Halfway through sanding, still dark, now what?

We decided to sand our deck rather than use a chemical stripper for, let's call it environmental reasons. I'm not sure what the previous surface was, stained but with a somewhat glossy finish. Anyway it had worn very unevenly between the bits that were in the sun and the part that was covered. We're about halfway through sanding and this is the result from the sanded part.

We're committed to an Olympic Elite semi-solid stain that I gather will show the uneven color here if I don't do something more. Is the best solution to finish with the sanding, then use a stripper and brightener to even out the look? Or what would you suggest?