Upgrades your existing cheap prism or mirror diagonal (ie the ones you commonly get bundled with telescopes) for vastly improved resolution at the eyepiece.

Top-performance, the nosepiece is aluminium and is fully threaded for standard 1.25" filters. The nosepiece is internally flat-blackened to eliminate reflections for improved contrast. The eyepiece holder is aluminium finished in black-electrophoretic paint with two chrome cross screws. Screw-assembled mirror body in dense resin (ie not flimsy thin plastic), gives the whole unit a good quality feel.

What do you want from a good 90-degree star diagonal? The answer, nothing. That's to say, we do not wish to see a detectable change in the image quality compared with the straight-through view. We require only that the diagonal deflects the image for our observing comfort through 90 degrees, but without altering its resolution in any way. To achieve this the mirror surface must be manufactured to a very high standard of flatness - and this is hard to do. The process is at least as stringent as grinding lenses to a high-precision figure, if not actually harder. In the last decade we have seen the quality of the Sky-Watcher mirror found in this, their 'work-horse' star diagonal, steadily improve in our tests. We recommend it without reserve, and you can be confident that you would need to spend nearly twice as much to have a diagonal with a detectable improvement in flatness.