9
7. Using the accessories, a bit of math
to understand how all it works.
Using the accessories is easy and fun. To
change magnification simply swap
eyepieces. To get more magnification
simply use the barlow lens. But how does
all of this work?
7.1. Power (magnification)
Your telescope has a focal length of
1200mm. This is approximately the distance
between the telescope’s primary mirror
and its focal point (very similar to the
distance between the focus point of a loupe
and the loupe lens). This is a very important
feature, that allows to determine several
interesting facts such as magnification.
The magnification is determined by the
telescope’s focal length and the used
eyepiece. To determine the magnification
when using a 20mm eyepiece (just an
example, there any many eyepieces with
different focal lenghts – all 1.25” and 2”
should be compatible with this telescope)
just divide the telescope’s focal length by
the eyepiece’s focal length. Let’s give an
example for our telescope and the eyepiece
from the example above:
Telescope’s focal length is 1200mm.
Eyepiece’s focal length is 20mm.
1200𝑚𝑚
20𝑚𝑚
= 60 𝑝𝑜𝑤𝑒𝑟
This means that the 20mm
eyepiece
provides a 60x power (magnification). This
seems low, but when you try it, you will
see a bright image with some (very good)
details.
7.2. Barlow Lens (not included)
The barlow lens is a very interesting device.
It is a negative lens, that multiplies the
telescope’s focal length. So a 2x Barlow
multiplies the original focal length by 2x, in
this case
1200𝑚𝑚 𝑥 2 = 2400𝑚𝑚
.
A 3x Barlow lens multiplies by 3x.
When used with the 20mm eyepiece a 2x
Barlow provides 2x the magnification as
obtained before
:
60 𝑝𝑜𝑤𝑒𝑟 𝑋 2𝑥 𝐵𝑎𝑟𝑙𝑜𝑤 = 120 𝑝𝑜𝑤𝑒𝑟
7.3. Erecting lens (not included)
The erecting lens gets you an upright image
view with the telescope. It also adds some
power like the barlow lens. The Erecting
Lens provides an extra 1.5x power.
Some possible accessory combinations
Terrestrial
View
Moon
Deep Sky
Jupiter and
Saturn
Barlow Lens 2x
Yes
20mm Eyepiece
Yes
Yes
6mm Eyepiece
Yes
Power
Does not apply
200x
60x
120x
Omegon®/Vixen®/Celestron®/Orion®/ Meade® are registered trademarks.
