Given the amount of energy available per square meter at a distance of 1 AU from the Sun, it is possible to calculate that most known substances would be reradiating energy in the infrared part of the electromagnetic spectrum.
I was thinking visible spectrum but obviously I forgot that there are many, many other spectra that we can observe with instruments lol.
I admit to have been thinking of it functionally like trying to see a blackhole - this would be far easier.
Or it would be, unless of course the hypothetical Type II civilization that can make a Dyson Sphere (I think that the wiki there points out how difficult and probably unreasonable making one would be). also has as-of-yet-discovered (by humanity) supermaterials that don't waste energy by radiating all kinds of waste all over the place.
Honestly, if you're going to go through the trouble of making a DS, you're going to want to capture all that energy and use it for something useful. Its not
too crazy to believe that this might be the case.
That said, I fully admit I wasn't thinking about this in my earlier post. Clearly, using something other than the visible spectrum makes my original point entirely moot, and now I'm off into the land of science fiction. Thanks for the clarity