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 2011

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 2011

LOWER YOSEMITE FALL

 

OBSERVING LOCATION:

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

 

 

DATE

IN

2011

TIMES

(PACIFIC

DAYLIGHT

TIME)

LUNAR

PHASE

 

REMARKS

April 16

(Sat)

8:15pm

(Sat)

to

10:20pm

(Sat)

99%

waxing

moonbow becomes visible when sky gets dark enough at about 8:15pm

April 17

(Sun)

9:30pm

(Sun)

to

11:50pm

(Sun)

100%

 

VERY BRIGHT MOONBOW

 (full Moon occurs at 7:44pm PDT on April 17)

night of

April 18-19

(Mon-Tues)

11:30pm

(Mon)

to

1:15am

(Tues)

98%

waning

 

night of

April 19-20

(Tues-Wed)

12:55am

(Wed)

to

2:30am

(Wed)

93%

waning

 

May 14

(Sat)

8:45pm

(Sat)

to

9:20pm

(Sat)

93%

waxing

moonbow becomes visible when sky gets dark enough at about 8:45pm

May 15

(Sun)

8:50pm

(Sun)

to

10:45pm

(Sun)

98%

waxing

moonbow becomes visible when sky gets dark enough at about 8:50pm

night of

May 16-17

(Mon-Tues)

10:25pm

(Mon)

to

12:05am

(Tues)

100%

VERY BRIGHT MOONBOW

 (full Moon occurs at 4:09am PDT on May 17)

night of

May 17-18

(Tues-Wed)

11:40pm

(Tues)

to

1:15am

(Wed)

99%

waning

moonbow appears just as Moon clears south rim of valley

night of

May 18-19

(Wed-Thurs)

12:45am

(Thurs)

to

2:10am

(Thurs)

96%

waning

moonbow appears just as Moon clears south rim of valley

June 13

(Mon)

9:20pm

(Mon)

to

10:55pm

(Mon)

97%

waxing

moonbow appears just as Moon clears south rim of valley

June 14

(Tues)

10:30pm

(Tues)

to

11:55pm

(Tues)

100%

moonbow appears just as Moon clears south rim of valley

night of

June 15-16

(Wed-Thurs)

11:25pm

(Wed)

to

12:55am

(Thurs)

100%

moonbow appears just as Moon clears south rim of valley

night of

June 16-17

(Thurs-Fri)

12:05am

(Fri)

to

1:40am

(Fri)

98%

waning

 

July 12

(Tues)

9:15pm

(Tues)

to

10:40pm

(Tues)

95%

waxing

moonbow appears just as Moon clears south rim of valley

July 13

(Wed)

10:05pm

(Wed)

to

11:30pm

(Wed)

99%

waxing

moonbow appears just as Moon clears south rim of valley

night of

July 14-15

(Thurs-Fri)

10:35pm

(Thurs)

to

12:15am

(Fri)

100%

 

night of

July 15-16

(Fri-Sat)

10:35pm

(Fri)

to

12:45am

(Sat)

99%

waning

 

night of

July 16-17

(Sat-Sun)

10:10pm

(Sat)

to

1:00am

(Sun)

96%

waning

moonbow appears just as Moon clears south rim of valley

 

 

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/