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Originally Posted by Rastis
Sorry just thought of this, Where can I get a f8 8 or 10 inch dob from. This sounds like a perfect scope to me. Would be a awfully long scope though. Seems to me that they are all f4 to f6
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Rastis
I have a 4" f9 apo on a motor driven equatorial mount and it produces lovely views of Jupiter and Saturn, and reasonable images using a digital camera.
I also have a 9.25" f10 Schmidt Cassegrain on a motor driven equatorial mount which provides brighter, more detailed and larger views, with superior images using a digital camera.
However, when using the 9.25” SCT, if I turn power off to the motors so the mount does not track and then I try to nudge the 9.25" SCT by hand, it is a pain in the bum trying to keep the planetary image in the field of view (FOV). An f8 dobsonian would also share the same difficulties in keeping the image in the FOV as at the longer focal length (and higher magnification) the FOV becomes quite small and the planet literally races across the field of the eyepiece.
Personally, viewing a smaller but stationary Jupiter and Saturn using my 4" apo on a driven mount is much more pleasing for me, than trying to chase a larger, brighter image of the planet on a non-driven mount. However, people do practice the latter quite competently and appear to be as fulfilled as I am when using my 4" apo.
If you are keen on planetary viewing, prior to making a purchase, I would recommend that you get to look through a 4” scope tracking and an 8” dob non-tracking, so you can experience the realities of using both instruments as it is almost impossible to convey the experience via words alone.
Cheers
Dennis