Multiple off-axis apertures?

[koputai (Jason)]

Now this is probably obvious to some, so please take it easy on me!

We all know that if you want to stop down an SCT or Newt, you
make an off-axis aperture, like this:



Or on a refractor, it's in the middle.

Now what if we want more aperture, but instead of making a bigger
hole, we make more small holes, like:



What happens to the image?

I'm actually thinking about this in relation to using multiple small
(affordable) red ERF filters for solar observation (in conjunction
with the appropriate blocking filter) using a refractor, but this
could also be applied to an SCT or Newt.

Cheers,
Jason.

[multiweb (Marc)]

You would get a lot of diffraction spikes at focus. Like a hartman mask.

[Merlin66 (Ken)]

In terms of solar imaging there would be a loss of contrast due to the distrubance of the diffraction pattern.
Also you'll probably be disappointed if you hope to use std red camera filters as substitute ERF's. Unfortunately I've found from bitter experience that they are not of the optical quality required for astro imaging with longer focal lengths......