Thank you for the comments. We haven't taken over a small observatory. We are building a replacement observatory for our old one which was seriously compromised by nearby development. In moving our equipment, much was found which we did not know we had. One item was a commercially made Herschell wedge(another was a bi-filar micrometer). There are neutral density filters with it and the prism is fixed in position. From your comments it sounds as though it will be safe enough with the filter(s) in place. We will check it with a photographic light meter. Our concerns were about the UV levels reflected into the EP and the eye. Actual light levels are easy enough to handle.

It would be used with several scopes from 4" refractors to 11" SCT's. The attraction of the wedge is that it can be used on many scopes. The Mylar filters are usually fitted to just one scope.

Thanks for the comments.