122 
CELKSTIAL DAY OBSERVATIONS. 
Observations 
upon the 
planet Venus 
in the day- 
time. 
view'ed at a high altitude, and the sky serene, her disc will i' 
appear suffic iently luminous and well defined for this purpose 
free of that glare, and tremulous aspect she generally exhibits 
■?, 
in the evening, when near the horizon ; w hich makes her appear 
larger than she ought to do, and prevervts her margin from being 
accurately distinguished. 
2. Another conclusion from the observations on Venus is : — 
1 
That during the space of 583 days, or about ig months, thej^ 
'1 
time she takes in moving from one conjunction with the sun, to: 
a like conjunction again, when her latitude at the time of her I 
superior conjunction exceed.s 3“, — she may be seen with an .1 
equatorial telescope, every clear day, without interruption j ; i 
except at the time of her inferior conjunction, when her dark ■ 
side is turned towards the earth, and 3 or 4 days before and t ; 
after it. When her latitude is less than 3“ she will be hid only o 
1 1 days before, and the same time after her superior conjunc- ,J 
tion. During the same period she wdll be invisible to the 
naked eye, and consequently no observations can be made on '4 
her with a common telescope, for nearly 8 months, and some- iC 
times more, according as her declination is north or south ; viz.j 
above three months before, and the same time after her superior!* 
eoujunction, and above 2 weeks before and after her inferior;* 
conjunction ; except where there is a very free and unconfinedjS 
horizon. — It follows, 
3. 'Iliat every variation of the phases of this planet, from af 
slender crescent to a full enlightened hemisphere, may, on , 
every clear day, be conveniently exhibited. This circumstance!* 
I have found extremely useful, when explaining the appearances^ 
of the inferior planets to young persons, and endeavouring top 
convince them of the truth of the solar system. The phases ' 
•f the inferior planets, considered in reference to their situa-H 
tion with respect to the sun, isj perhaps, the best popular J 
argument for convincing a tyro of the truth of the Copernicanp 
system. — Having placed Venus ’in her true position on dn - 
orrery, by means of an epherneris, I desire the pupil to mark| 
her phase, as seen fiom the earth, which is also placed in its true: ' 
poshion. I then adjust the equatorial telescope for Venus, and . 
shews* 
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