A little ramble through 19th century astronomy - The Nebulae in the Pleiades

 Nature October 7^th 1875

In No.5 of “Publicazioni del Reale Osservatorio di Brera in Milano”, Herr Tempel has laid down the stars from the Pleiades, from the Durchmusterung , and traced the outline of the nebula near Merope as it appeared to him with a magnifying power of twenty four on a telescope of four inches aperture. The outline is shown to be elliptical, one extremity of the longer axis, the northern one, at Merope, and the inclination of this axis to the circle of declination about 18 degrees, so that as referred to Merope, the angle of position of the longer axis is 198 degrees.

M Wolf, of the Observatory of Paris, observing with the telescope of 0.31m aperture  in March 1874, perceived two nuclei, one almost concentric with Merope, the other and brighter of the two at a distance of about seven seconds, on the same parallel, following.  From the month of November 1874 to the end of February 1875 the nebula could not be seen notwithstanding the very favourable atmospheric conditions, and at the same time M Stephan was unable to detect it with the telescope of 0.80m. M Wolf concludes that the nebula is certainly variable and that its period is pretty short.

Herr Tempel remarks that generally the nebula has been much more readily seen with small telescopes than with large ones, and doubt has been expressed as to any real variability of light; yet it is not easy to understand, except upon this supposition, why the nebula should be visible at certain times in a particular telescope and invisible at others, the circumstances of the sky appearing to be about the same in all cases.

The Nebula was first remarked by Herr Tempel at Venice on the 23rd of October 1859

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