What size Baader filter should I get for my Maksutov telescope?
The following are suggested sizes for various telescope main objectives. Never use solar filters with an eyepiece, attached either in front of the eyepiece, or on the viewing portion. The already magnified sunlight coming through the main objective may burn through the filter to your eye. The correct placement of any solar filter material is in front of the main objective (large light-gathering lens at the front of the telescope or binoculars).