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the Phillips-head screw is unthreaded, the secondary mirror
and its holder can be removed from the telescope. The sec-
ondary mirror does not need to be removed from its holder for
cleaning. Then follow the same procedure described below
for cleaning the primary mirror.
To clean the primary mirror, first carefully remove the mirror
cell from the telescope. To do so you must remove the six
screws on the exterior of the mirror cell (Figure 15). Then pull
the cell away from the tube. You will notice the primary mirror
is held in the mirror cell with three clips held by two screws
each. Loosen the screws and remove the clips.
You may now remove the primary mirror from its cell. Do not
touch the surface of the mirror with your fingers. Lift the mirror
carefully by the edges. Set the mirror on a clean soft towel. Fill
a clean sink or large bucket with room temperature water, a
few drops of liquid dishwashing detergent, and if possible, a
capful of 100% isopropyl alcohol. Submerge the mirror (alu-
minized surface facing up) in the water and let it soak for a
few minutes (or hours if it's a very dirty mirror). Wipe the mir-
ror under water with clean cotton balls, using extremely light
pressure and stroking in straight lines across the mirror sur-
face. Use one ball for each wipe across the mirror. 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 surface with a
stream of air (a "blower bulb" works great). Cover the mirror
surface with tissue, and leave the mirror in a warm area until it
is completely dry before placing it back in the mirror cell. Then
reinstall the mirror cell in the telescope optical tube with the
six screws.
Specifications
Orion
8" f/4.0 Newtonian Astrograph
®
Optical configuration: Newtonian reflector
Aperture:
200mm
Focal length:
800mm
Focal ratio:
f/4.0
Primary mirror:
BK-7 optical glass, parabolic figure
Mirror coatings:
Enhanced aluminum (>91%
reflectivity) with SiO
Secondary
mirror minor axis:
70mm
Focuser:
Machined aluminum, dual-speed
(10:1) Crayford with linear track
bearing, accepts 1.25" or 2"
accessories
Drawtube travel:
50mm
Optical tube:
Rolled steel, gloss enamel exterior
finish
Outside diameter:
229mm (9.0")
Weight:
7.3 kg (16.0 lbs.)
Length:
69.7cm (27.5")
Tube rings:
Included, hinged, felt-lined
Finder Scope:
8x50, with spring-loaded X-Y dovetail
bracket
Extension tube:
35mm length, 2" compression ring
holder
overcoat
2
11
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