CELESTRON C90 MAKSUTOV SPOTTING SCOPE-OPTICAL TUBE ONLY
The Maksutov optical design is recognized for being a portable design that is easy to use and has a variety of applications, making it an excellent choice for both terrestrial and astronomical usage. This C90 Mak has excellent optics with razor sharp images over a wide field.
Maksutov-Cassegrain Optical Design
The MAK is a catadioptric spotting scope, which means the optical design includes both a lens and a mirror. The light coming through a MAK passes through the corrector lens to the primary mirror and back to a spherical secondary mirror before it hits the eyepiece. Images are bright, sharp, and virtually free of chromatic aberration.

The Maksutov-Cassegrain’s optical design offers several unique benefits. Instead of a secondary mirror, the MAK features a “secondary spot” of reflective coating applied directly to the inside of the corrector plate. Because of this, the spotting scope does not require frequent collimation. Also, the secondary spot is significantly smaller, giving the MAK its signature high-contrast views.
One important thing to note about Maksutov-Cassegrain spotting scope is that the larger, heavier Maksutov corrector plate takes longer to cool down and adjust to ambient air temperature.
GENERAL
Magnification: 39x (with included eyepiece)
Objective Lens Diameter: 90mm (3.54")
Eyepieces: 32mm Plössl (1.26")
Angular Field of View: 1.3° with included eyepiece
Linear Field of View (@1000 yds) / @1000 m): 68 ft (20.7 m) with included eyepiece
Focal Length: 1250mm (49")
Exit Pupil: 2.3mm (0.1") with included eyepiece
Eye Relief: 20mm (.78") with included eyepiece
Close Focus: 15 ft (4.6 m) with included eyepiece
Twilight Factor: 59.2 with included eyepiece
Relative Brightness: 5.3 with included eyepiece
Lens Coatings: Multi-Coated
Prism Glass (Type): BaK4
Prism Coatings: N/A
Weight: 74 oz (2,100 g)
Environmental Protection: Water Resistant
Nitrogen Filled: No
Tripod Adaptable: Yes
Carrying Case: Black heavy woven nylon backpack
Camera Adaptable: Yes
Dimensions: 400mm x 260mm x260mm (15.7" x 10.2" x 10.2") with include eyepiece
Included Items: Plössl 32mm eyepiece
45° diagonal
8x21 finderscope
Objective Lens Cover
Eyepiece Lens cap
Backpack Case
Solar Warning • Never look directly at the Sun with the naked eye or with this optic. Permanent and irreversible eye damage may result.
• Never use your optic to project an image of the Sun onto any surface. Internal heat build-up can damage the optic and any accessories attached to it.
• Never leave your optic unsupervised. Make sure an adult who is familiar with the correct operating procedures is with your optic at all times, especially when children are present.
