Yup- the distance is actually 90 feet and useful is certainly a subjective term LOL. The stage (actually church chancel) is sort of a thrust stage that's about 32 feet wide and 18 feet deep at the deepest point. The Director wanted to divide the stage in two parts, but it was impossible to...
Disclaimer: I'm an amateur and this was my first attempt a lighting - I also do audio. I work with a community theater that performs in a church that has no permanent theatrical lighting so we have to set up light trees at the back of the house which is about 90 feet to the back of the stage...