Find Solar Filter by Tube Diameter

The white light solar filters in this table fit over the top of your telescope's tube. To check the proper fit, measure the outer diameter (OD) of your tube using a caliper, ruler, or tape measure. Measure the widest distance of the telescope tube end starting from the exterior of the casing, across the center, and over to the exterior part of the casing of the other side.

After you have your tube's OD measurement, you can check to make sure you select the right solar filter by comparing it to the inside diameter (ID) of the solar filter. In general, you should select a solar filter with the ID that is just slightly larger than your tube (by 1/8” to 1/4”).

This table can be used for telescopes, binoculars, spotting scopes, camera lenses, finders, etc. For binoculars, do not forget to consider the clearance between the filters on the two objectives depending on your IPD (inter-pupillary distance).