scope with the dust cover when it is not in use will prevent
dust from accumulating on the mirrors. Improper cleaning can
scratch mirror coatings, so the fewer times you have to clean
the mirrors, the better. Small specks of dust or flecks of paint
have virtually no adverse effect on the visual performance of
the telescope.
The large primary mirror and the elliptical secondary mirror of
your telescope are front-surface aluminized and over-coated
with hard silicon dioxide, which prevents the aluminum from
oxidizing. These coatings normally last through many years of
use before requiring re-coating (which is easily done).
To clean the secondary mirror, you will need to remove it
from the telescope. Before doing so, orient the telescope tube
horizontally so that nothing accidentally falls down and hits
the primary mirror. Hold the secondary mirror holder station-
ary while loosening the center Phillips-head screw. Handle
the mirror by its holder; do not touch the mirror surface itself.
Once the mirror (still in its holder) is removed from the tube,
follow the same procedure described below for cleaning the
primary mirror. You do not need to remove the secondary mir-
ror from its holder when cleaning.
To clean the primary mirror, you must carefully remove the
mirror cell from the telescope. To do this, remove the six
screws on the side of the tube near the primary mirror. You
do not need to remove the collimation screws on the bottom
of the mirror cell. Remove the mirror cell from the tube. You
will notice the primary mirror is held down with four clips fas-
tened by two screws each. Loosen the screws and remove
the clips.
You may now remove the mirror from the mirror cell. Do not
touch the surface of the mirror with your fingers; lift it carefully
by the edge. Set the mirror, aluminized face up, on a clean,
soft towel. Fill a clean sink free of abrasive cleanser with
room-temperature water, a few drops of liquid dishwashing
detergent, and if possible a capful of 100% isopropyl alco-
hol. Submerge the mirror (aluminized face up) in the water
and let it soak for a few minutes (or hours if it’s a very dirty
mirror). Wipe the mirror under water with clean cotton balls,
using extremely light pressure and stroking in a straight line
across the mirror. Use one ball for each wipe across the mir-
ror. Then rinse the mirror under a stream of lukewarm water.
Any particles on the surface can be swabbed gently with a
series of cotton balls, each used just one time. Dry the mirror
in a stream of air (a “blower bulb” works great), or remove any
stray drops of water with the corner of a paper towel. Water
will run off a clean surface. Cover the mirror surface with a tis-
sue, and leave the mirror in a warm area until it is completely
dry before reassembling the telescope.
7. Specifications
Primary mirror: 254mm diameter, 1200mm focal length, BK7
optical glass
Focal ratio: f/4.7
Focuser: Crayford, accepts 2" and 1.25" eyepieces with
included adapter, collimatible
Optical tube material: Rolled steel
Eyepieces: 25mm & 10mm Sirius Plössls, multi-coated, 1.25"
barrel diameter
Eyepiece magnifications: 48x (25mm) and 120x (10mm)
Finder scope: 9x power, 50mm aperture, right-angle, correct-
image, achromat, cross-hair. 5° field of view
Finder scope bracket: Dovetail base, spring-loaded X-Y align-
ment
Eyepiece rack: Holds three 1.25" eyepieces and one 2" eye-
piece
Mirror coatings: Aluminum with SiO
2
overcoat
Minor axis of secondary mirror: 63.0mm
Optical tube weight: 30.8 lbs.
Base weight: 22.6 lbs.
Tube length: 47.25"
Tube outer diameter: 12.0"
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