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 features a computer controlled secondary ASCOM compliant Active Focus system. This enables computer control by programs such as FocusMax or Maxim DL.

Takahashi’s original secondary focusing system was included with the  Mewlon-250 and 300 beginning in 1989, this latest refinement uses a pulse motor which allows for the ASCOM compliant focus programs to operate the Active Focus 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.

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

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