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Eyepieces
:
While the telescope’s light-gathering power depends on the size of the telescopes
objective lens, its magnification power depends on the eyepiece used. In order to see objects
clearly at the proper magnification power, we recommend having four or more eyepieces. Here is
why:
1. Low-power, wide-field eyepiece
:
You need a low-power, wide-angle eyepiece to more easily
locate objects in the sky and to observe extended objects like the Andromeda galaxy. Our best
wide field eyepiece is the Stellarvue Optimus 20.
2. Medium-power eyepiece
:
Boosting the power darkens the sky background and shows more detail in deep
sky objects such as nebulae, star clusters and galaxies. We recommed the Stellarvue Optimus 9 and 13.5
eyepieces as the best for use at medium power.
3. Two High-power eyepieces
:
Viewing planets, close double stars, and small craters on the moon requires a
high- power eyepiece. We recommend having two high-power eyepieces because the atmospheric seeing con-
ditions cannot always support the highest power. Having two high-power eyepieces of different focal lengths
will allow you to adjust the magnification based on the seeing conditions.
We recommend the Optimus 3.6 and 4.7 eyepieces.
The amount of magnification is determined by dividing the focal length of
the telescope by the focal length of the eyepiece. Your telescope has a
focal length of 480 mm. A 20 mm eyepiece, when used with this telescope,
will provide a magnification of 24 power (480/20). 24 power means that
objects will appear 24 times larger. Notice that the smaller the focal length
of the eyepiece, the higher the power becomes. So our 4.7 mm eyepiece
provides 102 power (480/4.7).
The ability of a telescope to magnify is limited by:
A. The accuracy of the optics
B. The steadiness of the atmosphere
Under perfect conditions this telescope is capable of magnifying
bright objects 20 - 250 times. Unfortunately, the air is often un-
steady due to air turbulence. This causes the stars to twinkle and
limits the ability of any telescope to show fine details. Boosting
the power darkens the view and only increases the size of the
burry image. This is referred to as “empty magnification” since it
is too high of a power for the conditions and actually shows you
less. Under turbulent conditions, it is best to use an eyepiece
that provides a lower power.
If you purchase the entire set of Optimus eyepieces you will
notice on turbulent nights the view through the 3.6 mm eyepiece
may be soft. This indicates that the seeing conditions are not
optimal. Under these conditions, you should switch to the 4.7 mm
eyepiece and view the planets, craters on the moon and double
stars at a slightly lower but clearer magnification.
Stellarvue optics are extremely accurate. If details are soft when
you observe through it, you are observing under less favorable
conditions. Be patient. On a steady night you will see magnificent
detail.
Magnification is not as important on larger extended objects so
many amateur astronomers switch from planets to star clusters and nebulae when the air is unsteady.
Jupiter appears sharp under steady skies and its
moons appear as disks.
Unsteady air distorts the moons
and Jupiter is soft with little detail
OPTIMUS EYEPIECES
