A Sloka, A Pun, A Number, A Date, A Book

हेविष्णो निहितं कृत्स्नं जगत् त्वय्येव कारणे । ज्योतिषां ज्योतिषे तस्मै नमो नारायणाय ते ॥ hE vishNo nihitaM kRtsnam jagat tvayyEva kaaraNE | jyOtishaaM jyotishE tasmai namO naaraayaNaaya tE || ஹே விஷ்ணோ நிஹிதம் க்ருத்ஸ்னம் ஜகத் த்வய்யேவ காரணே | ஜ்யோதிஷாம் ஜ்யோதிஷே தஸ்மை நமோ நாராயணாய தே || The opening verse of Nilakanta Somayaaji's work on astronomy "Tantra Sangraha" translated into English with excellent notes, by Professor K Ramasubramaniam of IIT Bombay and Professor MS Sriram of Madras University.
The verse is a salutation to Vishnu & Narayana -
"Oh Vishnu, creator of everything, you are the cause of the earth Jyothishas shine because of you, I salute you Narayana" is the meaning.

Narayana is not just a second reference to Vishnu but a reference to Netra Narayana, the king who was the benefactor of Nilakanta!!

Sloka letter	हे	विष्	णो	नि	हि	तं	कृत्स्	नं
Active letter	ह	व	ण	न	ह	त	क	न
Number	8	4	5	0	8	6	1	0

Also, there is a hidden numerical reference - the first 8 letters हेविष्णो निहितं कृत्स्नं translated into an AhargaNaa अहर्गणा number 1680548 according to the Katapayaadi system. That is the number days that have passed since the start of the Kali Yuga in the Hindu astronomical reckoning. Kali Yuga starts on the day Mahabharatha ended, on Feb 17, 3102 BC according to a system used by Indian astronomers. So 1680548 would translate to the day March 22, 1500 AD : this is Nilakanta Somasatvan's way of encoding the date of his composition in the first sloka of his work, say the translators!!

Other Essays on Astronomy

VarahaMihira's Eclipse Proof
Tiruvaadirai and Agastya
Some Slokas on Indian Astronomy
Maya Date 0.0.0.0.0 - Long Count Calendar