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15
Fig. 11: Viewfinder Assembly.
Collimation
Screws
Mounting
Slot
Viewfinder
Eyepiece
Track
Fig. 12: Viewfinder collimation screws
and eyepiece.
Fig. 13a & 13b: Jupiter; examples of
the right amount of magnification and
too much magnification.
Thumb-
screws
The power, or magnification of a telescope is determined by the focal length of the tel-
escope and the focal length of the eyepiece being used (an eyepiece's focal length is
printed on the side of the eyepiece). To calculate eyepiece power, divide the tele-
scope's focal length by the eyepiece's focal length. For example: A 26mm eyepiece is
supplied with
LX200GPS models. The focal length of the 8" f/10 LX200GPS is 2000mm
(see
SPECIFICATIONS, pages 47 through 49).
Eyepiece Power = Telescope focal length ÷ Eyepiece focal length
Eyepiece Power = 2000mm ÷ 26mm
Eyepiece Power = 77
The eyepiece power, or magnification is therefore 77X (approximately).
Note: For a list of magnification ratings of the eyepieces available for the
LX200GPS telescopes, see OPTIONAL ACCESSORIES, page 41.
Mounting and Adjusting the Viewfinder
To align the viewfinder, perform steps 1 through 5 during the daytime; perform step 6
at night.
1. Slide the track on the bottom of the viewfinder into the slot in the viewfinder
mounting assembly. See Fig. 11. To secure the viewfinder to the mounting
assembly, tighten the two thumbscrews (Fig. 11) to a firm feel only.
2. If you have not already done so, insert the Super Plössl 26mm eyepiece into the
diagonal prism.
3. Unlock the R.A. (12, Fig. 1) and Dec. (17, Fig. 1) locks so that the telescope
moves freely on both axes.
4. Point the telescope at some well-defined and stationary land object at least 200
yards distant, such as the top of a telephone pole or street sign. Center the object
in the telescope eyepiece. Re-tighten the R.A. and Dec. locks.
5. Look through the viewfinder eyepiece (Fig. 12) and loosen or tighten, as appro-
priate, one or more of the viewfinder collimation screws (Fig. 12) until the
viewfinder crosshairs are precisely centered on the object you previously cen-
tered in the telescope eyepiece.
6. Check this alignment on a celestial object, such as the Moon or a bright star, and
make any necessary refinements, using the method outlined in steps 3 through 5.
Note: Seeing conditions vary widely from night-to-night and site-to-site.
Turbulence in the air, even on an apparently clear night, can distort
images. If an image appears fuzzy and ill-defined, back off to a lower
power eyepiece for a more well-resolved image (see Fig. 13a and 13b).
Too Much Power?
Can you ever have too much power? If the type of power you’re referring to is
eyepiece magnification, yes, you can! The most common mistake of the begin-
ning observer is to “overpower” a telescope by using high magnifications which
the telescope’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 Figs. 13a and 13b). Powers
above 400X should be employed only under the steadiest atmospheric condi-
tions.
Autostar II can calculate the best eyepiece for you to use. Try out the “Eyepiece
Calc” feature in the Utilities menu.
Most observers should have three or four additional eyepieces to achieve the full
range of reasonable magnifications possible with the LX200GPS telescopes. See
OPTIONALACCESSORIES
, page 41.
LX200GPS TIPS
Tip:
Because the space
between the GPS receiver
and the viewfinder is a bit
tight, it is helpful if you
tighten the front, bottom
viewfinder collimation
thumbscrew first and use
the other screws to set the
alignment. However, if you
determine you need to
adjust the front thumb-
screw, choose an alignment
object that allows you to
slightly elevate or rotate the
telescope to a convenient
position for adjustment of
this thumbscrew.
GPS
Receiver