> Keep an eye on the weather reports. Some truly spectacular electrical > storms come through the Aspen/Vail valley ( W to E) . I think it has > to do with the altitude. Its a bit of "hit and miss" but if you are > lucky it can look great.
Also be sure to bring a UV filter and a warming filter. The high altitude (esp in Summer) will have a real strong UV exposure. Worst than visiting the beach. That can alter the sky/clouds noticably. The "blue" sky can also give you the "blueish" cast that appears in some beach shots as well.
And while we're at it, bring some sunblock SPF 30 for yourself as well. Also a sweater if you are going out at night (30+ degree temp swings during the day are normal there).
As a final reminder, DO NOT WANDER OFF the main trails or roads without taking precautions. The USGS lost an entire survey team in the mountains about 30-40 yrs ago ( multiple people, full gear, etc). They were never seen again after the weather turned bad. When we lived there in the 1980s, it did SNOW on July 4 so it can happen at any time.
Maroon Bells are definately one of the greatest shots in the country at dawn. Be aware that now during the tourist season, the usual way up to the Lake, etc. is by bus from Aspen. If you are lucky, and it is early (or late)enough, the gate keeper may, or may not, let you in with your vehicle. I believe that the cost at the gate is $10.00, at least this was the fee a few years ago when I was up there.