TO KNOW THE STARRY HEAVENS 



207 



How to Observe the Sun With a Small 



Telescope. 



During the last several weeks the 



reader may have noticed occasional 



newspaper announcements of the dis- 



destroy the (Cyesig'ht. Sometimes a 

 dark paper is placed over the larger 

 lens, having a small circular hole cut 

 from its center, but this is a poor plan, 

 for it greatly increases the blurring of 



Fig. 2. Arrangement for viewing the sun with a small telescope. 



covery of one or more great sun spots, 

 the discovery being sometimes credited 

 to one astronomer and sometimes to 

 another. As a matter of fact, any sun 

 spot large enough to be noteworthy 

 is visible even in the smallest telescope, 

 and sometimes even without any tele- 

 scope at all, and therefore it will be sure 

 to at once be seen by any observer who 

 happens to look at the sun's disc after 

 it has appeared. It is thus hardly more 

 reasonable to speak of the "discoverer" 

 of a great sun spot than to credit a 

 single observer with the discovery of a 

 iull moon or of an equinoctial storm. 

 At the present time, and for several 

 months to come, every possessor of a 

 small telescope will find that a frequent 

 ■examination of the sun's disc will af- 

 ford a most profitable and interesting 

 study. For we are now very near to 

 an epoch of sun-spot maximum, an 

 •epoch which will not occur again until 

 II years from the present time. 



With even a small telescope one 

 •cannot look directly at the sun, for were 

 this done the large lens would act as a 

 "burning glass and concentrate upon 

 the eye all of the light and heat rays 

 which fall upon the area of its surface. 

 This would injure or even com])letelv 



the solar image. A far better arrange- 

 ment is that shown in Figure 2. The 

 eyepiece at E is removed and the card- 

 board screen A. D. is adjusted at the 

 position of most perfect focus, a clear 

 image of the sun will appear upon 

 the screen, especially if a dark cloth 

 be thrown over the top and farther 

 sides, ABKD, so as to cut off all out- 

 side light. (The figure is taken from 

 Kelvin McKreadv's "A Beginner's 

 Star Book.") 



The amateur should be warned 

 against looking at the sun directly, 

 even with the red glasses provided 

 with small telescopes. If the observa- 

 tion is prolonged, which is apt to be 

 the case when an enthusiastic observer 

 is intently watching the marvelous 

 changes going on in this wonderful 

 star, the heat may suddenly crack the 

 red cover with disastrous results to the 

 observer's evesight. 



' :i: ' ;!: * ^ * 



The Sun a Great Ball of Fire. 



AX'hen care is used in arranging this 

 simple apparatus an image of the sun 

 will appear on the screen which will 

 have all the sharpness and clearness of 

 a steel engraving, its appearance re- 

 sembline more or less that shown in 



