Image 1: Noctilucent clouds (NLCs), or "night-shining clouds," photographed by Vince Varnas from the roof of his house near Portland, Ore., on July 23, 2009. The NLCs were in the north-northwest sky about 10 miles west of Portland.
On viewing the NLCs Varnas says, "I first observed the NLCs at approximately 9:30 p.m. PDT. The NLCs were mostly iridescent white, at that time, but gradually changed color to iridescent blue over the next 25 minutes. I took this photograph at 9:55 p.m. PDT. I have only seen NLCs from my location one other time. That was on July 15, 2009, at about the same time. Then the NLCs were more in the northwest and not as intense as those on July 23. I had been watching for NLCs all summer, as I knew they were occurring over Europe, but not in the United States. I am an amateur radio operator and also observed intense sporadic-E propagation on July 23, during the occurrence of these NLCs." (Date of Image: July 23, 2009)
Image 2: Noctilucent clouds (or "night-shining clouds") over Mount Tabor Park, Portland, Ore., July 23, 2009.
This photo was taken by Mark Seibold, an artist, astronomer and astronomy art lecturer from Portland, Ore. Here's Seibold's first-hand account experiencing these iridescent, nighttime clouds (originally posted on www.spaceweather.com):
"I ensconced myself on top of Mount Tabor in central Portland, Ore., to render a pastel sketch of the two-day-old crescent moon, observed through a Nexstar 5i Cassegrain as one of my usual works. As I was showing the public the moon setting onto Portland's West Hills through the telescope, I noticed a strange silver light in what appeared as the north-northwest sky, lighting up with I thought was aurora borealis. I then realized that I was seeing the most amazing display of noctilucent clouds that I had ever witnessed. Perhaps my first ever. I had to drop the pastel chalks, grab the camera and take a vantage point on the slopes of the west of Mount Tabor over the large reservoir, with the city skyline to the west. It was at 10:15 p.m. PDT, an hour and a half after sunset in dark sky with only a hint of twilight glow at the horizon's edge."