William Optics Pleiades 68 Astrograph F/3.8 7-Element WIFD

What the Pleiades 68 Is For

The Pleiades 68 is a 7-element imaging APO telescope in the William Optics WIFD series, designed for astrophotographers, with a fast f/3.8 ratio for deep-sky captures with reduced exposure times. It suits both seasoned astronomers and astrophotography enthusiasts.

The 260mm focal length frames large regions of sky: big emission nebulae, star clouds and large galaxies. The tube is compact, with a 366mm retracted length.

A 7-Element Design with 3 Super ED Elements

It is a 7-element astrograph with Super ED glass x3, and the advanced 7-element optical system produces sharp, vibrant images while minimising chromatic aberration. A new lens cell design in the Pleiades series uses high-quality FPL-53 glass.

The correction is part of the telescope's own optics: William Optics' optional flattener entry reads "No Flattener Required". The manual includes a full-frame spot diagram and a longitudinal aberration plot across 0.436 to 0.680 micrometres.

68mm Aperture and 260mm Focal Length at f/3.8

With a full-frame sensor (36 x 24mm), 260mm gives about 7.9° x 5.3°, enough to frame the Andromeda Galaxy (M31) or the whole Veil Nebula complex in one shot. A 68mm objective has a Dawes limit of about 1.71 arcseconds.

At f/3.8, each sub-frame needs about 58% of the exposure an f/5 system needs for the same signal, which helps on a portable mount and in short clear spells.

A 48mm Image Circle for Full-Frame Sensors

The 48mm image circle covers the 43.3mm diagonal of a 36 x 24mm sensor. Full frame, APS-C and M4/3 are supported formats.

The WIFD Focuser: 45mm of Travel

The manual lists the focuser as WIFD (WO Internal Focus Design), patented and compatible with EAF; the page calls it a WIFD R&P focuser with 0 to 45 mm of travel and a ruler to 50mm. It has a 2 speed 10:1 ratio fine knob and a focuser adjusting knob with a thermometer.

• Tension: tension screws (5mm Allen key) increase focuser tension. Do not over-tighten the focuser tension screw, and release it when focusing.
• Smoothness: push and pull gear spacing screws (3mm and 2mm Allen keys), adjusted only when necessary.
• EAF: remove the top screw (2mm Allen key), release the two inner knob screws, remove the knob, align the screw holes, lock the two set screws on the shaft and tighten both bracket screws. With a motor fitted, do not over-tighten the tension screw.

55mm Back Focus, Rotator, Tilt Adapter and Adapters

The manual says the recommended back focus is precisely 55mm and, given the fast focal ratio, maintaining exactly 55mm is crucial. The drawing marks it "Already preset at best result 55mm" from the M48x0.75 or M54x0.75 camera thread to the sensor.

• Camera adapters: M63 to M48 and M63 to M54 adapters are included.
• Camera angle rotator: a camera angle rotation device with a locking screw lets you frame your target.
• Tilt adapter: inside the rotator. Remove the rotator knob, twist the cover and remove it, then adjust with the push and pull screws.
• Filters: the manual says there is no internal M48 filter thread, because of the second lens group near the camera adapter, and recommends a filter wheel on the M48 or M54 thread.

Visual Use

William Optics presents the Pleiades 68 as an imaging telescope and does not describe a visual configuration. Ask us before buying a diagonal or eyepieces for it.

Rings, Handle Bar and 210mm Dual Dovetail

The tube sits in mounting rings with knobs on a 210mm dovetail. The manual lists a Vixen style dovetail plate, and William Optics' page gives the dovetail type as Vixen and Arca-Swiss (dual-side plate). Riser blocks are included. The manual advises setting the tube so both focuser knobs are even and clear of the mount's saddle plate.

On top is a 120mm saddle handle bar with M4 locking screws and M4 and M6 screw holes for a finder bracket; remove the two finder bracket holder screws (2.5mm Allen key) before use. The manual's accessories map shows a red dot sight and the M-G32PB-BU guide scope (optional, listed as coming soon).

Weight, Length and Case

The optical tube weighs 2.98 kg (6.57 lbs); with ring, dovetail and saddle the manual gives 3.835 kg (8.45 lbs) and the page 3.83 kg (8.44 lbs). Add your camera and compare the total with your mount's rated payload.

The dew shield retracts (with a lock screw), giving a length of 366mm retracted and 410mm extended. The dew shield is 103mm across and the front cover threads on at M102. A soft carry case is included.

First Night Setup and Care

Mount the telescope with both focuser knobs clear of the saddle and attach the camera at exactly 55mm. Fit the dust cover with its Bahtinov mask, aim at a bright star and adjust focus, with the tension screw released, until the central spike is centred between the other two.

Before storing it, let it acclimatise to room temperature with the tube uncovered and open, and make sure it is dry and free of dew. Store it in a consistent-temperature, dry place. Never aim the telescope or finder at the Sun without proper solar filters installed on the front of the telescope; doing so for even a moment may permanently damage your vision. Solar eyepiece filters are not considered safe.