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.
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Designed to avoid back-clipping issues commonly seen when pairing filter wheels + OAGs across different camera ecosystems
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Configurable total thickness: 16.5mm / 17.0mm / 17.5mm to hit backfocus targets without creative spacing hacks
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Double-helix focusing mount does two jobs:
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Multi-brand filter wheel compatibility thanks to multiple mounting hole patterns
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Strong emphasis on light blocking and sealing between the OAG, adapters, and filter wheel—designed to reduce internal reflections and light leaks
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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”)
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The prism pillar uses M28.5x0.6 external threads, matching the common M28.5x0.6 internal thread found on many guide cameras
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You can raise/lower the prism using the dial on the double-helix mount:
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6mm total travel per full dial rotation
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1mm per large graduation (0–5 markings)
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0.05mm per small graduation (20 subdivisions per 1mm)
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Start position reference: with travel set to minimum and prism fully down, distance from prism front edge to optical axis center is 8mm
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Adjustments can be made fully assembled on the scope, even at night, without breaking the imaging train
Specifications
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Product type: Off-Axis Guider (OAG), M48 system
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Prism size: 8mm x 14mm
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Prism coating: Anti-reflective coating on both sides
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Configurable thickness: 16.5mm / 17.0mm / 17.5mm
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Telescope-side thread options: Supports M68x1 / M54x0.75 / M48x0.75 via interchangeable couplings
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Each thread set includes 3 coupling thicknesses: 4.5 / 5.0 / 5.5mm
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Kit includes one set of couplings (thread type specified as M68, M54, or M48)
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Focusing/prism adjustment mechanism: Double-helix focusing mount
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Guide camera interface (common standard): Prism pillar front uses M28.5x0.6 external thread
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Filter wheel compatibility (as provided): MokKong / Ready Player One / QHYCCD / TuPu (Graph) / Zhenwang
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Light sealing features: O-ring recesses, plug-able unused threaded holes, extension ring grooves for sealing
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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?
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AstroAsis Oasis OAG body (M48 system)
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Prism assembly (8mm x 14mm, AR-coated)
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Double-helix focusing mount (guide camera focus + prism height control)
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One set of telescope-side threaded couplings (choose/specify thread: M68, M54, or M48)
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Set screws / hardware provisions for plugging unused mounting holes (for light leak prevention)
Software and Docs
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.
