Glossary | Telescopes | General | Series | Gran Turismo
The Gran Turismo series of telescopes have a three-element lens with ED glass (FPL-53) in the centre. This special glass ensures an image that is virtually free from colour errors. These telescopes therefore belong to the class of apochromatic refractors or apos for short.
An apo with such a triplet lens delivers a sharp, high-contrast image. This has a very positive effect on planetary observation and compensates for the lower resolution capability of a large mirror telescope.
A special feature of the new William Optics apochromats is the specially created Bahtinov focus mask: the embossed pattern ensures a diffraction pattern that is about three times brighter than that of classic metal masks. The acrylic mask thus delivers a clearer diffraction image and allows focusing even with the help of fainter stars. It is integrated in a custom-fitted attachment.
With such a focus mask, you can easily determine the correct focal position for razor-sharp astrophotography. You must, of course, remove the mask from the lens before you actually start imaging.