Celestron CGEM II 925 EdgeHD Telescope

EdgeHD Optics: A 0.49 Arc Second Flat-Field System

The EdgeHD optical system is an aplanatic Schmidt-Cassegrain design that produces aberration-free, pinpoint stars across its entire 42mm image circle, fully illuminating full-frame camera sensors. Unlike standard designs that project sharp stars onto a curved plane, the EdgeHD system creates an intrinsically flat focal plane, ensuring every star is in sharp focus from the center to the edge of your CCD or DSLR sensor. This astrograph-quality performance means improved resolution and limiting magnitude compared to other designs of the same 235mm aperture.

• Dawes Limit Resolution (0.49"): Resolves fine details in planetary cloud bands, close double stars, and the cores of globular clusters like the Hercules Cluster (M13).
• StarBright XLT Coatings: Maximizes light transmission for brighter images and higher contrast, crucial for revealing faint structures in nebulae and galaxies.
• 42mm Flat Image Circle: Provides a wide, unvignetted field of view that is perfectly corrected for large-format sensors, eliminating the need for additional field flatteners.

Imaging-Focused Design: Clutches, Vents, and f/2 Versatility

The EdgeHD 9.25" optical tube is engineered with mechanical features that directly address the challenges of long-exposure astrophotography. Flexible tension clutches secure the primary mirror after focusing, significantly reducing image shift during an imaging sequence. Integrated cooling vents on the rear cell allow hot air to escape from behind the mirror, enabling the telescope to reach thermal equilibrium faster for sharper, more stable views.

For ultimate versatility, all EdgeHD optical tubes are Fastar-compatible. By replacing the secondary mirror with a third-party lens accessory, you can convert the telescope into an ultra-fast f/2 wide-field imaging system, perfect for capturing vast nebulae and rich star fields in a fraction of the time required at f/10.

CGEM II Mount: 40 lb Capacity and Ergonomic Design

The redesigned CGEM II mount provides a stable, vibration-free foundation for the 21 lb optical tube, leaving a substantial 19 lbs of capacity for your imaging equipment. The mount rests on a heavy-duty tripod with 2" diameter steel legs, ensuring rigidity. Large, ergonomic altitude and azimuth adjustment knobs make the polar alignment process smooth and precise, while internal RA and DEC motor wiring prevents cable snags during operation.

• 40 lb (18 kg) Instrument Capacity: Comfortably supports the 9.25" OTA plus a full astrophotography setup including a guide scope, camera, filter wheel, and other accessories.
• Dual Saddle Plate: Compatible with both CGE and CG-5 style dovetails, allowing you to mount a wide variety of optical tubes.
• 2" Steel Tripod: Features graduated markings on the lower leg sections, making it easy to extend the legs to the same height for a level setup every time.

NexStar+ Intelligence: 40,000 Objects and All-Star Alignment

The brain of the CGEM II is the proven NexStar+ hand controller, giving you access to a database of over 40,000 celestial objects. The mount features Celestron's innovative All-Star Polar Alignment, which allows you to use any bright star to achieve an accurate alignment, even if you can't see Polaris. For dedicated imagers, Permanent Periodic Error Correction (PPEC) lets you train out the periodic error of the worm gears and stores the recording for future sessions. The mount can also track objects well past the meridian, preventing interruptions during long exposures through the best part of the night sky.

CGEM II 925 vs. 800/1100 EdgeHD: The Imaging Sweet Spot

The 9.25" EdgeHD occupies a unique and highly sought-after position in Celestron's lineup. It offers a significant increase in light-gathering power and resolution over the 8" model, allowing you to resolve finer detail in galaxies and planetary features. At the same time, its 21 lb optical tube is considerably lighter and more manageable than the 11" model, placing less demand on the mount and making it easier to transport and set up. For many astroimagers, the 9.25" represents the ideal compromise between aperture and portability.