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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Orion Optics UK 85mm Fixed Adaptor Ring with 30mm BFD

Orion Optics UK 85mm Fixed Adaptor Ring with 30mm BFD

by Orion Optics UK
SKU OOUK-85MM-FIXED-ADAPTOR-RING-30MM
$141.11 - $141.11
$141.11
$141.11 - $141.11
$141.11
Price Match Policy!
  • Provides a fixed 30mm back focus distance
  • Designed for 85mm threaded interfaces
  • Solid, single-piece construction for maximum rigidity
  • Machined in the UK by Orion Optics
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Orion Optics UK 85mm Fixed Adaptor Ring with 30mm BFD

    The Orion Optics UK 85mm fixed adaptor ring is a precision-machined spacer that provides exactly 30mm of back focus distance (BFD), essential for building a rigid and accurate imaging train for astrophotography.

    Achieving a Fixed 30mm Back Focus with an 85mm Interface

    In astrophotography, achieving the precise back focus specified by a field flattener or reducer is critical for sharp stars across the entire frame. This 85mm fixed adaptor ring is engineered to provide exactly 30mm of spacing, eliminating the guesswork and potential flexure of adjustable systems.

    The single-piece design ensures a perfectly rigid connection between your components, preventing tilt that can ruin an otherwise perfect image. While it lacks the flexibility of variable spacers, its strength and precision make it the ideal choice when your required spacing is exactly 30mm.

    • Zero Flexure: The solid, fixed-length construction is inherently more stable than multi-part adjustable spacers, ensuring your camera sensor remains perfectly parallel to the focal plane.
    • Precise Spacing: Delivers a non-negotiable 30mm of distance, crucial for optical correctors that have strict back focus tolerances for optimal performance.
    • Large Aperture: The 85mm diameter provides a wide, unvignetted light path suitable for large format sensors when used with a compatible optical system.

  • What is the purpose of the Orion Optics UK 85mm fixed adaptor ring?

    This component is a precision spacer. It's designed to establish an exact 30mm distance between two parts of an optical train that use an 85mm thread, such as between a focuser and a camera setup. This is critical for achieving the correct back focus distance required by field flatteners or coma correctors.

    What does "30mm BFD" mean for my astrophotography setup?

    BFD stands for Back Focus Distance. Most optical correctors require the imaging sensor to be placed at a very specific distance to deliver sharp, aberration-free stars. This 30mm adaptor ring is used as a component to help achieve that exact total distance.

    Is this 85mm adaptor compatible with my specific telescope or camera?

    Compatibility is determined by the physical threads on your equipment. This adaptor is designed for an 85mm diameter threaded interface. You must confirm that the components you intend to connect both have matching 85mm threads before purchasing.

    Why should I choose a fixed 30mm adaptor instead of an adjustable spacer?

    A fixed adaptor like this Orion Optics UK ring offers superior rigidity and stability. It eliminates the potential for tilt or flexure that can be introduced by adjustable, multi-part spacers, ensuring a solid and square connection. The trade-off is its lack of adjustability; it is only useful when you need exactly 30mm of spacing.

    How do I calculate if the Orion Optics UK 30mm ring is the right spacer for my imaging train?

    First, identify the total back focus requirement of your flattener or reducer (e.g., 55mm is common). Next, add up the back focus contributed by your camera, filter wheel, and any other accessories. If the remaining distance needed is exactly 30mm, this adaptor is the correct component for your setup.

    Will this Orion Optics UK 85mm adaptor cause vignetting with my full-frame sensor?

    The large 85mm clear aperture of this ring is generally sufficient to prevent it from being the source of vignetting, even with full-frame sensors. However, vignetting is a property of the entire optical system, so final performance also depends on your telescope's focuser, corrector, and any other adaptors in the light path.

  • Interface Diameter 85mm
    Back Focus Provided 30mm
    Type Fixed Adaptor Ring / Spacer
    Manufacturer Orion Optics UK

    • 85mm fixed adaptor ring (30mm BFD)

      × 1

  • Orion Optics UK 1-Year Warranty