Manual Bresser AR-90 (page 17 of 44) (English)

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Observation

Observing by Moving the Telescope Manually

After the telescope is assembled and balanced as described previously,

you are ready to begin manual observations. View easy-to-find terrestrial

objects such as street signs or traffic lights to become accustomed to the

functions and operations of the telescope. For the best results during obser-

vations, follow the suggestions below:

• When you wish to locate an object to observe, first loosen the telescope’s

R.A. lock (33, Fig. 1d) and Dec. lock (17, Fig. 1d). The telescope can now

turn freely on its axes. Unlock each axis separately and practice moving

your telescope. Then practice with two unlocked axes at the same time.

It is very important to practice this step to understand how your telescope

moves, as the movement of an equatorial mount is not intuitive.

• Use the aligned viewfinder to sight-in on the object you wish to observe.

When the object is centered in the viewfinder’s crosshairs, re-tighten the

R.A. and Dec. locks.

• A telescope’s eyepiece magnifies the image formed by the telescope’s main

optics. Each eyepiece has a focal length, expressed in millimeters, or “mm.”

The smaller the focal length, the higher the magnification. For example, an

eyepiece with a focal length of 9mm has a higher magnification than an eye-

piece with a focal length of 25mm. Low-power magnification eyepieces offer

a wide field of view, bright, high-contrast images, and relief of eye strain dur-

ing long observing sessions. To observe an object with a telescope, always

start with a low power eyepiece such as the 25mm supplied with your tel-

escope. When the object is centered and focused in the eyepiece, switch

to a higher power eyepiece to enlarge the image as much as practical for

prevailing viewing conditions.

• Once centered, an object can be focused by turning one of the knobs

of the focusing mechanism (8, Fig. 1b). Notice that when observing

astronomical objects, the field of view begins to slowly drift across the

eyepiece field. This motion is caused by the rotation of the Earth on its

axis. Objects appear to move through the field more rapidly at higher pow-

ers. This can be compensated with the RA drive shaft or the (optional) RA

drive motor.

Observe the Moon

Point your telescope at the Moon (note that the Moon is not visible every

night). The Moon contains many interesting features, including craters,

mountain ranges, and fault lines. The best time to view the Moon is dur-

ing its crescent or half phase. Sunlight strikes the Moon at an angle dur-

ing these periods and adds a depth to the view. No shadows are seen

during a full Moon, making the overly bright surface to appear flat and

rather uninteresting. Consider the use of a neutral density Moon filter when

observing the Moon. Not only does it cut down the Moon‘s bright glare, but

it also enhances contrast, providing a more dramatic image.

Looking at or near the Sun will cause instant and irreversible damage to your eye!

ob s e r v a t I o n

Important Note:

Objects appear upside-down

and reversed left- for-right when

observed in the viewfinder. With

refracting tele scope models,

objects viewed through the main

telescope with the diagonal mir-

ror in place are seen right-side-

up, but reversed left-for-right.

This image inversion is of no

consequence when observing

astronomical objects, and in fact

all astronomical telescopes yield

inverted images.

WARNING

Never use a Telescope to look

at the Sun! Looking at or near

the Sun will cause instant and

irreversibledamage to your eye.

Eye damage is often painless, so

there is no warning to theobserver

that damage has occurred until

it is too late. Do not point the tel-

escope or its viewfinder at or near

the Sun. Do not look through the

telescope or its viewfinder as it is

moving. Children should always

have adult supervision while

observing.

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Bresser AR-90 Manual

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