6
5. Using the accessories, a bit of math to
understand how all it works.
Using the accessories is easy and fun. To
change magnification simple swap eyepieces.
To get more magnification simply use the
barlow lens. But how all of this work?
5.1. Power (magnification)
Your telescope as a focal length of 300mm.
This is approximately the distance between
the telescope lens to 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
telescopes focal length and the used
eyepiece. You probably noticed that the two
supplied eyepieces are H20mm and H6mm.
This means that the H20mm is a 20mm focal
length eyepiece while the H6mm is a 6mm
focal length eyepiece.
To determine the magnification just devide
the telescope focal length by the eyepiece
focal length. Lets give an example for our
telescope and the supplied eyepieces:
Telescope focal length is 300mm
H20 eyepiece focal length is 20 mm
300
20
= 15
This means that the H20 eyepiece provides a
15x power (magnification). This seems low but
try it, you will see a a bright image with some
very good detail.
5.2. Barlow Lens
The barlow lens is a very interesting device. It
is a negative lens that multiplies the
telescopes focal length. So a 2x Barlow
multiplies the original focal length by 2x, in
this case
300
2 = 600
.
A 3x Barlow lens multiplies by 3x.
Your telescope is supplied with a 2x Barlow
lens. When used with the H20 eyepiece you
get 2x the power obtained before
15
2
= 30
5.3. Erecting lens
The erecting lens gets you a upright image
view with the telescope. It also adds some
power like the barlow lens. The supplied
Erecting Lens provides and extra 1.5x power.
Here are some examples on how to use the
accessories.
Some possible accessory combinations
Terrestrial
View
Moon
Deep Sky
Jupiter and
Saturn
Erecting Eyepiece 1.5x
Yes
Yes
Barlow Lens 2x
Yes
H12.5 Eyepiece
Yes
H20 Eyepiece
Yes
Yes
H6 Eyepiece
Yes
Power
23x
48x
15x
100x
