Page:Philosophical Transactions - Volume 095.djvu/71

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of ascertaining the Magnitude of small celestial Bodies.

larger, equal to that of the equal, and larger than that of the smaller star. The gradual difference between the three stars is exceedingly small.

"With 490,3, and the air uncommonly pure and calm, I see so well that I am certain the disk, if it be not a spurious one, is less than one of the smallest globules I saw this morning in the tree."

The diameter of this globule was ,02. It subtended an angle of 0",429, and was of sealing-wax; had it been a silver one, it would have been still more visible.

With 879,4, All comparative magnitudes of the asteroid and stars, remain as with 496,3.

I see the minute double star q Ophiuchi[1] in high perfection, which proves that the air is clear, and the telescope in good order.

The asteroid being now in the meridian, and the air very pure, I think the comparative diameter is a little larger than that of an equal star, and its light also differs from star-light. Its apparent magnitude, however, can hardly be equal to that of the smallest globule I saw this morning. This globule measured ,01358, and at the distance of 9620,4 inches subtended ah angle of 0",214.

When I viewed the asteroid with 879,4 I found more haziness than an equal star would have given: but this I ascribe to want of light. What I call an equal star, is one that in an achromatic finder appears of equal light.

Oct. 7. Mr. Harding's asteroid has continued its retrograde motion. The weather is not clear enough to allow the use of high powers.

  1. See Cat. of double Stars I. 87.

I 2