PAR Degradation through air?

[Soylent Wrasse]

Second guesstimate:
ATI 6 tube 48" fixture.
Assuming approx 7" off water 24" deep tank.
fixture is 2.1" thick but assuming you only see about 1:" of that, each square.
Random PAR chart picked from above video
Sig more than prev estimate.

Did find an error in prev. estimate. Thought I used a 48" "model" 4 tube but on further review is was 36"
t5PAR

So at 27, i.e. the bottom of my tank, center roughly 300ish par. Top 600ish. Seem about right-ish?

 

[oreo54]

So at 27, i.e. the bottom of my tank, center roughly 300ish par. Top 600ish. Seem about right-ish?

Barring any real measurements and based on limited data, seems logical.