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Big eyepiece .......

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And you thought that the 31mm Nagler was a beast :icon_scratch:

The middle one is a Zeiss 4" fitting 100mm focal length eyepiece. It's for sale on a certain US forum. I'm not a member there so I can't see the asking price but it does include a 2" adapter.

This would definitely affect both the balance of your scope and your bank account ........ :)


Edited by John
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That is one big beastie :) I'm thinking 4'' concrete block to counter balance it and even then my focuser would probably whimper like a baby before falling to the ground in defeat! I would imagine the price would be truly astronomical.

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I think any eyepiece can potentially add CA. I think the degree to which this is likely to be a problem depends on how steeply it's bending the light. More bending means a greater degree of potential aberrations. That's why the olde refractors were all really long focal ratio. Many aberrations become tamed under these conditions. That's the same for mirrors, by the way: less coma at longer f/ratios. That leads me to wonder if, in fact, a long focal length eyepiece such as this would have less likelihood of CA. It's the extreme wide-field designs which are most likely to suffer. They, of course, are carefully corrected for CA.

Edited by umadog
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I recently made a 100mm focus Plossl with 2" fit for a 8" F25 achromat. The eyepiece composed of two 50mm binocular objectives still had the usual 50 degree AFOV but there is no CA and images are very bright and pin sharp across the field.

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