The CCA-250 is Takahashi’s first corrected Cassegrain Astrograph. It was developed as a replacement for the BRC-250 corrected Ritchey. This instrument was developed to take advantage of the digital age and provide image circles to cover large format imaging chips. The large ø88mm can cover these large chip with a flat field filled with pin point stars.

This astrograph offers versatility. It is a tri-focal instrument that can be used at its native f/5, at f/3.6 with the small and large 645 reducer or at f/7.5. It will support wide field to narrow field imaging

The design of this instrument includes a carbon fiber tube and a temperature compensated holder to maintain focus during long exposures.

During long exposures temperatures can change and cause the optics to change focus. The CCA-250 is equipped with three computer controlled cooling fans that are operated by three sensors: one on the primary, a second in the tube and a third in the air to measure ambient temperature to help prevent image shift working in concert with the carbon fiber tube and temperature compensated holder. This cooling system can also be operated manually.

The manual controls and computer interface are conveniently located in a control box attached to the rear of the mirror cell.

The control box also includes an input for the supplied 12v power source and a USB input for computer control of the focusing system.

The CCA-250 employs a corrected cassegrain optical system with a large three element corrector to produce a flat ø88mm circle with Stars 6 microns or less out to 50mm and 10 microns or less out to 88mm.

SPECIFICATIONS for the CCA250

Optical System	Corrected Cassegrain
Effective aperture	250mm
Focal ratio	f/5
Metal back distance	193.5mm
Tube diameter	ø306mm
Tube length	870mm [34.25”]
Tube weight	22.8kg [50.16lbs]
Power source	12vDC x 2A

Balancing is very important to insure the best possible tracking. The CCa is supplied with a heavy duty 18” long dove tail which Is an integral part of the tube assembly and a wide 15” bridge plate to allow attaching a variety of guide scope if needed. An extra heavy duty saddle plate is also supplied to couple with Takahashi mounts.

The CCA-250 is a very versatile optical system. It can be used at three different focal lengths 910mm [f/3.6] with the small or large 645 Reducer QE which produces a 60mm flat circle to support large format cameras, 1250mm [ f/5] prime focus and 1880mm [f/7.5] with Extender CR 1.5x.

CR 0.73x Small Reducer

Focal length	910mm
Focal ratio	f/3.6
Image circle	ø38mm

CR 1.5x Extender

Focal length	1880mm
Focal ratio	f/7.5
Image circle	ø40mm

645 0.72 x Large Reducer

Focal length	890mm
Focal ratio	f/3.6
Image circle	ø60mm