8
Carrying the Telescope
Moving the Bintel Dobsonian is easy to do. Remove
any eye-pieces from the telescope and eyepiece
rack, and place them in an eyepiece case. You can
also remove the finder scope and finder scope brack-
et, if you wish.
To carry the base, simply grasp the handle on the
front of it. The tube should be carried with two
hands. One way to do this is to grasp the tube with
one hand while grasping the mirror cell end with the
other . Another way is to grasp the tube with both
hands around its circumference. Be careful when
setting the tube down on its end so as not to bend or
damage the primary mirror collimation screws on the
bottom of the primary mirror cell.
When putting the Bintel Dobsonian into a vehicle,
common sense prevails. It is especially important
that the optical tube does not knock around; this can
cause the optics to become misaligned, and could
dent the tube.
Note About High Magnifications:
Maximum magnifications are achieved only under
the most ideal viewing conditions at the best
observing sites. Most of the time, magnifications are
limited to 200x or less, regardless of aperture. This
is because the Earth’s atmosphere distorts light as it
passes through. On nights of good “seeing”, the
atmosphere will be still and will yield the least
amount of distortion. On nights of poor seeing, the
atmosphere will be turbulent, which means different
densities of air are rapidly mixing. This causes
significant distortion of the incoming light, which
prevents sharp views at high magnifications.
Magnification
Now that the object you want to view is well
centered in the 25mm eyepiece, you may want to
increase the magnification to get a closer view.
Loosen the thumb screw on the 1.25" eyepiece
adapter and remove the eyepiece. Place it in the
eyepiece rack, if you wish. Insert the 9mm eyepiece
into the 1.25" eyepiece adapter, then retighten the
thumb screw. If you were careful not to bump the
telescope, the object should still be centered within
the field of view. Notice that the object being viewed
is now larger, but somewhat dimmer.
The Bintel Dobsonians are designed to accept any
eyepiece with a barrel diameter of 1.25" or 2".
Magnification, or power, is determined by the focal
length of the telescope and the focal length of the
eyepiece. Therefore, by using eyepieces of different
focal lengths, the resultant magnification can be
varied.
Magnification is calculated as follows:
Magnification = Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
The Bintel BT 202 Dobsonian has a focal length of
1200mm. So, the magnification with the supplied
26mm eyepiece is 1200mm ÷ 26mm = 46x.
The Bintel BT 252 Dobsonian has a focal length of
1250mm. So, the magnification with the supplied
32mm eye-piece is 1250mm ÷ 32mm = 39x.
The Bintel BT 302 Dobsonian has a focal length of
1500mm. So, the magnification with the supplied
32mm eye-piece is 1500mm ÷ 32mm = 46.8x.
The maximum attainable magnification for a tel-
escope is directly related to how much light its
optics can collect. A telescope with more light
collecting area, or aperture, can yield higher
magnifications than a smaller aperture telescope.
The maximum practical magnification for any
telescope, regardless of optical design, is about 40x
per inch of aperture. This translates to about 320x
for the Bintel BT 202 and 400x for the Bintel BT 252
and 480x for the Bintel BT 302
Keep in mind that as magnification is increased, the
brightness of the object being viewed will decrease;
this is an inherent principle of the physics of optics
and cannot be avoided. If magnification is doubled,
an
image
appears
four
times
dimmer.
If magnification is tripled, image brightness is
reduced by a factor of nine!
