About Ritchey-Chretien Telescopes
In 1910, American optician & astronomer George Willis Ritchey & 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 astro-photography 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.
10" f/8 Ritchey-Chretien Truss Tube Astrograph Highlights…
Optical Highlights: This Third Planet Optics (TPO) Ritchey Chretien telescope has 10" (254mm) of aperture and a focal length of 2032mm . The concave hyperbolic primary and convex hyperbolic secondary are made from low expansion quartz, and finished with a scratch-resistant highly reflective 99% 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.
Carbon Fiber Truss Tube Design:
Lightweight yet strong carbon fiber truss tubes have low thermal expansion characteristics. Shifts in focus due to temperature changes are minimized because of this design. The trusses are also designed to flex equally, keeping the optics in collimation regardless of the position of the telescope.
Cooling Fans: The 10" Ritchey has three small cooling fans in the rear cell that help create an ambient temperature within your telescope for more stable viewing and less fluctuation in focus. The fans are powered by an external battery pack. This battery holder accepts 8-AA batteries (sold separately).
A Fixed Primary Eliminates Image Shift Schmidt-Cassegrain & 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 moveable 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 D Style Losmandy Dovetails Included Talk about versatility! Two Losmandy-style dovetails are attached to the truss tube support rings so that they ride at the top of the scope as well as at the bottom.
TPO 3" Focuser A 3" dual-speed linear-bearing Crayford-style focuser rounds out this package. The ridged focusing knobs are easy to turn, even with gloves on, and the 10:1 microfocusing dial allows for very small changes, or tweaks, in focus. It takes ten turns of the microfocusing knob to equal just one turn of the larger knob. There is also a little knob on the bottom of the focuser that controls the tension, so that you can make adjustments depending on the weight or distribution of your load. The 3" opening steps down to a 2" compression ring adapter, and you will receive 1.25" compression ring adapter so that you can make use of all your eyepieces. Two 25mm and one 50mm extension tube is also included to help you match the back-focus requirements of your imaging equipment. This is one nice focuser, and due to its steel drive rail and other upgrades, you will find that it suffers from very little flexure, even under heavier imaging payloads.
- Additional Information
SKU OS-10RC-TT Manufacturer TPO Telescope Series TPO Ritchey-Chretien Optical Design Ritchey-Chretien Mount Type None - Optical Tube Only Warranty 2 Year Warranty Telescope Aperture 254mm Telescope Focal Length 2032mm Telescope Focal Ratio f/8 Optical Tube Weight 35 lb. Optical Coatings Fully Multi-Coated Tube Color or Finish Carbon Fiber Diagonal Included? No - Not Required Focuser Size 3" Focuser Style Crayford Finder Included None Manual or Electronic Focusing? Manual Focusing Speeds Two-Speed OTA Mount Type Losmandy-Style Dovetail
Customer Reviews 2 item(s)
This is an awesome telescope for astrophotographs. It seems to have the correct balance between focal lenght and aperture for CCDs.
I use and recommend TPO reducer 0.8x. The set has round stars from side to side in a 8300 CCD.
Ive never used the fans and focus hold all night.
An incredible scope for the price.
1= Houston, We Have a Problem & 5= It's Out of This World
- Great scope for the price
This scope is beautiful, great fit and finish. Scope maintains collimation and is very easy to setup with provided spacers and mammoth focuser. Really a great value for the price. You get a dust cover for the secondary, but no cover for the primary. You also do not get any documentation. It would be nice to get both.
1= Houston, We Have a Problem & 5= It's Out of This World
- Included Items
- TPO 10" f/8 Ritchey-Chretien Truss Tube OTA
- 3" Crayford Focuser
- Two Losmandy D Style Dovetails
- Questions & Answers
Product QuestionsQuestion by: Kevin Dixon on Oct 8, 2015 5:23:00 AMThere is an option for sensor sizes up to APS-C (crop DSLR format up to ~30mm). The AP-CCDT67 has had very good results with the RC scopes at f/5.3 to f/6 and would cover sensors of this size. The reducer is hosed in a 2" diameter tube with M48 threads and so would act as part of the nosepiece for the camera. The metal back distance from reducer to camera sensor would be 85mm for 0.67x and 60mm for 0.75x, so there is some flexibility for different systems.
For full-frame sensors, there are a couple options that we could explore, but they are fairly restrictive on back focus and what sort of focuser can be used due to their large size. Please contact me at email@example.com and we can discuss what options will work best for your system.
Answer by: Chris Hendren (Admin) on Oct 8, 2015 10:51:00 AMAre your scopes the V2 version with the focuser split from the mirror cell?
Question by: David Pearson on Mar 22, 2015 8:20:00 PMThe manufacturer does not currently state any specification on the optics of the TPO scopes except to claim that they are diffraction limited. Every scope has to pass an inerferogram inspection at the factory, but the results are not publicly listed by the manufacturer.Answer by: Chris Hendren (Admin) on Mar 27, 2015 5:06:00 PMQuestion by: Jack on Sep 24, 2014 6:44:38 AMUnfortunately not. With the addition of the Teleskop-Service RCKORREKTOR flattener, you can use sensors with a diagonal of up to 45mm maximum, but the PL09000 has a diagonal of 52mm. You would need a telescope with a larger corrected image circle for that camera or you would need to crop the sensor down by around 1/3.Answer by: Chris (Admin) on Sep 29, 2014 11:23:22 AM
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