* Astronomy

Sky-Watcher Long Eye Relief (LER) Eyepieces

These multi-coated eyepieces provide a generous 20mm eye relief, and all focal lengths including the 2mm model feature particularly wide diameter eye lenses for maximum viewing comfort. These eyepieces are especially valuable for spectacle wearers, as the long eye relief allows the entire field to be viewed whilst spectacles are being worn.
Twist-up eyecups are provided for added comfort and to keep out extraneous light.

Apparent Field of View:    45º (2mm & 5mm).
Apparent Field of View:    50º (9mm, 15mm, 20mm & 25mm). 
Eyepiece diameter: 31.7 mm (1.25").
£ 29.99

Read more

Ed ~ These eyepieces are substantial and well manufactured.
For ultra fast focal length telescopes the economical high powered (2 and 5mm) eyepieces are 'a must have' for their generous eye relief  (The eyepieces use an integrated Barlow lens system to achieve their outstanding performance).
The view is somewhat dim and slightly restricted (as to be expected) in the 2mm and 5mm, but they do not suffer any 'kidney bean effects' and are free from defects.
The eyepieces are reasonably Parafocal with older skywatcher 'silvertop' and wideangle eyepieces.

A bonus feature is that the built in barlow lens in the barrel can be removed (unscrew the silver barrel first) in the 2mm eyepiece and the lens will perform as a 12mm eyepiece; a standard 2x barlow lens can be attached to the end of the barrel to transform it into a very useful 8mm eyepiece. The barrel has a male 30mm thread fitting to the eyepiece, and a standard eyepiece filter thread on the open end. Inexpensive 30mm Camcorder filters can be fitted between the silver barrel and the eyepiece.

Note: The obvious note to make about the 2mm eyepiece is that it will give a magnification that is probably way beyond the ability of most telescopes.
The focal length divided by two will give you the magnification produced by this eyepiece.  And to work out what the potential magnification ability of the telescope is,  the rule of thumb is to multiply by 50 the size (in inches) the diameter of the mirror or objective.  For a 3" telescope this produces 150 X (maximum magnification). This means the 3" scope will have to have a maximum focal length of 300mm for the 2mm eyepiece to be useful...