The Washington times., 1904-11-20

she can be observed visually with the
largest refractors. and that she "can
doubtless be photographed with largo te>
fectors." The circular also states that
.it Is probable that IN the future there
will be no difficulty in securing suf-
ficient number Of observations. not only
10 correct the present elements, but 10
study the large and interesting pertur-
bations TO which IL Is subject"
From this il viii be seen that Phoebe
improves upon acquaintance. The mys-
terry Of her absence from the plates
made during July has not yet been
cleared up. Prof. Eric Doolittie. OF the
University Of Pennsylvania suggested
that the observation Of the little moon
might have been due 70 moisture or 10
very fine dust in the air Some photo
graphic plates are more sensitive than
others he suggested. although intended
to be uniform. yet he thought it i'm
probable that three different plates
would be found to be defective just
where it was desired they should be per-
feet.
Phoebe was discovered with the great
Bruce Photographic telescope. which
has twenty-fOur-inch opening the
largest apparatus Of its kind IN the
world. Oae diniculty In pereeiving this
coy little moon Of Saturn is the fact
that Phoebe shows no clear disk; she
| is only a minute spot OF life, as formless
as one OF those distant sums which we
call stars.
In photogTaphing the heavens IL has
been discovered that the longer the ex-
| posure the more stars are found upon
the photographic plate when il is de-
veIoped In this way millions OF stars
have been photographed large NUM-
Der OF D1ars. nebulae and comets having
| been discovered which would have for
! ever remained unknown if only visual
| observations had been made.
| As the magnituGes OF the stars de-
/ crease a much Icnger time IS required
| 10 photograph them. Thus star OF
the fifteenth magnitude viii require the
| photogFa phic plate 20 be exposed upon
| Il for an hour before II becomes eNi-
dent The brightest stars may De pno-
tographed with a seconds exposure An
/ exposure of four hours or l4v99 times sts
] long. fails 10 record stars whlch. VIII
I appear when the exposure OF hVe or SIX
hours is used.
| and rated as very nearly or the seven
| teenth magnitude. her portrait mas bech
taken with the Bruce telescope IN Two
/ hours. ana EEhfs B4EAtdkn Ub9FA
| I-fsIIsilv nv means OF the fOrty-inch
| Yerkes telescope This IS a feat which
had not been considered possible. al
/ though theoretically an instrument with
l an a1erfure of $3.50 is supposed 10 be
/ capable OF showing a star OF tire sew
| enteenth magnitude. Even with this IN
/ strument il requires practiced observer
10 discern the object
/ AT the Arequipa Observatory they are
making photographs Of all the stars
/ within range, and some idea or the eA-
/ fraordfnary character OF the undertak-
ing may be CLEANED when II Is known
II mat i'm a few years IL is expected 20
have records of no less than lO0,u1JUp
4 stars After the photographs are made
! - stsrs on the plates are carefully cat
aIoe1ted. The great advantage OF pho-
Biography lies In the fact that the images
4 made may be enormously Iurtner en-
lareed. and il is from these enlarge
Tne1ts that some OF the most important
tnforTnation about the heavenly bodies
has been learned.