AstroAsis OAG (M48) Off-Axis Guider — Adjustable Thickness, Precision Prism Control, Filter Wheel Friendly

If you’ve ever built an imaging train and found out (at the worst possible moment) that your OAG + filter wheel combo causes back-clipping or awkward assembly headaches, the AstroAsis Oasis OAG (M48) is basically your “thank you” note to future-you. It was designed specifically to solve the back clipping problem users ran into with different camera brands and third-party OAGs—then evolved into a surprisingly clever, highly configurable guider with precision prism control and excellent light sealing.

• Designed to avoid back-clipping issues commonly seen when pairing filter wheels + OAGs across different camera ecosystems

• Configurable total thickness: 16.5mm / 17.0mm / 17.5mm to hit backfocus targets without creative spacing hacks

• Double-helix focusing mount does two jobs:

  • Focus the guide camera

  • Precisely adjust prism height/position without disassembling your imaging train

• Multi-brand filter wheel compatibility thanks to multiple mounting hole patterns

• Strong emphasis on light blocking and sealing between the OAG, adapters, and filter wheel—designed to reduce internal reflections and light leaks

• Optional motorized guide camera focusing via the add-on kit (for remote/observatory users who don’t want to touch anything at 2 a.m.)

Precision prism adjustment (the “secret sauce”)

• The prism pillar uses M28.5x0.6 external threads, matching the common M28.5x0.6 internal thread found on many guide cameras

• You can raise/lower the prism using the dial on the double-helix mount:

  • 6mm total travel per full dial rotation

  • 1mm per large graduation (0–5 markings)

  • 0.05mm per small graduation (20 subdivisions per 1mm)

• Start position reference: with travel set to minimum and prism fully down, distance from prism front edge to optical axis center is 8mm

• Adjustments can be made fully assembled on the scope, even at night, without breaking the imaging train

Specifications

• Product type: Off-Axis Guider (OAG), M48 system

• Prism size: 8mm x 14mm

• Prism coating: Anti-reflective coating on both sides

• Configurable thickness: 16.5mm / 17.0mm / 17.5mm

  • OAG body thickness: 12mm

  • Uses threaded couplings of 4.5mm / 5.0mm / 5.5mm to reach total thickness options

• Telescope-side thread options: Supports M68x1 / M54x0.75 / M48x0.75 via interchangeable couplings

  • Each thread set includes 3 coupling thicknesses: 4.5 / 5.0 / 5.5mm

  • Kit includes one set of couplings (thread type specified as M68, M54, or M48)

• Focusing/prism adjustment mechanism: Double-helix focusing mount

  • Travel: 6mm per full rotation

  • Adjustment resolution: 0.05mm per small graduation

• Guide camera interface (common standard): Prism pillar front uses M28.5x0.6 external thread

• Filter wheel compatibility (as provided): MokKong / Ready Player One / QHYCCD / TuPu (Graph) / Zhenwang

• Light sealing features: O-ring recesses, plug-able unused threaded holes, extension ring grooves for sealing

• Special assembly benefit (7x2 filter wheel use case): Designed to avoid housing screws so disassembly/cleaning can be done without removing the OAG (specific to the mentioned 7x2" wheel scenario)

What’s in the box?

• AstroAsis Oasis OAG body (M48 system)

• Prism assembly (8mm x 14mm, AR-coated)

• Double-helix focusing mount (guide camera focus + prism height control)

• One set of telescope-side threaded couplings (choose/specify thread: M68, M54, or M48)

  • Includes 4.5mm / 5.0mm / 5.5mm thickness options

• Set screws / hardware provisions for plugging unused mounting holes (for light leak prevention)

Software and Docs

• None required (hardware OAG)

• Optional accessory: Motorized focusing kit (Mikkuri/MokkElectric-style kit) for motorized guide camera focusing via belt drive (ideal for remote setups)

Optional spacing note (from provided info): For short backfocus cameras (example given: QHY268), an optional 5mm extension ring can be placed between the OAG and filter wheel to meet backfocus requirements.