Mars retrograde begins on 6 December 2024, when, if you observe the planet in the run-up, it will appear to stop and reverse its apparent direction in the sky.
This retrograde motion of Mars will last between 6 December 2024 until 23 February 2025.
The illusion is caused by the relative position and speed of Mars in its orbit compared to Earth: our faster orbit allows us to overtake Mars, and this creates the looped path in the sky.
The term planet comes from the Ancient Greek meaning ‘wandering star’.
They’re called this simply because, looking to the naked eye like stars, they appear to wander against the background of fixed constellations.
All the planets appear to perform retrograde loops, decreasing in apparent size with distance from Earth.
And this is the key point: it is Mars’s close proximity that makes its opposition and retrograde loop really impressive.
You can reveal the loop by photographing Mars against background stars with a mid- to wide-angle lens on a camera.
Take a photograph on every clear night through to the end of the year, load each into a layer-based editor like GIMP and align using the stars.
Set the blend mode of all upper layers to lighten and Mars will show through, revealing the loop.
In 2024 and 2025, Mars's retrograde loop will bring it close to the Beehive Cluster, making for a great photograph opportunity.
Photograph Mars retrograde loop
It’s possible to show Mars retrograde against the background stars using a camera. The basic idea isn’t that complicated.
The stars are your reference markers and, as long as you have three or more common stars recorded across shots, it's possible to align your images to show how Mars is moving between them.
It’s exciting to collect yet another Mars positional image to add to the set.
Add them all together as described below and you’ll have an amazing record of the temporarily backward motion of Mars in the sky.
For this project you will need:
- DSLR camera
- Fixed tripod
- 50mm or shorter focal length lens
- Remote shutter release
- Layer-based graphics editor
Step 1
The positional shot can be made with a high ISO (800–1600), low lens f/number and a fixed tripod. The shorter the focal length, the longer the exposure you can take before star trailing appears. Use an equatorial tracking mount for deeper shots to keep the stars sharp.
Step 2
Focus the lens as accurately as possible. If the Moon is up, turn the lens focusing to auto-focus, point the camera at the Moon and half-press the shutter button. Once focused, set the lens to manual focus. If you have Live View focusing, use that directly on Mars.
Step 3
Using the same focal length lens, take exposures that record Mars and at least three stars. Start with around 15 seconds. A remote shutter release avoids camera shake. Sky brightness becomes an issue from May, so use shorter exposures to counteract this.
Step 4
Load all images into a layer-based editor on separate layers. Using the bottom image as a reference, align the stars in each frame. Make the upper image temporarily transparent to do this. Then turn the blend mode of each upper layer to lighten to reveal the retrograde loop.
If you manage to observe or photograph Mars's retrograde loop, let us know by emailing contactus@skyatnightmagazine.com or getting in touch via Facebook, Twitter and Instagram.
