The times. [volume] (Richmond, Va.) 1890-1903, 1890-09-05
rHs SEPTEMBER HEAVENS.


.oaaething About thc stars and Planets
During hi- Month.
H. oar last article Ne discussed tle carly
Stages in thD Development Of the telescope.
We followed ile successive attempts to eei
powerful instruments without chromaic
operation through ,lc period f"aorial Ielc-
SCOPES" a- tle loug Irirlrtor- I'd ta--tmi
aud others We're called. down tO the improve
mcnt in 90. quality Oi 90. lens DIS DDllard.
Il viii Boz remembered that This improve
mont consisted iu substituting fDr the single
lens. i0Imerf used. tW0 lenses. One OF Iiut
gia,, aud tlD other Oi crown glass. From
TINS time the coi0nd frir-e- tlat u0rd rcd
every object seen bon tle old tcie-oour-
almost entirely di-app liu, tne oili-
Guilty ot making lenses of iut glass 0l c0u-
siderable size effectively checked m}
marked advancement Dos mean, OF r0ilrc-
tors. sir Isaac Newton. thinking ile dlfli-
cultic- that opticians met with boo lrlcurir-
lllut glass were insurm0ugtahle iJt least fui
that timer. be-an tO develop the powers of
rejecting telescopes. which, however, bad
been devised before his time, uut little
used.
Rejecting telescopes are so seldom seen IN
this country thar few words 40 eApl1na-
ton may NOT be am.-s. Instead oi "a lens
there is c0ncaye minor NC either silver
ell glass OF some alloy capahl. of retaining
"a very hi-h polish. This mirror is set in
the lower end oi "A telescope tube. Tie
light entering the other end is brought % %
focus. a- in the ease oi reirlct0r-, and There
viewed with magnIiFiug glass called am
eve piece. The fact tn1t Cine focus anG
consequently the IMAGE Of the object is on
the same SIDE &C the mirror Jas The object 30
self presents difficulty oi "a very practical
nature. namely: where clu one put hi, mead
while observing so a- not iO cIl ou All the
light. Various plans have been suggested
and each used iu It's turn. ller-rhcl, the
great English astronomer " the last CELL
fury. used % Nd ke hi. mirror, of such "a
shape that the c,e-piece came 0n tbe edge
OF the tube. and. as bis telescopes Nere If
two and four feet I'm diamater. this device
necessitated very little loss Oflight The dir
hcully, however. Of grinding par1DOllc sur-
face 50 a. % bring the oyc-piece on tLe edge
and at the same time preserve the distinct
ness of the IMAGE j. so great that NeWtOn's
plan Is now always preferred. lie placed
avery small mirror, which was aficrward
substituted fora prism, near the focus al
such an angle a. t0 reflect the cone a. light
90 one side through an opening in the tube.
IL an eye piece WAS then properly adjusted
the image would appear at right angle 10
the direction in which the light came from
the object Thus the sun al noon through
such telescope would appear toward the
eastern or western horizon.
such il very briefly the fundamental prin-
ciple Of "a reflector. Simple as this appears
in a short explanation. the mechanical skill
required 10 shape and polish the mirror was
80 great that little progress was made until
Herschel began his astronomical career.
With superior skill he at once commenced
mirrors Of larger size, and soon completed
one Of TWO feet in diameter, the result, how
ever, of large number al unsuccessful at-
tempts. Win this telescope he discovered
the planet Uranus. Next he made one
Of enormous size Of four leet in diam
eter and forty feet focal length. But
such dimensions OSerlaXed the eng-