12
Image orientation as seen with the
unaided eye & using erecting devices
on refractors & Newtonians
Inverted image, normal with
Newtonians & as viewed with
eyepiece directly in a refractor
Reversed from left to right, as viewed
using a Star Diagonal on a refractor
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The image orientation changes depending on how the eyepiece is inserted into the telescope. When using a star diagonal
with refractors, the image is right-side-up, but reversed from left-to-right (i.e., mirror image). If inserting the eyepiece
directly into the focuser of a refractor (i.e., without the diagonal), the image is upside-down and reversed from left-to-right
(i.e., inverted). However, when using the PowerSeeker refractor and the standard erect image diagonal, the image is
correctly oriented in every aspect.
Newtonian reflectors produce a right-side-up image but the image will appear rotated based on the location of the eyepiece
holder in relation to the ground. However, by using the erect image eyepiece supplied with the PowerSeeker Newtonian,
the image is correctly oriented.
Figure 3-3
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To focus your refractor or Newtonian telescope, simply turn the focus knob located directly below the eyepiece holder (see
Figures 2-13, 2-14 and 2-15). Turning the knob clockwise allows you to focus on an object that is farther than the one you
are currently observing. Turning the knob counterclockwise from you allows you to focus on an object closer than the one
you are currently observing.
Note:
If you wear corrective lenses (specifically glasses), you may want to remove them when observing with an
eyepiece attached to the telescope. However, when using a camera you should always wear corrective lenses to
ensure the sharpest possible focus. If you have astigmatism, corrective lenses must be worn at all times.
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You can change the power of your telescope just by changing the eyepiece (ocular). To determine the magnification of
your telescope, simply divide the focal length of the telescope by the focal length of the eyepiece used. In equation format,
the formula looks like this:
Focal Length of Telescope (mm)
Magnification
=
Focal Length of Eyepiece (mm)
Let’s say, for example, you are using the 20mm eyepiece that came with your telescope. To determine the magnification
you divide the focal length of your telescope (the PowerSeeker 60AZ for this example has a focal length of 700mm) by the
focal length of the eyepiece, 20mm. Dividing 700 by 20 yields a magnification of 35x.
Although the power is variable, each instrument under average skies has a limit to the highest useful magnification. The
general rule is that 60 power can be used for every inch of aperture. For example, the PowerSeeker 60AZ is 2.4” inches in
diameter. Multiplying 2.4 by 60 gives a maximum useful magnification of 144 power. Although this is the maximum
useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 48 to 84
times for the PowerSeeker 60AZ telescope. You can determine the magnification for your telescope the same way.
Note on Using High Powers –
Higher powers are used mainly for lunar and sometimes planetary observing where you can
greatly enlarge the image, but remember that the contrast and brightness will be very low due to the high magnification.
Using the 4mm eyepiece together with the 3x Barlow lens gives extremely high power and can be used on rare occasions –
you will achieve the power but the image will be dark with low contrast because you have magnified it to the maximum
possible. For the brightest images with the highest contrast levels, use lower powers.
