Imac dual monitor issue

Using an iMac and new led tv hookup

The only problem i am having is that i want to turn off my iMac monitor while leaving my TV on to use as my monitor while leaving the imac running.

I have yet to find anything that shuts off the iMac monitor but still leaves my tv on.

I am currently using a program called shades. I have to use the mirrored monitors and the iMac screen to almost 0. but it is still not all the way off.

Does anyone know of how to control the dual displays?

If you were using a Mac notebook computer it would be possible by operating in clamshell mode, however, that mode of operation is not available with an iMac. I don't know of a way to do it but that doesn't mean there isn't a way.