Solar Analemma 2015: A Year-Long Picture

Analemma_Web.jpg

If you took a picture of the Sun every day, always at the same hour and from the same location, would the Sun appear in the same spot in the sky? A very fine image, compiled by astrophotographer Giuseppe Petricca from Italy, proves the answer is no.

"A combination of the Earth's 23.5 degree tilt and its slightly elliptical orbit combine to generate this figure "8" pattern of where the Sun would appear at the same time throughout the year," said Petricca.

This pattern is called an analemma, the full version shown below:

[caption id="attachment_126534" align="aligncenter" width="659"]

A compilation of images of the Sun taken at the same time and place over the course of 2015, as seen from Sulmona, Abruzzo, Italy. Credit and copyright: Giuseppe Petricca.[/caption]

The analemma is considered by many to be one of the most difficult and demanding astronomical phenomenon to image. Astrophotographers need to dedicate an entire year to the project. It requires diligence to take images 30 to 50 times throughout the year at the same time of day and same location.

It is interesting to note that analemmas viewed from different Earth latitudes have slightly different shapes, as well as analemmas created at different times of the day. Also, analemmas on the other planets have different shapes. Here's one created by the Opportunity rover (ready more about the Martian analemma

here

):

[caption id="attachment_117337" align="aligncenter" width="580"]

The Opportunity rover captured this analemma showing the Sun's movements over one Martian year. Images taken every third sol (Martian day) between July, 16, 2006 and June 2, 2008. Credit: NASA/JPL/Cornell/ASU/TAMU [/caption]

If the Earth were not tilted, and if its orbit around the Sun were perfectly circular, then the Sun

would

appear in the same place in the sky throughout the year. But then, we also wouldn't have seasonal change, so I vote to keep axial tilt!

[caption id="attachment_126546" align="aligncenter" width="659"]

The analemma created by Giuseppe Petricca, annotated with the dates each picture of the Sun was taken. Each image of the Sun was taken at the same time and place over the course of 2015, as seen from Sulmona, Abruzzo, Italy. Credit and copyright: Giuseppe Petricca.[/caption]

In this compilation image, Petricca combined 32 pictures of the Sun taken at 12pm local time throughout the months and seasons, all shot with the same settings and exposure times (ISO 100, f/8.0 and 1/1000" exposure time).
"I was lucky to have the last year with good sunny skies at the right times, even if some months were really difficult to image," he explained via email. "The background view is the one from the first picture, January 4th, 2015, after three days of snow."

Petricca used a Nikon Coolpix P90 Bridge Camera mounted on a fixed tripod, with images taken from a field nearby his home Sulmona, Abruzzo, Central Italy. "To take pictures of the solar disk I used an Astrosolar filter in front of the camera, then I composed the analemma digitally, via Photoshop CC," he said.

Our David Dickinson has written

a great piece explaining the dynamics and history of analemmas

, with instructions on how you can compile your own.

Also the the Stanford University Solar Center has a

great page about it,

with analemmas taken from around the world.

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com