Thousand Oaks Solar Filters 127mm Clear Aperture 152mm OD

What Size Do I Order?

The size chart below lists sizes by clear aperture (filter size in center of cell) and outside diameter (O.D.) of aluminum cell (inside cell wall that fits over and around telescope tube). The O.D. of our cells needs to be at least 1/16″ larger than the OD of the telescope tube or binocular barrel etc. Choose the closest cell O.D. that is LARGER than the O.D. measurement of your instrument. Example: Part number S-4250 (4 1/4″ O.D.) would fit instrument O.D. measurements from 4″ to 4-3/16″. Do not choose a size the same as your O.D. since it will be too tight. Self adhesive felt is included for custom fitting. If your application requires additional felt; Velcro, felt, and other types of material can be found at most fabric or home improvement stores.

OPEN TRUSS TELESCOPES:

If the solar filter is to be used on an open truss telescope, the open area from front (secondary mirror) to back (primary mirror) must be covered. No direct sunlight should enter the optical path or the concentrated beam from the mirror can focus on the back of the solar filter film and cause damage and void warranty.