ENGLISH
I
11
DETERMINING MAGNIFICATION
AND SELECTING EYEPIECES
To change the magnification of the telescope, you’ll need
to swap out the eyepiece in the telescope’s focuser. To
calculate the magnification you can achieve with a given
eyepiece, use this formula:
Focal length of telescope ÷
Focal length of eyepiece
= Magnification
The SSE Dobs have a focal length of 1200mm. They come
with a 25mm Omni Plössl eyepiece. Using the formula, we
can calculate that this combination yields a magnification
of 48x (1200mm ÷ 25mm = 48x). This is an excellent
magnification for locating and observing wide-field deep
space objects. You may want to consider purchasing a
higher-magnification eyepiece, like a 10mm Omni Plössl,
for higher-power views of the Moon and planets. Do not
increase magnification too much though, or the view may
degrade due to atmospheric seeing conditions (i.e. air
turbulence).
The maximum magnification for any telescope is about 60
times per inch, which equates to 480x for the 8” SSE Dob,
and 600x for the 10” SSE Dob. In many locations, however,
it will be difficult to achieve sharp images much over 100x
magnification due to turbulence in the air above you. If you
notice that the stars overhead are twinkling heavily, seeing
conditions are poor. You should stick to lower magnification.
If the stars appear to shine steadily, seeing conditions are
good. You can try using higher-magnification eyepieces.
The SSE Dobs can accept both 1.25” and 2” format
eyepieces. 2” eyepieces generally provide a wider field of
view but can cost significantly more. To use a 2” eyepiece,
remove the 2”-to-1.25” adapter from the focuser and insert
the eyepiece directly into the 2” extension tube. Secure the
eyepiece with the thumbscrews on the 2” extension tube.
The eyepiece rack located on the front of the base provides
a convenient place to put eyepieces when they are not
in use. It can accept three 1.25” eyepieces and one 2”
eyepiece (Figure 13).
Figure 13:
The eyepiece rack is a convenient place to store additional
eyepieces during your observing session.
DETERMINING MAGNIFICATION AND SELECTING
EYEPIECES
COOLING YOUR
TELESCOPE’S OPTICS
You’ll get the best views through your telescope when it
has reached thermal equilibrium with the ambient air. If the
telescope is warmer than the outside air, the mirror will
be acclimating to the temperature and its figure will be
changing. The images you see through a telescope that
has not cooled will not appear as sharp as they otherwise
would. If you are taking your telescope from a heated house
to the outdoors, allow around one hour before expecting it
to produce sharp images. For this reason, we recommend
storing your telescope in a dry but unheated area like a
garage or storage shed.
For the 10” SSE Dob, there is an optional USB Cooling Fan
for Dobsonians available. It mounts onto the rear of the mirror
cell and blows air on the mirror to expedite cooling (Figure
14). The fan will help the optics reach thermal equilibrium
faster. (The 8” SSE Dob does not have a fan mount so it is
not compatible with the Cooling Fan.)
Figure 14:
The optional USB Cooling Fan for Dobsonians is compatible with
the 10” SSE Dob..
