Solar Safety: Proper Use of Optical Solar Filters

Universal Solar Safety

Looking at the Sun without proper protection can cause instant, permanent eye damage. Solar observation is only safe when all of the following conditions are met:

• A proper solar filter is installed before pointing any optical device at the Sun
• The filter is mounted on the front (sun-facing) aperture
• The filter is secure and cannot be dislodged by wind or handling
• The filter is undamaged and inspected before every use
• The optical device is never left unattended while aimed at or near the Sun
• Children are supervised at all times

Viewing vs. Optical Filters

Not all solar filters are the same.

• Solar viewing eyewear (eclipse glasses) are designed for unaided, direct viewing of the Sun.
• Optical solar filters are designed to be mounted on telescopes, binoculars, spotting scopes, and camera lenses.

The ISO 12312-2 standard applies to wearable solar viewing eyewear, not to optical filters used on instruments. Optical solar filters are safe only when used as directed on the front of an optical device. For a clear explanation of where the standard applies—and where it does not—see our ISO 12312-2 scope overview.

Equipment-Specific Safety Rules

Telescopes

• The solar filter must fully cover the front aperture
• Never install any solar filter behind the eyepiece or inside the optical path
• Finder scopes must be covered or filtered separately
• Do not leave the telescope aimed at the Sun unattended

Binoculars

• Both barrels must be filtered
• Never attempt to filter only one side
• Ensure both filters are equally secure before observing

Camera Lenses

• Filters must be installed on the front of the lens
• Threaded camera filters must not be used as drop-in or internal filters
• Confirm the filter is properly threaded and snug (do not overtighten)

Filter Types & Handling

Glass Solar Filters

• Inspect before each use for scratches, cracks, coating damage, or bright pinholes
• If damage is present, discontinue use immediately
• Clean only with gentle methods recommended by the manufacturer
• Store in protective packaging when not in use

Solar Film Filters & DIY Film Sheets

• Only one intact layer is required
• Film must be mounted in a rigid front-mounted cell
• Inspect for holes, tears, creases, or edge separation before each use
• Punctured or damaged film must be replaced, not repaired
• Film must never be placed at the eyepiece or inside the optical path

Installation & Use Principles

Before observing

• Confirm correct sizing and secure fit
• Allow equipment and filter to equalize to outdoor temperature
• Verify the filter cannot be knocked or blown off

During observing

• Observe only while the filter is securely installed
• Monitor children and inexperienced observers closely

After observing

• Point the instrument away from the Sun before removing the filter
• Store the filter properly to prevent damage

When It Is Never Safe

• Without a properly installed front-mounted filter
• With a damaged or loose filter
• Using rear-mounted, eyepiece, or internal filters
• Through an unfiltered finder scope
• If the filter fit is uncertain or incorrect

If there is any doubt, do not observe.

Manufacturer Instructions & Downloads

The following documents provide product-specific instructions and must always be followed:

• Seymour Solar Filter Instruction Sheet (PDF)
• Hyperion Solar Film Instruction Sheet (PDF)

Need Help?

Technical Support: +1 (435) 503-9270
Email: info@seymoursolar.com

Not sure about sizing? See our Sizing & Fit Guide.
For coverage after purchase, view our Warranty & Returns.