The solar transit This account of the solar compass, and the meridian attachment for transit instruments was written for Young & sons . ers Transit being an altitude and azimuth in-strument, can be used to take equal altitudes of the sun or of astar from which the meridian is readily determined, or the lati-tude and declination being known, the azimuth and hour anglemay be computed from a single altitude of the sun or a star asfollows : In the spherical triangle P Z S are given the three sides,P Z the complement of the latitude, P S the polar distance orcomplement of the declination, and Z S t
The solar transit This account of the solar compass, and the meridian attachment for transit instruments was written for Young & sons . ers Transit being an altitude and azimuth in-strument, can be used to take equal altitudes of the sun or of astar from which the meridian is readily determined, or the lati-tude and declination being known, the azimuth and hour anglemay be computed from a single altitude of the sun or a star asfollows : In the spherical triangle P Z S are given the three sides,P Z the complement of the latitude, P S the polar distance orcomplement of the declination, and Z S the zenith distance orcomplement of the altitude, whence P Z S (== O C M) the azi-muth, Z P S the hour angle, and Z S P the parallactic angle maybe calculated. These methods all result in a sure determination of themeridian, but the time involved in taking and reducing the ob-servations is not always available to the engineer. Hence, thegreat value of a Meridian Attachment which will mechanicallyand instantly solve the problem above mentioned from a singleobservation of the sun, the apparent motion of which will benext Fig. 2. If observations be takenat C, Fig. 2, during a wholeyear, it will be found thatindependently of the diur-nal motion which the sunhas in common with thestars, it has also a motionin declination causing it toappear to describe annu-ally the great circle B Tcalled the ecliptic, theplane of which forms anangle of about 230 28 withthe celestial equator A sun will appear to describe the circle B D at its greatestnorth declination on the 21st of June, and the circle E T at itsgreatest south declination on the 22d of December. Its declina-tion will be zero when crossing the equator on the 21st of Marchand 23d of September, respectively. The Meridian Attachment is simply an instrument made toimitate, on a small scale, the motion of the celestial vault asabove described, consisting of a Solar Telescope revolving aboutits polar axis, wThich corresp
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Keywords: ., bookcentury1800, bookdecade1880, bookidsolartransit, bookyear1887
