Dr Halley

I received from you formerly a Table of the motions of the Comet of 1680 in an Elliptic Orb. You there put the Node ascendent in Capricorn 2gr.2. The Node descendent Cancer 2gr..2. The inclination of the plane of the Orb to the plane of the Ecliptic 61gr.6.48. The Perihelium of the Comet in this plane Sagittarius 22gr.44.25. The equated time of the Perihelium December 7d.23h.9. The distance of the Perihelium from the ascending Node in the plane of the Ecliptic 9gr.17.35. The Axis transversus 138,29571. And the Axis conjugatus 1,84812, the mean distance of the earth from the Sun being 100000. And in this Orb you computed the places of the Comet on November 3d.16h.47. November 5d.15h.37 & November 10d.16h.18, as follows.

___________1680p ____________________________________________________________ Tempus verumLong. comp.Lat. comp. ___________Novem0d0dLeb.100d ____________________________________________________________ 3d.16h.47. 29°.51.22. 1°.17.32.bor 5d.15h.37. 03°.24.32. 1°.06.09. 7_d.16h.18. 15°.33.02. 0°.25.07.

The first of these three places you have inserted into the Table of the motions of this Comet in an Elliptic Orb, which you have printed in your Astronomical Tables where you treat de motu Cometarum in Orbibus Ellipticis. I beg the favour of you to reexamine the two last of them, viz those on November 5d.15h.37 & November 10d.16h.18.

In the same printed Table you have calculated the place of this Comet upon March 9d.8h.38, true time. I beg the favour of you to calculate its place in the Parabolic Orb also upon March 9d.8h.38 true time, & send me its computed Longitude Latitude and distance from the Sun. For I would add them to the Table of the motion of this Comet in a Parabolic Orb printed in the third book of the Principia Mathematica pag. 459. Edit. II. By its distance from the Sun I mean the distance of its centre from the centre of the Sun in parts whereof the Radius of the Orbis Magnus is 100000. I am

Your most humble Servant

Isaac Newton

St Martin's Lane
by Leicester fields
Decem. 3. 1724.


For Dr Edmund Halley, the Kings
Professor of Astronomy at the
Observatory in Greenwich
in          Kent.


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