On 9/18/11, jcarman6@q.com <jcarman6@q.com> wrote:
Refractors do not have central obstructions. They take ALL the light from a source and focus it at a single point.
ONLY if the source is itself a point. Virtual images of planets and lunar features have a real size, they are most certainly not points. This illustrates a common misconception in that a typical image of say, a star field, is composed of many light cones spread across the entire FOV. Each cone corresponds to a single star in the field. The primary (be it lens or mirror) does not focus all light in the field to a single point, as I've heard some people express. Anywhoo, I understand what you say about the resolution of refractors being very good, but lets face it- Dawes' limit is Dawes' limit. I just played the aperture trump. Bigger aperture can and will give you better resolution. With identical apertures, it would depend on the individual quality and cleanliness of the telescopes being compared. And what about an unobstructed reflector? There goes the central obstruction complaint. I'm working on 3 six-inch refractors and a five-inch at present, as well as 3 50mm refractors (not the solar scopes). Obviously I like the sharpness of refractors. But from my experience, with the right reflector, the comparison with refractors is much more favorable. I'm not choosing. I'm going to keep using both and have it both ways. :o)