Sharpstar Z4 Sextuplet Dual-ED APO Refractor
A Sextuplet Refractor: The Z4 from Sharpstar
This flat-field sextuplet from Sharpstar is a high performance refracting astrograph. Featuring a 100 mm aperture and a 550 mm focal length, the Z4 has a focal ratio of f/5.5.
The optical design of this astrograph is a sextuplet in a 3+3 configuration. One lens in the front, and one lens in the rear are made from extra-low dispersion (ED) glass to minimize chromatic aberration. The optical design creates a flat field, eliminating the need for a separate field flattener accessory or having to calculate backfocus. The Z4 has a 36 mm, APS frame image circle. It is not recommended to use full frame cameras with the Sharpstar Z4 astrograph.
A Powerful and Attractive Refracting Astrograph
Unlike other Sharpstar designs, the Z4 comes in an attractive, two-tone matte gray. The tube and retractible dew shield is a light gray and the lens cover, handle, tube ring, and dovetail provide a nice darker gray accent.
The Z4 includes the optical tube, tube ring, carry handle, lens cap, a dovetail, a four-piece photographic adapter, manual, and carrying case.
Sextuplet Optical Design
The sextuplet design of this refractor is composed of two lens groupings in a 3+3 configuration. One lens from the front, and one from the rear are made of extra low-dispersion (ED) glass to minimize chromatic aberration. This design also provides a flat field, with no additional field flattener required. Also, there is no need to calculate backfocus.
Focuser and Rotator
The Z4 features a large 3.4" rack-and-pinion focuser with a 1:10 fine adjustment knob. Attached to the focuser is a convenient 360° rotator, which allows an attached camera or accessory to be rotated to the desired orientation.
Adapter Rings
Integrated adapter rings allow for connection of a broad assortment of cameras or other accessories. Included is an M86x1 to M68x1, an M68x1 to M54x0.75, an M54x0.75 to M54x0.75, and an M54x0.75 to M48x0.75. The M54 to M48 adapter ring also has threads to accommodate filters.