130 



THE GUIDE TO NATURE 



the constellations, easily acquired, a 

 "Star Atlas," (a good one can be pur- 

 chased for $1.25), and the charts which 

 the writer will gladly furnish to those 

 who wish to take up the work. The 

 method of observing is briefly as fol- 

 lows : 



On each of the charts the Right As- 

 cension and Declination of the Variable 

 is designated, that is to say. its latitude 

 and longitude terrestrially speaking. 

 First the position of the \"ariable is 

 roughly plotted on the "Star Atlas," 

 and then the region is swept over with 

 the telescope, using a low power ocular 

 until the immediate field given on the 

 chart is identified. The \'ariable is then 

 easily located. This may strike the 

 reader as difficult, but it does not prove 

 so as many have found out who have 

 essayed this form of c>bservational 

 work. 



The observation of the \ ariable then 

 follows. On each chart are a number 

 of constant stars that have been photo- 

 metrically measured, and their definite 

 magnitude is designated. These are the 

 comparison stars. Note one a trifle 

 brighter and one fainter than the Vari- 

 able and you have the means of ascer- 

 taining and estimating visually the 

 magnitude of the Variable on the date 

 observed. 



Observe the \'ariable a few nighis 

 later, and you will note a change in its 

 degree of brightness. Continue the 

 work for a time and you can trace out 

 its light curve in full, thus determining 

 very closely its exact magnitude at 

 maximum and at minimum, and the 

 date of each, which constitute valuable 

 scientific data. 



There is nothing monotonous about 

 the work, and every observation you 

 make has a positive and scientific value 

 which renders observing a pleasurable 

 and interesting task. You always have 

 the assurance that your time is well 

 spent, and that you are not engaged 

 in the desultory work in which class 

 so much that the amateur does with the 

 microscope and telescope falls. 



Once you engage in \'ariable star ob- 

 serving you will l:)ecome fascinated 

 with it, and will wish to join the Ameri- 

 can Association of \"ariable Star Ob- 

 servers, a group of amateurs who de- 

 light in this interesting telescopic em- 

 ployment. 



There are no dues to frighten vou a- 



away, or exacting obligations of any 

 sort. You simply agree to observe Var- 

 iables when it is convenient, and pay 

 a nominal tax of twenty-five cents per 

 annum to cover postage. You are fur- 

 nished with a valuable set of charts 

 gratis, and in return make a monthly 

 report of your observations to the Har- 

 vard College Observatory and the wri- 

 ter. The observations appear each 

 month in "Popular Astronomy," and 

 later are published in the Harvard An- 

 nals. 



Here is a chance you have been look- 

 ing for. An opportunity to assist if 

 even by the contribution of a mite in 

 adding to the sum total of scientific 

 knowledge. 



The work is endorsed by Professor 

 E. C. Pickering, Director of the Har- 

 vard College Observatory, who consi- 

 ders it to be the most valuable and use- 

 ful that the amateur can engage in. 



Get out that old glass up in the attic. 

 It is a valuable scientific instrument in 

 intelligent hands. You can do as good 

 work with it in observing Variables 

 as can be done with an expensive tele- 

 scope of great aperture. You will not 

 find the work difficult, of that I can 

 assure you, for many write me that 

 they have success from their initial ef- 

 forts. 



Naturally the cjuality of the esti- 

 mates depends on constant practice, but 

 in a wonderfully short time the eye 

 yields results that are reliable and val- 

 uable. 



Some day we will know the secret 

 these inconstant stars now possess, and 

 the fame and satisfaction of the discov- 

 ery will be shared in a great measure 

 by the faithful group of amateur astro- 

 nomers now engaged in this delightful 

 and intellectually profitable telescopic 

 work. 



Fm willin' a man should go tollable 

 strong 

 Agin w'rong in the abstract, for that 

 kind o' wrong 

 Is oilers unpop'lar an' never gits pitied, 

 Because it's a crime no one never 

 committed ; 

 But he musn't be hard on partickler 

 sins, 

 'Coz then he'll be kickin' the peo- 

 ple's own shins. 



J.4MES RUSSEL LoWELL. 



