Just my two cents in my familiar Cyclops advocate role:
- Someone asked a while back in this thread when Cyke got a power upgrade. There is one definite time in canon, and that is when Cyke comes back from Krakoa (so UXM #94 or so) and his powers return. His blasts are so powerful compared to before that he can't control his balance and the force of the beams send him flying backwards. His visor was re-modified to the fatter version he had throughout all of Claremont's run. Which, if we're being picky, seems to get retconned in Morrison's run, where Grant decides to give Cyke a thinner visor again.
- Cyke consistently shows much more power in his blasts at around the start of X-Factor (ie. in the 1980s). Kudos to pr for identifying this period. If anyone ever has the time to read all 70+ issues of the original team's run, you'll see how much the team rely on Cyke's blasts to keep them going. For one thing, he "kills" Apocalypse with them, which is a pretty high end feat IMO.
- Although it's never been explicitly stated, i really don't think Cyclops needs that much sunlight to maintain his blasts. It kind of got retconned in the official MU Handbooks, where they stated his blasts were extradimensional energy. To be honest, although Cyke has looked pooped when blasting WWH (or Green Scar), that's the only time in some 20 odd years he's looked fatigued using his blasts. My guess (and it's only a guess) is that Cyke has matured a bit and physically become stronger - hence he can maintain his output a lot more easily. It's akin to Colossus growing up in the comics and increasing his strength over the years.
- Without the visor, Cyke's blasts defintiely have a massive radius increase, and i'd agree with previous posters that his most powerful blasts have all been with his visor off. So IMO, visorless blast > visored blast (in terms of concussive force). This is just my opinion though.
- Someone asked about what he did in Unlimited X-Men #1. Where he appeared to be fixing the hull of the Blackbird. I always thought the focussed force through his shard of rubyquartz hammered the metal back into place - he controlled the intensity to make his blasts "malleable", as opposed to simply blowing a new hole in the hull.