Don Olson
Russell Doescher,
Roger Sinnott (Sky & Telescope) Moonbow May 11, 2006
Department of Physics
Kellie Beicker, Ashley Ralph, and Don
Olson Photo by Robert Stavers
Texas State
University
at the Lower Yosemite Fall Viewing
Area
www.galleriehare.com
MOONBOW PREDICTIONS FOR 2013
LOWER YOSEMITE FALL
based on the methods described in this article:
"Moonbows over
Yosemite," Sky &
Telescope, May 2007
related story:
http://www.txstate.edu/news/news_releases/news_archive/2007/04/Moonbow041207.html
visual
observers generally report that moonbows appear
"white," "gray," or "silvery"
but
time-exposure photographs reveal the full palette of colors
MOONBOW
PREDICTIONS FOR 2013
OBSERVING LOCATION:
VIEWING AREA, TERRACE AT THE WEST END OF THE BRIDGE
NEAR THE BASE OF
|
DATE IN 2013 |
TIMES (PACIFIC DAYLIGHT TIME) |
LUNAR PHASE |
REMARKS |
|
March 26 (Tues) |
(Tues) to 10:10pm (Tues) |
100% |
moonbow is just beginning when sky gets dark enough at about 8:00pm |
|
March 27 (Wed) |
9:05pm (Wed) to 11:55pm (Wed) |
99% waning |
moonbow appears just as Moon rises into sky between Half Dome and |
|
night of March 28-29 (Thurs-Fri) |
10:05pm (Thurs) to 1:20am (Fri) |
95% waning |
moonbow appears just as Moon rises into sky between Half Dome and |
|
April 23 (Tues) |
8:25pm (Tues) to 9:25pm (Tues) |
96% waxing |
moonbow is already in progress when sky gets dark enough at about 8:25pm |
|
April 24 (Wed) |
8:25pm (Wed) to 10:55pm (Wed) |
99% waxing |
moonbow is already in progress when sky gets dark enough at about 8:25pm |
|
night of April 25-26 (Thurs-Fri) |
8:55pm (Thurs) to 12:15am (Fri) |
100% |
moonbow appears just as Moon rises into sky between Half Dome and |
|
night of April 26-27 (Fri-Sat) |
10:10pm (Fri) to 1:30am (Sat) |
97% waning |
moonbow appears just as Moon rises into sky between Half Dome and |
|
May 23 (Thurs) |
9:15pm (Thurs) to 11:05pm (Thurs) |
99% waxing |
|
|
night of May 24-25 (Fri-Sat) |
10:30pm (Fri) to 12:10am (Sat) |
100% |
bright moonbow (full Moon occurs at 9:25pm PDT on May 24) |
|
night of May 25-26 (Sat-Sun) |
11:40pm (Sat) to 1:20am (Sun) |
98% waning |
|
|
June 21 (Fri) |
9:20pm (Fri) to 11:00pm (Fri) |
98% waxing |
(brightness and duration depend on snow season and snowmelt runoff) |
|
night of June 22-23 (Sat-Sun) |
10:25pm (Sat) to 12:05am (Sun) |
100% |
(brightness and duration depend on snow season and snowmelt runoff) |
|
night of June 23-24 (Sun-Mon) |
11:10pm (Sun) to 1:00am (Mon) |
99% waning |
(brightness and duration depend on snow season and snowmelt runoff) |
|
night of June 24-25 (Mon-Tues) |
11:35pm (Mon) to 1:40am (Tues) |
95% waning |
(brightness and duration depend on snow season and snowmelt runoff) |
CONDITIONS REQUIRED TO OBSERVE A MOONBOW IN
for observers at the viewing area, the terrace just west of the bridge near the base of Lower Yosemite Fall
1. bright moonlight (nearly-full Moon)
2. Moon risen above the south rim of the valley (so moonlight can strike Lower Yosemite Fall)
3. sufficient mist and spray (during snowmelt runoff season: April, May, June, sometimes July)
4. clear skies
5. dark skies (Sun more than 9 degrees below the horizon)
6. geometry (the angle between the “anti-lunar direction” [observer’s shadow cast by the moonlight] and the
direction toward the base of Lower Yosemite Fall must be near the “rainbow angle” of 42 degrees)
NOTE
If the snowmelt runoff is unusually strong, then moonbows could appear earlier and last longer than the predicted times.
If the snowmelt runoff is unusually weak, then moonbows would be visible for shorter intervals than the predicted times.
LINKS
Texas State University Honors Program
http://www.txstate.edu/honors/
Sky & Telescope
http://www.skyandtelescope.com/
Don Olson, Physics Department, Texas State University
http://uweb.txstate.edu/~do01/
Marilynn Olson, English Department, Texas State University
http://www.english.txstate.edu/people-contacts/faculty/olson.html