I would probably do it differently ( depending on some assumptions I am making). Thats one of the fun things about doing lighting, you get to think about multiple ways to do something.
Assuming that you want this to look realistic:
When moonlight goes through the window ( I'm assuming a full moon here ), and the room is dark ( again I am assuming that ) - you will see several things.
1 - you will see the moonlight as it passes through the glass / or sheer
curtains in the window. You will also see highlights on any window mullions,
etc. To get this look ( if you only have four feet) I would put some kind of wide
throw fixture behind the window. Get it as far away as you can. The purpose of this
fixture is simply to add highlights to the window,
curtains,
etc. ( by the way - get your designers not to just make an empty hole in the wall and not put in something to represent glass. ( don't use glass ). Black
screen, bobinette,
etc work pretty well.
2 - you want to see the shaft of moonlight as it hits the bed. As Brandon suggests - hang a S$ sharp focus with appropriate gobos to match the shape of the window in the wall of the set. ( ideally get the designer to
build the window to match your gobos). I would likely put a very pale blue in both of these fixtures as ( for me) this is the color of moonlight.
3 - There is some bouince in the room from the moonlight hitting the bed, and bouncing off of the walls and ceiling. On your set there are a lot of missing walls, so I would use some area lights ( or a
wash) at a low
intensity to repreoduce this light.
I'm assumin that you have area lights,
etc so you can get the
intensity up when you are not using the special.
One strong suggestion. ( almost a commandment ) Go outside on the next full moon, look at the shadows that the moon light makes. Look at the color of the moon light. Turn off the lights in your
house and see what the moon looks like coming in through a window. Then think how to replicate that look on
stage with the direction of the light, the shape of the beam ( hard or soft), color, and
intensity.