Which light do we use to measure flux?

[Phys12]

When we record the flux of a light coming to us from outer space, which light do we use? Do we use visible light or X-ray or UV? Or is it all? Or does it depend on what we're looking at?

 

[davenn]

anything you like ... you just need to state at what freq or wavelength the flux (signal strength) was taken at

for example the daily solar flux reading from the sun is done at 10.7cm (2800 MHz)Dave