वेध · the observation companion

The text predicts, and you observe with your own śaṅku and kapāla. The ledger keeps both, hash-chained, with each prediction written before its night. Every computation runs here, on your device; the line below says where the ledger is kept. Export it after every night and keep the file.

The engine is the Sūrya-Siddhānta's own model with Mādhava's sine (sphuta.js, ss-*.js, vedha-lekha.js). Times are counts of your bowl from sunrise, in ghaṭī–vināḍī–prāṇa of the star-wheel's turn (SS 1.11-1.12). The rough hour beside each count only tells you when to be ready.

१ · स्थान — your place

Start with an approximate latitude: your first nights on the Dhruva star replace it (the mean of its upper and lower meridian altitudes). Your equinox noon shadow gives the palabhā; give it when you have it. The deśāntara is in degrees east (+) or west (−) of the Laṅkā–Ujjayinī meridian, and your first timed lunar eclipse measures it. A ledger keeps its place, so a new place means a new ledger.

२ · यन्त्र — the two instruments, as the text gives them

śilātale ambusaṃśuddhe vajralepe api vā same । tatra śaṅkvaṅgulairiṣṭaiḥ samaṃ maṇḍalaṃ ālikhet ।।
SS 3.1: on a level stone cleaned with water, or a hard plastered floor, draw a circle with the gnomon's aṅgulas as its measure.
tanmadhye sthāpayecchaṅkuṃ kalpanādvādaśāṅgulam । tacchāyāgraṃ spṛśedyatra vṛtte pūrvāparārdhayoḥ ।।
SS 3.2-3.3: set a gnomon of twelve aṅgulas at the centre. Where the shadow's tip touches the circle in the forenoon and the afternoon are west and east. Through their middle, by the "fish" (intersecting arcs), draw the north–south line.
tāmrapātraṃ adhaśchidraṃ nyastaṃ kuṇḍe amalāmbhasi । ṣaṣṭirmajjatyahorātre sphuṭaṃ yantraṃ kapālakam ।।
SS 13.23: a copper vessel with a hole beneath, set in a basin of clean water, sinks sixty times in a day and night: the kapāla.

SS 1.11-1.12: 6 prāṇa = 1 vināḍī, 60 vināḍī = 1 nāḍī (ghaṭī), and 60 nāḍī = one turn of the stars (the nākṣatra day). Your bowl is the clock; one star's two returns to the meridian are its calibration.

The first season (design §7.6)

  1. Calibrate the bowl. Start it when a bright junction star crosses your north–south line (a plumb-line over it). Count its sinkings until the same star crosses again. Record it as kapāla. Sixty is a perfect bowl; anything else is its rate, which the ledger applies to every count.
  2. Every clear noon, the shadow. Mark where the śaṅku's shadow crosses the north–south line, and measure it in aṅgula and vyaṅgula. Record it as madhyāhna.
  3. Stars on the meridian. Start the bowl at sunrise. Note the count when each star in tonight's list crosses the plumb-line, and its altitude if you have an arc. Record it as yāmyottara.
  4. The Dhruva star, twice. Its altitude when highest and when lowest: the mean is your latitude (SS 12.72-12.73).
  5. The crescent. On the evenings after amāvāsyā, look for it after sunset, and record both the evenings it is not seen and the evening it is. Record it as candra-darśana.
  6. Every visible lunar eclipse. Time sparśa, the middle and mokṣa by the bowl from that day's sunrise. Record it as grahaṇa.

३ · गणित — the text's predictions for a day

Your instruments (yantra.js)

Tick the instruments you have. Each line is the text's reading in the instrument's own graduation — a nata in ghaṭī–vināḍī–prāṇa from the meridian, an arc in aṃśa–kalā–vikalā — so no size is needed. The meridian wall and the ṣaṣṭhāṃśa read at the text's noon, the rāśivalaya at a sign's culmination, the rest at the bowl count from sunrise given here. The attribution of these instruments to Jai Singh II is unverified here; their geometry is derived from the sphere.

The text's eclipses in the next 400 days, at this place

आँखों की रक्षा · Protect your eyes. सूर्य-ग्रहण को कभी भी नंगी आँखों, धूप के चश्मे, दूरबीन या कैमरे से सीधे न देखें — "पूर्ण" बताए गए ग्रहण में भी नहीं; केवल प्रमाणित सौर-फ़िल्टर से, या पिनहोल से पर्दे पर पड़े प्रतिबिम्ब को देखें (पानी में सूर्य का प्रतिबिम्ब भी सुरक्षित नहीं)। Never look at a solar eclipse with the naked eye, sunglasses, binoculars or a camera — not even one listed here as "total". Use only a certified solar filter, or watch its image projected through a pinhole onto a screen (the Sun reflected in water is not safe either). The magnitude below is the text's prediction, not a safety guide: the sky may differ from it.

These are the Sūrya-Siddhānta's predictions, to be tested — not a forecast. Against the ancestors' own records (Jyotirmīmāṃsā, 1398–1517) this model's solar contacts came up to 3 ghaṭikā early, and it judged wrongly whether 4 of 15 eclipses were seen. Watch, and record what you see — including nothing.

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४ · लेख — record what you saw

५ · लेखा — the ledger

No ledger yet.