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View Full Version : How Does A Parabolic Reflector Work?



GrassHopper
26-04-10, 11:05 PM
I've just ordered a parabolic reflector, can't wait for it to arrive. Anyway, as with most things I like to get into how shit works and I'm sure most of you stoners are the same, lol. So I've been trying to find some info on how they work.

Now I remember from school about parabolas and x and y axis and all the rest as in the diagram http://images4.wikia.nocookie.net/__cb20080728030646/solarcooking/images/f/fd/Parabolic_diagram_1.jpg

I've found a very basic little applet (http://www.analyzemath.com/parabola/parabola.html) that demonstrates how it works, it is VERY basic lol.

Thing is, everything I find has to do with Antennas and Solar Cookers which collect rays of sun in the solar cooker and whatever rays from satellaites etc for the antenna - you with me so far? lol.

So am I correct in thinking that the lamp is the focal point and rays from the lamp are bounced off the wall of the parabola? ie. working opposite to the satellite dish and solar cooker?

Also, as the lamp is in a vertical position ie. following the y axis, mean that light is not only coming from the focal point but some inches either side causing light to scatter when reflected off the parabola?

Also, anyone used CFLs in 'em? I was wondering if a 300w or even bigger if they exist, would work as well as a HPS or is that just defeating the object?

Any info/experience on this would be good.

yoko2009
26-04-10, 11:29 PM
Hi GH i use the parabolic growstar and basically with a normal reflector where the bulb is horizontal straight away you are losing quite a bit of light as a good percentage is bouncing straight up and back to the bulb, even though the basic reflectors do help reflect light, most of it is aimed straight down which creates hot spots directly under the lamp and you will also get a pyramid effect of growth with the plants, the ones in the center being larger and as they move out they gradually get smaller. With the parabolics the bulbs are positioned verticle so straight away the full 360 degree of the light is being used and the parabolics simply help reflect this light down in a much more even manner which you will find gives you a much more level canopy overall. As well as the light being spread you will find the heat is much better spread and you dont have hot spots under the bulb. For example using a normal reflector with the bulb horizontal i had my 600w 18-22" away, using the parabolic i could have it as close as 10" away with no heat issues. You will be really pleased with your choice mate, im about to get 2 parabolics for my large tent, i wish i could afford to grow stars but they are pricey!

hope this helps im stoned as im writing this so might come out as a right load of drivel but i cant be arsed reading it back to myself so good luck desyphering my stoned code waffle hehe

GrassHopper
27-04-10, 04:29 PM
Ah Cheers Yoko, that's simple, makes sense. I was looking at it too technically, as always. I've already got a 600w HPS that I've hardly used because of heat issues, I guess it's about to be put to proper use at last :)

How many plants do you get under 1x 1m dia. parabola? I'm talking typical size plants ie. Orange Bud, Blue Cheese.

Thanks again yoko mate. Can't wait to get it up n running.

yoko2009
27-04-10, 08:36 PM
No worries hopper, i had my parabolic in a 1.2 x 1.2 and had 9 in there, i vegged for 6 weeks from cuttings and then moved to a bigger tent for flower, by the end of the veg period the tent was crammed out, however i reckon you could get 9 x 10 ltr pots in there as long as you veg for 3-4 weeks (from cuttings not done from seed so not sure how long they take to get to the size of a rooted cutting) and do a bit of pruning on some of the lower leaves and i reckon you could do 9 for a full grow. Anotehr thing with the parabolics is they get light further through the canopy than your normal reflectors. If you wanted to do a 6 week veg in there i would go 4-6 plants depending on strain and shit