Quote:
Originally Posted by Ian Robinson
Do you think the truss rather than a baffled tube will loose a fair bit of the contrast you would have otherwise ?
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Nope, a premium truss dob has excellent contrast. The only reason tubed newtonians need baffling is because they have a tube there for the light to bounce around off.
The truss design with a good fabric light shroud has nothing there to facilitate internal reflections affecting contrast.
Another plus for the truss design is that you can use a smaller secondary mirror size than is possible with the tube design. With the tendency to go to faster and faster newtonians, this aids contrast as it is easier to get the secondary obstruction under 20% with the truss design. The MTF curves on a scope with a <20% obstruction are essentially the same as for an unobstructed scope.
Cheers,
John B