Jeff, if you're intending on doing Astrophotography you'll want a focal reducer, a barlow is useful for visual sometimes but rarely for photography, your mak at f12 is fairly slow and will have a narrow FOV. If your HEQ5 doesn't have a Synscan handbox (Go-to) then finding targets, especially faint ones will be difficult. It's also possible to interface an
Argonavis to the HEQ5 and if you haven't already got the Sysncan handbox the Argonavis would be well worth considering. For longer exposures over a couple of minutes you'll need a guidescope (to provice correction of tracking errors) and some sort of guide camera as well as an interface to connect your laptop to the HEQ5 guideport.