- This is a used item in excellent condition
- Great for deep sky astrophotography
- Flat-field RC design
Used TPO 8" RC Metal Optical Tube
In 1910, American optician and astronomer George Willis Ritchey and French astronomer Henri Chretien designed a specialized Cassegrain that would later become the telescope of choice for many observatories and professionals around the world. The Ritchey-Chretien astrograph has many benefits that make this design appealing to anyone who is serious about astrophotography or imaging. Here are a few of those benefits:
- Good-bye Coma: An RC has virtually no coma (stars look like little comets around the edges of the field), which means there will be greater image quality across a wider field of view.
- No Chromatic Aberration: Because a Ritchey-Chretien does not use lenses or corrector plates, the design does not suffer from chromatic aberrations, or false color. If you've ever looked through an achromatic refractor (non-APO), you will have seen chromatic aberration.
- No Spherical Aberration: The use of hyperbolic mirrors for both the primary and secondary removes the problem of spherical aberration from this optical system, an optical effect caused when light rays do not all come to focus at the same point, resulting in an image that is not in perfect focus.
- Flat Focal Plane: The Ritchey-Chretien design has a flat focal plane. Do you know that astronomers using glass photographic plates had to bend the glass to conform to the focal plane of their telescope in order to get the entire image in focus? A flat focal plane is important, especially for those using larger sensors, so that focus will be sharp across a wider field of view.
8 inch f/8 Ritchey-Chretien Astrograph Highlights...
Optical Highlights: This TPO Ritchey Chretien telescope has 8-inches (200 mm) of aperture and a focal length of 1600 mm. The concave hyperbolic primary and convex hyperbolic secondary are made from low expansion quartz, and finished with a scratch-resistant highly reflective 99-percent dielectric coating for great contrast. The primary mirror is fixed in place in a metal mirror cell, and the secondary resides in a metal housing that can be collimated.
Multiple Knife-Edge Baffle System: The computer designed and optimized baffle system in the TPO Ritchey-Chretien works wonders at keeping stray light at bay. Inside the tube are ten light baffles, and the primary and secondary mirrors are baffled as well.
2-inch Dual Speed Crayford Focuser You'll love the 2-inch 1:10 Dual Speed Crayford focuser that comes standard on this RC. The dual knobs allow you choose the speed with which you focus. One turn of the larger knob equals ten turns of the smaller knob, so minute adjustments (when you are "almost there") are easy to do with this high quality focuser. A 1.25-inch compression ring adapter is also included so you can use both 2-inch and 1.25-inch eyepieces. Two spacers are included as well, which allows you to adjust the focus position for different cameras with various back focus requirements.
A Fixed Primary Eliminates Image Shift Schmidt-Cassegrain and Mak-Cassegrain telescopes achieve focus by moving the primary mirror back and forth inside the optical tube assembly, and this movement can cause image shift. While manufacturers have done a pretty good job of minimizing image shift on their telescopes, a movable mirror makes it almost impossible to eliminate it completely. The Ritchey-Chretien has a primary that is fixed in place, removing the possibility of image shift and also the job of collimating the primary.
Two Dovetails Included Talk about versatility! One Vixen-style dovetail is attached to the bottom of the OTA, while another Vixen-style dovetail rail is attached to the top for quick and easy attachment a variety of mounts. The rails can be removed if you wish to use mounting rings (sold separately) instead.
|Warranty||90 Day Covered By OPT|
- 8-Inch RC metal optical tube
- TPO 2-inch Crayford style focuser
- Vixen size dovetails top and bottom
- Focuser extension tubes
- Lens cap and original box