Originally posted by PentaxScott A tabletop tripod is going to be purchased regardless of a full tripod replacement. It may work in this case?
I do think so, although it will necessitate stooping down to see the screen (absent wifi tethering, or if it's set up on top of a table or rock or the like). They are extremely stable with the legs splayed out wide. You will still want a good full fledged head on it, and for long lenses a gimbal type has definite advantages IMO.
I'm not sure what declination the eclipse will be at; this option may start to be impractical if it's close to straight upwards. In that case even a flippy/articulating screen could be hard to access, and you could run into physical interference of the camera body with the ground, tripod, or head.
Nevertheless, I really like mine. If you can get one with a leveling base, which is under the head and allows for some leveling adjustment without using the legs or head, that is ideal. Those are very useful for gimbal heads, and also for ballheads that have a pan feature. The
Berlebach one I linked has it, and the Leofoto one I linked has
a counterpart with the leveler, although it's only rated for 11lbs (not sure why, probably just the extra projection upwards of the COG). They can also be bought separately and put on top of any tripod (I've got
this one, which I put on top of
my Berlebach because I didn't know I wanted it when I bought the tripod), but that will add to the cost compared with getting it built in. It would then be usable on a full size tripod later, though.
If buying one of these, and planning to use it as the base of your monopod setup for your Theta, I would make sure in advance that there's a monopod/extension available that connects to the standard tripod plate. I would guess so, since it's about the most standard attachment there is: a 3/8 thread with a wide flat base. I don't know anything about those, though. I've seen the video monopods with the 3 tiny foldout feet, and those might work for the Theta, but won't do a thing for your 150-450 + DSLR shooting at the sky.
All in all, since you say you want a tabletop tripod anyways, this might be a good way to go. It will let you put more of your budget into getting a top notch head, which should always be something like half of the package (some people overlook that even if they get a nice sturdy tripod).
Just double check that everything is going to be compatible for all the uses you have planned for it. And be ready to be the guy squatting down while you're trying to get your eclipse shots