Why 'knife edge' baffles.
Posted 22 December 2009 - 06:20 PM
Posted 22 December 2009 - 06:24 PM
Posted 22 December 2009 - 06:34 PM
Without too much more effort, i use a circle cutter on my drill press and reverse the blade. Simple method
Posted 22 December 2009 - 09:15 PM
Posted 22 December 2009 - 10:10 PM
Just to be sure the picture is clear, a baffle of non-zero thickness will have its own 'tube wall' section. The thicker the baffle ring, the more surface area this effectively short tube will have, thus potentially scattering more light in the same way a non-baffled tube would.
Yes, this area is *physically* very much smaller than the main tube being baffled. But if there are several such 'thick' baffles installed so that as seen from the focal surface their edges are nearly in line, the *angular* extent of these scattering surfaces is now relatively large when seen in projection, closely surrounding the objective aperture.
One way to easily make knife-edged (or nearly so) baffles is to use a thicker material for support but which has a slightly oversized hole. A much thinner, correct hole size material can then be attached on the objective (skyward) side. In this way the thin sheet shadows the thick material's own 'tube wall' section.
Posted 23 December 2009 - 08:06 AM
Posted 23 December 2009 - 04:03 PM
Posted 23 December 2009 - 05:02 PM
Posted 27 December 2009 - 02:30 PM
The angle creating the knife-edge is on one side of the baffle and is usually located on the focuser-side of the baffle to avoid back scatter of stray light towards the objective.
Posted 27 December 2009 - 02:40 PM