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TPO 10" f/4 Newtonian Reflecting OTA Telescope


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  • Aperture: 10-inches
  • Focal Ratio: f/4
  • Focal Length: 1016 mm
  • White rolled steel exterior, flat black interior for higher contrast
  • Cooling Fan included
  • Dual hinged rings with Vixen-style dovetail

Product Details

  • If you are looking for a telescope that does a great job of imaging but doesn't come with the cost of a Ritchey Chretien, check out the Third Planet Optics (TPO) Imaging Newtonian line of telescopes! All of our Imaging Newtonian optical tube assemblies, offered in apertures from 6- inch to 12-inch, have very fast optics for the widest fields possible. Image with a DSLR or small webcam all the way up to large sensor CCD cameras with these inexpensive yet effective Newtonians.

    The optics on all TPO Imaging Newtonians consist of a parabolic primary mirror and an elliptical secondary, or diagonal. The mirrors are made from B270 white water optical crown glass, which is more thermally stable than glass traditionally used on other reflectors. A 91-percent aluminum coating is applied, and then over-coated with a layer of quartz for the ultimate in durability. The primary mirror cell is very sturdy, and has six collimation knobs that can be adjusted by hand with a push or pull of the knob. Collimation is made even easier due to the center spot marked on the primary mirror. The diagonal mirror is held in place with a thin four-vane spider.

    The optical tube assembly on the TPO Imaging Newtonian telescope is made of rolled steel and painted white. The ends of the tube are die-cast aluminum, which contribute to the OTA's rigidity. Steel is a bit heavier than traditional aluminum, but since it has a lower coefficient of thermal expansion, your telescope will tend to hold its shape (and therefore, hold focus) as temperatures fluctuate throughout the night. The inside of the OTA is painted in a matte black finish, which stops stray light in its tracks.

    A low vibration cooling fan is built into the primary mirror cell of the telescope to assist in cooling your optics down quickly. The fan is powered by a eight (8) AA batteries (not included) which are housed in an external battery pack.

    A 3.3-inch dual-speed 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 3.3-inch opening steps down to a 2-inch compression ring adapter, and you will receive 1.25-inch compression ring adapter so that you can make use of all your eyepieces. A 35 mm 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.

    The telescope comes with dual split-hinged mounting rings that are made of die-cast aluminum and felted on the inside to cradle the OTA without scratching. There are threaded holes on the underside of the rings that allow installation on either a Vixen-style (included) or Losmandy-style dovetail plate. The top of the rings is also drilled so that you can mount accessories.

    All TPO Imaging Newtonians come with an 8x50 straight-through finderscope. The ocular has a non-illuminated crosshair and has 13 mm of eye relief. A quick-release mounting bracket is also included.


    OPT Product Number: OS-10IN


  • specifications

    Aperture254 mm (10")
    Camera/Eyepiece Connection2" Nosepiece
    Dawes Limit0.46 arcseconds
    Focal Length1016 mm
    Focal Ratiof/4
    Glass TypeB270
    Highest Magnification508x
    Light Gathering Power1317x
    Limiting Magnitude15.8
    Optical DesignNewtonian
    Secondary Obstruction70mm
    Tube Diameter303mm
    Tube Length1150mm
    Tube Weight29.3 lbs
    Warranty2 Year Warranty
  • included items

    • Aperture: 10-inches
    • Focal Ratio: f/4
    • Focal Length: 1016 mm
    • White rolled steel exterior, flat black interior for higher contrast
    • Cooling Fan included
    • Dual hinged rings with Vixen-style dovetail

Product Reviews

Customer Reviews
4.7 Based on 3 Reviews
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Morris Y.
United States United States

Not perfect, but close

I have been using this OTA for over a year now. It has served me well. I've paired it with a TV Paracorr and have been using it for astrophotography. I can recommend it. Here are a few observations. 1. The price is right. It gives a lot of telescope for the money. No complaints here. 2. The edge of the mirror is imperfect (not unusual). I 3D printed a mask to cover up the rough outer edge of the primary. This also hides the mirror clips from the light path and gives a smoother halo of scattered light around my stars. 3. The focuser works well. It's solid enough to hold my QHY168C camera and Paracorr without issues. I've been able to pair it with an autofocuser from ZWO to focus remotely and precisely. 4. The cooling fan needs to be used carefully, if at all. I've noticed a change in focus when the fan is being used. If I happen to use it, I have to give it a few minutes for the focal point to stabilize. 5. The collimation process is straightforward and not too difficult. 6. The spider vanes that hold the secondary were not all pointing directly away from center. Some of the diffraction spikes in my images were doubled up as a result. I loosened the nut holding the vane closest to the focuser then shaved and tightened the nut farthest away from it. This gave me a perfect + shape and fixed the problem with the diffraction spikes. 7. The images through the scope tell the final story. The large aperture can capture amazing detail.

OPT Telescopes TPO 10 f/4 Newtonian Reflecting OTA Telescope ReviewOPT Telescopes TPO 10 f/4 Newtonian Reflecting OTA Telescope ReviewOPT Telescopes TPO 10 f/4 Newtonian Reflecting OTA Telescope ReviewOPT Telescopes TPO 10 f/4 Newtonian Reflecting OTA Telescope Review
Daryl M.
United States United States

Beyond GREAT for Views and Photos

Over half a century of telescopic viewing provided experience from a child's 60mm draw-tube to Palomar's cage. Like all serious sky scanners, I struggled with aperture fever. Hunting for the instrument yielding hoped-for, breath pausing resolution is a seriously formidable process when absent wealth. Fortunately, such quality instruments today are readily available through better market sources such as OPT. I must commend them for this product offering. You receive what you see: an OTA complete with the now-standard primary fan; a nice Crayford focus system (the 10:1 micro-focus ultra-defines beautifully); deep inset secondary locus for contrast enhancement equivalent to flocking; and nicely portable for either storage or travels [This IS a mirror set you will want to realize in dark sky, low LP setting]. For those who have been working with 200 mm and below, the additional 50 mm's with this FL4 primary provides exciting resolution that literally yields definition to most here-to-fore gray smudge images to details yet seen. For example, M13, the great Hercules closed-cluster, is seen in its glory with separation and definition of the stars themselves. Same for the Swan and Trifid nebulae with a relieving definition of the actual shapes and separations, even defined gas cloud subtleties. That extra 2" of diameter is the doorway to such observations. This particular F4 mirror is top-notch in design and coating, provides very sharp detail discerning ability. Pair this instrument with good objectives and filters, please. I recommend an LPR and lunar filter set (polarizers are really nice for lunar work); standard colors for planetary views are always very nice. You'll find that other than lunar viewing, most will work within the 14 to 40 mm objective range. The Orion Nebula system was (for me) so perfectly portrayed using a 2" 20 mm erfle. You'll lose time when trapped by the sublte definition. Pardon the verbosity but this is an instrument requiring real experiences provided as well as allowing those newer to the study to know the system that will answer their viewing desires. Besides, it is an exciting scope and felt the need to share a little of that. Daryl

United States United States

Haven't actually been able to use it yet, too cloudy. I did get the telescope collimated, happy with that. I like the focuser it seems solid.