This chart is (slightly modified) from Uranometria, Vol I by
Tirion, et. al., and is based on coordinates as of the year 2000.
The cross just above center (vertical portion is nearly superimposed
on the 12h RA line) is the position of the pole as of the year 1950.
This is from page 2008 (vol 3) of Burnham's Celestial Handbook.
The slightly curved line down the center shows the position of the pole
over a two hundred year period. This curve is a portion of a circle
of radius 23.45 degrees centered at RA 18h, dec 66.55 (90-23.45=66.55).
That point is the pole of the solar system's rotation. The earth's
axis is tilted 23.45 degrees to this pole and precesses (wobbles like a
top) around this circle in about 26,000 years (about 1/3 of an arcminute
per year). At any given time, the 0h line of RA (in the current epoch)
is (by definition) tangent to this circle. The circular arc near
bottom is of radius 1 degree and is centered on the pole as of 1950 (this
slightly outdated book is still one of the best around).