Don Olson green shirt Yosemite X.jpg    group at night Lower Yosemite Fall X.jpg    Robert Stavers 5-11-2006 X.jpg
         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

LOWER YOSEMITE FALL

 

OBSERVING LOCATION:

VIEWING AREA, TERRACE AT THE WEST END OF THE BRIDGE

NEAR THE BASE OF LOWER YOSEMITE FALL

 

 

DATE

IN

2013

TIMES

(PACIFIC

DAYLIGHT

TIME)

LUNAR

PHASE

 

REMARKS

March 26

(Tues)

8:00pm

(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 Mount Starr King

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 Mount Starr King

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 Mount Starr King

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 Mount Starr King

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 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.

 

 

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