Occurring exactly a week after its close pairing with Venus, Uranus’ conjunction with Mars is somewhat wider and the contrast in brightness is not so great, but the pair’s proximity to the horizon in deep twilight means that you’ll need to pick your time carefully to see them so that the sky will be dark enough to see Uranus, but not so late that the pair will be too close to the horizon. An hour after sunset is about the ideal time, something you can determine with our Almanac.
As with last week’s event, let Venus be your guide. Mars and Uranus will lie 8° (about the apparent length of your thumb with your arm outstretched) to the lower right of the brightest planet. The separation of Mars and Uranus will be just 1/4°, half the apparent size of the Full Moon. In your telescope, choose an eyepiece that gives 50x magnification (Tip: Our Scope Calc can help with eyepiece selection) so that you have a field of view to one degree, if possible.
The close proximity of Mars makes finding Uranus very easy since they will be in the same low-power telescopic field of view, but their difference in brightness is 70 times or will be 4.6 magnitudes.
As seen from the Earth, Mars is currently on the far side of the Sun which explains why it displays a gibbous phase. At magnitude of +1.3, the Red Planet is 98% illuminated and displays a tiny 4.1-arcsecond disc since it is 2.28 astronomical units, which is equal to 212 million miles or 341 million kilometers, away.
In contrast with this, the gas giant planet Uranus, known to be the third largest planet in the Solar System, lies upon a staggering 20.90 astronomical units, which equals to 1,943 million miles or 3,127 million kilometers, from Earth tonight. It is very evident that the planet is nine times farther away than Mars. The planet Uranus will appear as a tiny 3.4-arcsecond disc shining at magnitude +5.9.
If you get the chance to see Mars and Uranus together through a telescope, consider the contrast not only in the brightness of these worlds as seen from Earth, but also their physical characteristics. Take note that Mars is a rocky, terrestrial planet with a rarefied atmosphere half the size of Earth, while Uranus is four times larger than our planet and gaseous in composition.