The iOptron Photron 355mm f/8 Ritchey-Chretien Catadioptric Truss-Tube Telescope builds on the success of the solid tube models in the series with a completely redesigned housing that utilizes an open truss system to improve the overall thermal dynamics that allow the optical system to settle into the ambient temperature faster and resist heating up better than traditional closed steel tubes. Carbon fiber tubes used in the trusses are also thermally stable so they won't expand and contract like metal does, ensuring accurate alignment throughout the night and throughout the year. This new optical tube design enables larger apertures than closed steel tubes, making this model one of the largest in the Photron family of scopes. Intended for those who have a solid and reliable support system, iOptron is offering the RCT here as an (optical tube assembly) OTA-only option. A long Losmandy-style dovetail plate is factory installed to make it compatible with a wide variety of heavy-duty mounts and piers that can carry a minimum payload of at least 66 pounds.
As with all Photrons, the Ritchey-Chretien (RCT) optical system utilizes the same hyperbolic primary and secondary mirror design used in the Hubble Space Telescope, the Keck telescopes, and the ESO Very Large Telescope to deliver the wide field of view and superb performance advanced amateur astronomers and imagers demand. Complementing the improved heat management of the open truss system are low thermal-expansion quartz primary and secondary mirrors and three cooling fans that further help keep the optical system cool during long observation sessions. Each mirror is treated with highly reflective dielectric coatings that maximize the light being transmitted, so greater than 99% of the available light makes it to your eye or imaging sensor. All of this translates to bright and sharp high-contrast views or images with accurate color fidelity across the entire wide distortion-free field of view. The 14" aperture has the light-gathering capability required to see dim deep-space objects like galaxies with a respectable f/8 focal ratio that is ideal for long-exposure astrophotography techniques.
Unlike other catadioptric designs, this RCT has a fixed primary mirror to eliminate the image shift that is common with conventional configurations that move the mirror forward and back to focus the image. With the primary mirror fixed in place, iOptron opted for a precise two-speed Crayford-style focuser with a 10:1 reducer that allows for fast coarse and precise fine focusing without the backlash that occurs in the more common rack-and-pinion design—essential for astrophotography or splitting binary stars. To ensure complete coverage of today's imaging sensors, the focuser has a large 3" drawtube and comes with three extension rings to help users achieve the proper back focus distance. The larger drawtube also allows the use of large 2" eyepieces, which generally have longer eye reliefs to make visual observations much more comfortable, and comes with a 1.25" reducer to enable the smaller and more common-sized eyepieces and accessories to be easily used.
Optical Tube Assembly
- Open truss tube design for improved thermal dynamics, allowing the optical components to adapt and settle to the ambient temperature much faster and resist heating versus conventional closed steel or aluminum tubes
- Carbon fiber truss tubes offer greater thermal stability than steel or aluminum without sacrificing strength, ensuring accurate optical alignment when transitioning between inside and outside as the temperature drops overnight during observation sessions and as the temperature fluctuates with the seasons throughout the year
- Large 355mm (14") aperture has the ability to resolve dim deep-sky objects like wispy nebulae and galaxies and to split close binary stars
- Long 2848mm focal length provides a high magnification potential and moderate focal ratio for astrophotography
- f/8 focal ratio is ideal for long-exposure astrophotography techniques used for faint deep-space objects
- Ritchey-Chretien catadioptric design delivers views free from off-axis comas and spherical and chromatic aberrations
- Low thermal-expansion quartz primary and secondary mirrors limit distortion as the mirrors heat
- Highly reflective dielectric mirror coatings transmit more than 99% of incoming light to ensure bright and clear images
- Fixed-position primary mirror eliminates image shift common in other catadioptric designs
- Three integrated primary mirror cooling fans reduce acclimation time and help to eliminate distortion due to mirror heating; runs on eight user-supplied AA batteries
- 10:1 dual-speed linear-bearing Crayford focuser provides tack-sharp focusing, allowing for fast coarse and precise fine focus without backlash
- Tension-adjustment knob and drawtube lock knob
- Large-diameter 3" drawtube maximizes light throughput and ensures complete coverage of imaging sensors to eliminate or limit vignetting during astrophotography/imaging
- Drawtube has an etched scale in inches and millimeters for precise focus repeatability
- 2" compression ring holder allows the use of larger eyepieces and accessories like diagonals and Barlows to make viewing easier and more comfortable
- 1.25" reducer adapter enables the use of the more common size of eyepieces and accessories
- Two 1" and one 2" stackable extension tubes provided to fit between the threaded back and focusing assembly provide additional back-focus distance to ensure the focal plane properly lands on imaging sensors for imaging if required
- Compatible with an optional ASCOM-compliant electronic focuser
- Optical tube assembly only—mount and tripod required for proper use
- 17" long Losmandy-style dovetail plate is compatible with larger high-payload capacity mounts and piers to handle the weight of the OTA and imaging rigs
- Length: 38"
- Weight: 66 pounds