CDK12.5 Astrograph f/8 with Fused Silica Optics (1323212Q)

CDK12.5 Astrograph f/8 with Fused Silica Optics

Description:
The PlaneWave CDK12.5 is a high-performance 12.5" astrograph designed for demanding astrophotography. As a compact and affordable alternative to the CDK20", it delivers equivalent optical quality in a smaller format accessible to advanced amateur astronomers.

The CDK optical design (Corrected Dall-Kirkham) includes a concave primary, convex secondary, and integrated lens corrector, yielding zero off-axis coma and astigmatism. The result is a flat 52 mm image circle, fully illuminating modern full-frame CCD and CMOS sensors.

This version uses fused silica glass, a high-purity synthetic amorphous silica with outstanding thermal and mechanical stability. With an ultra-low thermal expansion coefficient, fused silica maintains its shape over temperature shifts, ensuring constant focus and stable optical performance. Its high transmission and resistance to thermal shock make it the material of choice in professional observatories.

The optical tube includes a robust 3.5" Hedrick focuser (EFA motor kit not included), a 3" dovetail mount, and generous back focus of 265 mm (from mounting surface). Spot diagrams confirm diffraction-limited imaging across the entire field, with star images remaining tight to the edge of the corrected field (26 mm off-axis). Final image quality is limited only by seeing and tracking accuracy.

Precise spacing must be maintained when using CCD cameras like SBIG systems (with or without AO8), and dedicated adapters are available for optimal field flatness.

Technical specifications:

Optical design: Corrected Dall-Kirkham (CDK)
Aperture: 12.5" (318 mm)
Focal length: 2541 mm
F-ratio: f/8
Corrected image field: 52 mm
Back focus: 10.45" (265 mm) from mounting surface, 7.2" (183 mm) from racked-in focuser
Central obstruction: 42% of primary mirror
Glass type: Fused Silica
Optical length: 31" (787 mm)
OTA weight: 46 lbs (21 kg)
Focuser: 3.5" Hedrick (manual, EFA-ready)
Mounting: 3" dovetail
Crating: requires crate #1323512 (charged separately)

Additional information:
Optimized for use with large-format sensors. Delta T Ready design allows optional dew control heating integration. Specific adapters available for SBIG and other CCD configurations.