The ETX-90 is removable from the fork mount easily by removing four screws, though repeatedly removing it dozens of times would eventually wear out the screw holes. It also has a pair of holes on the bottom threaded for standard 1/4" x 20 bolts used on many tripods.
I own both an ETX-90 RA and an ETX-90 EC--same optical tube, different fork mounts, different eyepieces. Actually, for casual planetary observing, the RA fork mount is OK, IF you have a solid ASTRONOMICAL tripod to put it on, such as the equatorial version of the JMI Megapod--which costs about as much as the scope itself. The nice thing about the RA fork mount, or any motorized polar mount, is automatic tracking of celestial objects once you locate them. You lose that ability with a standard photo tripod. The RA isn't meant for long-exposure astrophotography, but no $200 scope has a polar mount good enough for that, though the RA is good enough for piggybacking a 50mm camera lens (rather than using the scope itself as a lens)--I've done it, with exposures of 5 minutes. A very sturdy table, such as a concrete picnic table, is also OK for using the scope in equatorial mode with its screw-in legs.
The drawback to the ETX-90 for astronomy is its small light grasp. You'll see pleasing views of Jupiter, Saturn, and the Moon, plus a few of the brightest Messier objects, but a lot of "faint fuzzy" objects will be mighty dim. Still, for its price of about $200, its only competition is Orion's smallest Dobsonian scope, and that scope is not suitable for birding. The ETX-90 would be nice indeed for birding.
The RA fork mount base is HEAVY for its size--metal, not plastic, unlike the computerized EC mount. Actually, on the Megapod, you could use the scope on the original fork mount for birding or equatorial tracking, but it would be a heavy combo. The optical tube is pleasantly lightweight.

Daniel Johnson ("Dan"), owner of
ETX-90RA, ETX-90EC, Meade 12.5" Dob, LX-200 GPS, and Megrez 80. I love this stuff.