Sky-Watcher has a passion to produce some of the finest optics to capture the night sky. In 2010, Sky-Watcher sent ripples through the astronomical community by unleashing a rumor of a 150mm Apochromatic refractor. Fast-forward to the end of 2011, and the rumor is reality.
The Esprit 150mm is the largest Apochromatic refractor made by Sky-Watcher. This formidable instrument produces razor-sharp, false color-free views, highly suitable for astrophotography and visual observing. Our comparison with a high priced competitor's scope was a draw.
The objective and field flattener lenses are crafted from premium optical substrate. The objective comprises one element of Ohara FPL-53 extra low dispersion glass and two elements of Schott BK-7. This combination produces high contrast images with no detectable false color.
The two-element field flattener threads to the rear of the focuser, and provides improved image resolution across a full-frame 43mm diameter field circle, with about 100mm of back focus
Knife-edge baffles have been installed to ensure contrast-robbing stray light is eliminated.
Sky-Watcher's new 3" dual-speed linear power roller bearing focuser is tough enough to drive heavy accessories with virtually no slippage. Unlike traditional Crayford focusers which surround the drawtube with roller bearings, the linear power focuser places the bearings along a single metal track mounted along the drawtube, so the drawtube is never flexed nor placed under compression.
The locking mechanism of the linear power focuser improves on the Crayford design by retaining the desired focus with no flexure or bending of the drawtube. An engraved linear scale helps set the focus close to where you need it.
The focus knobs can be rotated to change their orientation to suit the user. A built-in camera angle adjuster means easy and precise rotation of the camera and star diagonal independent of the focus knobs.
Apochromatic refractors have something of a cult following; their zero obstruction, color error-free optics make them among the finest instruments to observe and photograph the skies. Once relegated to a price range affordable only by the well heeled with deep pockets, they are now accessible to those wading in the shallow end.