TEL 



and extremely faint objects depends more upon the penetrating, than on 

 the magnifying- power, of our telescopes ; and with a ten feet Newto- 

 nian, charged with a power of only GO, Sir W. Herschell saw all the five 

 old satellites. 



Georgium Sidus. The satellites of this planet were discovered by 

 Herschel with a power of 157 ; but their faint scintillations were only 

 perceived by interrupted glimpses, but magnifiers of 300, 460, 600, and 

 800, were most effective. It is in vain, however, to attempt any consi- 

 derable power, unless in telescopes which have a prodigious quantity of 

 light j and in Herschell's ten feet telescope, Avith none of its highest 

 powers, could he possibly ascertain even the existence of the satellites. 

 Ceres, Pallas, Juno, and Vesta. Herschel applied a distinct magnify- 

 ing power of 500 or 600 and even higher to these asteroids, and yet no 

 disc was discoverable, any more than in very small stars. 



Double stars. In a fine telescope the powers employed should be from 

 200 to 400. 



List of a few double stars t which are proper objects for common telescopes. 



Ursae Majoris. 

 y Delphini. 

 13. Cygni. 

 y Arietis. 

 y Andromedae. 

 S Orionis. 

 a- Orionis double. 

 1 1 Monocerotis appears double 



i Lyrae appears double. 



J9- Serpentis. 



/3 Lyrae. 



t Delphini. 



* Bootis. 



y Virginis. 



/ Cassiopeae. 



ft Cygni. 



List of a few double stars, in ichich proximity or faintness renders one of 

 them difficult to be seen, and which arc proper objects for the finest tele- 

 scopes. 



% Aquarii. ^ Herculis. 



ft Draconis. Geminorum. 



/S Orionis. | Librae Seq, 



Piscium. ^ Bootis. 



Ursae Majoris. s Lyrge. 



*> Aurigse. 11 Monocerotis. 



& Geminorum. x. Bootis. 



k Cygni. /$ Scorpii. 



t Persei. Polaris. 



Lyra. y Herciilis. 



301 R3 



