William Optics Flattener 4 - 0.8X Reducer

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William Optics Flattener 4 - 0.8X Reducer
Item # WO-P-FLAT4
  • This William Optics AFR-IV Flattener is made for refractors with a focal length of 500mm - 1000mm.
  • The AFR-IV, also called the Flattener 4, fits into 2" focusers and has a built-in rotating T-ring adapter which accepts any standard camera T-ring.
  • The lens-to-sensor distance range on the William Optics AFR-IV Flattener is 66-86mm, and the clear aperture is 54mm.
  • The William Optics Flattener 4 is made with Ohara glass and is Super Transmission Coated.


William Optics Flattener 4 - AFR-IV

The revolutionary William Optics AFR-IV Adjustable Flattener and (0.75x-0.8x) reducer is made for 500-1000mm refractors, including the William Optics FLT98, FLT110, FLT132, and others. This 2-element, 2" is black-anodized for durability and beauty. All internal surfaces are blackened to eliminate reflections.

The WO AFR-IV Flattener has a rotating t-ring thread that will accept any standard t-ring for your camera. The included T-ring adapter comes with a locking screw and extra retaining screws. This field flattener inserts directly into a 2" focuser. It is easy to set the optimum back focus distance...just twist.

William Optics AFR-IV Flattener Highlights...

  • The lens is designed to cover full size DSLR cameras with a clear lens aperture of 54 mm
  • The WO Flattener 4 has an excellent air-spaced doublet design with STM coatings, and is made with the best Ohara optical glass.
  • Superb William Optics anodized finish.
  • All internal surfaces are threaded and blackened.
  • Rotating T-ring thread for any 35mm camera. The T-ring adapter is provided with a lock screw and extra lock retaining screws.
  • Will accept any standard T-ring for your camera.
  • Inserts directly into 2" focuser.
  • Lens-to-chip distance : 66-86mm
  • 0.75x-0.8x Reducer
  • Rotating T-ring adapter
  • Clear Aperture : 54mm
  • L 84mm : W 95mm : H 144mm
  • Weight : 595 g
Additional Information

Additional Information

Manufacturer William Optics
Barrel Size 2"
Warranty 2 Year Warranty

Customer Reviews 1 item(s)

The Quality Standard of Service
The FLAT-4 focal reducer did not work on my ES102 apo. However, Chris Hendren, the OPT imaging specialist, gave me a thorough clinic on how reducers work with just enough technical information so that I could understand. He had suggestions which I tried but ultimately it was just an equipment mismatch. I had worked with the product for more than 30 days so knew my right to a refund was forfeit. OPT gave me an RMA for store merchandise minus a 10% restocking charge . When I sent it back, though, the full purchase price showed up as a refund on my credit card. This is a great company that will go to those lengths for their customers. I would recommend OPT without reservation, and look forward to more purchases in the future.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by exmedia / (Posted on 9/5/2014)
Included Items

Included Items

  • William Optics Flattener 4 - AFR-IV
  • Rotating T-Ring Adapter
Questions & Answers

Product Questions

I have a William Optics FLT 110, wich flattener is better for it? This one or the WO flattener 68II? Another question, the thread for the T-ring is m42 or m48 in the flattener 4? Thank you.
Is there a 2" filter thread on a barrel side? Thanks
Do you know if this will work on an Astro-Physics 130 GT with a focal length of 819mm?
I am imaging with a Canon 60Da DSLR.

I have a TS120 mm 900mm f7.5 telescope and a Televue TV-76 I use with an Atik infinity camera. My question is how does one calculate the adjustable focus distance the flattener 4 should be adjusted to? Is there a formula to use? I think the Atik Infinity has a 13mm distance from chip sensor to coupling ring.
Will this work with Orion EON 120mm (900mm focal length with 7.5 focal ratio) and QSI583 WSG CCD?
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