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Mike, I've chosen to drop the focal length back so the scope picks up less wind loading. The new camera I'm looking at (Grasshopper2) has smaller pixels so I'll gain back the magnification there.
I have a larger central obstruction with the new scope - 25% vs 20% with LEXX but all the simulations I've done with abberrator etc show that's not a problem.
ps I'm testing a bintel 5x barlow, haven't had good enough conditions yet to see how the quality compares with my 5x powermate but I have found that the bintel 5x gives a lot more "gain" than the powermate, I can get the same size with no extension tubes on the bintel barlow as with 100mm extension tubes on the powermate.
But one potential gotcha with the bintel barlow is that the rgb channels focus at very different offsets, so maybe that's not so good. Definitely bad if you're using a colour camera but even with a mono camera this may lead to a softer image even within each channel. I'll know more when I get good conditions again...
cheers, Bird
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