The Farpoint SSF Solar Filter line is a complete white-light solar viewing system designed around your specific telescope. Fifty-eight sizes — fifty-two on a continuous 5 mm grid from 120 mm to 380 mm tube outer diameter, plus six specialty SKUs — cover virtually every consumer telescope in production. Every filter uses ISO 12312-2 certified silver-coated polymer solar film, the international standard for direct solar observation, paired with a laser-cut ABS plastic mounting ring and ultra-adhesive hook-and-loop straps that hold securely against wind tested to 200 mph.

Whether you observe with an 80 mm refractor, a 14″ Dobsonian, or anything in between, there is a Farpoint SSF sized for the tube you are pointing at the sun. No drilling. No adapters. No guesswork. Use our Solar Filter Finder to match by telescope brand and model, or by direct tube outer-diameter measurement.

Designed for Your Specific Telescope

Each SSF SKU is engineered for a 5 mm window of telescope tube outer diameter, with a laser-cut ABS ring sized to that window. The continuous grid from SSF-125 through SSF-380 covers tube ODs from 120 mm to 380 mm in 5 mm increments. Six specialty SKUs — SSF-172, SSF-188, SSF-207, SSF-239, SSF-316, and SSF-397 — fine-tune coverage for popular telescope clusters where a single SKU can serve multiple high-volume models. SSF-239, for example, fits all current Celestron 8″ Schmidt-Cassegrain models (NexStar SE, EdgeHD, Advanced VX, CPC), the entire GSO-made 8″ Dobsonian family (Apertura, Sky-Watcher, Zhumell, Celestron StarSense), and 8″ Ritchey-Chrétien astrographs.

Field-Tested at 200 mph

The ultra-adhesive hook-and-loop straps are the system’s structural innovation, and they have been tested under hostile conditions. We mounted an SSF filter on a telescope, pointed a 200 mph backpack leaf blower directly at it from short range, and let it run. The filter did not budge.

→ Watch the 200 mph leaf-blower test on YouTube

The video is short and the result is uneventful — which is the point. Solar observation requires absolute confidence that the filter cannot work loose while the telescope is pointed at the sun. The ultra-adhesive system delivers that confidence in a removable, repositionable mount that does not require tools, adhesive promoters, or permanent attachment hardware.

How SSF Solar Filters Work

Three materials work together:

  • Laser-cut ABS plastic mounting ring. Rigid structural backbone. The outer diameter is sized so the ring extends slightly past the tube OD, providing wrap-around contact for the straps. The inner aperture is cut to fit the telescope.
  • ISO 12312-2 silver-coated polymer solar film. The film blocks 99.999% of incoming ultraviolet and infrared radiation and transmits a uniform 0.001% of visible light. View is sharp, natural color, well-suited for sunspot observation, transits, partial eclipses, and the full annual cycle of solar activity. The same film material is used in eclipse-viewing glasses and certified handheld solar viewers.
  • Ultra-adhesive hook-and-loop straps. The straps wrap around the telescope tube. The hook side engages the loop side, and the pressure-sensitive adhesive backing engages the tube directly. Removable, repositionable, and wind-resistant.

Find Your Filter

Two ways to find the right size:

  1. Pick your scope. The Solar Filter Finder includes most major telescope brands and models. Select brand, then model, and the chooser returns the recommended SSF SKU and alternatives if your scope fits more than one size.
  2. Measure your tube. If your telescope is not in the chooser catalog — or you want to double-check — measure the outer diameter of your telescope’s optical tube in millimeters or inches, enter the value, and the chooser returns the same recommendation.

→ Open the Solar Filter Finder

If your tube measures less than 120 mm, our small-aperture solar filter line is currently in design — the Coming Soon page lets you sign up for notification when it ships. If your tube measures more than 397 mm (Celestron C14 at approximately 401 mm is the only catalog telescope in this range), the chooser routes you to a contact form for a custom-order quote.

Featured Sizes

Six high-volume SSF SKUs spanning the line. Browse the full collection for all 58 sizes.

  • SSF-125 — fits 120–125 mm tube OD. 5″ refractors and small Maksutovs. $49.
  • SSF-188 — fits 183–188 mm. Celestron 6″ SCT family (NexStar 6 SE, C6). $57.
  • SSF-239 — fits 234–239 mm. All Celestron 8″ SCT models and GSO-made 8″ Dobsonians/Ritchey-Chrétiens. $66.
  • SSF-275 — fits 270–275 mm. Celestron 9.25″ SCT and 10″ Dobsonian families. $73.
  • SSF-316 — fits 311–316 mm. Celestron 11″ SCT and 12″ Dobsonian families. $82.
  • SSF-370 — fits 365–370 mm. 12″ Dobsonian families and Sky-Watcher 12″ Flextube. $95.

→ Browse all 58 SSF Solar Filters

Safety and Standards

Direct solar observation requires certified solar filtration. Unfiltered sunlight passing through a telescope, even briefly, causes instant and permanent damage to the retina. There is no warning sensation, no pain, and no chance to look away in time — the damage is done in microseconds.

The ISO 12312-2 standard defines the optical density and spectral transmission requirements for direct solar viewing equipment. All Farpoint SSF filters use polymer solar film certified to this standard. The same film material is used in eclipse-viewing glasses and certified handheld solar viewers.

Before each observation session:

  • Inspect the filter for pinholes, scratches, film separation, or any visible damage. Discard the filter and do not use it if anything looks off.
  • Confirm the ultra-adhesive hook-and-loop straps hold the filter firmly to the tube. The filter should not wobble, rotate, or shift under gentle hand pressure.
  • Verify the filter completely covers the front aperture of the telescope, including any finder scopes or guide scopes. Use a dedicated finder cap or smaller finder filter for the secondary optical paths.

Never look directly at the sun through any optical instrument without a certified solar filter properly mounted at the front of the objective.

Frequently Asked Questions

Are Farpoint SSF solar filters safe for direct solar observation through a telescope?

Yes, when used as designed. All SSF filters use ISO 12312-2 certified silver-coated polymer solar film, which blocks 99.999% of harmful UV and IR radiation and transmits a uniform 0.001% of visible light. The filter mounts at the front of the telescope’s objective, blocking sunlight before it enters the optical path. Inspect the filter for damage before every session and confirm the mount is secure.

How do I know which SSF size fits my telescope?

Use the Solar Filter Finder. The tool accepts either a telescope brand and model (most major manufacturers are catalogued) or a direct tube-outer-diameter measurement in millimeters or inches. The result returns the recommended SSF SKU and alternatives if your scope fits more than one size.

How does the ultra-adhesive mount stay on without wind blowing it off?

The hook-and-loop straps attach to the ABS mounting ring and wrap around the telescope tube. The hook side engages the loop side, and the pressure-sensitive adhesive backing engages the tube directly. We tested the mount with a 200 mph backpack leaf blower aimed at point-blank range — the filter did not budge. The video is on our YouTube channel and linked from every SSF product page.

What is the difference between SSF filters and DIY solar film?

SSF filters are complete, ready-to-mount solar filters: ABS ring, certified film, ultra-adhesive straps, sized to your telescope. DIY solar film is a sheet of the same ISO 12312-2 certified polymer film, sold in cut sizes from 3″×3″ through 12″×12″, for users building their own cells or filters for non-standard mounting geometries (camera lenses, mirrored solar projection setups, classroom demonstrations). Both use the same film material; the difference is in the housing.

Can I use one SSF filter on multiple telescopes?

Yes, if the telescopes have tube outer diameters within the same 5 mm SSF fit window. For example, an SSF-239 fits any telescope with a 234–239 mm tube OD — that includes most Celestron 8″ SCT models, GSO-made 8″ Dobsonians, and 8″ Ritchey-Chrétien astrographs. If your two telescopes have different tube ODs outside one 5 mm window, you will need separate SSF SKUs.

What happens if I cannot find a size that fits my scope?

If your tube outer diameter is between 120 mm and 397 mm, one of the 58 SSF SKUs fits. If your tube is smaller than 120 mm — finder scopes, guide scopes, very small refractors — a dedicated small-aperture filter line is in design; the Coming Soon page lets you sign up for notification. If your tube is larger than 397 mm (only Celestron C14 at approximately 401 mm falls here in our catalog), the Solar Filter Finder routes you to a contact form for a custom-order quote.

How long does the solar film last?

Stored flat in a clean, dry place between observation sessions, the ISO 12312-2 polymer film maintains its optical and safety characteristics for many years of normal use. Inspect for damage before every session. Common failure modes are pinholes, film delamination, and edge separation — all are easy to spot visually, and any one is sufficient reason to retire the filter and order a replacement.

Designed and Assembled in the USA

Every Farpoint SSF Solar Filter is designed, laser-cut, and hand-assembled in the United States. The ABS rings are cut to spec on our laser systems. The ISO 12312-2 polymer film comes from a certified domestic supplier. Filters are assembled and packaged in-house. Each filter ships in protective packaging with usage and care instructions.

Questions about fit, application, or anything else? Email support@cxbastro.com — we answer email and phone.

Also in the Farpoint solar viewing range: Lumicon-Farpoint Solar Viewing Goggles (single and 10-pack) for naked-eye viewing during eclipses and transits, and Safety Solar Filter Film for DIY filter builds.