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In short
A cusp is the degree that marks a house in a cuspal house system: the 1st cusp is the Ascendant degree, and the twelve houses come out of unequal width. This app does not use cusps. Its houses are whole signs counted from the Lagna, so a graha's house depends only on its sign.
What the term means
A cusp is a house boundary expressed as a degree. In a cuspal house system each of the twelve houses has its own cusp, the first being the Ascendant degree, and the houses come out of unequal width. A graha late in a sign can then fall in one house by cusps and in the next house by signs. This app does not use cusps at all.
Where the term comes from
The word is the translators'. In BPHS it appears only in the translation of Ch. 4 Sl. 25-30, the method for the Nishek Lagna, where the Lagna Bhava is glossed as "Madhya, or cusp" and the distance from it to the 9th Bhava's cusp is used. Advanced Predictive Astrology, a modern case-study book, prints a cuspal "Nirayana Bhava Chalit" table beside each sign chart, with a cusp column listing the twelve cusp degrees. Neither text is the source of this app's house rule.
How this app uses it
- It does not. Houses are whole signs: the sign holding the Lagna is the whole 1st house, the next sign the whole 2nd, and so on. A graha's house is decided by its sign alone.
- The Ascendant's degree is still computed and shown, because it sets the Lagna and the divisional charts. The project's methodology page compares it with a printed chart: for Advanced Predictive Astrology's Example-11 the engine's Lagna and the book's first cusp differ by 4 arc-seconds. That is a check on the rising degree, not a use of cusps.
- The astronomical mid-heaven is not used as a 10th-house cusp either: the 10th house is the tenth sign from the Lagna.
- Systems that read the sub-lords of house cusps therefore have no equivalent row here; only grahas, and the Ascendant when the place is known, get a sub-lord.
Pages that use this term
- The 10th house (Karma Bhava) - why the mid-heaven is not its cusp here.
- The Sun in the 10th house - a placement read by whole signs, not cusps.
- Nakshatra sub-lord and birth time - the cusp sub-lords this app does not compute.
- Methodology - the printed cuspal chart compared with the engine.
- Lagna calculator - the rising degree and the whole-sign houses.
Related terms
- Bhava - the houses a cusp would bound.
- Lagna - the sign that starts the count.
- Nirayana - the word in "Nirayana Bhava Chalit".
- Nakshatra sub-lord - computed for points, not cusps.