5
pressure on the main telescope tube to recenter the object in
the field of view, if it moved off center when you tightened the
lock knobs.
Now look through the finder scope. Is the object centered in
the finder scope’s field of view, i.e., on the crosshairs? If not,
hopefully it will be visible somewhere in the field of view, so
only fine adjustment of the three alignment screws will be
needed to center it on the crosshairs. If the object isn’t in the
field of view at all, you’ll have to make coarser adjustments to
the alignment screws to redirect the aim of the finder scope.
Once the target object is centered on the crosshairs of the
finder scope, look again in the main telescope’s eyepiece and
see if it is still centered there as well. If it isn’t, repeat the
entire process, making sure not to move the main telescope
while adjusting the alignment of the finder scope.
Check the alignment by pointing the main telescope at anoth-
er object and centering it in the finder scope. Then look
through the main telescope eyepiece and see if the object is
centered. If it is, your job is done. If it isn’t, make the neces-
sary adjustments to the finder scope’s alignment screws until
the object is centered in both instruments.
Finder scopes often come out of alignment during transport of
the telescope, so check it before each observing session.
One way to minimize any misalignment is to keep the finder
scope bracket tightly fastened to the main telescope.
Note that the image seen through the finder scope
appears upside down. This is normal for astronomical
finder scopes.
The finder scope can be focused by turning its rotating eyepiece.
5. Using Your Telescope
Choosing an Observing Site
When selecting a location for observing, get as far away as
possible from direct artificial light such as streetlights, porch
lights, and automobile headlights. The glare from these lights
will greatly impair your dark-adapted night vision. Set up on a
grass or dirt surface, not asphalt, because asphalt radiates
more heat, which disturbs the surrounding air and degrades
the images seen through the telescope. Avoid viewing over
rooftops and chimneys, as they often have warm air currents
rising from them. Similarly, avoid observing from indoors
through an open (or closed) window, because the tempera-
ture difference between the indoor and outdoor air will cause
image blurring and distortion.
It’s best, although perhaps less convenient, to escape the
light-polluted city sky in favor of darker country skies. You’ll
be amazed at how many more stars and deep-sky objects are
visible in a dark sky!
Cooling the Telescope
All optical instruments need time to reach “thermal equilibrium.”
The bigger the instrument and the larger the temperature
change, the more time is needed. Allow at least a half-hour for
your telescope to cool to the temperature outdoors. In very cold
climates (below freezing), it is essential to store the telescope
as cold as possible. If it has to adjust to more than a 40° tem-
perature change, allow at least one hour. Make sure you are
not looking over buildings, pavement, or any other source of
heat, which will radiate away at night, causing “heat wave” dis-
turbances that will distort the image you see through the
telescope.
Aiming the Telescope
To aim the telescope, first loosen both the azimuth and micro-
motion lock knobs, and slightly loosen the altitude lock knobs.
Aim the telescope at the object you wish to observe by first
“eyeballing” along the length of the telescope tube. Then look
through the (aligned) finder scope and move the telescope
tube until the object is visible in the finder scope. Center it on
the finder’s crosshairs. Then tighten the lock bolts. You
should now be able to see the object in the main telescope
using a low-power eyepiece. (Always use the lowest-power
eyepiece available for locating an object, then you can switch
up to higher powers if desired.)
Fine adjustments of the telescope’s vertical position can be
made by rotating the altitude micro-motion knob. Fine adjust-
ments in the azimuth position can be made by applying slight
sideways pressure to the back end of the telescope (make
sure the azimuth lock knob is slightly loosened) to turn it.
Note that the altitude micro-motion knob has a limited range
of movement. If it reaches the end of its travel, loosen the
micro-motion lock knob and rotate the micro-motion knob
back a few turns, then retighten the lock knob.
Focusing the Telescope
Practice focusing the telescope in the daytime before using it
for the first time at night. Start by positioning the focuser near
the center of its adjustment range. Insert an eyepiece into the
focuser and secure with the thumbscrew. Point the telescope
at a distant subject and get it in the field of view. Now, slowly
rotate one of the focusing knobs until the object comes into
sharp focus. Go a little bit beyond sharp focus until the image
just starts to blur again, then reverse the rotation of the knob,
just to make sure you hit the exact focus point. The telescope
can only focus on objects at least 50 to 100 feet away. It will
not focus without the star diagonal in place.
As with all refractor telescopes used with a standard 90° star
diagonal, the image you see will be right-side up, but
reversed left-to-right. (Correct-image diagonals are available,
and may be purchased separately, though the image quality
is slightly reduced.)
Do You Wear Eyeglasses?
If you wear eyeglasses, you may be able to keep them on
while you observe, if your eyepieces have enough “eye relief”
to allow you to see the whole field of view. You can try this by
looking through the eyepiece first with your glasses on and
then with them off, and see if the glasses restrict the view to
only a portion of the full field. If they do, you can easily
observe with your glasses off by just refocusing the telescope
the needed amount.
