A full-aperture white-light filter shows the visible surface — sunspots and granulation. H-alpha instruments isolate one emission line and show the chromosphere above it, with prominences and filaments. They are different products entirely.
Both look at the Sun and they show different layers of it, which is why owners of one often want the other.
White light
A full-aperture filter rejects the great majority of the light before it enters the telescope, leaving the visible surface. Sunspots, their structure, the faint darkening towards the limb, and on a steady morning the fine mottling of granulation.
H-alpha
An instrument built around a passband narrow enough to isolate a single emission line of hydrogen. It shows the layer above the visible surface: prominences at the edge, filaments across the disc, and the bright regions around active areas.
Why one is a filter and the other an instrument
Isolating a single line to that precision requires an optical assembly rather than a coated sheet, which is why H-alpha equipment is sold complete and costs accordingly.
What governs use, for both
The manufacturer’s instructions supplied with the product. This site reports what makers publish — the standard cited, the construction, the inspection asked for — and defers to those documents.
If this page and the manufacturer’s own documentation disagree, follow the documentation. Every aperture, focal length, payload rating, field, eye relief, transmission figure and thread size on this page comes from the maker’s own published figures, with the unit as printed and the source named. None of it is measured here, and no figure is converted into another convention, because a converted number is a different number. And the limit this page does not cross: no filter, no pair of eclipse glasses and no mounting described here makes an observation safe. The page reports what a maker specifies for its own product — the standard the listing cites, the construction, the fitting, the inspection asked for before use — and what applies to your own equipment is decided by those instructions and by the condition of the filter in your hands.
The questions that keep arriving
Can I add H-alpha to an ordinary telescope?
Not with a simple filter. The instruments that do this are specialised and built around an extremely narrow passband, which is why they are a separate category rather than an accessory.
Which shows sunspots?
White light, clearly and in detail. H-alpha shows a different layer, where sunspots appear as part of a more complex structure.
Last reviewed 17 September 2026