Can I copy the mac OS directly from my macbook pro to a card in the SD slot? I bought a refurb macbook pro a few years back, to use for video editing. It came with Snow Leopard installed. I never upgraded beyond 10.6.8 as I still edit in FCP 7 and didn't want compatibility issues. Now I've reached the point where I need to upgrade my OS for pretty much everything other than video editing.

So I thought a good workaround might be to plug a microSD adapter into the SD slot, with a 128GB microSD card in it, and to install the OS 10.6.8 software on that. That way I could boot up from the SD drive when I need to do video editing, but the rest of the time I can just run the computer with the latest mac OS installed. 

So here's my conundrum. When I bought the macbook pro as a refurb, it didn't come with software install disks. Is there a way to copy the 10.6.8 OS directly from my laptop to the microSD card? Or do I have to shell out the additional $ to buy another copy of 10.6.8 from the app store?
You can use Disk Utility to make bootable copies of the OS. It's always preferable to use an OS that's not booted (i.e. you're not copying yourself), but in practice, OS X generally behaves well. Worst thing - you waste time with a non-bootable copy.

You could also look into something like SuperDuper or CarbonCopy Cloner. They will serve you for more than the initial need of making a backup copy of the OS.

Worst case, you end up with a broken system and have to pick up a secondhand disk from craig's list or similar. Apple also sells replacement media, but used media is usually less expensive.