Very dry wood table

You might get a good answer here, however you will definitly get some informed opinions from a specialist site such as woodworking Australia.
http://www.woodworkforums.com/f9/
thats the finishing and restoration area of the board
Australians know a bit about sun damge as well.
I suggest you post a pic of the product if possible or give the brand name of the product you intend to use.

Without seeing the table, it would be hard to say, but i would never advise using polyurethane on good wood. I would say that you should definitely oil the table, and for god's sake, get it out of the sun and keep it out of the sun. Linseed oil would work, and is not expensive, but it will also leach out in your dry climate quickly. Tung oil would be best, but it would not be cheap. Be careful when pricing tung oil, there are any number of people out there who sell it in pint containers (and you're like to need one or more quarts) for five to ten times the actual worth of the product. Look around for something like a refinishing/restoration web site, and price tung oil. I would advise against polymerized tung oil, or tung oil finishes. I would advise pure tung oil. Even if you're not getting ripped off, though, it ain't gonna be cheap . . .

heres a link to a discussion about using oil and poly.
http://www.woodweb.com/knowledge_base/NaturalLooking_WipeOn_Finishes.html

Natural-Looking Wipe-On Finishes
Finishers discuss how to apply Danish Oil and wipe-on poly to a table top. December 15, 2005

You should certainly check out the sites DP has linked for you. The reason i have advised against polyurethane or polymerized tung oil, or any kind of finish, is because you don't yet know how much oil you will need to restore your wood. If, after you have oiled the wood, you wait a few days, and try a few drops more in an inconspicuous place, you may find that the wood will take more oil, which will be just what it needs if it is so dry that it's beginning to separate at the joints.

When the wood has had sufficient oil to restore it, time enough then to consider finishes. I personally don't like polyurethane finishes, but that doesn't mean that you shouldn't use one. Definitely check out the discussions DP has linked.

I'm with Set. Poly looks like plastic because it is plastic. Go get the Tung Oil, brush it on, wait twenty minutes or so and rub off the excess.
Go away.
Leave it alone for a day or two.
Do the Tung Oil again, this time rubbing off the excess with good lint-free cotton cloths until the finish has a warmth to it.

Joe(I hope you save that table)Nation

How far apart?

I doubt very much that dryness has caused the joints to separate, Myrna. Individual pieces of wood for a table, unlike those in say, wood flooring, are glued together and there is always a seasonal fluctuation in moisture levels.

How is the table held together underneath? Slats with screws in them?

My guess is that these are stress fractures at the gluelines, probably caused by the effects of the Sun and possibly by the method used to attach the table to the legs.

If the boards have bowed then you're likely not going to get them back together again. Is it a round table or a rectangular/square one?

I'd wet a flannelette [sp?] sheet then put it thru the spin cycle to get rid of most of the moisture and then lay it over the table's surface. Of course, move the table out of the sun. Repeat as necessary to "close" up the gaps, then let it airdry once more, again, out of the sun.

Tung oil, French polih or, an orange oil (which has the highest conc of limonene oil) Water will cause the tenons or dovetails to swell and rupture. (Think what happens if you take a wooden boat out of the water for a long time without a surface treatment). The next time you put it in the water the swelling joints will break at the strakes and joints and your boat'll be on the bottom.

It takes care to bring something back from the dead. What kind of wood is it? If its pine or poplar, Id suggest just making kindling out of it and forgetting about it.

I doubt that the table surface has been put together with either tenons or dovetails, FM. Possibly, dowels or biscuits depending on how old it is.

i also have an antique oak table that is dowelled and i moved it from a moist environment to a very dry one. it has started to rock and roll since moving it and i am wondering if a careful application of tung oil to the affected dowels might help.