Solar Filters

✅ Solar Filters

What do you do on a sunny day? Chances are you slip a pair of polarized sunglasses over your eyes. They cut down glare and appear to make colors, such as a cobalt-blue sky, look snappier.

Backyard astronomers do the same thing when they thread eyepiece filters into a telescope eyepiece to, say, cut the Moon's glare or bring out cloud bands on Jupiter. Eyepiece and telescope filters improve the view. And in the case of solar observing, they actually provide a safe way to look at the Sun directly.

Solar filters come in two main varieties: metal-coated black-polymer film and glass. In both instances, it's a metal alloy electrostatically applied to a surface that filters out the Sun's blinding intensity and harmful infrared radiation. Glass solar filters typically slip over a telescope's front aperture to block the light before it enters the scope. Film solar filters can be found in rolls or sheets of material that is wrapped around the front of a telescope, and more deluxe versions can have a plastic filter cell specially fitted for the front aperture of the telescope.

By some measures, glass solar filters offer greater durability than foil-like black-polymer film. On the other hand, black polymer can take an occasional drop on the ground without worry of cracking or shattering, like glass.
The type of metal coating applied to black polymer film makes the Sun appear blue or neutral-white, while the coating on glass solar filters yields a more realistic yellow image.

Solar filters designed to fit a telescope eyepiece should be avoided. They are extremely dangerous because they sit right where the sunlight is most concentrated (focused). Remember burning dried leaves with a magnifying glass when you were a kid? Well, likewise, the heat that builds up at the eyepiece will eventually cause the filter to crack, which can permanently damage your eyes. If you come across a filter like this, get rid of it.

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Solar Filters