Some more questions about the 66mm

David Colton said:

A couple of questions about the WO 66:

1. Is it the same telescope as the Astro-Tech 66mm? - Sort of. Come from same manufacturer, but they have different focusers and my guess is different lens (slightly different F/ratio) and maybe coatings. Note WO makes three (or did) different versions, a doublet APO (similar to the AT), a triplet APO, and a Petzval Achro.

2. Do you need an extender to bring eyepieces to focus without a diagonal? - Not usually but that is an individuakl eyepiece issue.

3. An earlier post (Don Pitt, 11/2) indicated problems bringing eyepieces to focus and the reply was use a Nagler Type 6. So what about Plossl’s and Ortho’s; will they work? Are there eyepiece sizes that just won’t work with the 66’s short focal length? As Jon stated usually because of the diagonal. These work well with 1.25 diag, and most of the time with 2" SCT Diag (Short versions like the WO one). Refractor type diag are a no no.

4. Considering the primary use of a 66mm scope is birding or wide-field astronomy, is CA a critical factor? CA is always a factor. CA is not just annoying "color" - you are not focusing some of the light/energy - so your views will not be as sharp and contrasty...If that is important to birding I can't say, And while less so with wide angle low power view, it is none the less and important consideration.