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:
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type 1: 5 filters x 2″ mounted
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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:
The EFW 2" filter wheels come with darkening rings intended to prevent light leaks due to the small gaps between the filter wheel and camera or OAG. The below diagram shows where to install them: