Half Dome Mirage

On Novemeber 20th, 2023 I looked towards the Sierra Nevada to see if Half Dome in Yosemite National Park was visible. It is frequently visible from Lick Observatory on Mount Hamilton, CA on clear weather days, particularly during the winter after storms have passed through. On this date, I discovered that I didn't recognize the view for the first time in my 25 years on Mount Hamilton. The view was distorted by a fata morgana mirage. Seeing as how rare this phenomenon was for this view, I went back inside to get my camera and capture the moment.


Half Dome view from Lick Observatory distorted by fata morgana mirage. Image copyright Elinor Gates.

The above photo was taken from Ptolemy Peak, the location of the historic Crossley 36" Telescope at Lick Observatory. Half Dome in Yosemite National Park is 119 miles distant. Image was taken with a Canon EOS R with 500mm lens at f/10 and 1/500 sec at about 11:45am on November, 20th, 2023.

On a typical clear day, the view of the Sierra Nevada, Half Dome, and El Capitan is show in the photograph below, taken from the same location and using the same camera and exposure settings on December 8th, 2023 at about 11:40am to roughly match the conditions of the mirage photo.


Half Dome view from Lick Observatory, usual view. Image copyright Elinor Gates.

Fata morgana mirages are caused by warmer air being above cooler air, refracting the light so that images of the object appear above their actual location. Most often this affect is seen over the ocean. In this case, the cooler air in California's Central Valley was topped by warmer air above, distorting the usual view of the Sierra Nevada and Yosemite National Park from Lick Observatory. See the Wikipedia article for more basic information about fata morgana.

I have created an animated GIF showing how the fata morgana refracted the light between the usual view and the mirage view. One of the interesting things to note is that El Capitan and the lower reaches of Half Dome are not distorted in either image, and it is just the higher elevations of Half Dome and the Sierra Nevada that are distorted.


Animated GIF morphing from non-distorted to mirage image of Half Dome view from Lick Observatory, highlighting the amount of atmospheric refraction and distortion. Image copyright Elinor Gates.

Also, here is a similar image labeling Half Dome, El Capitan, and other peaks visible in the image, taken on an extraordinarily clear day.


Sierra Nevada view from Lick Observatory with prominent landscape feature labeled. Photo taken Jan 6, 2022, copyright Elinor Gates.

Historical Notes:

Fred Chappell took the first known photo of Half Dome from Lick Observatory in December 1931, using an infrared camera.
Half Dome from Lick Observatory Low resolution version of Chappell's image taken from some unknown web page and other information from Dan Allen about viewing Mt. Whitney from Mount Hamilton. A large version of the image is displayed in the Lick Observatory Vistor's Center. A labeled image of Chapell's image used to be for sale in the Lick Observatory Gift Shop (if I ever have time, I'll work on figuring out how to make it available for sale again in the gift shop as it was a favorite image).

Donald Osterbrock, former director of Lick Observatory, wrote a paper describing the techniques used by Chappell in photographing the famed panorama shot. It is available on-line via NASA Astrophysics Data System.

Elinor Gates
Last modified: Sun Dec 10 12:39:33 PST 2023