Does anyone know the origin of the principle that Rahu and Ketu cast aspects to the 5th and 9th houses from their natal position ?

Does this idea follow logically, from some other principle about the nodes ?

Are there charts which illustrate this principle in a compelling way ? For example, where a house or planet, otherwise unaspected and unremarkable, is strongly influenced by the node which aspects it (from 5 or 9 houses away) ?

Thank you :-)

Welcome to Skyscript, Ken! As we discussed off-list, I have so far been unable to locate any Sanskrit text that specifically states that the nodes cast trinal aspects. I do have a vague memory of having seen such a statement quoted, though, so with luck, someone else may be able to point it out.

Ken I have no expertise in Indian astrology myself, and I don't know if this might be of relevance to your query, but the notion reminds me of the principle that Morinus labours on in his Cabal of the 12 Houses, which stresses the importance of seeing each house as part of a trinity, so what is commenced in house 1, is unfolded in house 5 and 9:

" because every one of the 4 Cardinal parts of Heaven, which govern the beginning, vigour, Declination, and Death of things do by a Trine Aspect, behold two other Coelstial parts, which be of its own Nature: whence shall arise three places out of each of the 4. Cardinal, of he same nature, for three times 4 doth make neither more nor less than 12."

It's a complex passage to read; I'm not sure it has value for you anyway, as it does not mention any Indian sources or teminology, but if you want to glance through it you can find it at https://skyscript.co.uk/cabal.html

Thank you, that's a fine and concise statement. I would love to hear more about the difference between initially commencing and subsequently unfolding.

In some of the traditional Indian reasoning, planets may all cast the same aspects, but some are more equal than others, so to speak. For example, because Jupiter/Sagittarius/9th House/Trine correspond to the same basic benefic principle, traditional Indian astrologers will consider a Trine from Jupiter as "full strength", while a Trine from other planets, of lesser strength.

They are more likely to consider a Square from Mars as full strength - but not a Square from a benefic like the Moon or Venus. In a nutshell, malefic aspects from malefics are really malefic, while benefic aspects from benefics are really benefic. The rest, is often relegated to the status of background noise: present, but relatively inconsequential.

That is why it may be puzzling to consider that Rahu/Ketu cast a Trine aspect. The nodes are generally viewed as malefic influences, while the Trine aspect is not. Wouldn't it be more consistent for them to behave like other malefics, whose full-strength aspects are of a malefic nature ?

One exception to this, is the idea that Saturn casts a "3 house" aspect, a Sextile as it were. I have often wondered if someone accidentally blundered when copying an old text. It would certainly be more consistent if Saturn's important "Vedic" aspects were solely malefic.