Why is Meade ACF optics better than conventional systems?
A telescope concentrates the starlight into a Airy disc, see upper images . The more light an
airy disc contains, the brighter it appears. The airy disc is surrounded by diffraction rings,
that are very faint in an ideal telescope. You can see the first and brightest ring in the upper
If we compare two telescopes with the same aperture, the telescope that concentrates more
starlight into the airy disc will show brighter stars.
However, in conventional telescopes for amateur astronomers this ideal light concentration only
happens on one point in the field of view: the middle. Outside the middle the stars get deformed
because optical aberrations occur. The most disturbing of those aberrations is coma. When a
optical system has coma, the starlight gets spread into a cometlike tail, see the image in the
middle left. This not only happens at the very edge of the field: the image shows a star that
is only 5mm from the middle of the field of view. If the distance to the middle gets larger,
so does coma, see the picture below left. The starlight gets spread over a large area. For
comparison see the images that a Meade Advanced Coma Free telescope provides: small round
stars that are losing only very little contrast on the very edge of the field.