2
Figure 1-1
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A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused.
Some telescopes, known as refractors, use lenses. Other telescopes, known as reflectors, use mirrors. The Schmidt-Cassegrain
optical system (or Schmidt-Cass for short) uses a combination of mirrors and lenses and is referred to as a compound or
catadioptric telescope. This unique design offers large-diameter optics while maintaining very short tube lengths, making them
extremely portable. The Schmidt-Cassegrain system consists of a zero power corrector plate, a spherical primary mirror, and a
secondary mirror. Once light rays enter the optical system, they travel the length of the optical tube three times.
The optics of the Celestron Schmidt-Cassegrain telescopes have Starbright® coatings - enhanced multi-layer coatings on the
primary and secondary mirrors for increased reflectivity and a fully coated corrector for the finest anti-reflection characteristics.
8” OTA
8” OTA-CF
9.25” OTA
9.25” OTA-CF
11" OTA 11" OTA-CF 14" OTA 14" OTA
Part
Number
91024 91023 91027 91026 91036 91035
91037
91038-XLT
Focal Length
2032mm F/10 2032mm F/10 2350mm F/10 2350mm F/10
2800mm F/10 2800mm F/10 3910mm
F/11
3910mm
F/11
Eyepiece
25mm –
1.25" (81x)
25mm - 1.25"
(81x)
25mm - 1.25"
(94x)
25mm - 1.25"
(94x)
40mm -
1.25" (70x)
40mm - 1.25"
(70x)
40mm - 2"
(98x)
40mm - 2"
(98x)
Star Diagonal
90° - 1.25"
90° - 1.25"
90° - 1.25"
90° - 1.25"
90° - 1.25"
90° - 1.25"
90° - 2"
90° - 2"
Finderscope
6x30 6x30 6x30 6x30 9x50
9x50 9x50
9x50
Optical Tube
Aluminum Carbon
Fiber
Aluminum Carbon
Fiber Aluminum
Carbon Fiber Aluminum Aluminum
Fastar
Compatible
No Yes No No No No No Yes
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The visual back is the accessory that allows you to attach all visual accessories to the telescope. The 8", 9.25" and
11" optical tubes come with the visual back installed. The 14" OTA comes with a thread on 2" star diagonal instead
of a visual back. If it is not already on the tube it can be attached as follows:
1. Remove the rubber cover on the rear cell.
2. Place the knurled slip ring on the visual back over the threads on the rear cell (Fig 1-2).
3. Hold the visual back with the set screw in a convenient position and rotate the knurled slip ring clockwise until tight.
