Messer Ya. Star atlas for celestial observations.

Messer Ya. Star atlas for celestial observations.
St. Petersburg. Edition of K. L. Rikker, 1901. - XIX, 260 p., 26 l. fig., maps and two maps in a special pocket. Publisher's calico binding, slightly narrowed format (13 x 23 cm). The cover covers are worn and dirty, the block is beveled; a through tear in the center of the free flyleaf sheet; single temporary and household spots, tears at the base of the cards; no pages 253-258.

Two general maps of the Northern and Southern sky and 26 special maps of stars visible to the simple eye up to 35 degrees of southern declination with the designation of variable and double stars, star piles and fog spots. With an explanatory text and 51 figures in the text.

[ For the convenience of describing the boundaries of the constellations, it was decided to draw them in the form of broken lines passing exactly along the grid of constant celestial coordinates – declinations and right ascents. At the same time, the constellations began to resemble some African countries and American states, whose borders are drawn along parallels and meridians. This is a completely rational way to easily fix the boundaries in mathematical form. 

 However, over time, this elegant idea began to show one minor flaw.

The fact is that the system of geographical coordinates is in some sense more reliable than the coordinates of the sky. The Earth's parallels and meridians are rigidly "nailed" to the surface of the planet by the position of the axis of its rotation, which determines the equator, and the location of the Greenwich Observatory, which sets the zero meridian. Therefore, once established and described in the documents of the administrative boundaries (for example, the border drawn on the 120th western meridian between the northern part of California and Nevada) will always pass along the original strip of land, without disturbing the beauty of geographical atlases.

 With the boundaries of the constellations, the situation is different. The stars are located in the sky, but the celestial equator reflects the position of the earth: the orientation of the earth's axis changes as a result of precession – the equatorial coordinate system "walks" in the sky.

When astronomers began to demarcate the heavens in the early twentieth century, they drew the boundaries of the constellations along the arcs of the celestial "parallels and meridians" in the equatorial coordinate system of 1875; at that time, this was the standard. But years have passed, and if you take the modern star atlas of the 2000 era, it is easy to see that the boundaries of the constellations no longer coincide with the lines of the coordinate grid, but slightly deviate from them. In the future, this difference will increase as the vernal equinox, which plays the role of Greenwich in the sky, moves inexorably along the ecliptic, dragging the network of celestial coordinates with it. The only consolation is that after 26 thousand years (the period of precession), everything will return to its original state.]