Astronomy Specialist

ZWO EFW 5 x 2" / 7 x 2"


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ZWO developed two filter wheels for 2" filters. Cameras with large sensors such as the ASI 6200 require 2" filter to avoid any vignetting.

These electronic filter wheels are CNC machined and they have an optical thickness of only 20mm.

There are two models available:

  • type 1: 5 filters x 2″ mounted 
  • type 2: 7 filters x 2" mounted

The power absorption of the EFW is only 120mAh @ 5V so any USB cable can power it up. The distance between the filter and sensor of the ASI 6200 is only 18 mm. 

Unmounted filters with a diameter of 50.4mm ± 0.5mm can be used in both filter wheels. 

Mounted filters from third-parties producers can be used but they have to meet the following requirements:





    This off axis guider is specifically designed for the ASI 6200 cameras. The combination ASI6200MM Pro camera (12.5mm)+ 2”EFW(20mm)+ M68 OAG(17.5mm)+ sensor tilt adapter(5mm) result in a total backfocus of 55mm.

    1. Remove the 5mm tilt adapter using a screwdriver

    2.  Remove the cover of the EFW 2"

    3. Disassemble the filter wheel carousel (Note: Please do not disassemble or move the central screw of this carousel, otherwise the EFW will be damaged):

    4) Align the four screw holes of EFW with these in the four corners of the camera chip as shown below:


    5. Tighten the screws at the interface between the EFW and the main camera:

    7) FConnect the M68 OAG to the back cover of EFW(Note: You may need to reposition the prism to make sure it would not block the sensor):


    8) Connect the 5mm sensor tilt adapter to this M68 OAG:

    9) Reconnect the  the back cover of EFW:

    10) Installation completed:


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