National Geographic NG50MM User manual

SUN HAZARD — Never look directly at the sun
with this device.
WARNING:
CHOKING HAZARD — Small parts.
Not for children under 3 years.
WARNING:
The lens contains lead that may be harmful.
Wash hands after touching.
WARNING:
This product can expose you to chemicals including lead,
which is known to the State of California to cause cancer.
For more information go to www.P65Warnings.ca.gov.
WARNING:
80-10051
EN
6+
NG50MM
INSTRUCTION MANUAL
50 MM TABLE TOP TELESCOPE
WITH AZ MOUNT

2
• SUN WARNING: WARNING: NEVER ATTEMPT TO OBSERVE THE SUN WITH THIS DEVICE! OBSERVING THE
SUN – EVEN FOR A MOMENT – WILL CAUSE INSTANT AND IRREVERSIBLE DAMAGE TO YOUR EYE OR EVEN
BLINDNESS. EYE DAMAGE IS OFTEN PAINLESS, SO THERE IS NO WARNING TO THE OBSERVER THAT THE
DAMAGE HAS OCCURRED UNTIL IT IS TOO LATE. DO NOT POINT THE DEVICE AT OR NEAR THE SUN.
DO NOT LOOK THROUGH THE DEVICE AS IT IS MOVING. CHILDREN SHOULD ALWAYS HAVE ADULT SUPERVISION
WHILE OBSERVING.
• RESPECT PRIVACY: WHEN USING THIS DEVICE, RESPECT THE PRIVACY OF OTHER PEOPLE. FOR EXAMPLE, DO NOT
USE IT TO LOOK INTO PEOPLE’S HOMES.
• CHOKING HAZARD: CHILDREN SHOULD ONLY USE DEVICE UNDER ADULT SUPERVISION. KEEP PACKAGING
MATERIALS LIKE PLASTIC BAGS AND RUBBER BANDS OUT OF THE REACH OF CHILDREN AS THESE
MATERIALS POSE A CHOKING HAZARD.
• RISK OF BLINDNESS: NEVER USE THIS DEVICE TO LOOK DIRECTLY AT THE SUN OR IN THE DIRECT PROXIMITY OF THE
SUN. DOING SO MAY RESULT IN A PERMANENT LOSS OF VISION.
• RISK OF FIRE: DO NOT PLACE DEVICE, PARTICULARLY THE LENSES, IN DIRECT SUNLIGHT. THE CONCENTRATION OF
LIGHT RAYS COULD CAUSE A FIRE.
• DO NOT DISASSEMBLE THIS DEVICE: IN THE EVENT OF A DEFECT, PLEASE CONTACT YOUR DEALER. THE DEALER
WILL CONTACT THE CUSTOMER SERVICE DEPARTMENT AND CAN SEND THE DEVICE IN TO BE REPAIRED
IF NECESSARY.
• DO NOT SUBJECT THE DEVICE TO TEMPERATURES EXCEEDING 60 °C (140 °F).
• DISPOSAL: KEEP PACKAGING MATERIALS, LIKE PLASTIC BAGS AND RUBBER BANDS, AWAY FROM
CHILDREN AS THEY A POSE A RISK OF SUFFOCATION. DISPOSE OF PACKAGING MATERIALS AS LEGALLY
REQUIRED. CONSULT THE LOCAL AUTHORITY ON THE MATTER IF NECESSARY AND RECYCLE
MATERIALS WHEN POSSIBLE.
• THE WEEE SYMBOL IF PRESENT INDICATES THAT THIS ITEM CONTAINS ELECTRICAL OR ELECTRONIC
COMPONENTS WHICH MUST BE COLLECTED AND DISPOSED OF SEPARATELY.
• NEVER DISPOSE OF ELECTRICAL OR ELECTRONIC WASTE IN GENERAL MUNICIPAL WASTE. COLLECT AND DISPOSE
OF SUCH WASTE SEPARATELY.
• MAKE USE OF THE RETURN AND COLLECTION SYSTEMS AVAILABLE TO YOU, OR YOUR LOCAL RECYCLING PROGRAM.
CONTACT YOUR LOCAL AUTHORITY OR PLACE OF PURCHASE TO FIND OUT WHAT SCHEMES ARE AVAILABLE.
• ELECTRICAL AND ELECTRONIC EQUIPMENT CONTAINS HAZARDOUS SUBSTANCES WHICH, WHEN DISPOSED OF
INCORRECTLY, MAY LEAK INTO THE GROUND. THIS CAN CONTRIBUTE TO SOIL AND WATER POLLUTION WHICH IS
HAZARDOUS TO HUMAN HEALTH, AND ENDANGER WILDLIFE.
• IT IS ESSENTIAL THAT CONSUMERS LOOK TO RE-USE OR RECYCLE ELECTRICAL OR ELECTRONIC WASTE TO AVOID IT
GOING TO LANDFILL SITES OR INCINERATION WITHOUT TREATMENT.
IMPORTANT SAFETY INSTRUCTIONS
READ AND FOLLOW THE INSTRUCTIONS BEFORE USE.
KEEP THESE INSTRUCTIONS FOR LATER USE.
Customer Service: Call 1-866-252-3811

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Parts Overview
1. Focus Wheel
2. Diagonal Mirror
3. Eyepieces (12.5 mm, 20 mm)
4. Telescope Tube
5. Dew Shield
6. Objective Lens
7. Locating Screw For The Vertical Adjustment
8. Locating Screw For The Vertical Axis
9. Tripod Legs
1
2
2
3
3
4
5
7
9
8
6
Available Downloads Visit:
www.esmanuals.com

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Telescope Terms To Know:
Diagonal: A mirror that deflects the ray of light 90 degrees.
With a horizontal telescope tube, this device deflects the light upwards so
that you can comfortably observe by looking downwards into the eyepiece.
The image in a diagonal mirror appears upright, but rotated around its
vertical axis (mirror image).
Focal length: Everything that magnifies an object via an optic lens has a certain focal length. The focal
length is the length of the path the light travels from the surface of the lens to its focal point. The focal
point is also referred to as the focus. In focus, the image is clear. In the case of a telescope, the focal
length of the telescope tube and the eyepieces are used to determine magnification.
Lens: The lens turns the light that falls on it around in such a way so that the light gives a clear image in
the focal point after it has traveled a certain distance (focal length).
Eyepiece: An eyepiece is a system made for your eye and comprised of one or more lenses. In an
eyepiece, the clear image that is generated in the focal point of a lens is captured and magnified still
more.
Magnification: The magnification corresponds to the difference between observation with the naked
eye and observation through a magnifying device like a telescope. If a telescope configuration has a
magnification of 30x, then an object viewed through the telescope will appear 30 times larger than it
would with the naked eye. To calculate the magnification of your telescope setup, divide the focal length
of the telescope tube by the focal length of the eyepiece.
How To Set Up
Note: We recommend assembling your telescope for the first time in the daylight or in a lit room so that
you can familiarize yourself with assembly steps and all components.
Please look for a suitable location for your telescope before you begin. Use a stable surface, e.g. a table.
Mount the telescope to the tripod with the locating screw for the vertical adjustment (7). Insert the eye
piece into the diagonal mirror (12.5 mm or 20 mm).
Azimuthal Mounting
Azimuthal mounting just means that you can move your telescope up and down, left and right, without
having to adjust the tripod.
Use the locating screw for the vertical fine adjustment (7) and the locating screw for the vertical axis (8)
to locate and lock the position of an object (to focus an object).
Which eyepiece is right?
First of all, it is important that you always choose an eyepiece with the highest focal width for the
beginning of you observation. Afterwards, you can gradually move to eyepieces with smaller focal widths.
The focal length is indicated in millimeters, and is written on each eyepiece. In general, the following is
true: The larger the focal width of an eyepiece, the smaller the magnification! There is a simple formula for
calculating the magnification:
Focal length of the telescope tube: Focal length of the eyepiece = magnification.
You see: The magnification is also depends on the focal length of the telescope tube. This telescope
contains a telescope tube with focal length of 360 mm. From this formula, we see that if you use an
eyepiece with a focal width of 20 mm, you will get the following magnification:
360 mm / 20 mm = 18 x magnification

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To make things simpler. I’ve put together a table with some magnifications:
Technical Data:
• Design: Achromatic
• Focal Length: 360 mm
• Objective Diameter: 50 mm
Telescope
Focal Width
Eyepiece
Focal Width
Magnification
360 mm 20 mm 18x
360 mm 12.5 mm 28.8x
f=26 mm f=9.7 mm
The Moon
f=26 mm f=9.7 mm
Terrestrial Images
Possible Objects for Observation:
Terrestrial objects
Take note of the examples below, including Mount Rushmore and the
golf course. Start with the 20 mm eyepiece and focus until the image
is clear. After mastering the 20 mm eyepiece, switch to the 12.5 mm
eyepiece and practice scanning and focusing until the image is clear.
Choose several terrestrial objects to practice focusing on, but never
point your telescope at or near the sun, or you risk blindness.
The Moon
Diameter: 3,476 km
Distance: Approximately 384,401 km
The Moon is the Earth’s only natural satellite, and it is the second brightest
object in the sky (after the Sun). Although it is our closest neighbor, a lot
of people have never really taken a good long like at the Moon. With your
telescope, you should be able to see several interesting lunar features.
These include lunar maria, which appear as vast plains, and some of the
larger craters. The best views will be found along the terminator, which
is the edge where the visible and cloaked portions of the Moon meet.
Troubleshooting Guide:
Problem Solution
No picture Remove dust protection cap and sun-shield from the
objective opening.
Blurred picture Adjust focus using focus ring.
No focus possible Wait for temperature to balance out.
Bad quality Never observe through a glass surface such as a
window.
Despite using star diagonal prism
the picture is “crooked”
The star diagonal prism should be vertical in the
eyepiece connection.

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Light
Light
Secondary Mirror
Primary Mirror
(Objective)
Focuser
Focuser
Light
Light
Objective Lens
Light
Light
Secondary Mirror
Primary Mirror (Objective)
Correcting Lens
Reflector
(Newtonian)
Refractor
Catadioptric
(Maksutov-Cassegrain/
Schmidt-Cassegrain)
Light
Light
Secondary Mirror
Primary Mirror
(Objective)
Focuser
Focuser
Light
Light
Objective Lens
Light
Light
Secondary Mirror
Primary Mirror (Objective)
Correcting Lens
Reflector
(Newtonian)
Refractor
Catadioptric
(Maksutov-Cassegrain/
Schmidt-Cassegrain)
Light
Light
Secondary Mirror
Primary Mirror
(Objective)
Focuser
Focuser
Light
Light
Objective Lens
Light
Light
Secondary Mirror
Primary Mirror (Objective)
Correcting Lens
Reflector
(Newtonian)
Refractor
Catadioptric
(Maksutov-Cassegrain/
Schmidt-Cassegrain)
Reflector
A reflector telescope uses mirrors to gather and focus light. Light enters the telescope through its open
front end and travels to the concave primary mirror at the back. From there the light is reflected back up
the tube to a flat secondary mirror, which sits at a 45° angle in relation to the eyepiece. Light bounces off
of this secondary mirror and out through the eyepiece. A reflector telescope is designed for astronomical
use. Terrestrial objects may appear inverted, sideways or at an angle depending on how your tube is
oriented due to optical design. This rotation is perfectly normal on all Newtonian reflectors and will not
affect astronomical viewing.
Refractor:
A refracting telescope uses a collection of lenses to gather and focus light. A refractor’s views will
be upside down if a diagonal is not in use. A standard diagonal will generate a “right side up” image,
however, it will rotate the image on the vertical axis (mirror image). To get the “right side up” image
without the rotation, you will need to use a special diagonal with an erect image prism.
Catadioptric:
A catadioptric telescope uses a combination of mirrors and lenses to gather and focus light. Popular
catadioptric designs include the Maksutov-Cassegrain and Schmidt-Cassegrain.
Types Of Telescopes:

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Aperture:
This figure, which is usually expressed in millimeters, is the diameter of a telescope’s light-gathering
surface (objective lens in a refractor or primary mirror in a reflector). Aperture is the key factor in
determining the brightness and sharpness of the image.
Objective Lens:
The objective lens is the main light-gathering component of a refractor telescope. It is actually composed
of several lens elements.
Diagonal:
This accessory houses a mirror that deflects the ray of light 90 degrees. With a horizontal telescope tube,
this device deflects the light upwards so that you can comfortably observe by looking downwards into
the eyepiece. The image in a standard diagonal mirror appears upright, but rotated around its vertical
axis (mirror image). To get an image without this rotation, you will need to use a special diagonal with an
erect image prism.
Eyepiece:
An eyepiece is an optical accessory comprised of several lens elements. It determines the magnification
of a particular observing setup.
Primary Mirror:
The primary mirror is the principle light-gathering surface of a reflector telescope.
Secondary Mirror:
A secondary mirror is a small mirror that sits at a 45° angle in relation to the primary mirror of a reflecting
telescope. Light from the primary mirror is reflected back up the tube to the secondary mirror. The light is
directed from this mirror up into the eyepiece.
Objective Lens
Aperture
(mm)
Aperture
(mm)
Eyepiece
Diagonal Focal Point
Focal Point
Focal Length Telescope
(mm)
Focal Length Telescope
(mm)
Focal Length
Eyepiece
(mm)
Focal Length
Eyepiece
(mm)
Focuser
Secondary
Mirror
Primary Mirror
(Objective)
Focuser
Eyepiece
Telescope Terms to Know:

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Magnification:
The magnification corresponds to the difference between observation with the naked eye and
observation through a magnifying device like a telescope. If a telescope configuration has a magnification
of 30x, then an object viewed through the telescope will appear 30 times larger than it would with the
naked eye. To calculate the magnification of your telescope setup, divide the focal length of the telescope
tube by the focal length of the eyepiece. For example, a 20mm eyepiece in a telescope with a 1000mm
focal length will result in 50x power, which will make the object appear 50 times larger. If you change the
eyepiece, the power goes up or down accordingly.
Focal ratio
The focal ratio of a telescope is determined by dividing the telescope’s focal length by its aperture
(usually expressed in millimeters). It plays a key role in determining a telescope’s field of view and
significantly impacts imaging time in astrophotography. For example, a telescope with a focal length of
1000mm and a 100mm clear aperture has a focal ratio of f/10.
Focal length (Telescope):
The focal length is the distance in millimeters between the objective lens or primary mirror and the point
at which entering light rays converge — otherwise known as the focal point. The focal lengths of the
telescope tube and the eyepiece are used to determine magnification.
Focal length (Eyepiece):
The focal length is the distance in millimeters between the center of the first lens element in an eyepiece
and the focal point. The focal lengths of the telescope tube and the eyepiece are used to determine
magnification. Short eyepiece focal lengths produce higher magnifications than long eyepiece focal
lengths.
Exit Pupil
The exit pupil is the diameter of the beam of light coming out of the eyepiece. To calculate exit pupil,
divide the focal length of your eyepiece by your telescope’s focal ratio. For example, if you use a 20mm
eyepiece with an f/5 telescope, the exit pupil would be 4mm.
Magnification = Telescope Focal Length
Eyepiece Focal Length
Focal Ratio = Telescope Focal Length
Telescope Aperture
Exit Pupil = Eyepiece Focal Length
Telescope Focal Ratio
Eyepiece Lens
Long Eye Relief Distance
Eyepiece Lens
Short Eye Relief Distance
Eyepiece Lens
Exit Pupil (mm)
Telescope Focal Length
1000mm
Eyepiece
Focal Length
20mm
Aperture
102mm

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Eyepiece Lens
Long Eye Relief Distance
Eyepiece Lens
Short Eye Relief Distance
Eyepiece Lens
Exit Pupil (mm)
Eyepiece Lens
Long Eye Relief Distance
Eyepiece Lens
Short Eye Relief Distance
Eyepiece Lens
Exit Pupil (mm)
Eye Relief
Eye relief is all about a comfortable viewing experience because it is the distance at which you need to
position your eye from the eyepiece’s outermost surface to enjoy the full field of view. This characteristic
is of special concern to observers who wear glasses to correct an astigmatism, because a long enough
eye relief is necessary to allow room
for glasses.
Huygenian Eyepieces:
A Huygenian eyepiece uses two plano-convex lenses separated by an air gap. They have a fairly narrow
apparent field of view.
Kellner Eyepieces:
A Kellner eyepiece uses three lens elements - two of which are paired together in an achromatic doublet
design to minimize chromatic aberrations. They typically produce an apparent field of view around 45°.
Plössl Eyepieces:
A Plossl eyepiece uses two doublets (a pairing of lens) for a total of four lens elements. This eyepiece
design delivers sharp views and an apparent field of view of approximately 50°, which works well for both
planetary and deep sky viewing.
Barlow Lens:
A Barlow lens effectively increases the focal length of a telescope. It is inserted between the eyepiece
and the focuser/diagonal (depending on the optical setup) and multiplies the magnification power of the
eyepiece. For example, a 2x Barlow will double the magnification of a particular eyepiece.
Barlow Lens
2 Lens Elements
Huygenian Eyepiece
2 Lens Elements
Light
Kellner Eyepiece
3 Lens Elements
Light
Plössl Eyepiece
4 Lens Elements
Light
Light
Eye Lens
Field Lens
Eye Lens
Field Lens
Field Lens

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Notes:

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Notes:

V042022
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