Star Finding. 



37 



" Notes and Memoranda" of our May number, we have given 

 it repeated trials, and have likewise obtained an excellent 

 report of its merits from a practical astronomer, to whose 

 care we consigned it for several weeks. It consists of a 

 steady bed, shown in the annexed sketch, furnished with two 

 spirit-levels and three adjusting screws. The polar support, 

 m, has the slope required by the latitude of the place in 

 which it is to be used, and being fixed by the makers at the 

 right angle, becomes free from error and always ready for work. 

 •a is the telescope, rotating 

 on an axis and carrying the 

 index e to any point of the 

 declination circle d ; h is 

 the hour circle, and i its 

 index, moving with the tele- 

 scope and giving the right 

 ascension in hours and de- 

 grees. 



If the student has a con- 

 venient place commanding' 

 a, sufficient sky view, he can 

 if he' pleases fix the instru- 

 ment upon a pillar after hav- 

 ing adjusted it according to 

 the directions given in an 

 excellent paper issued with 

 it, but in many cases it will 

 be convenient to preserve its 

 portability, and then it must 

 be brought to the right po- 

 sition each time it is em- 

 ployed. If required merely 

 as a finder it will be sufficient 

 to set the two circles for the 



right ascension, and declination of the pole star as given in the 

 Nautical Almanack, or any other ephemeris ; the polar support 

 should then be approximately pointed to the star, and the bed 

 accurately levelled by the adjusting screws. If this is properly 

 done a very trifling movement will bring the star into the cen- 

 tre of the field marked by the cross wires, and the instrument 

 will be ready for use. In this way we obtained good results as 

 a finder, and for measurements of position sufficiently near the 

 mark to distinguish and ascertain the name of any star not 

 easily confounded with its near neighbours. This mode of pro- 

 ceeding has certain obvious advantages, but every possessor of 

 the instrument should accustom himself to use it from one par- 

 ticular situation where he has obtained a good meridian line, 



