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MicroObservatory's Transit of Mercury Challenge

On both May 9th, 2016 and November 11th, 2019, the Western Hemisphere observed Mercury transit across the Sun.

Track these transits using MicroObservatory telescope images.

Start Guided Tour

Guided Tour

In this guided tour we’ll take you through the steps of using our JS9-4L image processing tool using data from either the 2016 or 2019 transit.

If you're familiar with animating images in JS9-4L, you can click the × in the upper right corner. You can always come back to this tour by clicking "Replay Guided Tour".


Select an Image

First, click on one of the image files of the Sun. It will open inside the JS9-4L frame.

After you've finished the guided tour, all of the images that you need for this challenge are available here, under the Transit of Mercury tab.


Adjust the Scale

Use these scales to highlight different regions of relative brightness in your image. Log scale works best for dim images.

Switch between the scales to see how regions that appear black suddenly reveal much greater detail.


Adjust the Brightness Limits

Hover over the darkest parts of your image. Watch the green number inside the parenthesis next to "Pixel Value" above. Type the lowest value you see into the Low Brightness Limit box.


Special Tools for Animating Images

In order to line up all of your sun images and animate through them, you will need to use the Shift, Blinking, and Blending tools. You can find these tools under the 'Tools' dropdown.

Watch this video tutorial to learn how to use these three tools:


Adjust the Color

Choose from this list of colormaps to either
add beauty to your image, or highlight the
relative brightness of different regions in your image.

You can also make real-color images with
RGB mode, but you ought to watch a tutorial
on creating RGB images first.


Save Your Images and Create a GIF

When you're done, save all your images to your computer or device. Go to a third-party website like, upload your images, set the animation rate, and download an animated GIF of your Transit of Mercury.

Post your GIF to our Facebook, or post it to Twitter and mention us (@microobs). We can't wait to see what you make!


Close the Tutorial Image

Now that you've practiced using JS9-4L, close any images that you opened during this Guided Tour so you can start from scratch. Just click the × next to any image files that are currently open.

Remember: you can reopen images for this challenge under the 'Transit of Mercury' tab.

Finish Guided Tour



Tour Guiado en Español

5 Ways to Find an Exoplanet: The Transit Method

This virtual model examines how scientists have used the Transit Method to detect over 3,000 exoplanets as they pass in front of their host stars. Explore the other 4 methods that have led to the discovery of over 900 others too!

Sun Screen: A ‘Pi in the Sky’ Math Challenge

This math challenge invites learners to take part in recent celestial discoveries, by using the mathematical constant pi to find out how much solar energy is lost on Earth when Mercury transits the Sun.

ExoLab: Exoplanets Modeling Lab

With this interactive, you can develop a model of an exoplanet orbiting its star in order to predict and interpret the signal of an exoplanet. What happens when the planet is different sizes, or orbits at different speeds?

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