Halftone moiré pattern mess

I scanned a black and white image from a magazine for upload into SL. It looked fine on my screen and still looked fine when I adjusted the scale to 512 x 512 pixels.

But when I uploaded it into SL, it then developed a moiré effect from the halftone screen dots. I once knew how to resolve this in Photoshop, but I have long forgotten. And I'm not sure how to resolve it anyway since it looked fine everywhere except SL.

Should I try rezzing it at different sizes? Or would uploading it in a different format than TGA make a difference? I think SL converts everything to a form of JPG anyway doesn't it?

(For the record, I own the copyright of this image. I just have no extant version of it other than the magazine photo.)

The magic google term is descreening, that should turn up a lot of hits for different fixes, most boil down to adding a little noise filtering and then blurring. Some scanner software has descreening built in these days, you might check for that too.

Also while scanning if you have the area, scan the image in at a 15 degree angle, apply your descreening method and then rotate to align, then you shouldn't need to blur.