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Going Mainstream: A Scientific Approach c. 1800–1900

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Part of the Astronomers' Universe book series (ASTRONOM)


Nothing quite like the modern science of astrophysics existed at the time Giovanni Riccioli made his observations of Venus in the first half of the seventeenth century. Even after the introduction of the telescope in the same era, the study of astronomy was largely one of phenomena only loosely attached to concepts of physics yet still firmly associated with the pseudoscience of astrology. Astronomers of the late pre-telescopic era such as Tycho Brahe (1546–1601) made precise observations of the positions of the planets that were used as inputs to mathematical models of their positions, but the models largely existed only to validate the preexisting belief in an Earth-centered Solar System. As it turns out, the seeds of geocentrism’s undoing were already sown in Brahe’s measurements. It just took an old idea to make them grow and bloom.

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Fig. 4.1
Fig. 4.2
Fig. 4.3
Fig. 4.4


  1. 1.

    Translation of Thomas L. Heath, Cambridge University Press, 1897, p. 520.

  2. 2.

    Schröter was observing some 2 to 3 weeks before inferior conjunction, which occurred on March 12.

  3. 3.

    Harding quotes von Hahn in the Berliner Astronomisches Jahrbuch für 1796, p. 188.

  4. 4.

    This is a reference to some well-known designers of telescopes and eyepieces in the late eighteenth and early nineteenth centuries: Jesse Ramsden (English, 1735–1800); Joseph Ritter von Fraunhofer (Bavarian, 1787–1826); and Peter Dollond (English, 1731–1820).

  5. 5.

    Pastorff here seems to refer to the practice of placing the bright crescent just beyond the curved edge of the field of view of the telescope, thereby suppressing the influence of light from the crescent that would otherwise scatter toward the night side.

  6. 6.

    Pastorff here compares the quality of the light from the night side of Venus to the phenomenon of Earthshine.

  7. 7.

    “The proof of the excellence of the 5 1/2-foot telescope is that stars of the first magnitude, such as Capella, appear completely rounded and close double stars appear completely separated.”

  8. 8.

    These are very probably comets C/1807 R1, C/1811 F1, and C/1819 N1 (Tralles), respectively. The “gleam of light” (Lichtschimmer) Pastorff describes is reminiscent of stellate apparent nuclei in the comae of many comets near where the tail is seen to begin.

  9. 9.

    Vol. 2., pp. 524–537.

  10. 10.

    Knott was an English amateur astronomer from Cuckfield, Sussex, known largely for observations of double, multiple, and variable stars who “always showed the keenest in astronomical questions of all kinds.” (The Observatory, Vol. 17, pp. 355–356, November 1894.)

  11. 11.

    Knott here refers to Earthshine seen on our own Moon, using a contemporary French phrase for the phenomenon (literally, ‘ashen light’).

  12. 12.

    Quoted by R. Baum, 2007, Insights into enthusiasm: The 1897–1898 Venus notebooks of P. B. Molesworth, JBAA, 117(1), 18.

  13. 13.

    Little is known of “Mr. Guthrie, a gentleman residing near Bervie” in Scotland (1854, Monthly Notices of the Royal Astronomical Society, 14, 169). Guthrie reported being “unexpectedly surprised by observing an annular fringe of light surrounding the dark side of the disk, and completing the circle which was partially formed by the outer margin of the crescent.” Richard Baum put this observation in around 1842, and identified it as indicating not the Ashen Light, but rather the elongation of the crescent cusps due to the forward scattering of sunlight in the atmosphere of Venus when seen very close to inferior conjunction. For an example of this phenomenon, see the series of photographs in Fig. 3.4.

  14. 14.

    William Henry Purchas (1823–1903) was better known as an English botanist than an astronomer. Augustin Ley memorialized Purchas with a short biography in September 1905, Transactions of the Woolhope Naturalists’ Field Club, Hereford: Jakeman and Carver, 341–344.

  15. 15.

    Fr. Francesco de Vico (1805–1848) was an Italian astronomer and Jesuit priest who discovered a number of comets in the 1840s.

  16. 16.

    Clemente Palomba (1819–1891) was an Associate Astronomer at the Observatory of the Gregorian University in the Collegio Romano at Rome. Palomba carried out an extensive Venus observing program between 1839 and 1841; from his measurements, totaling more than 11,000 in 1839 alone, Francesco de Vico claimed a rotation period of about 23 hours and 20 minutes. See S. C. Chandler, 1897, Historical note on the rotation of Venus and Mercury, Popular Astronomy, 4, 393–397.

  17. 17.

    1895, JBAA, 5, 412–414. Little about this Glaswegian amateur astronomer (c. 1860–1911) remains in the historical record. He was a Fellow of the Royal Astronomical Society and a founding member of the British Astronomical Association. As an observer, he made contributions to the literature on “the aurora, the zodiacal light, the visibility of the dark side of Venus, [and] the Milky Way.” (1911, JBAA, 21, 197).

  18. 18.

    Johann Karl Friedrich Zöllner (1834–1882) was a German astronomer known for his studies of optical illusions who also dabbled on the side in parapsychology.

  19. 19.

    Hermann Carl Vogel (1841–1907) was a German astrophysicist who made the extensive use of spectroscopy in astronomy, analyzing the atmospheres of stars and planets and measuring a precise rotation period for the Sun on the basis of the velocity shift of spectral lines in its atmosphere. Vogel also reported his own observation of the Ashen Light in November 1871 and had an idea about what explained it; see Chap. 5.

  20. 20.

    Angelo Secchi, previously encountered in Chap. 1, is mainly remembered for devising the first system of stellar classification according to features seen in the spectra of stars.

  21. 21.

    Sir William Huggins (1824–1910) was, with Vogel and Secchi, among the founders of astronomical spectroscopy who worked alongside his wife, Margaret Lindsay (Murray) Huggins (1848–1915). The two published An Atlas of Representative Stellar Spectra (1899), which remained a standard text for several decades.

  22. 22.

    1894, Die Spectralanalyse der Gestirne (“A treatise on astronomical spectroscopy”), Boston: E. B. Frost, Ginn and Co. The “Fraunhofer lines” are a set of strong absorption features in the solar spectrum first identified by the German physicist Joseph von Fraunhofer (1787–1826), who although not the first person to see the lines was the first to systematically study them and measure their wavelengths.

  23. 23.

    JBAA, 6, 35. Born in Wiltshire, Wardale’s varied interests included “cricket, astronomy, meteorology, and field botany.” (1943, Monthly Notices of the Royal Astronomical Society, 103, 73) He was known particularly for his studies of double stars and the planet Mars. Wardale was baffled by the unpredictability of Ashen Light sightings, reasoning that “surely in the twilight it ought in such a case to be an easy object to everyone in reasonably good air. No theory of the cause can be regarded as complete which fails to account for this peculiarity.”


  1. Schröter, J. H. (1806). Beobachtung der Nachtseite der Venuskugel, vom Hrn. Justizrath und Oberamtmann Doct. Schröter zu Lilienthal. Berliner Astronomisches Jahrbuch, 164–167.

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  2. Webb, T. W. (1873). Celestial objects for common telescopes. London: Longmans, Green & Co.

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Barentine, J.C. (2021). Going Mainstream: A Scientific Approach c. 1800–1900. In: Mystery of the Ashen Light of Venus. Astronomers' Universe. Springer, Cham.

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