Projection is a long-standing method for showing sunspots to a group, and makers differ on whether a given telescope or eyepiece is suitable for it. What a particular instrument permits is set out by its manufacturer, not by a comparison page.
Projection appears in every account of eclipse observing, and the important part of it is which instrument is being used.
What the method is
The telescope forms an image of the Sun, and an eyepiece projects that image onto a card held behind it. The image can be large, several people can look at once, and sunspots are plainly visible on it.
Why the instrument matters
Concentrating sunlight inside a telescope puts energy where the design may or may not have anticipated it. Manufacturers publish their own positions on whether a given design and a given eyepiece may be used for projection, and those positions differ between makers and between models.
Where to find the answer for yours
In the manual for the telescope and the eyepiece. This site reports what manufacturers publish and points to those documents; it does not offer a general rule, because there is not one.
The instrument-free alternative
A pinhole projector, which uses no optics at all and forms a small image of the disc on a surface. It is the method most often described for showing a partial eclipse to a group without equipment.
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
Why do makers care which telescope is used?
Because the method concentrates a great deal of energy inside the instrument, and manufacturers publish their own positions on which of their designs may be used this way. Follow what the maker of your telescope says about it.
Is a pinhole the same thing?
No, and it is a different scale entirely. A pinhole projector uses no optics, forms a small dim image of the disc on a surface, and is the method usually described for showing the progress of a partial eclipse to a group.
Last reviewed 17 September 2026