For info, I've come across an unexpected source for filters for my 6 1/2-inch Dagor lens. The filters from my wife's telescope eyepiece fit perfectly. These are listed in the catalog and web site of Orion Telescopes and Binoculars (www.telescope.com or (800) 447-1001. Orion carries the filters in various colors to fit 1.25-inch eyepieces. These are branded "Orion," and show no size in milimeters or the name of the manufacturer. The downside is that Orion only sells them in sets of 4 or 6 filters, and these sets are designed to meet the needs of amateur astronomers, not photographers. For example, the "advanced set," costing $44.95, contains a #8 light yellow, a #23 light red, a #38A deep blue, and a #56 light green. If you want a #15 yellow or #25 red, you have to buy the "basic set." The catalog also lists a polarizing filter, but it comes only as part of a set of 6.