With external monitor, prevent preview from opening in MacBook display

I don't believe this is a macbook-specific problem but this seemed like the most appropriate place to ask.

I have my macbook hooked up to an external/second display, have mirroring turned off, and have the desktop & dock on the external with nothing showing on the macbook.

The problem is that whenever I double click something that launches preview, the preview pane opens up on the macbook screen which is annoying b/c then I have to lift up the macbook screen, mouse off the main monitor and then click drag the preview pane to the display I'm actually using.

I don't see anything in preview's preferences to prevent/control this behavior nor can I find anything in system preferences > displays.

Does anyone know how to force preview to use the external monitor that every other application knows to use?

Thanks

Not sure about it on the MB, but on the MBP if you close the lid and have a usb keyboard hooked up it will only view on the external monitor even if you reopen the lid.

Turn on mirroring first. Then close the lid on your MacBook and let it go to sleep. Tap a key on your external keyboard or click your mouse to wake the MacBook up. You can either keep the lid shut or open on the MacBook - everything will be viewed on the external display only. Even preview.

That's the way it works with my MacBook and external Samsung display. I'm using an Apple aluminum wired keyboard and a Logitech optical mouse.

Regards.