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So, bill....you found that on ONLY the 5mm, taking off the negative lens group provided a far better viewing experience overall?
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Sorry ...not sure which lens group you are referring to. I found that removing only the Smyth group did NOT produce as good a view as removing both the Smyth group and the next doublet above it. There are 8 total lenses in a Hyperion (except the 24mm). Had to remove 1/2 of them before it became not so bad. To do this it is necessary for one to do some EP surgery and break the mid-seal on the 2in housing to unscrew it, then remove the retaining ring and lens cup from the lower half of the 2" housing, and of course leave the 1.25" barrel off with the Smyth group that it contains also.

-Bill

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250mm f/4.7 Orion XT10i Dobsonian
102mm f/8.0 Tak TSA Super-APO
66mm f/5.9 WO ZenithStar SD APO
40mm f/10 Coronado P.S.T.

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