290 The Pole Star and the Pointers. (July, 
as it were, the pole star and the pointers according to their 
true position relative to one another, and as seen by an ob- 
server in N. latitude 52°, at various times. 
The pole star is not situated exactly at the pole of the 
heavens, but is distant about 1° 27’ from the true pole, and 
therefore describes every twenty-four hours a circle round 
the pole, the radius of which circle is about 1° 27',—that is, 
nearly three times the apparent angular diameter of the 
sun, for the diameter of the sun subtends an angle of 
about 32’. 
The pointer nearest the pole is about 27° 34' from the pole, 
whilst the second pointer is about 32° 49’ from the pole. 
These two stars during every twenty-four hours appear 
to trace circles in the heavens round the pole of the heavens, 
the radius of each circle being 27° 34’ and 32° 49’. 
We will next refer to the lateral divergence of these three 
stars from what we may term a straight line, and in order 
to do this we must refer to what is called ‘“‘ Right 
Ascension ;”’ a term which probably some readers may not 
be acquainted with, but we will give such a popular descrip- 
tion thereof as shall render the explanation intelligible to any 
person. 
The right ascension of the pole star is about one hour 
and twelve minutes, which converted into degrees is 18°. 
The right ascension of the nearest of the pointers, viz., 
a Urse Majoris, is ten hours fifty-five minutes, whilst the 
second pointer 8 Urse Majoris has a right ascension of 
ten hours fifty-three minutes. Converting these differences 
of right ascension into degrees it follows that the difference 
in right ascension between the pole star and the pointers is, 
in round numbers, 145° 43’. 
Let us now explain this fact in more popular language. 
If in the following diagram P represent the pole of the 
heavens, Ss the position of the pole star distant 1° 27’ from 
Pp, aand @ the two pointers, then the angle s P a will be 
145° 43’ 
Fic. 4. 
Ss 
[pase ae PUY 
Now the point p always remains fixed in the heavens, and 
whilst s revolves round Pp, and a and £ also revolve round P, 
yet the angle s pa will always remain a constant in value, 
and will always be 145° 43’. 
Wecan now trace out the changes which occur in the 
apparent relative positions of the pointers and the pole star 
