Meade DS-90 Instruction Manual download pdf (Page 13)

5. Check this alignment on a celestial object, such as the Moon or a bright star, and make

any necessary refinements.

Choosing an Eyepiece

A telescope’

s eyepiece magnifies the light gathered by the optical tube. Each eyepiece has a

focal length, expressed in millimeters, or “mm.” The smaller the focal length, the higher the mag-

nification. For example, an eyepiece with a focal length of 9mm has a higher magnification than

an eyepiece with a focal length of 25mm.

Your telescope comes supplied with a low-powered 25mm or 26mm eyepiece which gives a

wide, comfortable field of view with high image resolution. Always begin your observations with

this eyepiece.

w power eyepieces offer a wide field of view, bright, high-contrast images, and eye relief dur-

ing long observing sessions. After an object is located and centered in the eyepiece, try switch-

ing to a higher power eyepiece to enlarge the image.

NOTE: Viewing conditions vary from night-to-night and from site-to-site. Turbulence in

the air, even on an apparently clear night, can distort images. If an image appears

fuzzy and ill-defined, return to a lower power eyepiece for a more well-resolved image.

The power, or magnification of a telescope is determined by the focal length of the telescope

and the focal length of the eyepiece being used. To calculate eyepiece power, divide the tele-

scope's focal length by the eyepiece's focal length. For example, you may wish to use a 25mm

eyepiece with the DS-2000 model DS-2114S. Look up the focal length of the DS-2114S under

SPECIFICATIONS: DS-2114S, page 32. The

focal length is listed as 1000mm.

Telescope focal length divided by

Eyepiece focal length = Eyepiece power

1000 v 25 = 40

The eyepiece power, or magnification is

therefore 40X (approximately).

The Barlow Lens

Some Meade telescopes include a power

multiplier called a Barlow lens. Consisting of

a lens mounted in a 4"-long (10cm) tube

the Barlow doubles or triples the power

obtained when an e

epiece is used alone. In

the example above, a 25mm eyepiece

results in 40X magnification with the DS-

2114S telescope;

when this same e

yepiece

is used in conjunction with a 2x Barlow lens,

power is doubled to 80X. To use the Barlow,

inser

t it into the diagonal pr

ism (

refr

actor

models only) or e

epiece holder, followed by

the eyepiece.

NEVER

point the

telescope

directly at

or near the Sun at any

time! Observing the

Sun, even for the

smallest fraction of a

second, will result in

instant and irre-

versible eye damage,

as well as physical

damage to the tele-

scope itself.

DS-2000 TIPS

Too Much Power?

Can you ever have too much power? If you’re

referring to eyepiece power (magnification),

yes, you can! The most common beginner’s

mistake is to “overpower” a telescope by using

too high of a magnification, which the tele-

scope’s aperture and atmospheric conditions

cannot reasonably support. Keep in mind that

a smaller, but bright and well-resolved image

is far superior to one that is larger, but dim and

poorly resolved (see below). Powers above

200X should be emplo

ed only under the

steadiest atmospheric conditions.

Autostar can calculate the best eyepiece for

you to use. Try out the “Eyepiece Calc” feature

in the Utilities men

Most observers should have three or four

additional e

epieces to achie

ve the full range

of reasonable magnifications possible with the

DS-2000 telescopes. See “OPTIONAL

CCESSORIES

”

page 28.

Fig.

14a & 14b:

upiter

;

xample of too m

uch

magnification.

Fig. 13: Red Dot Viewfinder

intensity slider. Slide the

switch to the right to turn on

the viewfinder. The switch

provides two levels of inten-

sity for the red dot.

Fig. 15: 25mm and

9mm eyepieces.

Intensity Slider

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 43 44

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Meade DS-90 Instruction Manual Page 13

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