- field flattener
- William Optics
OPT W.O telescope
Excellent service and guidance!
Professional-grade engineering, construction & optical performance
This scope has the fit, finish & feel of a premium-quality professional instrument, with robust machined parts and exquisite finish of metal & paint. Focuser action is smooth, and will easily support my heavy DSLR at high elevation angles. Optically it seems virtually perfect, though I am not yet an experienced imager. Visually, at the powers I’ve used, there is no false color. One observation, however, is that in order to give pinpoint stars to the corners of a full 35 mm frame, the field flattener is a must. Otherwise the useable field is less than APS-C size. With it, I have only a trace of elongation in one corner to suggest that centering or perpendicularity could be tuned up. This might be improved with adjusting the spacing of the flattener (easily done). Mated to a small GEM or az-el mount on a tripod, the GT81 would be an ideal field/vacation optic for visual observation & imaging alike, and the sheer quality of this instrument makes one wish that William Optics made a just-right sized mount for its small refractors. It’s as beautiful to look at as it is a joy to use.