BBC Sky at Night Magazine

William Optics GT71 apo refractor

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The GT71’s apochromat­ic triplet lens is manufactur­ed from high quality optical glass, including FPL-53 elements with high transmissi­on coatings, all held in place with a CNC-machined adjustable cell. By using three lenses in this way, the dominant colours of the spectrum can be brought together in close focus. Astrophoto­graphers will be able to enjoy pinpoint star images without bloated colour haloes, while visual observers will get to appreciate the views of bright targets such as the Moon or planets free from distractin­g colour fringes and colour aberration­s.

The focal length of the telescope is 420mm, giving a sensible focal ratio of f/5.9. This in turn enables astrophoto­graphers to speedily capture photograph­s of large nebulae and extended deep-sky objects. Indeed, all our captured images were short unguided exposures. The excellent colour-correcting properties of the telescope make it eminently suitable for DSLR and one-shot colour CCD photograph­y, appealing to those desiring a simple and compact option for holiday or travel astronomy.

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