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.

[Footnote 2:  Betelgeuse—­commonly interpreted the Giant’s Shoulder—­ibt-al-jauza.  The words, however, really signify, “the armpit of the central one,” Orion being so named because he is divided centrally by the equator.]

[Footnote 3:  I have never been able to see more than four with a 3-3/4-inch aperture.  I give a view of the trapezium as seen with an 8-inch equatorial.]

[Footnote 4:  Sir W. Herschel several times saw [epsilon] Lyrae as a double.  Bessel also relates that when he was a lad of thirteen he could see this star double.  I think persons having average eye-sight could see it double if they selected a suitable hour for observation.  My own eye-sight is not good enough for this, but I can distinctly see this star wedged whenever the line joining the components is inclined about 45 deg. to the horizon, and also when Lyra is near the zenith.]

[Footnote 5:  They were so described by Admiral Smyth in 1839.  Mr. Main, in 1862, describes them as straw-coloured and reddish, while Mr. Webb, in 1865, saw them pale-yellow and lilac!]

[Footnote 6:  Or the observer may sweep from [omicron] towards [nu], looking for R about two-fifths of the way from [omicron] to [nu].]

[Footnote 7:  Here a single period only is taken, to get back to a convenient hour of the evening.]

[Footnote 8:  Here a single period only is taken, to get back to a convenient hour of the evening.]

[Footnote 9:  I have constructed a zodiac-chart, which will enable the student to mark in the path of a planet, at any season of the year, from the recorded places in the almanacs.]

[Footnote 10:  It is convenient to remember that through precession a star near the ecliptic shifts as respects the R.A. and Dec. lines, through an arc of one degree—­or nearly twice the moon’s diameter—­in about 72 years, all other stars through a less arc.]

[Footnote 11:  Mercury is best seen when in quadrature to the sun, but not (as I have seen stated) at those quadratures in which he attains his maximum elongation from the sun.  This will appear singular, because the maximum elongation is about 27 deg., the minimum only about 18 deg..  But it happens that in our northern latitudes Mercury is always south of the sun when he attains his maximum elongation, and this fact exercises a more important effect than the mere amount of elongation.]

[Footnote 12:  It does not seem to me that the difficulty of detecting Mercury is due to the difficulty “of identifying it amongst the surrounding stars, during the short time that it can be seen” (Hind’s ’Introduction to Astronomy’).  There are few stars which are comparable with Mercury in brilliancy, when seen under the same light.]

[Footnote 13:  I may notice another error sometimes made.  It is said that the shadow of a satellite appears elliptical when near the edge of the disc.  The shadow is in reality elliptical when thus situated, but appears circular.  A moment’s consideration will show that this should be so.  The part of the disc concealed by a satellite near the limb is also elliptical, but of course appears round.]

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