Ceravolo 300 Astrograph - Mechanical Design
|
The Ceravolo 300mm Astrograph with a Finger Lakes Instruments large format CCD camera, filter wheel and Precision Digital Focuser. A typical setup ready for clear skies.
Advanced camera assemblies such as this can be quite heavy, weighing up to 20 lbs. The stress imparted on the telescope can flex the tube and adversely affect collimation - this is especially true for Newtonian systems. The Ceravolo Astrograph, being a Cassegrain optical system, allows accessories to be firmly bolted to the telescope's heavy-duty aluminum backplate, eliminating the potential for flexure.
Pictured below is the astrograph in the f/9 configuration, with an Apogee U16M large format camera and filter wheel. The generous 300mm (11.8") back focus is more than enough to accommodate off-axis guiders and a large focuser. This setup requires the use of spacer rings to place the camera at focus. Even with the back of the camera hanging 350 mm (14") away from the backplate, the system has proved to be rock solid as the astrograph is moved around the sky.
|
At 500mm, or 20" long, the Ceravolo astrograph's tube assembly is remarkably compact, a feature made possible by the short focal length, f/2, primary mirror. The astrograph features a carbon fiber tube for thermal stability, minimizing focus shift caused by changing nighttime temperature. However, as the carbon fiber tube alone is too flexible to support the high performance optics properly, Ceravolo designed a thermally isolated aluminum OTA cradle to support the carbon tube and accessories bolted onto the side plates. The carbon fiber tube is further reinforced by the aluminum end ring to which the secondary spider assembly is attached.
The side and top mounting plates are light-weighted and designed to accept a variety of guide/photo telescope mounting rings, finder scopes, and other accessories.
|
Pictured above is the Ceravolo 300mm dual configuration astrograph on a Losmandy Titan German equatorial mount, with a piggybacked 4" aperture Takahashi FSQ refractor. The SBIG STL-11000M large format CCD camera is mounted on a 3" Crayford focuser. Most commercial focusers can be easily adapted to the astrograph backplate.