The ZWO D90 Darkening Ring Set for the ZWO ASI461MM-P camera (manufacturer: ZWO; SKU: ZWO DR-D90) consists of two thin rings designed to optically seal connections in an astrophotography setup using the medium-format ASI461MM-P camera, also referred to as the ASI461MM Pro.
The rings cover gaps between the flanges of connected devices, reducing the possibility of unwanted light entering the optical path. Each component has an external diameter of 90 mm, a 72 mm internal opening and a thickness not exceeding 0.2 mm.
The manufacturer's installation diagram shows the rings being used in a configuration comprising a ZWO ASI461MM-P camera, an EFW-7x50 filter wheel and an OAG-L68 off-axis guider. The rings are placed between the flanges of the connected components, with their openings aligned with the mounting points.
The D90 designation refers to the external diameter of the rings and does not indicate a thread size. This variant is intended for the ASI461MM-P setup. For the standard EFW-5x2, EFW-7x2, EFW-7x36 and EFW-7x36-II filter wheels, the manufacturer specifies a separate D88 set.
• darkening ring set designed for the ZWO ASI461MM-P system
• reduces unwanted light entering through flange connections
• two identical rings included
• external diameter of each ring 90 mm
• internal diameter 72 mm
• thickness not exceeding 0.2 mm
• openings allowing alignment with the device mounting points
• application shown by the manufacturer with the ASI461MM-P camera, EFW-7x50 wheel and OAG-L68 guider
• D90 variant intended for the ASI461MM-P setup, different from the D88 version for standard EFW wheels
• 2 ZWO D90 darkening rings
• manufacturer: ZWO
• manufacturer's name: ZWO Darkening Ring D90
• manufacturer SKU: ZWO DR-D90
• product type: darkening ring set
• compatibility: ZWO ASI461MM-P / ASI461MM Pro astrophotography setup
• configuration shown by the manufacturer: OAG-L68 + EFW-7x50 + ASI461MM Pro
• number of rings: 2
• external diameter: 90 mm
• internal diameter: 72 mm
• thickness of each ring: ≤0.2 mm
• colour: black
The D90 set is a practical addition to an ASI461MM-P imaging train, particularly in a configuration with an EFW-7x50 filter wheel and an OAG-L68 guider, as it helps reduce unwanted light entering through the connections between individual components.
