occultation

Etymology

. A total eclipse was visible mainly in Europe.]] From Latin occultātiōnem, accusative singular of occultātiō (“concealment; insinuation”), from occultāre, present active infinitive of occultō (“to conceal, hide”); analysable as occult + -ation.

noun

1. (astronomy) An astronomical event that occurs when one celestial object is hidden by another celestial object that passes between it and the observer when the nearer object appears larger and completely hides the more distant object.
   [T]he diſtance of any place within this kingdom from it, will not much vary the manner of their Appearance in any of the Phænomena, except the Eclipſe of the Sun: for, in the Occultations, the Stars will appeare to paſs nearly under the ſame Angles and Spots of the Moon; […] 17 January 1670, John Flamstead [i.e., John Flamsteed], “An Accompt of such of the More Notable Celestial Phænomena of the Year 1670, as will be Conspicuous in the English Horizon; Written by the Learned and Industrious Mr. John Flamstead Novemb. 4 1669. and by Him Addressed and Recommended for Encouragement, to the Right Honorable, the Lord Viscount Brouncker, as President of the Royal Society”, in Philosophical Transactions: Giving Some Accompt of the Present Undertakings, Studies and Labours of the Ingenious in Many Considerable Parts of the World, volume IV, number 55, London: Printed for T. N. for John Martyn at the Bell, a little without Temple-Bar, printer to the Royal Society, →OCLC, pages 1101–1102
   The bright star Aldebaran is to be occulted by the moon on December 20th, at about 5 o'clock pm. Aldebaran is said to be eight hundred and eighty times the mass of the sun, with a diameter of over 8,000,000 miles; a distance so great that a meteor traveling at the rate of thirty miles per second, would require over three days to cross the disk of the star. Yet, notwithstanding the immense volume, the accultation will occur in a moment, so great is the distance of the star from us, and will continue for about one hour and eight minutes. 1904 December, Melville Dozier, “[Transactions for November. III. Meetings of Sections.] 2. Section of Astronomy”, in Bulletin of the Southern California Academy of Sciences, volume III, number 9, Los Angeles, Calif.: Published for the Association by R. Baumgardt & Co. 231 West First St., Los Angeles, Cal., →OCLC, page 147
   Stellar occultations potentially provide the highest precision data for relating solar system ephemerides to the stellar reference frame. For example, occultations by the Uranian rings can define the position of the occulted star relative to the rings to better than 0.02 mas (equivalent to a few hundred meters at the distance of Uranus). Occultations by atmospheres can be less precise than occultations by symmerical solid bodies, like rings and large asteroids, with a precision on the order of 1.0 mas. 1994, C. B. Olkin, J[ames] L[udlow] Elliot, “Occultation Astrometry: Predictions and Post-event Results”, in L. V. Morrison, G. F. Gilmore, editors, Galactic and Solar System Optical Astrometry: Proceedings of the Royal Greenwich Observatory and the Institute of Astronomy workshop held in Cambridge, June 21–24, 1993, Cambridge: Cambridge University Press, abstract, page 286
   […] I was thrilled at the prospect of seeing the waning crescent Moon swing over Venus in the predawn sky on Wednesday morning, April 22, 2009. While the occultation was visible from much of North America, it was only in Arizona and parts of other surrounding states, where Wendee and I live, that the ingress would take place in a completely dark sky. It would be a highlight of the International Year of Astronomy, which reached its peak during 2009. 2010, David H. Levy, “When the Moon Occults a Star or a Planet”, in David Levy’s Guide to Eclipses, Occultations, and Transits, Cambridge, New York, N.Y.: Cambridge University Press, page 129
2. The state of being occult (“hidden, undetected”).
   If Mr. [Thomas] Campbell's poetry was of a kind that could be forgotten, his long fits of silence would put him fairly in the way of that misfortune. […] [T]he re-appearance of such an author, after those long periods of occultation, is naturally hailed as a novelty—and he receives the double welcome of a celebrated stranger and a remembered friend. 1825 January, [Francis Jeffrey, Lord Jeffrey], “Art. I. Theodric, a Domestic Tale: With other Poems. By Thomas Campbell. 12mo. pp. 150. London, 1824.”, in The Edinburgh Review, or Critical Journal, volume XLI, number LXXXII, Edinburgh: Printed by the heirs of D[avid] Willison, for Archibald Constable and Company, Edinburgh; and Longman, Hurst, Rees, Orme, Brown and Green, London, →OCLC
   In western Europe, the most celebrated instance of the occultation of a river was that of the Rhone, near Bellegarde, on the confines of France and Savoy, about 18 miles from Geneva; but, alas, on visiting this interesting spot in the autumn of 1855, I found that the Perte du Rhone no longer exists; for the Sardinian Government, in which territory it was, had blown up the rocky roof, beneath which it had been engulfed, in order to facilitate the conveyance of timber on the river. 1857 July, Thomas M. Traill, “On the Occultation of Rivers”, in Thomas Anderson, William Jardine, John Hutton Balfour, Henry D[arwin] Rogers, editors, The Edinburgh New Philosophical Journal, Exhibiting a View of the Progressive Discoveries and Improvements in the Sciences and the Arts, volume VI, number 1 (New Series), Edinburgh: Adam and Charles Black; London: Longman, Brown, Green, & Longmans, →OCLC, page 41
3. (Shia Islam) The disappearance of the Twelfth Imam, or Mahdi, who is believed alive and present in this world, but hidden until his reappearance at the end of time.
   We are therefore, constantly hoping for the joy and happiness, personified in Imām al-Mahdi, the Imām who is alive at this very time, and who is himself awaiting the command of Allāh to reappear, so that he may strengthen the weak, and judge the oppressors. He will reappear "without having done Bay'ah to any oppressor". He went into occultation because he did not want [to] submit to any unjust ruler. 2002, Allamah Sayyid Saeed Akhtar Rizvi, Prophecies about Occultation of Imãm Al-Mahdi (A.S.), Dar es Salaam, Tanzania: Bilal Muslim Mission of Tanzania, page 7