Half-hours with the Telescope eBook

Richard Anthony Proctor
This eBook from the Gutenberg Project consists of approximately 116 pages of information about Half-hours with the Telescope.

At any of the hours above named, the constellation Hercules lies towards the east.  A quadrant taken from the zenith to the eastern horizon passes close to the last star ([eta]) of the Great Bear’s tail, through [beta], a star in Bootes’ head, near [beta] Herculis, between the two “Alphas” which mark the heads of Hercules and Ophiuchus, and so past [beta] Ophiuchi, a third-magnitude star near the horizon.  And here we may turn aside for a moment to notice the remarkable vertical row of six conspicuous stars towards the east-south-east; these are, counting them in order from the horizon, [zeta], [epsilon], and [delta] Ophiuchi, [epsilon], [alpha], and [delta] Serpentis.

Let the telescope first be directed towards Vega.  This orb presents a brilliant appearance in the telescope.  Its colour is a bluish-white.  In an ordinary telescope Vega appears as a single star, but with a large object-glass two distant small companions are seen.  A nine-inch glass shows also two small companions within a few seconds of Vega.  In the great Harvard refractor Vega is seen with no less than thirty-five companions.  I imagine that all these stars, and others which can be seen in neighbouring fields, indicate the association of Vega with the neighbouring stream of the Milky Way.

Let our observer now direct his telescope to the star [epsilon] Lyrae.  Or rather, let him first closely examine this star with the naked eye.  The star is easily identified, since it lies to the left of Vega, forming with [zeta] a small equilateral triangle.  A careful scrutiny suffices to indicate a peculiarity in this star.  If our observer possesses very good eye-sight, he will distinctly recognise it as a “naked-eye double”; but more probably he will only notice that it appears lengthened in a north and south direction.[4] In the finder the star is easily divided.  Applying a low power to the telescope itself, we see [epsilon] Lyrae as a wide double, the line joining the components lying nearly north and south.  The southernmost component (the upper in the figure) is called [epsilon]^{1}, the other [epsilon]^{2}.  Seen as a double, both components appear white.

Now, if the observer’s telescope is sufficiently powerful, each of the components may be seen to be itself double.  First try [epsilon]^{1}, the northern pair.  The line joining the components is directed as shown in Plate 3.  The distance between them is 3".2, their magnitudes 5 and 6-1/2, and their colours yellow and ruddy.  If the observer succeeds in seeing [epsilon]^{1} fairly divided, he will probably not fail in detecting the duplicity of [epsilon]^{2}, though this is a rather closer pair, the distance between the components being only 2".6.  The magnitudes are 5 and 5-1/2, both being white.  Between [epsilon]^{1} and [epsilon]^{2} are three faint stars, possibly forming with the quadruple a single system.

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Half-hours with the Telescope from Project Gutenberg. Public domain.
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