12 hours of light or 12 of hours dark, first.

[thepaan]

I was thinking more about this lately and it occured to me that 36 hours or a multiple of an entire day plus half would be the best length for an initial dark period. There was a study done on resetting the clock during the dark period (which I can't seem to find at the moment) where they had the most success resetting in a 12:12 light dark cycle at the 6 hour mark. with a 2 hour window. Take this with the fact that the rythm persists (although somewhat diminished) after a full day of darkness, then you have 36 hours as an excellent choice.

[ShittyJon]

To answer the first guys question I give them the darkness 3-5 days before harvest. Meaning when I think Im about 3-5 days out I go dark. AK-47 by the way.

[CovertCarpenter]

...but after my aforementioned Problems With Exhaust Fans, I kinda left a single 26w/100w Equiv. 2700k Warm White CFL starin' at 'em in their Dark Cycle, initially while they were used to 18 from the HPS above, and then, after a day and a half, the HPS was on for 12h, but the Single CFL persisted. For Three Days.

I am not sure why I did this. I suppose that I wanted to try the 'other' way of doing things, which was to give 'em a looooonng 'day' that said "LONGEST day of summer @ high latitude, and then when I turned the lights off for 12, well, let's just say that they /slept/...

Such lovely little (git'n BIG!) girls...

[shaimeless]

turn the lights off for 24 -36 hrs then run 12 on then 12 off cycle thats what ive done its very affective