Sloan Filters

Standard sizes are 1.25″, 31mm, 50mm round, and 50mm square. The 1.25″ is 27.5 mm of filter glass mounted in a 1.25″ filter cell. The 31mm is 27.5mm of filter glass mounted in a 31mm ring. More information here:

Unlike other Astrodon filters, the Photometric filters (Johnson-Cousins and Sloan) do not come as 36mm of unmounted glass. For those who want 36mm round for use in a 36mm filter wheel, 27.5 mm of filter glass can be mounted in our 36mm adapter. More information on 36mm mount here:

We also have a limited quantity of 12mm and 25mm (call for pricing and availability). All Astrodon Photometric filters are 100%-Coated for long-term durability and consistency of research with the highest throughput.

NOTE: In Astrodon part numbers we pronounce the ‘ character (apostrophe)  as “prime” and the _ character (underscore) we pronounce as “sub.” So u’2_27R should be read as “u prime 2 sub 27 R.”