* Astronomy

The eyepiece uses two separate ED (Extra-low Dispersion) glass elements of different glass types in its optical system to provide exceptional colour fidelity (with astonishingly low levels of chromatic aberration) so that the true colour differences between binary star pairs and planetary surface details are easily visible. It has a  60° field of view which is very flat and it is particularly recommended with telescopes with a f/5, or greater, focal ratio. It is uniformly sharp edge-to-edge, with markedly low astigmatism. Barrel distortion is essentially non-existent, eliminating the annoying "goldfish bowl" effect of distortion of the image which is often seen in some eyepieces when panning across a star field.
Each air-to-glass surface in the eyepiece is fully multicoated for high light transmission and exceptional contrast.  This high contrast makes it a good choice for splitting close binary stars, for examining low contrast lunar and planetary detail, and for finding small and faint planetary nebulae against a truly dark sky background.  The lens edges are blackened to eliminate internal reflections and further improve contrast.
As you would expect, the chrome barrel is threaded for standard 1.25" filters and has a capture ring to help reduce the chances of accidentally dropping the eyepiece out of the focuser.  Explorer eyepieces are parfocal, minimising the amount of refocusing needed when changing eyepieces within the series.
The eyepiece is set in a heavy rubber cladding which is grooved for easy grip.  It has a soft rubber twist up eyecup which will make it unbelievably convenient to those of us who wear spectacles. The colour coded body rings and clear lettering print will help you find the right one in the dark.
The eye lens is large in diameter and with 13mm eye relief this makes it very comfortable and easy to look through.  It weighs 7.4 ounces.

Coating: FMC fully multi-coating
Focal Length: 5, 8, 12 15, 18 &  25mm

15mm BST Explorer 'Starguider' Dual ED eyepiece

Apparent FOV: 60°
Lens Structure: 6 elements 4 groups
Weight: 172g
Price: £41.00

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