C90mm Mak - #52265
Congratulations on your purchase of a Celestron spotting scope! Whether your interest lies in nature or astronomy this
spotting scope offers the finest in optical quality guaranteed to give you years of viewing pleasure.
Erect Image
Finderscope
90°°°° Eyepiece
Barrel
Eyepiece
Flip Down
Lens Cap
Erect Image
Diagonal
Focus Knob
Tripod Adapter
Mount
Figure 1-1
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Your C90 Mak has an internal flip mirror that can divert light either through the 90˚ eyepiece barrel at the top of the rear cell or directly
through the erect image diagonal (for daytime use) at the rear of the spotting scope. Make sure that the flip mirror is in the "down" position
for viewing with an eyepiece at 90
To install the eyepiece directly into the 90˚ eyepiece barrel (for astronomical use):
1. Loosen the thumbscrew on the eyepiece barrel so it does not obstruct the inner diameter of the barrel.
2. Slide the chrome portion of the eyepiece into the eyepiece barrel.
3. Tighten the thumbscrew to hold the eyepiece in place.
4. To remove the eyepiece, loosen the thumbscrew on the eyepiece barrel and slide the eyepiece out.
˚ and in the "up" position for viewing through the diagonal (see Figure 1-2).
To install the eyepiece onto the rear of the spotting scope (for land use):
1. Unthread the cap from the rear cell.
2. Thread the metal ring of the erect image diagonal onto the threads of the rear cell.
3. Remove the caps and loosen the thumbscrew on the diagonal so it does not obstruct
the inner diameter of the barrel
4. Slide the chrome portion of the eyepiece into the eyepiece barrel.
5. Tighten the thumbscrew to hold the eyepiece in place.
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The C90 Mak comes with a 8x21mm erect image finder. The first number used to
describe the finder is the power. The second number is the diameter of the objective
lens in millimeters. For example, the C90 Mak finder is 8x21 which means it is 8
power and has a 21mm objective lens. Incidentally, power is always compared to
the unaided human eye. So, an 8 power finder magnifies images eight times more
than the human eye. The finderscope is adjusted using the three adjustment screws
located 120˚ around each finderscope ring.
The finderscope comes pre-assembled and is mounted inside the finderscope bracket
rings. To attach the finderscope:
1. Loosen the set screw on the mounting bracket on the spotting scope (see Figure 1-3).
2. Slide the finder bracket (with finderscope attached) into the mounting bracket on the spotting scope.
3. The finderscope bracket will slide in from the back. The finderscope should be oriented so that the objective lens is toward the front end of
the spotting scope.
4. Tighten the set screw on the mounting bracket to hold the finderscope in place.
Aligning the Finderscope:
To make things a little easier, you should align the finder during the day when it is
easier to locate objects. To align the finder:
1. Choose a conspicuous object that is over 500 yards away. This will eliminate any
possible parallax effect.
2. Point your spotting scope at the target and center it in the main optics of the
spotting scope (the eyepiece).
4. Check the finder to see where the object is located in the field of view.
5. Adjust the screws on the finder bracket, tightening one while loosening another, until the cross hairs are centered on the target.
Accurate alignment of the finder will make it much easier to find objects in the main optical tube.
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Figure 1-2 – Flip mirror shown in the
"down" position for viewing from the
top of the rear cell.
Figure 1-3 – The finderscope and quick-
release bracket.
The C90 Mak spotting scope focusing mechanism controls the position of the primary mirror which slides back and forth on the primary
baffle tube. Turn the focusing knob until the image is sharp. If the knob will not turn, the primary mirror has reached the end of its travel
on the focusing mechanism. Turn the knob in the opposite direction until the image is sharp. Once an image is in focus, turn the knob
clockwise to focus on a closer object and counterclockwise for a more distant object. A single turn of the focusing knob moves the primary
mirror only slightly. Therefore, it will take many turns to go from close focus (approximately 20 feet) to infinity. For astronomical
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