meant by this because Ptolemy defines the period of day and night in his Almagest II.9. These are dependent upon the centre of the Sun's disc being aligned with the ascendant or descendant. So if the Sun is on, or 1 second of arc above, the ascendant, it is daytime and you have a diurnal chart; if it is on or 1 second below the descendant it is nighttime and you have a nocturnal chart.
Ptolemy also explains how this consideration is used in the determination of the seasonal (i.e., planetary) hours, so that the change from diurnal hours to nocturnal hours happens simultaneously with the alignment of the centre of the Sun's disc with the descendant (and vice versa).

Deb wrote:

zoidsoft wrote:

johannes susato wrote: ...
Is not the traditional - astrological - defnition of night and day that by the position of the Sun being below or above the true horizon, signified by the AC-DC Axis?

Did the ancients understand atmospheric refraction?

Irisalbus wrote:I asked the question because I had always thought that the below/above the horizon distinction was clear enough, until I learnt there are certain differences.

The definition of a diurnal/nocturnal chart is clear (and simple), being defined by the Sun, without any consideration of twilight, or whether the Sun's disc/light can be seen. It simply rests on whether the chart is cast in the "daytime" or "nighttime". We know what the ancients meant by this because Ptolemy defines the period of day and night in his Almagest II.9. These are dependent upon the centre of the Sun's disc being aligned with the ascendant or descendant. So if the Sun is on, or 1 second of arc above, the ascendant, it is daytime and you have a diurnal chart; if it is on or 1 second below the descendant it is nighttime and you have a nocturnal chart.
Ptolemy also explains how this consideration is used in the determination of the seasonal (i.e., planetary) hours, so that the change from diurnal hours to nocturnal hours happens simultaneously with the alignment of the centre of the Sun's disc with the descendant (and vice versa).

OK. So now there is an option (F3 Main Options | Hellenistic | Sect) in Delphic Oracle to use either "ideal" or "apparent" sunrise/sunset, ideal being Sun conj Asc or above = diurnal; 'apparent" uses atmospheric refraction visible sunrise/sunset. Seems though for Ptolemy that this would be strangely un-Aristotelian / un-natural...

It will be up in a few days after updating the time zones...

Deb wrote: Ptolemy also explains how this consideration is used in the determination of the seasonal (i.e., planetary) hours, so that the change from diurnal hours to nocturnal hours happens simultaneously with the alignment of the centre of the Sun's disc with the descendant (and vice versa).

This is a really good point.

Hi irisalbus,

What I learned from Robert Zoller. which has been proven right countless times since then in both delineations and predictions, is that it is only the chart that gives the most objective information about the native's life.

Therefore since you are studying traditional Astrology, study the chart itself and let the chart direct you. Moreover, in 99% of cases people do not know their exact time of birth or even within 5 minutes (the degree above/below the horizon), but the chart will easily show it to you. One of the best ways is to use the Firdaria technique. Since you even have the Ascendant it is very easy to determine whether the native was born during the day or night. The longer they have lived, the easier it is.
I wish you success in your studies.

P.S. For night births make sure you use the sequence given by Bonatti (the Nodes between Mars and the Sun) because this is the correct one.

Hello Zagata,

thank you for the reply adn the idea, I have not thought of the Firdaria as a rectification/verification method but will try it.
(As a sidenote, I use the nodes at the end of all the planets' periods as I was convinced of this by http://arhatmedia.com/firdar2.htm and http://www.astrologiamedieval.com/firdaria.htm )
I like the idea of "letting the chart direct me" but I am afraid I might misinterpret the directions Joking apart, there could be elements different from being a day/night chart indicating similar things.
In the chart I mentioned, the Sun being above the horizon would also mean a different Ascendant (Taurus instead of Aries), which I consider quite improbable but now I have decided to take time to consider this different chart, as well.

Thanks again, Zagata and everybody.

Iris