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Parfocal rings - Wot are these ???


Telescope40
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Hi. Just come across this subject on a couple of threads. Could someone kindly expalin wot they may be. Are they used for imaging purposes on eyepieces or can they be used visually as well. Where wud I get them from. Getting lazy and hoping my set of eyepieces can be totally parfocalled ! is that a word ??? Thx John

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John, Parfocalising rings, are a set of rings the you fix around the barrel of the eyepiece so that instead of the eyepiece barrel being inserted all the way in, the eyepiece sits a little proud, but at the same focal point as other eyepieces. Therefore negating the need to refocus when changing ep's. It may well work for your collection, I can't say I've ever tried it though.

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My WO eyepieces are not parfocal so I might buy a set of these oneday but as usual have never got round to it.

As John has said they are just a ittle ring maybe 5mm thick and with an internal diameter of either 1.25" or 2" depending on what eyepieces you have. You secure them to the eyepiece barrel via a llittle grub screw.

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Think I'm getting the picture now. May invest in a couple and see how I go. Guess may be a bit of a phaff in setting them set up but once sorted will be nice to swap EP's with no new focussing !! I have set of Meade 4000 ep's which are allegedly parfocal but in practice seem a little mismatched. Am I getting lazy or wot :)

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