Half-hours with the Telescope eBook

Richard Anthony Proctor
This eBook from the Gutenberg Project consists of approximately 98 pages of information about Half-hours with the Telescope.

The star [kappa] Herculis is not shown in the map, but may be very readily found, lying between the two gammas, [gamma] Herculis and [gamma] Serpentis (see Frontispiece, Map 2), rather nearer the latter.  It is a wide double, the components of fifth and seventh magnitude, the larger yellowish-white, the smaller ruddy yellow.[5]

Ras Algethi, or [alpha] Herculis, is also beyond the limits of the map, but may be easily found by means of Map 2, Frontispiece.  It is, properly speaking, a multiple star.  Considered as a double, the arrangement of the components is that shown in Plate 3.  The larger is of magnitude 3-1/2, the smaller of magnitude 5-1/2; the former orange, the latter emerald.  The companion stars are small, and require a good telescope to be well seen.  Ras Algethi is a variable, changing from magnitude 3 to magnitude 3-1/2 in a period of 66-1/3 days.

The star [rho] Herculis is a closer double.  The components are 3".7 apart, and situated as shown in Plate 3.  The larger is of magnitude 4, the smaller 5-1/2; the former bluish-white, the latter pale emerald.

There are other objects within the range of our map which are well worthy of study.  Such are [mu] Draconis, a beautiful miniature of Castor; [gamma]^{1} and [gamma]^{2} Draconis, a wide double, the distance between the components being nearly 62” (both grey); and [gamma]^{1} and [gamma]^{2} Coronae, a naked-eye double, the components being 6’ apart, and each double with a good 3-inch telescope.

We turn, however, to another region of the sky.  Low down, towards the south is seen the small constellation Corvus, recognised by its irregular quadrilateral of stars.  Of the two upper stars, the left-hand one is Algorab, a wide double, the components placed as in Plate 3, 23".5 apart, the larger of magnitude 3, the smaller 8-1/2, the colours pale yellow and purple.

There is a red star in this neighbourhood which is well worth looking for.  To the right of Corvus is the constellation Crater, easily recognised as forming a tolerably well-marked small group.  The star Alkes, or [alpha] Crateris, must first be found.  It is far from being the brightest star in the constellation, and may be assumed to have diminished considerably in brilliancy since it was entitled [alpha] by Bayer.  It will easily be found, however, by means of the observer’s star maps.  If now the telescope be directed to Alkes, there will be found, following him at a distance of 42.5 s, and about one minute southerly, a small red star, R. Crateris.  Like most red stars, this one is a variable.  A somewhat smaller blue star may be seen in the same field.

There is another red star which may be found pretty easily at this season.  First find the stars [eta] and [omicron] Leonis, the former forming with Regulus (now lying towards the south-west, and almost exactly midway between the zenith and the horizon) the handle of the Sickle in Leo, the other farther off from Regulus towards the right, but lower down.  Now sweep from [omicron] towards [eta] with a low power.[6] There will be found a sixth-magnitude star about one-fourth of the way from [omicron] to [eta].  South, following this, will be found a group of four stars, of which one is crimson.  This is the star R Leonis.  Like R Crateris and R Leporis it is variable.

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