TPO 10" f/4 Imaging Newtonian OTA

TPO 10" f/4 Imaging Newtonian OTA
Item # OS-10IN
6 Questions(s)

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  • This big, fast Newtonian will do amazing things paired with a heavy-duty equatorial mount and your choice of imaging gear!
  • A 3.3" dual speed Crayford style focuser is strong and smooth, and comes with a 2" and 1.25" adapter plus a 2" 35mm extension for adjusting back focus.
  • A built-in low-vibration fan assists in cooling down your mirror and OTA, getting you to ambient temperature all that much faster so you can start imaging!
  • Dual split-hinge rings are drilled on top and bottom for versatility.
  • The interior of the telescope is painted matte black to eat up any stray light that might wander in.


About 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 Third Planet Optics (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 3rd Planet Optics 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" 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" opening steps down to a 2" compression ring adapter, and you will receive 1.25" compression ring adapter so that you can make use of all your eyepieces. A 35mm 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 13mm of eye relief. A quick-release mounting bracket is also included.

TPO 10" f/4 Imaging Newtonian Highlights…

  • Aperture: 10"
  • Focal Ratio: f/4
  • Focal Length: 1016mm
  • White rolled steel exterior, flat black interior for higher contrast
  • 3.3" dual-speed 10:1 linear Crayford-style focuser with 35mm extension, 2" & 1.25" adapter
  • Dual hinged rings with Vixen-style dovetail
  • Cooling Fan included.
  • Push/pull oversized collimation knobs for easy adjustments
  • Weight: 29 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 10"
Telescope Focal Length 1016mm
Telescope Focal Ratio f/4
Optical Tube Outer Diameter 257.1mm
Optical Tube Weight 29 lbs.
Optical Coatings Aluminum
Tube Color or Finish Gloss White
Limiting Stellar Magnitude 14.5
Diagonal Included? No - Not Required
Finder Included 8 x 50 Optical Finder
OTA Mount Type Dual Rings
Included Items

Included Items

  • TPO 10" f/4 Imaging Newtonian OTA
  • 3.3" Dual Speed Crayford Focuser with 2" & 1.25" eyepiece adapters
  • 35mm Extension Tube - 2"
  • 8X50 TPO Finder - White
  • Finder Bracket
  • Two Split Hinged Rings Drilled to Accept Dovetails
  • One Vixen-style Dovetail
  • Battery Box for Fans
  • Hex Wrench for Screws
  • Dust Caps
Questions & Answers

Product Questions

What is the size of the image circle?  Is it compatible with full-frame DSLRs?  If so, what accessories are required to allow such use? 
How much backfocus is available for this telescope with the various adapters?
What ASCOM focus motor will work with the focuser on this telescope?
Several questions about the tube itself: First, is the inside of the tube baffled or just painted? Second, the specification tab says the OD of the tube is 257.1mm, which (allowing for a nominal wall thickness for the tube) would suggest the ID of the tube is something like 254 or less. But if the mirror is truly 10 inches (or 25.4mm), then the mirror alone is 254mm, so I question the correctness of the stated OD unless the mirror is really much less than 10 inches. Third and finally, how long is the OTA and how far beyond the centerline of the focuser does the tube extend?
I see that this is primarily an astrograph. I do plan on using with my DSLR, but would this scope be appropriate for general optical viewing as well with my son?
Hello! Question: is it right to say that this telescope is an astrograph? If not, what kind of accessories do I need for astrophotography to fit and focus my Canon 600D to get the images?
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