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
SKU OS-10RC-M 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
- 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 QuestionsQuestion by: John Dutton on May 24, 2015 10:18:00 AMHello John,
Thank you for your question. I would say that the best case for this is the Pelican 1660 Case.
This case is a hard waterproof case which will protect the telescope well. Keep in mind that you might need to
pack the focuser in a separate part of the case in order for this to fit.Answer by: Rod Gallardy (Admin) on May 24, 2015 4:04:00 PMWill the Teleskop Service Flattener work with this scope and focuser or will I need to add some adapters to make the connection?Question by: Karl Zimmerman on Oct 8, 2016 4:45:00 PMThe TS-RCKORREKTOR is 2" in diameter and will slide right into the focuser like a 2" nosepiece. You will need M48 threaded adapters (2" OD) to get the distance from the flattener to your camera's sensor to 109mm +/-2mm. Please contact us if you have questions on how to do this with your camera.Answer by: Chris Hendren (Admin) on Oct 28, 2016 2:39:00 PMShould I be aware of any issues mating this scope with an Orion Atlas EQ-G (manual states 40 lb limit)?Question by: vince allen on Aug 22, 2015 6:35:00 PMThis telescope has D-series dovetails (4" wide with 2.96" rails), so you will need to have the upgraded saddle from Orion or ADM to accept the wider dovetail. You will also need a minimum of 3x 11lb counterweights and will need to shield the telescope from the wind as you are very close to the upper limit of what the mount can carry.Answer by: Chris Hendren (Admin) on Aug 23, 2015 12:51:00 PMI 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?
Thanks.Question by: andy on Aug 20, 2015 3:58:00 PMThe back focus of this scope at f/8 is 235mm from the rear M117 thread on the rear of the scope. There are no f/5 focal reducers that work with this scope, and the 0.75x TPO is a reducer but not a corrector so it will only work with sensors up to 15mm diagonal. The AP CCDT67 is a good option and can be used at 0.67x-0.75x with image circles of up to 29mm at 0.67x.
Reducers almost always pull the focal point inward, usually based on the optical distance between the lens and the focal plane divided by the change in magnification and then that total subtracted from the current optical distance. A CCDT67 reducer at 0.67x would have an optical spacing of 101mm, and so (101/0.67x) - 101 = ~49mm, meaning that the focal plane would move inward by ~49mm with this configuration compared to f/8 spacing.Answer by: Chris Hendren (Admin) on Aug 20, 2015 4:24:00 PM
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