jolt Posted August 1, 2015 Share Posted August 1, 2015 I've been running a single Kessil A360WE about 6" above the water line for over a year. I am unhappy with the shadowing from the extreme single point lighting and angle, which causes some of my acros to thrive on one side and wither on the other side. So I bought the Kessil gooseneck extension. After installing it the light is now 13" above the water (which is now within Kessil's recommendation of 1'-2') Now comes intensity adjustment. I have been running at 43% intensity and 53% color. A while back I measured the PAR (which I know is a defective measurement for LED but I am going to rely on a *relative* analysis here). Measured with the light 5" above water, dead center measurements I read the following PAR at 50% color and 50%, 75%, and 100% intensity: This shows that PAR drops about 13% per inch in water, regardless of the light intensity. The refractive index of sea water is approximately 1.4 while air is approximately 1 (see: http://scubageek.com/articles/wwwh2o.html),so I estimate PAR would drop about 40% faster in sea water than in air. SOOOO that would mean it should drop about (1/1.4 * .13) or 9% per inch in air. Therefore, if I raised the light 7" and want to maintain the same intensity I'd like to figure out a formula to raise the intensity: SEE POST BELOW Any comments/feedback on this would be very appreciated .... 1 Quote Link to comment Share on other sites More sharing options...
Dan H Posted August 1, 2015 Share Posted August 1, 2015 I just wanted to say that's awesome math. 1 Quote Link to comment Share on other sites More sharing options...
jolt Posted August 1, 2015 Author Share Posted August 1, 2015 I think it may be like a fixed annual percent depreciation calculation. That is, at each inch it's 91% of what it was at the inch above. I only know how to solve this using a table but I am sure there is a fancier formula. So I *think* this is actually the right way to do the final calculation, basically match the expected surface value at the two heights (I am just gonna use relative percent power as a function of power loss per inch). SO I just plugged in my old intensity and figured out what it 'depreciated' to after 6 inches, and then plugged in new intensities until the value at 13" was about the same. Quote Link to comment Share on other sites More sharing options...
+etannert Posted August 13, 2015 Share Posted August 13, 2015 Hmmmm, interesting Quote Link to comment Share on other sites More sharing options...
jolt Posted August 13, 2015 Author Share Posted August 13, 2015 So I think it turned out to be too much. Some of my acans freaked out at 66% and would not come out for a few days. Lowered it to 48% and it seems better Quote Link to comment Share on other sites More sharing options...
FarmerTy Posted August 13, 2015 Share Posted August 13, 2015 Math is the universal truth! It can't be wrong! I'm pretty sure it's the acans. They need to get their act together! 1 Quote Link to comment Share on other sites More sharing options...
jolt Posted August 13, 2015 Author Share Posted August 13, 2015 Unfortunately my (green) red planet and my acans just cant seem to agree. I think the acans may need to find a different neighborhood 1 Quote Link to comment Share on other sites More sharing options...
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