Don Olson in Yosemite       
         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 2009

LOWER YOSEMITE FALL

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
LOWER YOSEMITE FALL
 
OBSERVING LOCATION:   VIEWING AREA, TERRACE AT THE WEST END OF THE BRIDGE
NEAR THE BASE OF LOWER YOSEMITE FALL

DATE
IN
2009

TIMES
(PACIFIC
DAYLIGHT
TIME)

LUNAR
PHASE
 

REMARKS

April 7
(Tues)

8:10pm
(Tues)
to
9:01pm
(Tues)

98%
waxing

moonbow is already in progress when sky gets dark enough at about 8:10pm

April 8
(Wed)

8:10pm
(Wed)
to
10:50pm
(Wed)

100%
 

brightest moonbow for 2009
moonbow is already in progress when sky gets dark enough at about 8:10pm
(full Moon occurs at 7:56am PDT on April 9)

night of
April 9-10
(Thurs-Fri)

10:00pm
(Thurs)
to
12:15am
(Fri)

99%
waning

depending on snowmelt runoff, moonbow may even be visible as early as 9:15pm on Thursday evening

night of
April 10-11
(Fri-Sat)

11:50pm
(Fri)
to
1:25am
(Sat)

97%
waning

 

May 6
(Wed)

8:40pm
(Wed)
to
10:00pm
(Wed)

96%
waxing

moonbow is already in progress when sky gets dark enough at about 8:40pm

May 7
(Thurs)

9:25pm
(Thurs)
to
11:15pm
(Thurs)

99%
waxing

 

night of
May 8-9
(Fri-Sat)

10:45pm
(Fri)
to
12:25am
(Sat)

100%

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

night of
May 9-10
(Sat-Sun)

12:01am
(Sun)
to
1:25am
(Sun)

98%
waning

moonbow appears just as Moon clears south rim of valley near Sentinel Dome

June 5
(Fri)

9:50pm
(Fri)
to
11:15pm
(Fri)

98%
waxing

moonbow appears just as Moon clears south rim of valley between Moran Point and Sentinel Dome

night of
June 6-7
(Sat-Sun)

10:52pm
(Sat)
to
12:15am
(Sun)

100%

moonbow appears just as Moon clears south rim of valley near Sentinel Dome
(full Moon occurs at 11:12am PDT on June 7)

night of
June 7-8
(Sun-Mon)

11:46pm
(Sun)
to
1:10am
(Mon)

100%

moonbow appears just as Moon clears south rim of valley near Sentinel Dome
 

night of
June 8-9
(Mon-Tues)

12:32am
(Tues)
to
1:50am
(Tues)

98%
waning

moonbow appears just as Moon clears south rim of valley near Sentinel Dome


CONDITIONS REQUIRED TO OBSERVE A MOONBOW IN LOWER YOSEMITE FALL
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.

NOTE
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/