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How to View Mars

Mars rising at dusk near an opposition.


Introduction. 1

Mars Oppositions. 1

Telescopes for Mars. 1

Eyepieces for Mars. 1

A Mars-worthy Mount. 1

Location and Seeing. 1

Imaging Mars. 1

A Mars Challenge. 1



If you like lunar and planetary astronomy, you’ll probably love trying to spot surface features on Mars – the only planet for which that’s possible (the rest are just clouds). It’s something I’ve been trying to do since I was about nine.

But it’s just not as easy as it sounds (which is part of the fun). Why?

Mars’ visible features are mostly low-contrast differences in surface colour and brightness (albedo), or relatively small features (ice caps and clouds). Then there’s the problem that Mars isn’t around all that often…

Mars Oppositions

Mars only comes observably close to Earth for a few months every two years (about every 780 Earth days), when it is at ‘opposition’, i.e. when it is positioned on the opposite side of Earth from the Sun and so closer. This is because Earth completes an orbit in less time than Mars – in accordance with Kepler’s laws - and so it ‘overtakes’ Mars on the inside at 780 day intervals.

These oppositions change over longer cycles, making some more favourable than others, because Mars has a slightly elliptical orbit. How close it gets to Earth depends on whether Mars is at perihelion or aphelion - the nearest or furthest nodes in its orbit – at opposition.

Mars’ orbital plane is also slightly tilted with respect to Earth’s, overlaying yet a third level of cyclicity to its regular comings and goings. So how big Mars appears in the eyepiece and how high it gets in the sky – even close to opposition – varies. A lot.

Before space probes started to arrive at Mars in the 1960s, this cycle of oppositions ruled professional research on the red planet. For amateurs it still does.

What does all this mean to you? If you want to view the Red Planet, you’ll have short windows of opportunity and those opportunities will vary.

Here’s a table of the next five oppositions, with Mars’ maximum angular size and the approximate altitude it transits (when it crosses the N-S meridian and is at maximum altitude in the sky, so best for observing) at opposition for northern Europe.

As you can see, for Europe, the 2022 opposition is the most favourable for many years to come.



Max size

Transit Altitude EU


8th December




16th January




19th February




25th March




4th May




Telescopes for Mars

Do you need a special telescope to view Mars? In a word, no. But Mars - small, low-contrast and red - demands a lot from a scope.

Some guidelines:

·       Aperture matters less than you think: a small telescope will resolve the maximum the seeing will allow on most nights

o   Even a fine 3” refractor will give good views near opposition (see example below), but…

o   ~~4” is the minimum for detailed views in a refractor, 5” in a Maksutov, 6” for a reflector

·       Optical quality is very important – poor optics usually just show a fuzzy orange ball. Optical quality is probably even more important in reflectors

·       Reflectors and catadioptrics with smaller central obstructions work better in all but the best seeing

·       Doublet refractors are best at F7 or over: faster doublets are often optimised for imaging and so compromised in the red, giving a less sharp view of Mars

·       Critical focus is vital. If your focuser isn’t great, consider an eyepiece micro-focuser – an accessory that slots into your diagonal

·       Collimation needs to be spot-on (usually more of a factor for reflectors)

For locations with average seeing, I’d choose one of the following:

·       Refractor: 4 – 6” aperture:

o   Achromat - F10+

o   Doublet apochromat - F7+

o   Triplet apochromat – F6+

·       Newtonian reflector: 6 – 10” aperture, F8 with an obstruction of ~25% and good optical quality

·       Cassegrain or Maksutov: 4 – 8” aperture, F10+ with an obstruction of ~33% or less

If you’re viewing from somewhere with really stable seeing, then a larger aperture will show more and other telescope types will likely work just as well (e.g. 12-16” Schmidt Cassegrains with 35-37% obstructions).

I take a deeper dive into telescopes for planets here.

These are just guidelines – get out and view with whatever you’ve got. I’ve seen Mars’ classic standout feature – the arrow-head (or sometimes bikini) of Syrtis Major – with a 50mm achromat!

This classic 80mm fluorite apochromat on a tracking equatorial mount gives good views of Mars for a small scope.

For ED doublet refractors, longer focal ratios are best, like this 100mm F9 Skywatcher ED Pro.

Only the best corrected triplets work well on Mars at F6 and below: this F6 William Optics FLT-123 gives outstanding views of Mars.

Newtonians with small secondaries, like this 200mm F8, work well for Mars (this one gave my best ever view of Mars with an amateur scope – at the 2003 opposition).

Orion Optics’ excellent planetary Maksutov – the OMC140.

A stable focuser with an inner micro-focus wheel is ideal.

Eyepieces for Mars

Eyepieces matter less than many think - less than the telescope itself, less than the mount and much less than the seeing. But again, some factors to consider:

·       You’ll need relatively high magnification (at least 80-100x up to 200x or more, even when Mars is at its largest), so eyepiece focal lengths:

o   2.5mm – 6mm for small refractors

o   10mm-20mm for small to medium SCTs and Maks and Newtonians

·       For telescopes with driven mounts, a high-quality simple eyepiece like an Orthoscopic is best. Field of view matters less than eye relief (for comfort, but also to avoid getting it greasy or steamed-up from your eye whilst viewing)

·       If you’re using a manual push-pull mount like a Dobsonian, an eyepiece with a big flat field is best, because otherwise the vibes will only just have settled before it’s time to move the scope again!

·       Eyepiece comfort is underrated for seeing fine detail: the tiny eyelenses and zero eye relief of short focal length Plössls and basic Orthos don’t help

·       Most important – keep the eye lens clean. Baader’s Optical Wonder cleaning fluid works for me

Again, I’ve taken a deeper dive on eyepieces for planets here.

Zeiss’ Abbe Orthoscopics are well-regarded (if rare and expensive) planetary eyepieces.

Takahashi’s MC Orthos are another traditional choice, since replaced by their own Abbe Orthos – cheaper than Zeiss’!

For scopes on push-pull mounts like Dobs, eyepieces with wide fields work best: Tele Vue’s Ethos range are surprisingly good for planets.

A Mars-worthy Mount

A solid, stable, preferably tracking mount is an under-rated factor for viewing at high magnification. Keeping Mars steady in the field of view for minutes at a time really helps you to relax, enjoy the view and see those low-contrast features.

For alt-azimuth mounts, I prefer one with slow-motion controls rather than simple push-pull for high magnifications (see below).

In my experience, it’s remarkable how much better the same scope seems when it is tracking and vibe-free.

Alta-azimuth mounts work best for high magnifications if they have slo-mo controls, like this Vixen APZ.

Tracking equatorial mounts are best for high powers. Scope is another planetary ‘classic’ – Takahashi’s FC-100 with an MC Ortho eyepiece.

A mini planetary setup you can grab and go with: Takahashi’s FOA-60 on PM-SP driven mount.

Location and Seeing

Good seeing is the most vital factor for high power viewing and especially for those low contrast albedo markings on Mars. Fine seeing makes a mediocre scope seem great; bad seeing a fine one mediocre.

Dark skies aren’t important, but a lot of ambient light can be distracting. If Mars looks like a mushy ball, don’t give up, it’s probably not your scope. Keep trying until you get a night of good seeing.

If travel is an option, consider desert areas with dry and stable air and higher altitudes. Lay-bys and car parks off roads leading to observatories are a good place to start – pro’s choose their locations carefully for good seeing. The desert location for the first photo is a lay-by off the ET Highway in Nevada.

Seeing matters most - almost any scope gives great views from Mauna Kea with an average of 0.45”.

Imaging Mars

I’m not an expert planetary imager, but the requirements for imaging Mars are a bit different from viewing. Contrast delivery by the scope is less important because the stacking process automatically increases contrast. The same is partly true of seeing, because stacking helps eliminate the blur caused by atmospheric turbulence. Meanwhile, any false colour fringing is really noticeable in stacked images.

To get the best image you’ll want a large image scale on your chip, so smaller refractors that might give you a good view aren’t ideal for imaging Mars. If you want to try imaging with a smaller refractor you will need a barlow lens to multiply the effective focal length (and so image scale).

Ideally, you need a longer-focal-length telescope (maybe a Maksutov or SCT) with accurate tracking to keep the image on the (small) chip of the camera, whether a specialist planetary CCD, a consumer camera in video mode or an old webcam. Then you’ll need stacking software to process the video stream frame by frame and combine the best.

Fantastic results can be had by the patient and skilled. For what’s possible, check out Damian Peach’s images online.

A Mars Challenge

I’ve always wanted to see Nix Olympica, the Snows of Olympus - the name given to the bright cloud cap that sometimes cover Olympus Mons, the highest (known) volcano in the Solar System. So far, I never definitively have done, but it’s a fun challenge to sustain those chilly Martian vigils at the eyepiece!

Viewing Mars with one of my favourite telescopes – Takahashi’s FS-128.