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D. ABOUT MAGNIFICATION:
The magnification power of a telescope indicates how much an image is enlarged or
how big and close it appears to the viewer. The focal length of the eyepiece, combined
with the focal length of the telescope, determines the magnification power. To calculate
the power of your telescope with any particular eyepiece, simply divide the focal length
of the telescope (700mm) by the focal length of the eyepiece (indicated in “mm” on the
eyepiece collar).
Example:
700 mm focal length (tube)
9mm focal length (eyepiece)
The 2X Barlow lens and interchangeable eyepieces provide the following magnification
values:
EYEPIECE
POWER
Power With 2X Barlow Lens
K25
28x
56x
K9
78x
156x
When you are looking at astronomical objects, you are looking through a column of air
that reaches to the edge of space, and that column of air seldom stays still. Similarly,
when viewing over land (terrestrial viewing), you are often looking through heat waves
radiating from the ground, homes, buildings, etc. Your telescope may be able to
provide very high magnifications, but you often end up magnifying all the turbulence
between the telescope and the object you wish to view. The level of magnification
required depends on the object.
Optimal performance is obtained if the magnification is typically not more than about
30x for every 10mm of objective lens diameter. Another good rule of thumb is that the
usable magnification of a telescope is about 3x per mm of the aperture (for the
CDB767AZ1, the aperture is 76mm) under good conditions. Thus, magnification of
around 225x or less is ideal for a telescope with a 76mm diameter objective mirror
(aperture) and is best for observing most celestial objects. A lower magnification power
and a wider field of view are advisable for observing galaxies and nebulae. The highest
magnification power should be used for highly detailed observations of the moon,
Jupiter, Saturn, or any object that is quite bright.
The highest magnification power of the Barlow lens with a 4mm (not included) eyepiece
combination should only be used for large or bright objects such as the moon and the
brightest planets.
= 78x magnification power
