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  • Australian Sky & Telescope

    A giant breakthrough

    Jan 09, 2019 5 minutes
    by Jerry Oltion

    MEL BARTELS HAS BEEN ON something of a crusade lately. Long a proponent of large, thin mirrors, he has also become a proponent of fast mirrors, resulting in what he calls “richest-field telescopes”. He has previously completed 32.5-cm f/3 and his 15-cm f/2.8 telescopes. He’s since taken it up a notch both in size and speed: He has just finished a 62.5-cm (25-inch) f/2.6.

    That in itself would be exciting enough, but Mel has come up with an innovative new twist on the standard alt-azimuth mount that completely eliminates ‘Dob’s hole’ (see box).

    But wait, there’s more! Pierre Lemay (originator of the tracking ball scope years before I came up with the same concept) has devised a new two-speed helical Crayford focuser for the same scope. Together, these design elements have created a completely new observing experience.

    Mel caught the thin-mirror bug

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