What causes dotted diffraction spikes?

[JamesF]

That makes it look as though the interference pattern changes, but the spikes don't get obviously longer or brighter overall.

James

[wimvb]

2 minutes ago, JamesF said:

That makes it look as though the interference pattern changes, but the spikes don't get obviously longer or brighter overall.

James

It somehow makes sense. In a two-slit experiment, the wider apart the slits are, the closer the maxima/minima. But as I wrote, I'm not convinced that Maskulator always comes up with the correct diffraction pattern. Maskulator only simulates a 2D shadow pattern. Any 3D effects or collimation is not taken into account.

Defocus only widens the diffraction spikes (and splits them eventually).

[andrew s]

Have a look at this 

"Accordingly, a thinner vane will diffract less light, and additionally will diffract this light farther away from the star (or planet)."

from http://www.astrosurf.com/viladrich/astro/instrument/sensitivity/spider-diffraction.htm

Regards Andrew

More information here https://www.telescope-optics.net/spherical1_files/spider.htm and here https://www.telescope-optics.net/spider.htm

Edited December 3, 2019 by andrew s

[wimvb]

Interesting.