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Frequently Asked Questions
1. Why is the image in my telescope eyepiece upside-down and/or backwards?
If you hav ins rt d your y pi c dir ctly into th t l scop ’s focusing tub , you will s an imag that is
upsid -down and backwards. This is normal for an astronomical t l scop . Aft r all, th r ’s no up or down in
spac so it do sn’t matt r how th fi ld is ori nt d. For t rr strial vi wing, wh n you want imag s to b
ori nt d prop rly (as s n with th nak d y ), ins rt th imag r ctor according to th dir ctions on pag 9
of this guid .
2. Why can’t I see anything when I look through my telescope?
If you s only whit , gray, or black through th t l scop , th r ar two lik ly caus s. Th first is that you
hav ins rt d an y pi c that is too pow rful. To solv this probl m, switch to a low pow r y pi c . As a
rul , always start with th low st pow r y pi c (20mm), gradually switching to th high r pow r y pi c s
only aft r you hav locat d an obj ct. Th s cond caus is that th find r scop is not prop rly align d. S
pag 7 of this guid for th proc dur to prop rly align your find r scop .
3. When I use my high power eyepiece, why does everything look darker?
As t l scop magnification incr as s, brightn ss diminish s. Brightn ss incr as s wh n magnification is
r duc d. If an imag app ars dark or uncl ar, try using your low pow r y pi c . It is asi r to study small,
bright vi ws of c l stial obj cts than larg , dark, or blurry on s. You do not n d v ry high pow rs to study
most c l stial obj cts.
4. Why do objects in the sky move out of view when I look through my telescope?
Wh n you vi w a c l stial obj ct through a t l scop , th rotation of th arth mak s it app ar as though
obj cts ar moving across th vi wing ar a. You can l ss n this ff ct and obs rv th larg st ar a of th sky
by using your low pow r l ns.
Observing the Night Sky
Your t l scop can bring you th moon and stars—and som plan ts, too.
Planets
Th plan ts ar our solar syst m companions. Th y rang in siz from Pluto, a rocky plan t small r than our
moon, to Jupit r, a giant gas ball that could hold 1,000 Earths. Vi wing th plan ts pr s nts som chall ng s. As
th plan ts in our solar syst m orbit th sun, th ir position in our night sky chang s. To find out wh r to look for
plan ts at a particular tim , ch ck an astronomy magazin , such as Sky and Telescope. You can also visit th
magazin ’s w b sit , list d on pag 12 in this guid .
Most p opl who hav look d up at th night sky hav probably s n som plan ts but did not r aliz it. A
plan t, wh n it is abov th horizon, will not twinkl lik a star. Plan ts ar r solv d by th y as tiny balls, as
oppos d to stars, which ar infinit ly small points of light. Th asi st plan ts to vi w, wh n th y ar visibl , ar
th fiv “nak d- y ” plan ts: Saturn, Jupit r, Mars, V nus, and M rcury. M rcury is th most difficult to s sinc
it is usually b low th horizon.
Each of th plan ts has its own s t of uniqu charact ristics, making th m a wond r to b hold. V nus is cov r d
with clouds, so all that is visibl is an xtr m ly bright light. How v r, V nus, lik th moon, go s through phas s
that ar visibl through your t l scop . Mars app ars to bright n and dim, d p nding on its distanc from Earth.
You can obs rv four of giant Jupit r’s many moons and its unusual cloud b lt patt rn through your t l scop
wh n vi wing conditions ar right. Sighting Saturn’s sp ctacular rings is a r warding xp ri nc for amat ur
astronom rs of all ag s.
Stars
Th stars ar so far away that wh n you look at on with your t l scop , you won’t s a disk as you do wh n
you look at a plan t. Ev n with a larg , pow rful t l scop , a star is s n as a point of light. Som stars look
larg r than oth rs, but what you ar actually s ing is bright r points of light compar d to dimm r points of
light. Th bright r stars ar n’t n c ssarily larg r, but th y app ar that way to us. With your t l scop , you should
b abl to s doz ns of galaxi s, star clust rs, and n bula .
The Moon
Th silv ry moon is an xciting subj ct to vi w with your t l scop . As Earth’s n ar st n ighbor, it’s about
a quart r million mil s away. That may sound lik a long distanc , but it’s clos nough that your
t l scop will r v al a fascinating lunar landscap of crat rs, plains, and mountain p aks.
H r ar a f w int r sting lunar f atur s to look for:
Mare Crisium
Mar Crisium (“S a of Cris s”) is actually a hug plain form d wh n gr at lava flows cool d and hard n d on th
moon’s surfac .
Crater Copernicus
Crat r Cop rnicus is a bright crat r with a hug ncircling ring of d bris that was thrown out of th crat r wh n it
was form d by an impacting m t or mor than 100 million y ars ago. It is 60 mil s (97 km) across and mor than
2 mil s (12,600 f t, or 3,840 m) d p.
Crater Tycho
Bright str aks or rays, b st s n during a full moon, manat from this crat r. Th rays indicat that this is a young
crat r. Ov r tim , m t ors constantly bombarding th crat r’s surfac will caus th rays to disapp ar. Crat r Tycho
is 56 mil s (90 km) across and almost 14,000 f t (4,627 m) d p.
Crater Grimaldi
This larg crat r looks lliptical in shap , but it is actually circular. It app ars to b lliptical b caus w s it on
th w st rn horizon of th moon, which is curving away from us. This ff ct is call d foreshortening. Crat r
Grimaldi is about 140 mil s (225 km) across and 10,500 f t (3,200 m) d p.
E
N
S
W
Mare
Crisium Crater
Copernicus
Crater
Tycho
Crater
Grimaldi
© Copyright 1982 Th Royal Astronomical Soci ty of Canada
Not : This map, lik your t l scop ,
shows a mirror imag of th moon.
