MegaMOAG Off-Axis Guider

MOAG means Manual Off-Axis Guider, a non-moving part of your optical train. 

The MegaMOAG™ is the largest member of our off-axis guider product line.  It is specifically designed to accommodate the larger CCD detectors (36 x 36 mm), such as the Kodak KAF16803E and KAF9000E used on larger telescopes with 4" accessories and extension tubes. It is a 4"-to-3" version of our popular  MonsterMOAG™, where the camera side accepts all 3" MonsterMOAG™ adaptors.  Furthermore,  it retains the thin 1.25" backfocus of  MonsterMOAG™, and is an ideal choice for systems having minimal backfocus such astrographs made by Dream Telescopes. It also integrates nicely with the 4" systems at the back of larger RC Optical Systems Ritchey-Cretien telescopes.  


  • For largest CCDs (KAF16803, KAF9000)
  • Smallest backfocus 1.25"
  • 4" opening on the telescope side
  • 3" opening on the camera side
  • Guide in front of your filters
  • More guide stars with unfiltered light
  • Guide in the main optical beam
  • Avoid differential flexture and cost of guide scope
  • Fixed guider position for automated data acquisition


  • Solid body (1.25" backfocus) for no flexure for the heaviest cameras
  • Helical focuser for easy focusing of guide camera
  • Short, manual 1.25" camera holder also included
  • Additional prism spacers included
  • These provide maximum flexibility to come to focus
  • 4 1/16"-24 Male dovetail adapter  (0.2" backfocus) for telescope side included*
  • 2.7"-24 Female dovetail adaptor included  (0.1" backfocus)
  • Female 2.7"-24 also has 3"-24 Male threads for CFWs
  • Dovetail connectors to align with camera / telescope
  • Low reflectivity inner surfaces
  • Wide variety of camera side adaptors

*We are now supplying our MegaMOAGs with a 4 1/16"-24 male threaded adapter that fits the current RC Optical Systems (RCOS) 100 mm systems.  Initially our adapters were made as 4"-24 based upon early protoype RCOS tubing that is no longer used.  If you want the 4"-24 instead of the 4 1/16"-24 adapter, please add a note to your online order.


For those requiring multiple guide ports, Astrodon introduces the MegaMOAG-Dual.  We place identical pick-off assemblies on opposite sides.  We supply extra prism spacers and an additional short 1.25" nose cup for the second port.  The same 4" and 3" adaptors as in the MegaMOAG are included.

MoAG and MonsterMOAG are registered trademarks of Astrodon Imaging


MegaMOAG Schematic

Adaptor Details

MegaMOAG Installation Video

New Way to Attach Guider to Helical Focuser

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MegaMOAG-Dual™ (MeMOAG-Dual)


Adaptor - 3" Male, 3/4" long for CFW (MMOAG-3-L)


Adaptor - 2" Male 3/4" long for STL (MMOAG-STL-L)


Adaptor - T-thread 3/4" long for ST (MMOAG-ST-L)


Adaptor - T-thread 0.1" long for ST (MMOAG-ST-S)


Adaptor - 2" Male 0.1" long for STL (MMOAG-STL-S)


Adaptor - M 2.7" spacer 0.2" long (Spacer27)


Adaptor - 4" Male 3/4" long (MMOAG-STL-S)


Adaptor - M/M CFW - AP/Male 3"-2.7" (CFW-APM)


Adaptor - TAK CAA- AP 2.7" Female 1/2" long (CAA-APF)


Eyepiece extender (MOAG-EYE)


Lens f/-250 (Lens-250)


Stop Ring (Stop_Ring)