I set up my 7 inch Starmaster scope last night in Palo Alto for my first view of the Hesiodus sunrise ray on the Moon. I didn't get home till after 8 pm, so missed the beginning of the ray. However, at 8:15 pm, the ray was clearly visible as a pencil thin shaft of light completely bisecting the otherwise dark floor of the Hesiodus crater. The pencil widened to a 25 or 30 degree pie shaped wedge of light over the next 45 minutes or so, and lit up a smaller crater on the previously darkened floor. An hour later, the ray had not widened any further, but the Hesiodus crater itself began to fill with sunrise light along the edge closest to the terminator.
I first got interested in sunrise rays on the moon when I stumbled on the Walter sunrise ray completely by accident during a quick look at the moon in August of 1999. The beautiful "search light in the dark" effect got me reading more about them.
The Walter Ray had first been reported only two years earlier by Dave Mitsky ( http://www.ezonline.com/ash/walter.htm.)
Several other well known rays are described here:
http://www.shallowsky.com/moon/ruklindex.html#R and http://shutter.vet.ohio-state.edu/astronomy/lunar rays/)
Timing is critical, since the angle of the sun has to be just right to shine through low points in crater walls and create the ray effect. Rob Robinson has a nice page for predicting the timing of future rays.
http://www.lunar-occultations.com/rlo/moon/lunarray.htm
For local California observers, the next well placed examples of the Hesodius ray will be the evening of October 6th and December 4th. The next night time chance for catching the Walter ray is not until 1 or 2 am on December 18th.
I like to put these sorts of events into my Palm Pilot well ahead of time, with an alarm to remind me the day of the event. Yesterday I was up at Berkeley when the Pilot beeped to reminded me to look for the Hesiodus ray that evening. The play of light and shadow was beautiful, and I recommend a look if you haven't seen these before.