William Optics Ultra Wide ANgle (UWAN) eyepieces
Ian King Imaging — +44 (0)1892 834004 — were £170-300
Written: ~5 years ago
It's sobering to think that over two decades have elapsed since the introduction of Tele Vue's Nagler range of premium eyepieces. Their 'spacewalk' viewing experience and high level of image correction across such a wide field means they have become a benchmark against which all other extra wide-angle oculars are compared. One recent line of eyepieces that comes close to matching the Naglers at an attractive price is the UWAN (Ultra Wide Angle) range from respected Taiwanese manufacturer William Optics.

UWAN 4
The shortest focal length in the range, the 4mm model is physically the tallest of the three 1.25-inch format eyepieces. William Optics' trademark black anodised finish, contoured rubber grips and silver engraved lettering cultivates an air of quality that is immediately confirmed upon looking through it. The UWAN 4 is ideal for the current vogue of short tube 80ED refractors. Edge performance suffers a little with instruments under f/5, but it makes for a superb highest power ocular with excellent contrast and resolution for 'scopes with focal lengths under a metre.

uwan4_m
Model: UWAN 4
Focal length: 4mm
Focuser fitting: 1.25-inch (31.7mm)
Lens elements: 7 (in four groups)
Apparent field: 82 degrees (stated)
Eye relief: 10mm
Coatings: fully multi-coated
Parfocal: yes
Filter thread: yes
Weight: 220g
Height: 93mm
Diameter: 47mm
Price: £169.99

UWAN 7
Like all its siblings, the 7mm focal length model has a focuser barrel that's threaded for filters and a tapered safety undercut on the barrel so that it won't drop out of your focuser if the lock nut works slightly loose. Each UWAN also possesses a twist up rubber eyecup that makes for optimal positioning of your eye. Given that there are seven lens elements in the 1.25-inch models, the multi-coatings do a superb job of suppressing flares and ghost images. The UWAN 7 makes an excellent high power eyepiece for 8-inch Schmidt-Cassegrains and similar focal length instruments.

uwan7_m
Model: UWAN 7
Focal length: 7mm
Focuser fitting: 1.25-inch (31.7mm)
Lens elements: 7 (in four groups)
Apparent field: 82 degrees (stated)
Eye relief: 10mm
Coatings: fully multi-coated
Parfocal: yes
Filter thread: yes
Weight: 230g
Height: 84mm
Diameter: 48mm
Price: £169.99

UWAN 16
If you're looking for a general purpose wide-angle eyepiece but can't afford the Nagler equivalent, the 16mm UWAN may be all that you need. It's worth bearing in mind that this eyepiece will give you essentially the same field of view as a conventional 25mm Plössl ocular, but at over 50 percent higher magnification. To put this in context, the UWAN 16 delivers a magnification of 125x in an 8-inch SCT, presenting a 0.6-degree true field easily encompassing the Moon - all with a comfortable eye relief.

uwan16_m
Model: UWAN 16
Focal length: 16mm
Focuser fitting: 1.25-inch (31.7mm)
Lens elements: 7 (in four groups)
Apparent field: 82 degrees (stated)
Eye relief: 12mm (stated)
Coatings: fully multi-coated
Parfocal: yes
Filter thread: yes
Weight: 240g
Height: 86mm
Diameter: 51mm
Price: £169.99

UWAN 28
For those with appetites for the widest, brightest views for 'scopes equipped with 2-inch focusers, William Optics offers this behemoth. A competitor for the 26mm Type 5 Nagler (but at 70 percent its cost), the UWAN 28 is an eyepiece that will require all but the largest instruments to be rebalanced owing to its mass of nearly a kilogram. In common with the other oculars in the range, the 28mm works best with f/6 instruments and longer. Viewing the Pleiades with a 6-inch f/11 Dobsonian, I was able to see truly pinpoint stars across a 1.5-degree field.

uwan28_m
Model: UWAN 28
Focal length: 28mm
Focuser fitting: 2-inch (50.8mm)
Lens elements: 6 (in four groups)
Apparent field: 82 degrees (stated)
Eye relief: 18mm (stated)
Coatings: fully multi-coated
Parfocal: yes
Filter thread: yes
Weight: 990g
Height: 125mm
Diameter: 76mm
Price: £299.99