Viewing in comfort

I have a 200mm Newtonian scope, and the tube cover for the open end has a 50mm removable cap. I find it much more comfortable on the eye to look at the Moon with the cover fitted and the 50mm cap removed. Aside from reducing the brightness, I am not sure what impact this has on performance, especially the ability to resolve small objects. Does the scope, in effect, become a 50mm model, or does it retain the optical abilities of the 200mm mirror?

Tony Teperek, via email

CORRECTIONS

In April’s ‘Astrophotography Gallery’, the caption for Bob Bowers’s picture ‘Rosette Nebula’ indicated the wrong photo. The correct photo is included in this month’s Gallery on page 73.