|
I like the curved spider design on this scope. I never really thought about it before but looking at this thing makes me realise it's the most efficient design that is free from anisotropic diffraction artefacts, i.e., from directional preference: diffraction spikes, or even much more gentle brightening of the diffraction amplitude in certain directions.
The vanes look to be 60 degrees of a circular arc, and the three of them cover 180 degrees, i.e., all possible orientations of a spider vane, in equal proportion. Normally in curved spider designs, you see one spider vane covering 360 degrees or 2 with 180 degrees each, even though 90 deg each would be more efficient.
I cannot be bothered to do the numbers now, but for 2,3,4,or more curved spider vanes to cover a semicircle (180 degrees) which is required to eliminate any hint of diffraction spikes, 3-vane setup seems (by inspection) to give the shortest total length thus being the most efficient (i.e., yields max. contrast).
|