Débutant

To summarise, what we have here is a re-writing of telescope making history. Companies intentionally manipulating accepted optical standards and definitions. According to the apophyles who covet these telescopes, all refractors prior to recent ED & Fluorocrown triplets suffer from unacceptable secondary spectrum, whereas Ed & Fluorocrown triplets exhibit essentially zero colour error. Yet what do we find? The apo's they so fervently champion are mostly not true apo's at all, and the secondary spectrum exhibited by a standard doublet is only 2.5 times that of a fast triplet "apo". In their over-ebullient enthusiasm for their respective manufacturing heroes, all perspective is lost. The principal advantage of an apo like my TEC ED140 is its portability. A 6-inch f/15 refractor is a big, and necessarily heavy telescope. It needs a permanent mounting and an observatory. A TEC ED140 does not. To claim that no useful observations can be made with a 6-inch f/15 achromat as many apophyles do is a canard, as any proud Unitron owner will testify. And when I hear neophytes deriding owners of such marvellous refractors as "old school" my response is simple, "time for you to get back to school, you have a lot to learn.