FWIW, I'd just try to find the studs and attach your rod hardware where there is a stud. Then patch the plaster. The hangers might not end up perfectly symmetrical, but you wouldn't have any "mending braces" on your wall. Sometimes, it is hard to find a stud with plaster and lathe - and the studs in old houses aren't always spaced a uniform distance apart. One way to locate a stud is to measure from a known stud (or a corner) 16 inches to the center of the next stud (works on new walls). Or look at baseboards for nail holes - they may be attached to studs. Another way is to use a very small drill bit and drill a series of consecutive holes in a line, low on the wall, until you reach a stud - then try the 16 inch measuring technique to find the next one. Or drill a very small hole and poke a wire in and feel both directions for a stud. Of course, you have to go back and patch and paint the little holes!

Thanks kimitchy. I found what looks like a covered nail hole in the base board, so I will probably try to use that. I may be able to poke a wire into the hole that is already there since I think it is close to the stud. I suspect that the fine crack may actually be next to the stud, so I may already be there, but just didnt use deep enough screws. So hopefully problem solved- I'll find out this weekend!

thanks

Or use molly anchors.

I might consider molly anchors too. I guess I need to see where the stud is. If it is close by, I'll use that. My worry about molly anchors and toggle anchors is that if the fail, they could rip out a bigger hole in plaster- but I am probably worrying too much since the curtains and rods are not that heavy!

The problem with curtain rod anchoring is that the rods stick out from the wall and place a significant withdrawal load on the anchor.

Plastic sleeve anchors in plaster cannot get a good grip (like they can in masonry) since the plaster tends to crumble under the loading as the anchor expands.

Molly anchors go all the way through and expand behind the plaster to spread the load out over a larger area.

It can be a chore to find long enough molly anchors if the plaster is 3 coat and thick.

Thanks for all of the help! There was actually a stud directly behind the hardware. I filled the holes with vinyl spackling, put in new anchors while the spackling was wet (I hope this holds), painted, drilled a pilot hole when everything was dried, and used much longer screws. So hopefully this works. If the other ones pop out of the plaster, I will use molly anchors if there is not a stud behind them.

thanks!
Mike