Thousand Oaks Optical Full Aperture (Solarlite) 90mm\3.50″
108mm .25" SolarLite Filter for 90mm .50" instruments. This filter should fit the following models: C-90, ETX 90, Questar 3.5, Wm. Optics ZS80II ED, Orion Obs. 70 & Astroview 90, Exployer 90 and instruments of similar outer diameter. Part # S4250.
Please read carefully: 108mm .25" is the diameter of the filter. The filter fits like a cap by friction. To be absolutely sure that the filter will fit, please measure the outer diameter of your instrument and make sure that it is not larger.
SolarLite filters have the optical quality of the glass with the advantages of impregnated polymer (Thousand Oaks Optical Black Polymer). The sun will appear in a natural yellow-orange color when viewed through your telescope using this filter.
This is a high quality product of Thousand Oaks Optical (Arizona), a manufacturer of safe solar filters for over 30 years. Words of the producer: "stronger than any other solar film on the market. Guaranteed 15 years."
WARNING: ALWAYS MAKE SURE THE FILTER IS WELL ATTACHED TO THE TELESCOPE/BINOCULARS/CAMERA. IN CASE NECESSARY, USE STICKY TAPE TO SECURE IT. NEVER OBSERVE SUN WITHOUT A PROPERLY ATTACHED FILTER!

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. We cannot take orders for felt.