I have an IMac with time machine & time capsule. If I buy a large external hard drive can I backup all my Lightroom info as well as everything else by going to time machine & having it backup to the new hard drive after it has made a backup on time capsule? This way I would have two backups.
I am not sure about the time capsule/time machine backup but I believe it backs up the complete data on your hard drive.
Yes, you can backup Lightroom catalog on the external hard drive.
You can setup backup time under Catalog Settings > backup > it would prompt to backup when you will quit Lightroom > click on choose next to the location and specify the location as your new hard drive.
If you want to backup original images as well, you can setup to create a second copy of images on your external drive while importing.