TPO 10" f/8 Ritchey-Chretien Steel Astrograph with TPO 3.3" Focuser

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TPO 10" f/8 Ritchey-Chretien Steel Astrograph with TPO 3.3" Focuser
Item # OS-10RC-M
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  • Are you looking for a 10" astrograph that doesn't break the bank? This Ritchey-Chretien, brought to you by TPO, is a true RC, with optics that produce flat, sharp images with virtually no false color or coma.
  • Both mirrors of this fixed two-mirror system are made of quartz, and are overlaid with 99% dielectric coatings for durability and high reflectivity.
  • Sometimes being baffled is a good thing! This Ritchey-Chretien telescope has 9 computer-optimized light baffles in the tube, the primary mirror tube has four internal baffles, and an internal glare thread baffle is part of the secondary mirror light shield.
  • Three cooling fans are built into the rear cell for fast cool-down of the primary and tube interior. The faster you can get to ambient temperature, the quicker you can begin your imaging session for the night!
  • A 3.3" 1:10 Crayford focuser is included with this package. Focusing is super smooth, and the dual speed knobs allow you to make minute changes to focus as well as larger focus movement. A fully rotatable collar allows you to position the focuser just where you want it.



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 Astrograph Highlights…


Optical Highlights: This Third Planet Optics (TPO) Ritchey Chretien telescope has 10" (250mm) of aperture and a focal length of 2000mm. 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.

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 nine light baffles, and the primary and secondary mirrors are baffled as well.

Cooling Fans: The 10" Ritchey has three small cooling fans in the rear cell that help cool the inside of the tube down and bring it to ambient temperature so that you can start imaging sooner! The fans are powered by an external battery pack. This battery holder accepts 8-AA batteries (sold separately).

3.3" Dual Speed Fully-Rotatable Crayford Focuser You'll love the 3.3" 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 2" & 1.25" compression ring adapter is also included so you can use both 2" & 1.25" 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 & 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 Dovetails & Finderscope Base Included Talk about versatility! A Losmandy-style dovetail is attached to the bottom and top of the OTA. The dovetail(s) can be removed if you wish to use mounting rings (sold separately) instead. While a finderscope is not included, the OTA comes standard with a finderscope base that will accept Vixen-style brackets (if you want an optical finder) or most red dot finders.


Additional Information

Additional Information

Manufacturer TPO
Telescope Series TPO Ritchey-Chretien
Optical Design Ritchey-Chretien
Mount Type None - Optical Tube Only
Warranty 2 Year Warranty
Telescope Aperture 10"
Telescope Focal Length 2000mm
Telescope Focal Ratio f/8
Length of Optical Tube 29"
Optical Tube Weight 34.5 lbs.
Optical Coatings 99% Dielectric
Tube Color or Finish Gloss White
Limiting Stellar Magnitude 14.5
Highest Useful Magnification 300x
Diagonal Included? No - Sold Separately
Finder Included None
OTA Mount Type Losmandy-Style Dovetail
Included Items

Included Items

  • TPO 10" f/8 Ritchey-Chretien OTA - White Aluminum Tube
  • (2) M117 X 25mm Spacers
  • M117 X 50mm Spacer
  • Top & Bottom Losmandy Dovetails
  • TPO 3.3" Two Speed Crayford Focuser w/2" and 1.25" Adapters
  • Vixen Finder Shoe
  • Battery Box for Fans
  • Dust Caps
Questions & Answers

Product Questions

What Cases are available for this OTA?
Will the Teleskop Service Flattener work with this scope and focuser or will I need to add some adapters to make the connection?
How long is the waiting list if I were to place an order in the next 15 days ?
What vixen mount would best handle this OTA?
Should I be aware of any issues mating this scope with an Orion Atlas EQ-G (manual states 40 lb limit)?
I don't suppose there's any chance at ordering this OTA without a stock focuser is there? I really don't want to pay for a 3" focuser I'm not going to use. I have a thing for Feathertouches and it seems a waste if it could be avoided.
what is the backfocus length of this telescope, and what would it be with a .75X or a .5X focal reducers?

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