Farpoint Mounting Adapter for Coronado SolarMax II Solar 40mm Filters, 380 adapterSolarMax II 40mm solar filter holder for telescopes with dew shield diameter of 2. 7 3. 7 inches If you have a Coronado SolarMax II Filter and you want to mount it to your telescope, you need one of these adapters. First select the size solar filter that you have; 40mm, 60mm, or 90mm. Measure the outside diameter of your OTA where a dew shield would attach. Then select the proper part number of the adapter. The FSMF40 380 indicates that it is for the