ConJiruBlm of the Heavens. 2^7 



lis with the irrefolvable, much lefs with the colourlefs and 

 ir.ilky fort of nebuJofities. 



ud Perforated Nebula, or Ring of Stars., 

 Among the curiofities of the heavens (hould be placed a 

 nebula, that lias a regular, concentric, dark Ipot in tiie middle, 

 and is probably a Ring of liars. It is of an oval {hape, the 

 iliorter axis being to the longer as about 83 to 100 ; fo that, if 

 the ftars form a circle, its inclination to a line drawn from the 

 lun to the center of this nebula mufl be about ^6 degrees. The 

 light is of the refolvable kind, and in the northern fide three 

 very faint ftars may be feen, as alfo^ one or two in the fouthern 

 part. The vertices of the longer axis feem lefs bright and not 

 fo well defined as the reft. There are feveral fmall ftars verv 

 near, but none that feem to belong to it. It is the 57th of 

 the CQfinoiJjance des Temps, Fig. 5. is a reprefentation of it.. 



Planetary Nebula. 



I fhall conclude this paper with an account of a few hea- 

 venly bodies, that from their lingular appearance leave me almofl; 

 in doubt where to clafs them. 



The tirft precedes v Aquarii k^' ^^ in time, and is i^ more 

 Horth. Its place,, with regard to a fmall ftar Sept. 7, 1782, 

 was, Diftance 8^ j 3^^ S^^^' '•> ^^^ °" account of the low iituation, 

 and other unfavourable circumftances, the meafure cannot be 

 very exaft. Auguft 25, 1783, Diftance 7' 5'^ ii-^\ veryexa^l^, 

 and to my fatisfatlion ; the light being thrown in by an opaque- 

 microicoplc-illumination (^). Sept. 20, 1783, Pofition 41° 24' 



foutli 



{g) It may be of ufe to explain this kin^ of illumination for which the New- 

 tonian refleftor is admirably conftrudtetl. On the fide oppofite the eye-piece an 

 ©pening is to be made in the tube, through which the light may be thrown in, fo 

 a* to fall on fome refleding body, or concave perforated mirror, within the eye- 



piece;,^ 



