We have measured by type 1A and approximate candle power as well as other means but we all know light moves at different speeds in different mediums.

All I know is that I can't see it except for gravitational lensing.
The damn dark stuff has no electromagnetic radiation.

They say right before the annihlation of matter vs. antimatter there were 1 billion and 1 particles of matter and only 1 billion particles of antimatter. Visible matter barely won, but the left over debris and energy is in my opinion the dark matter.