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I do not agree with the "consensus" against fast Newts for visual.
I have two 8" f/4 instruments, one is exclusively for visual, and the other I can use on a dobbie mount or on a GEM. I have no problem with collimating them, and both hold collimation really, really well. Mind you, the primary mirror cell of both scopes were fabricated by me, including that of the solid tube where I have also modified the secondary assembly. This is where the majority of collimation problems lie with mass production scopes - the primary cell is not adequately manufactured, same with the secondary mirror holder. If these two vital components are properly made, collimation is not an issue.
For visual, I do use a coma corrector when using 30mm and 24mm eyepieces, but not with any other shorter focal length EP.
These two dobbies are phenomenal as rich field scopes. With a 30mm 82° eyepiece, I can get a HUGE 3° true field of view. And having made both dob mounts myself too, manual tracking at high power is a breeze too - no backlash, silky smooth and balanced (no need to use clamping devices to provide quasi balance).
It is incorrect to dismiss really fast Newts for visual. What is critical is that these instruments, and mounts, be properly made. There are plenty of BIG dobs that are faster than f/4 too, and none of these have collimation issues beyond what any other well made Newtonian has.
Alex.
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