hours of light needed from a metal Halide for fgrowing orchids?

[playtime8978]

Does anyone know the length of time I should have my orchids under a metal halide lamp, I am guessing less than daylight hours as the light is more intense than the levels over a daylight hours period, I have a range of them under one at the moment just put up tonight and dont wanna mess these guys up by giving them too much or too little, I am thinking around 8 hours a day average maybe more in summer and less in winter to mimic the seasons light changes. Some are further away from the light that need more shade and some are in the middle and to the side for more light. I am going to have to watch them closely to look for any changes in leaf colour. but an indication of how long I should have the lamp on would be much appreciated. Lastly do orchids need a strict dark period like some plants to thrive? if so this might be an issue as they are in my dining room where my computer is and if the halide isnt on my desk lamp which is a flourescent will be on. Thank you in adavnce for any help you can give me.

[Magnus A]

Hi, everything depends on the distance and what species you have. I suggest that you start with 10 hours during a weekend when you can monitor you orchid regulary. Remember that you can get large effect in the beggining before the plants have adjusted to the new high light.
Your problem will be heat buildup in the leaf, probably not radiation damage. You will never get the maximum lightlevel the orchid get in nature! But you have to let them adjust, and slowly increase the light.
/Magnus

[playtime8978]

Thank you so much Magnus that is great, I thought I would have to watch them rather closely and I am guessing it is a good idea to gently touch the leaves to check they are not getting too hot, I have a thermometer there as well to check whats going on I have to go out for a couple of hours today so I am tempted to turn it off and put the flourescents on for the time I am not home, but I am worried this will confuse them, I have no choice but to go out its a medical appointment, I am normally home to keep an eye on them.