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  • Australian Sky & Telescope

    Become a planetary pro

    Oct 08, 2020 4 minutes
    by Thomas A. Dobbins

    IMAGES WITH SOUTH at the top and west at left have long been the convention for drawings and photos of astronomical objects, as well as lunar atlases and maps of Mars intended for telescopic observers.

    A Newtonian reflector produces an inverted image, making comparisons with the eyepiece view straightforward — simply rotate the photo or drawing to match the view. Unfortunately, the image through a refractor or Cassegrain reflector (including Schmidt and Maksutov variations) equipped with a conventional mirror or right-angle prism star diagonal is erect but flipped left-to-right. This mirror-image reversal occurs in any optical system that reflects light an odd number of times.

    Righting the view

    Observers with refractors and

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