TPO 8" f/4 Imaging Newtonian OTA - Rolled Steel

TPO 8" f/4 Imaging Newtonian OTA - Rolled Steel
Item # OS-8IN
  • Very fast f/4 focal ratio 8” Newtonian reflector optics provide wide field views of the universe...perfect for imaging with your choice of equipment, from a small webcam to a large sensor CCD camera.
  • The 8" f/4 Imaging Newtonian from TPO has a low vibration cooling fan installed in the primary mirror cell to help your telescope reach ambient temperature quickly, and the interior of the tube is painted matte black to eat up stray light.
  • Push-pull collimation knobs on the heavy-duty center-spotted primary mirror cell are easy to adjust without tools.
  • This Newtonian's OTA is made from rolled steel and is painted white.


About Third Planet Optics (TPO) Imaging Newtonian Telescopes…

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 Imaging Newtonian line of telescopes! All of our Imaging Newtonian optical tube assemblies, offered in apertures from 6" - 12", 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% 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" 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" compression ring adapter for use with 1.25" eyepieces, and a 35mm 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 finderscope. The ocular has a non-illuminated crosshair and has 13mm 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.

Third Planet Optics 8" f/4 Imaging Newtonian Highlights…

  • Aperture: 8"
  • Focal Ratio: f/4
  • Focal Length: 800mm
  • White rolled steel exterior, flat black interior for higher contrast
  • 2" dual-speed 10:1 linear Crayford-style focuser with 35mm extension & 1.25" adapter
  • Dual hinged rings with Vixen-style dovetail
  • Cooling Fan included.
  • Push/pull oversized collimation knobs for easy adjustments
  • Weight: 16 lb.

Additional Information

Additional Information

Manufacturer TPO
Telescope Series TPO Imaging Newtonian
Optical Design Newtonian Reflector
Mount Type None - Optical Tube Only
Warranty 2 Year Warranty
Telescope Aperture 8"
Telescope Focal Length 800mm
Telescope Focal Ratio f/4
Optical Tube Outer Diameter 9.25"
Length of Optical Tube 28.5"
Optical Tube Weight OTA is 16 lb., 20 lb. with all accessories
Optical Coatings Aluminum
Tube Color or Finish Gloss White
Limiting Stellar Magnitude 14
Diagonal Included? No - Not Required
Finder Included 8 x 50 Optical Finder
OTA Mount Type Dual Rings

Customer Reviews 2 item(s)

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. Review by jwaters125 / (Posted on 12/21/2014)
Great Imaging Scope
Excellent for imaging, especially at this price. Can't go wrong here!
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Chunky Monkey / (Posted on 6/18/2013)
Included Items

Included Items

  • TPO 8" f/4 Imaging Newtonian with Steel OTA
  • 2" Dual Speed TPO Crayford Focuser w/1.25" Adapter
  • 35mm Extension Tube - 2"
  • Dual Hinged Rings
  • Vixen Dovetail
  • 8X50 Crosshair Straight Thru Finder - White
  • Finder Bracket & Dovetail Shoe
  • Battery Box for Fan with 60" cord
  • Mounting Hardware
  • Hex Wrench for Screws
  • Dust Cap
Questions & Answers

Product Questions

Is this telescope also acceptable for visual use?
I have the Orion Sky view Pro mount will the Vixen dove tail work on my existing mounting
I know it meets weight specifications
The primary mirror has 6 same shape/size knobs on the back (3 black and 3 white). Which are the locking knobs and which are the alignment knobs? Suggest a short instruction about the scope be available as a download or in the box.
Does this telescope have internal light baffling rings?
Support / Downloads