MOONBOW PREDICTIONS FOR 2009
UPPER YOSEMITE FALL

Brent Gilstrap moonbow 425x471.jpg Sentinel Bridge parking lot Google Earth.jpg
                       Photo by Brent Gilstrap                                                   Google Earth

                  http://groundhog.smugmug.com/Nature

based on the methods described in this article:
       "Moonbows over Yosemite," Sky & Telescope, May 2007
related story with photo gallery:
          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 2009
UPPER YOSEMITE FALL

 

TIMES CALCULATED FOR COOK’S MEADOW

OBSERVING LOCATION:  PARKING LOT JUST NORTH OF SENTINEL BRIDGE

 

DATE
IN
2009

TIMES
(PACIFIC
DAYLIGHT
TIME)

LUNAR
PHASE
 

REMARKS

night of
April 10-11
(Fri-Sat)

11:30pm
(Fri)
to
12:25am
(Sat)

97%
waning

 

May 7
(Thurs)

8:40pm
(Thurs)
to
9:55pm
(Thurs)

99%
waxing

moonbow becomes visible when sky gets dark enough at about 8:40pm

May 8
(Fri)

10:55pm
(Fri)
to
11:35pm
(Fri)

100%

(full Moon occurs at  9:01pm PDT on May 8)

night of
May 9-10
(Sat-Sun)

12:15am
(Sun)
to
12:50am
(Sun)

98%
waning

 

June 5
(Fri)

10:05pm
(Fri)
to
10:40pm
(Fri)

98%
waxing

 

June 6
(Sat)

11:15pm
(Sat)
to
11:45pm
(Sat)

100%

(full Moon occurs at 11:12am PDT on June 7)

night of
June 7-8
(Sun-Mon)

12:10am
(Mon)
to
12:40am
(Mon)

100%

 
 

night of
June 8-9
(Mon-Tues)

12:50am
(Tues)
to
1:20am
(Tues)

98%
waning

 


CONDITIONS REQUIRED TO OBSERVE A MOONBOW IN UPPER YOSEMITE FALL 
 
1.  bright moonlight (nearly-full Moon)
2.  Moon risen above the south rim of the valley (so moonlight can strike Upper 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 Upper 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.

NOTE

This is our first attempt to calculate times for moonbows in Upper Yosemite Fall.
Feedback from photographers / observers regarding the accuracy of our predictions is welcomed

by Don Olson at
dolson@txstate.edu

 

 

 

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

 

Christopher Olson, JD, Hawaii Lawyer, Oahu Lawyer, Oahu, Hawaii
http://hawaiiattorneyonline.com/