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focuser
The fine focus control option of the 10:1 makes focusing easier. The f5 10" GSO dob will be a more touchy focus point than the f6 8". The in-focus point is narrower with the f5 (faster) scope, because the light cone is "steeper" coming in from the primary mirror. I have the 10" f5 Bintel Dob and notice the absence of the 10:1 option which i have on a different (faster) scope, so I, too, was going to upgrade to the 10:1. It's on SALE!
The absolute gain is probably modest, and most noticed on scopes in the f4-4.5 range. But if the difference is cheap (it seems to be!) AND you really like planets, you might find it does make a difference on the enjoyment factor. Collimation tool and accuracy are probably more important overall by the way...
Scott
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