The RedCat AP 51/250 WIFD APO refractor from William Optics. The well-proven optics in the new model are equipped with an internal focus adjustment, two-speed Crayford focusing system, which is also compatible with the EAF system. The William Optics RedCat AP 51/250 WIFD APO refractor is a truly attractive "jewel", boasting not only professional imaging but also an eye-catching design, a true curiosity in its class. Its two main applications are astrophotography and nature photography.
Astrophotography has special criteria and high demands on optics, which the William Optics RedCat AP 51/250 WIFD APO refractor meets with the same elegance as its predecessor. The compact tube's Petzval system optics consist of four optical elements arranged in three groups, using high quality FPL53 and FPL51 glass materials. Of course, the result is not lost. The entire field of view is flat all the way to the corners, so the optics work with point-like imaging at the edges of the image, while also delivering, in terms of colour, impressive performance.
It's perfect for astronomy cameras, or even for shooting with full-frame cameras, as it can crop out a circle with a diameter of more than 44mm! Also optimized for photography in terms of brightness, it has a F/4.9 ratio for short exposure times. Thanks to fluorite glass materials, it has beautiful imaging free of chromatic aberration, as you would expect from an APO.
To ensure that no edge darkening occurs when focusing, unlike conventional diffusers, the RedCat AP 51 WIFD refractor has an internal focus adjustment system. In essence, the focusing process is achieved by moving the optical elements. Thanks to the internal focus adjustment system, the length of the telescope tube does not change and the centre of gravity does not shift.
The manufacturer has again paid attention to detail, with an accurate thermometer built into the focusing knob, and the focus adjustment can be read off the clearly visible moving scale. The Bahtinov mask built into the lens cap aids focusing accuracy when shooting astrophotography. At the end of the hood is a rotating design M54 thread, with an M54-M48 thread adapter supplied by the manufacturer. A 2" filter can be mounted directly into the adapter.
For such a compact instrument, portability and protection are important, and with this in mind, the instrument comes with a lined carrying case.
