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TPO 6" f/9 Ritchey Chretien Reflecting OTA Telescope


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  • No Chromatic Aberration
  • Coma-Free
  • Long back focus of 230mm
  • Fixed Primary to eliminate mirror flop
  • Knife Edge Baffling System to improve contrast

Product Details

  • Based on George Willis Ritchey and Henri Chretien optical design, the TPO 6" f/9 Ritchey Chretien Reflecting OTA Telescope is a versatile astrograph that can also be used for visual use. The RC Design contains a Hyperbolic shaped primary and secondary mirror to eliminate coma, chromatic aberrations, and spherical aberrations. For expert or professional astronomers interested engaged in scientific study, this telescope makes an excellent choice for astrometric measurements. Rear cell thread size is M90x1.

    TPO 6" f/9 Ritchey Chretien Reflecting OTA Telescope Highlights

    • No Chromatic Aberration: a Ritchey Chretien doesn't use lenses or corrector plates, the design doesn’t suffer from chromatic aberrations ( false color).
    • Goodbye Coma: an RC has virtually no coma
    • No Spherical Aberration: The use of hyperbolic mirrors for both the primary and secondary removes the problem of spherical aberration.
    • Long Back Focus: 150mm from the focuser or 235mm from the rear thread allows you to mount lots of imaging gear.
    • Fixed Primary: eliminates image-shift/mirror-flop and removes the need to collimate the primary mirror.
    • Knife Edge Baffling System: computer designed and optimized baffle system prevent internal reflections and boost contrast.


    Specifications with Optional Reducers

      • Product Number: OS-FRRC-75
      • Effective Focal Length: 1028mm
      • Effective Focal Ratio: f/6.8
      • Resulting Image Circle: 15mm
      • Reducer Backfocus: 80mm
    • Reducer: Astro-Physics CCD Focal Reducer for f/9-f/18 Telescopes
      • Product Number: AP-CCDT67
      • Effective Focal Length: 918mm-1069mm
      • Effective Focal Ratio: f/6.-f/7
      • Resulting Image Circle:  29.5mm-34.3mm
      • Reducer Backfocus: 67mm-101mm
      • This reducer has different effects based on the spacing between the camera and the reducer. If you need assistance figuring this out, you can refer to the Astro-Physics 27TVPH and CCDT67 Compression & Coverage Document or contact us.


    Accessories Included in the Box

     Here are the adapters and accessories included from TPO when you purchase the TPO 6" f/9 Ritchey Chretien Reflecting OTA. They are listed in the same order that you would attach them to the rear threads of the telescope:

    • Two TPO 25MM Spacers for 6" RC (OS-TPORC-25MMSP)
    • TPO 50MM Spacer for 6" RC (OS-TPORC-50MMSP)
    • TPO LRS Crayford Focuser for Ritchey Chretien Telescopes (OS-CF-LRS)
    • TPO 2" to 1.25" Adapter (OS-A2125)

    It can be challenging to figure out which adapters and other accessories you need in order to use your TPO 6-Inch RC visually or photographically. Below you will find several lists that should help make that task a whole lot easier! Links to suggested or required products will be included when applicable so that you can read more about an item and easily add it to your cart. If you have any questions or concerns, feel free to give us a call, start a chat, or send us an email.


    Attaching the TPO 6" Ritchey Chretien to a Mount

     The TPO 6-inch RC comes with a preinstalled Vixen-style dovetail bar which will allow you attach the telescope smaller Bresser, Celestron, iOptron and Vixen telescope mounts. If you mount uses a Losmandy-Style saddle, we recommend using theADM D Series Dovetail Bar for 6" OTA's.


    Using the TPO 6" Ritchey Chretien Visually

     Below you will find two accessory chains that you can follow if you want to use this telescope visually ending in a 2” or 1.25” diagonal.


    Canon EOS, Nikon, Or Sony E-mount DSLR Imaging

    Below you will find the accessory chain that you can follow if you want to use this telescope with a Canon, Nikon, or Sony E-mount APS-C sized DSLRs. Items in the chain that are included as standard accessories are marked as such, otherwise, each piece will be linked to the accessory on our website. Items are listed in the order you would attach them to the telescope.


    Imaging With a Dedicated CCD or CMOS Telescope Camera

    Below you will find the accessory chain that you can follow if you want to use this telescope with a dedicated astronomy imaging camera. Items in the chain that are included as standard accessories are marked as such, otherwise, each piece will be linked to the accessory on our website. Items are listed in the order you would attach them to the telescope.

      • With Astro-Physics CCD Focal Reducer for f/9-f/18 Telescopes
        • Two TPO 25MM Spacers for 6" RC (Included)
        • TPO 50MM Spacer for 6" RC (Included)
        • TPO LRS Crayford Focuser for Ritchey Chretien Telescopes (Included)
        • Astro-Physics CCD Focal Reducer for f/9-f/18 Telescopes
        • The spacers that you will need will depend on several factors, how much you want to reduce the focal length by, how big is your camera sensor, the back focus of your camera, are you using an OAG etc. Generally, we recommend using the TPO M48 Spacers first then use an adapter to reduce down the thread size to get the correct spacing.

      The suggestion above is not the only solution for attaching a dedicated camera. You can a log of accessories in your imaging-train like an adaptive optics unit, field rotator, off-axis guider, or on-axis guider. If you plan on incorporating one of these accessories or still have questions about the adapters you need for your application, we recommend that you contact us. We would be more than happy to help.

    • specifications

      Aperture152 mm (6")
      Back Focus235mm
      Camera/Eyepiece Connection2" nosepiece
      Dawes Limit0.76 arcseconds
      Focal Length1370 mm
      Focal Ratiof/9
      Free ShippingYes
      Glass TypeQuartz
      Highest Magnification304x
      Limiting Magnitude14.7
      Optical DesignRitchey Chretien
      Secondary Obstruction67mm
      Tube Diameter191mm
      Tube Length485mm
      Tube Weight12.3 lbs
      Warranty2 Year Warranty
    • included items

      • Two TPO 25MM Spacers for 6" RC (OS-TPORC-25MMSP)
      • TPO 50MM Spacer for 6" RC (OS-TPORC-50MMSP)
      • TPO LRS Crayford Focuser for Ritchey Chretien Telescopes (OS-CF-LRS)
      • TPO 2" to 1.25" Adapter (OS-A2125)

    Product Reviews

    Customer Reviews
    4.2 Based on 9 Reviews
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    Filter Reviews:
    Blaine H.
    United States United States
    After 3 years I still love it.

    This has been my primary imaging telescope for several years now. I must admit I am still learning how to use it (and when I do I will probably buy up to an 8"). The 1370 mm focal length is good for most small and medium sized objects and with guiding the f 9 focal ratio is fine. Collimation has never been a problem as mine arrived in good collimation and recollimating was simple. The focuser has worked well with my DSLR and I use an old 500 mm mirror lens as a guide scope. I have other telescopes for visual.

    United States United States
    Solidly Built R/C Scope

    Unfortunately, I have not had time to use the scope so I can't comment on it's optical capabilities yet (sorry). What I can say it that this is a very well built optical tube assembly. It is well assembled and well painted. It looks and feels very nice. I am quite happy with this so far!

    Steve R.
    United States United States
    A book would be nice.

    When I picked up the telescope from the box, the focuser just banged in and out of the tube. There are NOT any gear teeth on the focuser. How is it supposed to work??? I don't think I would have picked this one if I had know how it was made. Maybe after I learn how to make it work I might change my rating. I really thought the focuser would have a rack and pinion to move it. I just looked at it and it looks like it is a polished steel 1/8th inch shaft pressed against the smooth aluminum of the focuser. REALLY, I am not happy right now... And to top it all off, by the time it was delivered the seller was closed for three days. PS I even looked inside the scope for the book, but nothing there either. I added a star since trying it out. I would give it five start if it came with a one page instruction about the focuser. I had never seen a Crayford focuser before this and did not know what to expect.

    United States United States
    A great addition to my APO refractors ...

    I got this TPO Ritchey-Chretien telescope from OPT a few months ago, and I could not be happier. I had used, and still have an Explore Scientific ES102 and ES80 APO refractors. I was quite happy with the astrophotography images the refractors gave me. But the TPO RC-6 took the magnification, and resolution up to a great new level. And perhaps what I like the most is the flat field of the images without the need for a field flattener. I know a lot of people are unsure about RC style scopes due to collimation horror stories and complicated tools. But, after a lot of research, I simply got a $30 Celestron collimation eyepiece and used it once. It basically let me set the collimation in the ball park. But the method that works perfectly every time, in 10 minutes or less, is the "star test". In the star test, you simply set the scope to look at a reasonably bright star overhead. Then you back the focus back away from the scope until the out of focus star looks like a big doughnut with a cross hair in the center. Align the three screws on the front of the scope's secondary meter a slight turn at a time until you move the inner dark circular region of the doughnut to be concentric to the outer circle. This is best done with an attached DSLR screen pointing toward the front of the scope so you can see your adjustments' effects ... or to let your astro camera show you the same thing on your computer's screen, while adjusting the screws. While looking at the out of focus "doughnut" image, place your hand slightly over the front edge of the scope until you see your hand's blurred shadow on the screen's image. Move your hand around the front side of the scope until it is over the "fat" portion of the "doughnut". That's the point where the center dark circle close to the center is farther away from the outer circle edge. Then find which one of the three adjustment screws on the front of the secondary mirror is closest to where your hand is. Adjust that screw (in or out) using very slight turns (1/8th of a turn or so at a time) until the dark inner circle is most concentric with the doughnut. (Don't adjust a screw too tight inward ... If you run out of threads while tightening, loosen one of the opposite side screws instead to accomplish the same thing.) As the dark circle shifts, reposition your hand as needed and adjust other screws closest to your hand as needed. WARNING: Don't touch the center screw on the secondary mirror.WARNING: And never use the 4mm hex wrench to adjust the screws without strapping it to your wrist. You don't want to drop it down the tube and onto your mirror. This procedure has given me absolutely beautiful pinpoint stars and collimation every time I've used it. A bit of a hassle ... but absolutely worth it ... at roughly 10 minutes per night. As a side note, make sure the TPO RC 6 you receive has the LRS focuser on the scope as the OPT website page says it will. To my knowledge OPT is the only vendor selling the RC 6 with the much stronger and more stable LRS focuser. Thanks OPT for, yet again, being the best supplier for all my astrophotography needs. (Sorry for the extensive write up ... too much coffee.)

    Tom H.
    United States United States
    A real “RC” scope

    Wife turned the Crawford focus know and was heard a block away exclaiming “WHAT”. That smooth hardware impressed her and examples all the threads and construction of the unit. AND the bloody images for photo work are heavenly (sorry about the pun). Saving for a BIG one now. I have lot to compare it too, this is more resolution and sharpness for the buck.

    mike i.
    Good optics bad focuser

    The scope is attached to my Ioptron CEM25 , used it visual and with a canon 6d. It is hard to get in focus because of the lousy focus mechanism, real jerky even though the scope is new. I am getting a linear bearing focuser from gso to put on it. Hopefully that will cure the problem. if the focuser was upgraded I would give it 5 stars.