TPO 8" f/4 Newtonian Reflecting OTA Telescope

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  • Regular price $499.00

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TPO 8" f/4 Newtonian Reflecting OTA Telescope

The 203 mm (8-Inch) f/4 Imaging Newtonian Telescope by TPO: 


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 TPO (Third Planet Optics) Imaging Newtonian line of telescopes! All of their Imaging Newtonian optical tube assemblies, offered in apertures from 6-inches to 12-inches, 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 2-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. You will also receive a 1.25-inch compression ring adapter for use with 1.25-inch eyepieces, and a 35 mm extension tube to help you match the back-focus requirements of your imaging equipment. 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 finder scope. The ocular has a non-illuminated cross hair and has 13 mm of eye relief. A quick-release mounting bracket is also included, and a dovetail foot is already installed on the OTA for easy on-off.


OPT Product Number: OS-8IN

  • Aperture: 203 mm (8-inches)
  • Focal Ratio: f/4
  • Focal Length: 800 mm
  • White rolled steel exterior, flat black interior for higher contrast
  • Cooling Fan included
  • Dual hinged rings with Vixen-style dovetail


Aperture200 mm (8")
Camera/Eyepiece Connection2" Nosepiece
Dawes Limit0.58 arcseconds
Focal Length800 mm
Focal Ratiof/4
Free ShippingYes
Highest Magnification400x
Light Gathering Power816x
Limiting Magnitude15.3
Optical DesignNewtonian
Secondary Obstruction70mm
Tube Diameter235mm
Tube Length730mm
Tube Weight19.2 lbs
Warranty2 Year Warranty
Customer Reviews
5 Based on 2 Reviews
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Good Value for The Money

OK value for the money. Expect to upgrade the secondary alignment screws so that you can better align the optics. The springs on the primary mirror should also be upgraded so that alignment can be better maintained. If you are doing astrophotography with a heavy DSLR or CCD I would recommend that the focuser be upgraded too.

Chunky M.
Great Imaging Scope

Excellent for imaging, especially at this price. Can't go wrong here!