Bushnell Refractor Equatorial Mount Instruction Manual

The World’s Easiest Equatorial Mount

Instruction Manual for Refractor Telescopes

Before you get started, you’ll need to know that your telescope is a Refractor telescope.
All telescopes turn the image they receive upside down and backwards. Refractor
telescopes have the ability to turn (erect) or turn the image right side up. Also, some
refractor telescopes can correct the right to left viewing with a special eyepiece. All of
this is especially helpful if what you are looking at is on land as opposed to outer space.

Without getting fancy or technical, equatorial mounts are star finders. Most all of the
visible stars in the sky have an address in a book called a Star Atlas (roadmap of stars)
that is expressed in terms of its Right Ascension and then its Declination. Basically it’s
outer space longitude and then latitude. It will look something like this:

23hr 42min 03sec, 78.3deg N

When using an equatorial mount, you can move your telescope to these settings and find
the star that corresponds to that address. You can purchase a Star Atlas at just about any
bookstore on earth

As well, you will need to be able to locate and identify 2 stars in the sky. The first star
will be the North Star. Coincidentally this star is perfectly north EVERY night you go
out. It is generally around 25 to 45 degrees up from the horizon in North America.

The second star you will need to be able to identify in the sky is a little bit harder. The
second star can really be any star in the sky other than our sun and the North Star. You
can pick a star from a constellation that is in the sky and use a particular star in it. You
will not only have to be able to identify it, but in Step 5 you will need to be able to center
it in the telescope. Unfortunately, there is no other alternative. If you want to use your
equatorial mount, you’ll need to be able to do this. We recommend using a star called
Mizar, as it is visible all months of the year in North America.

In most Star Atlas books there is a section that gives suggestions on which stars to use for
the second star, I recommend using it. Also, there is a section that has the latitude setting
for the North Star in certain areas. You will need this when going through Step 4.

Finally, you will need to set your telescope up to be able to use a Star Atlas. The
following instructions in steps 1-7 will show you how to do this. Good Luck and Have
Fun!!!!!

Table of Contents

Page 1 ….... Introduction

Page 2 ….... Table of Contents

Page 3 ….... Listing of all the Telescope Sections

Page 4 ….... Fine Adjustment Cables

Page 5 ….... The Telescope’s Axis’s

Page 6 ….... The Different Lenses

Page 7 ….... Figuring the Magnification

Page 8 …… The Lens Combinations

Page 9 ….... Aligning the Finderscope

Page 10 …...Aligning the Finderscope continued
Page 11 ….. Aligning the Finderscope continued
Page 12 ….. Step 1 – Getting the Mount at Right Angles
Page 13 ….. Step 2 – Facing the Telescope North
Page 14 ….. Step 3 – Putting in the Eyepiece
Page 15 ….. Step 4 – Finding the North Star
Page 16 ….. Step 5 – Setting the Declination Dial to 90 degrees
Page 17 ….. Step 6 – Finding the Second Star – Its Declination Address
Page 18 ..… Step 7 – Finding the Second Star – Its Right Ascension Address
Page 19 ….. Keeping the Telescope Aligned

Declination
Lock Knob

Declination
Setting

Right

Ascension

Lock

Knob

Right

Ascension

Setting

Latitude

Lock Knob

Latitude
Adjustment
Knob

Finderscope

Focusing Tube That you put

the eyepieces into and bring
the image into focus by
turning either of the two
Focusing Knobs on the sides.

Counter Weight

Makes Sure the
Telescope Doesn’t
Fall Because Of
Uneven Weight

Counterweight Shaft

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Horizontal Axis
Setting – If there

are numbers on this
just ignore them.
Only in step 2 will
you ever turn the
telescope here.

Telescope Tube

Horizontal
Axis Setting
Lock Knob

3

End That
Faces What
You Are
Looking At.
Never look at
the sun.

Fine Adjustment Cables

The fine adjustment cables move the declination and right ascension settings in very
small increments. When you are aligning the finderscope or centering a star or planet in
the telescope there will be a time when only small adjustments will be necessary. That is
when you’ll use these knobs. They look like the diagram below. Notice one is long and
the other is short. It really doesn’t matter which one goes on the declination and which
one goes on the right ascension. Generally though, they go on just like the below
diagram. They connect to the telescope mount only one way so I won’t cover their
attachment procedure.

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If your equatorial mount is set up correctly,
you can move just the Right Ascension Fine
Adjustment Knob ONLY to follow any star
across the sky!

4

Declination

Fine

Adjustment

Right

Ascension

Fine

Adjustment

Telescope Axis’s

This instruction manual refers to 3
axis’s in which the telescope will
turn. This diagram illustrates these
axis’s where the telescope can move.

When using your fine
adjustment cables, you’ll
be moving these two
axis’s.

The Different Lenses

There are many different lenses to know about on a refractor telescope. Each has a
specific function that also goes on in a specific order. Below covers these lenses. If you
try different combinations other than what is listed in the next few pages, you will not be
able to see out of your telescope clearly. I’ll introduce you to each of the lenses and their
functions.

The Eyepieces

The Barlow Lens

BARLOW

5

The Erector Lens

ERECTOR

4

The Penta Mirror

3

The Diagonal Mirror

3

4mm Eyepiece

This is the high-powered

eyepiece. It is generally

shorter than the 20mm

eyepiece.

20mm Eyepiece

This is the low-powered

eyepiece. It is generally

taller than the 4mm eyepiece

The Barlow Lens

This piece multiplies the

magnification by generally 2

to 3 times.

Most of the time it will say 2X or

3X on the side of it. Every once in

a while it will even have a different

number.

The Erector Lens

All telescopes turn the image
upside down. This piece can

“erect” the image.

Erecting the image is only available

on Refractor telescopes. Erecting

Lenses generally multiply the

magnification by 1.5 times.

The Penta Mirror

All telescopes make the image appear to move in

the opposite direction as you are turning it from
right to left. The Penta Mirror corrects this and

allows you to look down into the telescope instead

of having to look from behind.

The Diagonal Mirror

The Diagonal Mirror allows you to look down

into the telescope instead of having to look from

behind. It does not correct the right to left

viewing.

It multiplies the magnification

by 2 times.

This piece offers no additional magnification.

As well, most all Refractor telescopes come
with either the Penta Mirror or the Diagonal

Mirror but never with both.

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Figuring the Magnification

Magnification is generally referred to as “power”. Figuring the power on a Refractor
telescope sometimes can be tricky because of all of the different combinations possible.
Below I’ll go into the different combinations and how to figure each magnification. To
figure magnification you must first know the basic formula for determining it. It is:

Focal Length in mm ÷ Eyepiece in mm = Magnification (Power)

Example:

A telescope that has a 700mm focal length that has a 20mm eyepiece in it has 35 power
or magnification.

700 (focal length) ÷ 20 (eyepiece in mm) = 35 (power)

If you have in a 3X Barlow lens also then multiply the answer by 3. In this case it would
be 105 power or magnification.

700 (focal length) ÷ 20 (eyepiece in mm) = 35 (power)

35 (power) X 3 (Barlow Lens) = 105 (power)

Since the Penta Mirror doubles the magnification, then you would further multiply the
answer by 2 if you added to the lens example. In other words the magnification would be

210.

700 (focal length) ÷ 20 (eyepiece in mm) = 35 (power)

35 (power) X 3 (Barlow Lens) = 105 (power)

105 (power) X 2 (Penta Mirror) = 210 (power)

Finally, there is one Bushnell telescope (78-9470) that offers a Zoom Lens that magnifies
from 25 – 75 times. It can ONLY be used in conjunction with the Penta Mirror and
therefore offers actual magnifications of 50 – 150. (The Penta Mirror once again doubles
the magnification.) It also erects the image so you need no other lenses with it.

1

Lens Combinations

Zoom Eyepiece/Assembly

7

The different lenses offer many combinations. Using the previous definitions you should
be able to determine the effect each lens will have on the viewing. Using the below
diagram will help you understand the possible combinations your lenses can be put in
with.

Once again, only use these combinations as they are the ONLY ones possible for good
viewing through your telescope.

BARLOW

ERECTOR

1. Zoom Assembly

2. Eyepieces

3. 90 degree Penta Mirror / Diagonal Mirror

4. Erector Lens

5. Barlow Lens

1

Conf. A

Conf. B

Conf. C

Conf. D

2

4

5

3

3

3

(Generally Magnifies 2 to 3 times)

(Generally Magnifies 1.5 times)

Aligning the Finderscope

You will need to line up the Finderscope with your telescope. A finderscope acts kind
of like a riflescope in that it helps you aim. To get started you should always use the
highest number eyepiece (lowest power) without the Barlow lens. If you use too
powerful of an eyepiece (low number) then it may be very hard to find an object or it will
be too dark to see anything as higher powers cause light loss. Below is an example of
why aligning the finderscope is important.

Without an aligned finderscope you might think you are aiming
directly at a star or planet but you could actually be way off!

But with an aligned finderscope, you can find objects in
the sky a lot faster and easier!

Start with a large object about 200
yards away. You do not have to be
absolutely accurate with the distance as
it will not help you or hinder you if you
are not exact. In this example I’ll use a
house as the object

To get started, put the
20mm eyepiece in the
focusing tube without
the Barlow lens.

Since the finderscope has a slight magnification to
it, put it on so that when viewing through it you
see the magnification. If you put it in backwards,
everything will appear small and far away.

Note: It is recommended for best viewing to not look through a window when aligning the
finderscope or even when viewing things through the telescope. Ideally you should be outside with the
telescope. If fogging occurs let the telescope sit outside for approximately 30 minutes to allow it to
clear up.

Next, find the object in the telescope and center it in the viewing area.

Finally, get the object centered in the finderscope.
If the finderscope is not the crosshair type but
instead the dot kind, get the dot directly in the
middle of the object then tighten the finderscope
best as possible. Note: The finderscope just like
the telescope turns the image upside down also.

Know that finderscopes sometimes have a red dot in them as opposed to crosshairs. Sometimes they adjust with thumbscrews on the

outside of the mounting bracket and sometimes they have actual fine adjustment knobs on the finderscope itself. Regardless, you will

need to determine how to adjust them yourself using common sense and if you have it, the instruction manual.

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Get everything at right angles.
If you’re not sure, just make it
look like this picture. As well,
on level ground make sure the
tripod legs are fully extended or
at least even as far as length.

You can generally
leave the
Counterweight all
the way down and
tighten the screw
so it won’t move.

Note: It is recommended for best viewing to not look through a window when aligning the finderscope
or even when viewing things through the telescope. Ideally you should be outside with the telescope. If
fogging occurs let the telescope sit outside for approximately 30 minutes to allow it to clear up.

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With everything at 90-degree angles, turn the
telescope scope north along its Horizontal
Axis using a compass as reference to be
completely accurate. Once facing north,
tighten the Latitude Lock Knob and know
that you will not have to touch this setting
again for the rest of the evening.

S

Once again,
ignore these

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Put the Diagonal Mirror
or Penta Mirror in and
the 20 mm eyepiece into
the Focusing Tube. If
you do not have a 20mm
eyepiece, use the highest
number eyepiece you do
have. The eyepiece looks
like this.

(It will say 20mm on the
top of the eyepiece.)

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Next, you will need to
elevate the telescope up to
the North Star. Do this by
turning the Latitude
Adjustment Knob to the
number on the Star Atlas that
corresponds to your location.
Looking through the
eyepiece, find the North Star
then tighten the Latitude
Lock Knob. Note: when
this is done you will not have
to touch either of these knobs
again for the rest of the night.

(Has numbers on it)

There will be numbers on
the Declination Setting
and either an arrow or a
pointer. Turn the DIAL
‘til the pointer or arrow
is at 9 then tighten the
Declination Lock Knob.
(9 stands for 90 degrees.)

Once the Declination
Setting is set you will NOT
have to touch this again for
the rest of the night.

Next, you will need to find the
second star I talked about earlier.
See the Star Atlas and it will
show you some fairly easy stars
that should be bright in the sky
during different times of the
year. When you have identified
your star, move the
TELESCOPE TUBE along the
Declination Axis until the
pointer is on the declination
address of the star according to
the Star Atlas.

Finally, move the tube of the
telescope along the Right
Ascension Axis until the star
you have chosen as your
second star is visible in the
telescope. Then with your
fingers, move the dial on the
Right Ascension Setting to
match what the Star Atlas’s

Right Ascension Settings

are for that star. Once again,
there is a pointer/arrow that
you’ll align the Right
Ascension number up with.
You are done!

Even though it
is not shown,
the Right

Ascension
Setting has

numbers on it.

This is the 2nd star that
you are aligning your
telescope to. It is the
same star as in Step 7.

When you have centered the 2nd star,
it should look something like this.

As the earth rotates, the star will
appear to move like this.

Therefore, every few
minutes while you are
surfing the sky with
your telescope you will
need to repeat Step 7.

(Simulated views through your telescope)