PlaneWave CDK12.5 f/8 Optical Tube Assembly The CDK12.5 is a 318 mm Corrected Dall-Kirkham astrograph with a 2541 mm focal length. The design eliminates off-axis coma and astigmatism and gives a flat field across a 52 mm image circle, suiting large-format cameras for deep-sky imaging and research.
Manufacturer model: PlaneWave CDK12.5 f/8 OTA (125104Q) · Specifications checked against manufacturer data on 2026-11-03
The CDK12.5 is a 318 mm Corrected Dall-Kirkham astrograph with a 2541 mm focal length. The design eliminates off-axis coma and astigmatism and gives a flat field across a 52 mm image circle, suiting large-format cameras for deep-sky imaging and research.
Construction
Fused silica mirrors keep their figure and alignment as temperatures change, and the carbon fibre tube minimises focus shift. Cooling fans and boundary-layer fans speed thermal equilibrium, and primary and secondary mirror heater pads are ready for the Delta-T controller (sold separately). The OTA now includes PlaneWave's EFA box for automated focus, temperature monitoring and fan control through PWI4.
Optical system
Optical design
Corrected Dall-Kirkham
Aperture
318 mm (12.5")
Focal length
2541 mm
Focal ratio
f/8
Central obstruction
42% of primary diameter
Image circle
52 mm
Optical performance
2.8 µm RMS on-axis; 3.8 µm at 11 mm; 8.0 µm at 21 mm off-axis
Primary mirror
318 mm optical / 330 mm outer, prolate ellipsoid, fused silica, enhanced aluminium 96%
Secondary mirror
118 mm spherical, fused silica, enhanced aluminium 96%
Corrector lenses
70 mm, broadband AR (<0.5% reflection, 400–700 nm)
Mechanical
Back focus from mounting surface
265 mm (10.445")
Back focus from racked-in focuser
183 mm (7.2")
OTA length
787 mm (31")
Weight
19 kg (42 lb)
Tube
Carbon fibre
Fan power
User-supplied 12 V DC, 2.1 mm barrel, centre positive (if no EFA)
Standard manufacturer package
2.75" Hedrick focuser, motorised (1.3" travel, uses 3.25" of back focus)
EFA box (hand controller not included)
OTA cover
Primary and secondary mirror dew heaters (need Delta-T controller 600195)
Standard CDK12.5 (aluminium coatings), not IRDK12.5. Losmandy D-style dovetail; fits Keller EZ saddle on L-350. Optional 0.66x reducer gives f/5.3, 30 mm field.
Additional specifications
Bf focuser (mm)
183
1323212Q
Data sheet
Aperture (mm)
318
Bf mount (mm)
265
Design
Corrected Dall-Kirkham
Focal length (mm)
2541
Focal ratio
f/8
Image circle (mm)
52
Included
2.75in Hedrick focuser, EFA box, cover, dew heaters, fan cable
Length (mm)
787
Lenses
70 mm broadband AR
Obstruction
42% diameter
Performance
2.8 um on-axis; 3.8 um @11 mm; 8.0 um @21 mm
Primary
318/330 mm prolate ellipsoid fused silica, Al 96%
Secondary
118 mm spherical fused silica, Al 96%
Weight (kg)
19
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PlaneWave CDK12.5 f/8 Optical Tube Assembly The CDK12.5 is a 318 mm Corrected Dall-Kirkham astrograph with a 2541 mm focal length. The design eliminates off-axis coma and astigmatism and gives a flat field across a 52 mm image circle, suiting large-format cameras for deep-sky imaging and research.
Manufacturer model: PlaneWave CDK12.5 f/8 OTA (125104Q) · Specifications checked against manufacturer data on 2026-11-03
