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Mars Attacks - Preparing for closest approach this October

Mars Attacks - Preparing for closest approach this October

Mars is coming… in a few short months Mars will appear the largest it will be for Earth astronomers for the next 15 years. So it’s an opportunity not to be missed for viewing and imaging!

Mars is the most extreme of the planets from an observing point of view. It can be an unimpressive tiny orange dot, or about once every two years, it can dominate the night sky as an imposing bright red orb. No wonder the planet had such a reputation for the ancients as ‘The Bringer of War’.
The reason Mars apparent size and brightness varies so much is due to its proximity to Earth as well as its orbit around the Sun and its relatively small size. Unlike Venus, which is almost the same size as Earth, Mars is only about half the diameter and orbits further out from the Sun than Earth. Therefore when Mars is at the closest part of its orbit, known as opposition it appears large to observers on Earth, but when it’s on the other side of the Sun to Earth it is faint and small as it is so far away.
In addition to the roughly two-year cycle of Mars having close approaches to Earth due to opposition, there is a longer cycle of around 15 years where that closest approach varies. Mars appeared at its largest in 2003 and 2018, but this year is still a great chance to see Mars, and it won’t be bettered until 2035!

Mars Sizes Original Mars image from NASA Hubble Space Telescope

Image created by Chris Morrison, for illustration only - If your view is this sharp then many congratulations!

Apparent size in October

Although not quite as large as it appeared in 2018, Mars will be higher in the sky which will be good for observers in both the northern and southern hemispheres. Currently it is in the predawn sky but it will progress through the night and then eventually will be visible just after sunset by September. So from now until October 6th there are a few months to get prepared. It doesn’t take a huge amount of kit to get great view of Mars, but here are the basics:

Mars Imaging Essentials

During the months of build up to opposition it’s a great time to get in some practice observing and imaging Mars. With a good setup, a planetary camera and some serious stacking and image processing, really impressive results can be achieved by October.
  • There is no getting around it… focal length is king for planetary observing, so a long focal length telescope, such as a minimum 6 inch refractor or 8 inch reflector will produce the desired results.
  • A x2 or x3 Barlow lens or x5 Powermate - to get really good up-close magnification.
  • A planetary imaging camera, from a modified webcam to a dedicated state of the art CMOS astronomical camera capable of taking high frame rate video.
  • Imaging software such as Registax, Autostakkert, WinJUPOS and Photoshop.


To assist in viewing subtle features in detail, there are a range of colour filters available for weather and clouds. Dedicated Mars filters are produced that are tailored to the specific characteristics of Mars, but standard colour filters can also be used to enhance certain features for example:

Yellow - Increases contrast of clouds and ice

Red - Improves contrast of the polar caps against the red surface.


One particularly rewarding challenge for the really hard-core observer is capturing a partial rotation of Mars, through the night time hours. Amateurs have made impressive movies of Mars rotating by stitching together hours (or even days) of images.

Weather on Mars

Unfortunately something that cannot be predicted with the same certainly as Mars’s apparent size and location in the sky is its weather. Although Mars appeared very large and bright in 2018, closest approach also coincided with a huge global dust storm that hid a great surface detail. Mars appeared as one big red mostly featureless disc.
So let’s hope for better Martian weather this time around. Fingers crossed for good weather for where you are around October the 6th as well, but remember there is plenty of time both before and afterwards to get some great views. The long-term average of planet wide dust storms in a particular Martian year is one in three, so the odds are pretty good of avoiding one for this approach.
Happy viewing and clear skies… both here and on Mars!
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