mh 250w 4000k, is this ok for veg

i have been vegging with a 150w envirolite (power plant) and although i am happy with the results, would like to try mh.

after much seaching through the web have come across many varieties but none seem to be higher than 4000k (400s,600s and 1000s all have the 7200k option) but i only require a 250 to veg 4-6 plants for 4 weeks.

what im really asking is for some one to steer me in the direction of a decent mh bulb (250w as i have just got hold of a mh/hps ballast).

thanks in advance and plus rep for all

im in the uk and we dont seem to have much variety as our american counter parts

here's why a 4000 K is not very good, (You'd be better off sticking with the florescent IMHO)
https://www.rollitup.org/attachments/cfl-growing/240662d1226605588-5000k-vs-6500k-hortgraph2.gif
AFAIK nobody makes a 6500 K 250 watt MH.

I advise something like this. Get a MH conversion bulb and you're good to go.

i just bought a hps/mh ballast, have everything except a decent bulb, that was a hps light for flowering (2000k). allready have a hps (600w grolux dual spectrum, lightwave digital ballast).

thats a great chart , so photosynthesis is best at 6500k, gonna do a bit more searching.... would be interested if someone comes across one...... peace

just found a 5200k mh (250w) requires an enclosed luminaire (not to sure what that is). if anyone could help it would be very helpfull ....... thanks all

cocoxxx said:

just found a 5200k mh (250w) requires an enclosed luminaire (not to sure what that is). if anyone could help it would be very helpfull ....... thanks all

Click to expand...

buy a a 400 watt kit with a 6500 K bulb.

a 400 is to much for what i need

EYE Hortilux makes a 250 watt 6500k MH bulb. It produces 72 lm/W. The best CFLs produce around 75 lm/W. Their 1000W BLUE bulb produces 80 lm/W.

So there really isn't much difference in efficiency versus fluorescents.

Reference: http://www.eyehortilux.com/blue.html

thanks man, i think i will just get another 150 envirolite, i thought the mh was supposed to blow away cfls in terms of lumen output, i guess not... thanks again man. +rep

cocoxxx said:

i thought the mh was supposed to blow away cfls in terms of lumen output

Click to expand...

This is posted for the benefit of anybody else who was reading this thread, not cocoxxx who has made up his mind and finished with this thread.
even with the most efficient reflector on the planet it won't come near the output of HID. Most people don't even bother with one from what I've seen they just dangle them above the plants, bare bulb.
Here's why: #1 half the output is on the inside core of the bulb and can't radiate out efficiently #2 The glass coils are too close together for all the light to radiate out at 100 % efficiency, a large percentage of light is converted into heat because of that.#3 The light from a CFL won't penetrate as deeply into the plant to have as much effect as HID.
Maybe 400 watts would be overkill for cocoxxx but it would be far more energy efficient as it would produce more growth in a shorter time. Vegging is not time specific like flowering. The more ideal conditions you can give them the faster it will go.
Another thing, costwise HID is cheaper in the long run as your not throwing away your ballast after each bulb replacement.

Another concept to consider is the inverse decay of light. In simple terms, for every doubling of distance, there is 1/4th the amount of intensity. So, comparing a CFL that is 3 inches away from a plant, compared with an HID that's 1 foot away. Or 3"*2*2=12" means, roughly 1/4*1/4=1/16th resulting intensity. Or comparing a HID, it's really great they're so intense, because this difference of distance results in a substantial loss of intensity.

The law of inverse decay states: i1/i2=(d2/d1)^2, or: initial intensity / target intensity = (target distance / initial distance) squared
Making the initial intensity 1, lets find the factor of decay for these distances.
3" = 7.62 cm
12" = 1 foot = 30.48 cm

1 / i = (30.48/7.62)^2
1 / i = 16
i = 1/16

There we have it, using the equation for inverse square decay and units of centimeters, we have confirmed the theoretical decay difference. Indeed, what unit you use doesn't matter, as long as they match.

Also, all types of fluoros are available with external ballasts. That you do not throw away after each bulb, as it's not integrated. Also, I've found 4 packs of CFL bulbs(integrated ballasts) that net output around 6400 lumens and just under $8.

Which is 800 lumens/dollar. A decent 400w, 40k lumen HPS bulb, is probably around $50(an actual agro/horti-culture bulb). Which is 800 lumens/dollar! Probably no included ballast, though. Any ballast(s) makes HID more expensive.

Also, 1 CFL lumen has more PAR than 1 HPS lumen. Meaning the light is more photosynthetically useful.