Does this 4-inch apo re­frac­tor‘s lenses ef­fec­tively counter colour fring­ing?

Sky at Night Magazine - - SCOPE DOCTOR -

To en­joy views or pho­to­graphs of the night sky in nat­u­ral colour is a real plea­sure. How­ever, achiev­ing those im­ages re­quires an apoc­hro­matic te­le­scope with spe­cial lenses de­signed to re­move chro­matic aber­ra­tion. The Omegon 104/650 ED uses a triplet lens sys­tem with air-spaced el­e­ments con­structed from FPL-53 and FPL-51 glass to bring the ma­jor colour wave­lengths of light to a match­ing fo­cus point. At the eye­piece the ef­fec­tive­ness of the triplet lens was easy to see. We ob­served bright tar­gets in­clud­ing the Moon, Jupiter, Venus and Mars, care­fully check­ing for any tell-tale blue haloes or green and pur­ple fring­ing. At the cen­tre of the view we found the colour cor­rec­tion of this lens to be ex­cel­lent, al­low­ing ob­ser­va­tion of smaller de­tails in Jupiter’s bands and even on Mars, which was not best placed for ob­serv­ing. Our cam­eras con­firmed the find­ings from the eye­piece, a full frame DSLR and colour CCD cam­era pro­duc­ing im­ages of stars with­out bloated blue haloes, ably demon­strat­ing that the Omegon 104/650 ED de­serves its ‘apoc­hro­matic’ badge.

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