Spectrum Telescope Thin Film Binocular Solar Filter (Set of 2): 3.5" Cell Inside Diameter # ST350BPP

Our Price: $90.00
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Our Product ID: OFIL-SP-ST350BPP
Manufacturer SKU: ST350BPP
Item Can Ship: Worldwide
Spectrum Telescope Thin Film Binocular Solar Filter (Set of 2): 3.5" Cell Inside Diameter # ST350BPP

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ALL SALES FINAL. NO RETURNS OR EXCHANGES. PLEASE MEASURE YOUR TELESCOPE/LENS OUTSIDE DIAMETER VERY CAREFULLY AS EXPLAINED BELOW BEFORE ORDERING.

Product Details

Spectrum Telescope thin film polymer solar filter mounted in a 2.0" inside diameter cell. Set of two filters for binocular use. # ST200BPP.

1. Selecting the Correct Solar Filter for your Binoculars

This solar filter is designed to be fitted on the front (sky-end) of your binoculars. The filters slide over the front of the objective housing and are locked down in place with the included thumbscrew.

This filter cell has an inside diameter of approx. 3.5" and has a clear filter aperture of 2.85" (72mm). It is meant to fit on binocular objective tubes with an outside diameter between 3-1/8" (79mm) to 3-3/8" (86mm).

We very strongly recommend that you buy this filter only after measuring the front of your binoculars carefully (as explained below).

To get the proper fit, measure the outside diameter very carefully by using a caliper, ruler, or tape measure. See the 3rd product photo above. Measure the widest distance of the binocular objective housing starting from the exterior of the casing, across the center and to the exterior part of the casing on the other side. After you have your measurements, you should order a size slightly larger than what you measured. This is because your measurement is being compared with the solar filter ID (inside diameter). For instance, if you measure 4" across the outside of the tube end, you should order a 4.25" inside diameter size solar filter. This will make it just a little bigger than the measurement you took.

Also, for example, If you have a 50mm binocular, do not buy a 50mm solar filter! Binocular aperture is not the same as outer tube size. The outside objective housing diameter will always be slightly larger than the binocular aperture. Measure it carefully before ordering to avoid disappointment and expensive returns.

2. Filter Film and Cell Details

This full aperture thin film solar filter allows only a safe amount of light to pass through your binoculars for solar viewing. It is an ND 5 filter and therefore blocks 99.999% of the Sun's visible light. The .002" thick black plastic polymer used for the filter substrate is an extremely durable, high quality material that will last you for many years with proper care and handling. It is a single-layer design with absorptive filtering material spread throughout the substrate. Note that slight warps, bends or wrinkles present in the film will not affect the solar image. The Sun appears in a natural looking yellowish-orange color.

The filter film is mounted in an aluminum cell than can be securely attached to the telescope tube with the included nylon thumb screw.

3. Warning

Never look at the sun without special eye protection. When viewing the Sun, use this filter in front of your optical instrument at all times when any part of the Sun is visible.