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How to Measure my Optical Device >

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How do I determine the size of filter to order?

Spectrum Telescope filters slip over the sky end of the optical tube of the telescope. To get the proper fit, measure the outer diameter by using a caliper, ruler, or tape measure. Measure the widest distance of the telescope end starting from the exterior of the casing, across the center and to the exterior part of the casing of the other side.

After you have your measurements, you should order a size 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 optical tube end needs a 4.25” size solar filter. This will make it just a little bigger than the measurement you took.

Spectrum Telescope Full Aperture Glass Solar Filters

Solar Filter ID Part #
2.00” (50mm) ST200G
2.25” (57mm) ST225G
2.50” (60mm) ST232G
2.75” (70mm) ST275G
3.00” (76mm) ST300G
3.25” (82mm) ST325G
3.50” (90mm) ST350G
3.75” (95mm) ST375G
4.00” (101mm) ST400G
4.25” (108mm) ST425G
4.50” (114mm) ST450G
4.75” (121mm) ST475G
5.00” (127mm) ST500G
5.25” (133mm) ST525G
5.75” (146mm) ST575G
6.00” (152mm) ST600G
6.25” (158mm) ST625G
6.50” (165mm) ST650G
6.75’’(171mm) ST675G
7.12” (181mm) ST712G
7.50” (190mm) ST750G
8.00” (203mm) ST800G
8.37” (212mm) ST8376G
8.37” (212mm) ST8377G
8.75” (222mm) ST875G
9.312” (237mm) ST9187G
9.50” (241mm) ST950G
9.75” (247mm) ST975G
10.00”(254mm) ST1000G
10.50”(266mm) ST1050G
10.75” (273mm) ST1075G
11.50” (293mm) ST1150G
12.00”(305mm) ST1200G
12.50” (317mm) ST1250G
13.00”(330mm) ST1300G
13.75”(349mm) ST1375G
14.50’’(368mm) ST1450G
15.25” (387mm) ST1525G
15.75” (400mm) ST1575G
16.00” (406mm) ST1600G

Examples of our Solar Filters by OPT:

Telescope Make, Model, or Size

Product Categories

  • Binocular Glass Solar Filters
  • Binocular Thin Film Solar Filters
  • Center Axis H-Alpha Prominence Filter System
  • Chromium Film Solar Filters
  • Glass Solar Filters
  • Heliopod Sun Finder
  • Night Sky Filters
  • Off Axis H-Alpha Prominence Filter System
  • Off Axis Solar Filters
  • Solar Eclipse Viewer Glasses
  • Solar Optical Thin Film Sheets
  • The Universal Mobile Phone Telescope Kit with Solar Filter
  • Thin Film Solar Filters
  • Threaded Camera Solar Filters

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