How to Observe Mars

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Every 26 months, The orbits of Earth and Mars bring them close together. It's called opposition, in that at that time, Mars is on the opposite side of Earth from the Sun. Both Earth and Mars have elliptical orbits (more so for Mars), so the distance between the planets at closest approach varies. Because of that, the apparent or angular size of Mars varies from one opposition to another. Mars never appears very big, but does on the average appear about the size of Saturn, minus the rings.

In numbers, Mars appears to be about 12 arc-seconds in size at the worst oppositions, and about 25 arc-seconds at the best. We had one of the best oppositions a few years ago in 2003. You can see the drawings I made when observing that opposition at Mars 2003 Opposition.

The anticipation of observing Mars is always high for me, but the experience often doesn't live up to expectations.

Why?

Martian dust storms.

Mars has some whoppers. Sometimes dust storms on Mars are global in coverage. Observing Mars during one of the global dust storms reveals nothing but a glowing, orange orb.

But now and again a Mars opposition is a beautiful thing. I can't explain why, but even though ample photographs of Mars exist from the great observatories, there's nothing quite like seeing a few faint details in your own equipment.

What You'll Need to Observe Mars

Best Option, A Quality Refractor At left you my modest 2 inch refractor. It is a classic f/15 design achromat. You might scoff at the idea of using such a small instrument for observing Mars. But some years ago, when Mars was about 17 arc-seconds in size at opposition, I used this instrument to get some very enjoyable views of the planet. I could make out, even with this small instrument, some of the major dark areas on the Mars. Refractors of long focal ratio, f/10 or better, make the best planetary telescopes. If you have a 60mm refractor, use it. You'll see a few details on Mars. You can read about some of the characteristics of refractors at Refractor Tutorial

A Good Option, a Maksutov A good option that is less expensive than a sizable refractor is a Maksutov Cassegrain, like the Meade ETX pictured here. The Maksutov is a clever catadioptric design, using a corrector plate and mirror in combination to achieve superb images. All surfaces are spherical, making them easy to manufacture to high precision. Maksutovs tend to have focal ratios around f/15, making them perfect for high resolution observing. The f/15 means that these telescopes have effective focal lengths that are 15 times their diameter. Long focal length telescopes give higher power for any given eyepiece than do short focal length telescopes. The Maksutov's compact size makes the inclusion of a clock drive easy, and most are sold with that feature. You can get more information on the characteristics of Cassegrain telescopes at Cassegrain Tutorial

Another good option is a Schmidt Cassegrain Telescope, or SCT. These look similar to the Maksutov shown, but use a different design on the corrector plate. As a result, SCT's have focal ratios around f/10, and thus make pretty good general purpose instruments.

SCT's can give good planetary performance, enhanced by their short tube which gives good stability. They do have rather large secondaries however, which reduces the contrast on planetary images.

One of My Favorites -- the Long Focus Newtonian If you are on a budget and still want to see Mars when it's close to Earth, I recommend a long focus Newtonian. Even a 4 1/4 to 4 1/2 inch Newtonian of long focus makes a quite good planetary telescope. Such instruments cost typically less than $300. Shown is my specially designed 6 inch f/10 Newtonian on a Dobsonian mount. The telescope was designed by master telescope maker Steve Dodson. The instrument is descried in more detail on the Dob Review page. Additional characteristics of Newtonians are available at Newtonian Tutorial and Dobsonian Tutorial Steve also makes a 4 1/4 inch long-focus DOB that makes a good, budget planetary telescope. You can see Steve's offerings at Stargazer Steve. Steve offers his telescopes as easy to assemble kits. You can see other major manufacture possibilities at telescopes and SHOP.COM .

Finally, you can use any telescope of 3 inches or better diameter and see some details on Mars. But short focal ratio instruments have a few design issues that limit their capability for delivering superb planetary images.

You can use the following chart to see examples of telescopes for different types of observing. For seeing details on Mars and other planets, you'll want to concentrate on the general purpose and high resolution instruments.

The larger instruments will show you more with good observing conditions, but notice from the chart that with such instruments you'll be moving away from portability.

Telescope/Observing Preference Table

One online shopping mall that has telescopes in all of these categories is SHOP.COM . They carry very good prices on instruments and telescope accessories from Celestron, Meade, Tele Vue, Vixen, and Rigel Systems, to name a few.

Just enter astronomical telescopes, or the specific type of telescope or accessory in their search engine.

Now that You Have the Equipment Here are a few tips to help you get the most out of observing Mars. If you have an SCT or Newtonian, you want to have the alignment tuned as well as you can achieve. Let the Telescope Cool Down You need to let you telescope cool down to ambient temperature. For larger telescopes, this may take an hour or more.

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Have a Steady Mount

You want a very steady mount on your telescope. There are some fine telescopes out there have have good optics, but inadequate mounts. The longer telescopes especially may be on inadequate mountings.

If you are observing at high power, a slight tap on the telescope should damp out in just a few seconds. If not, see what you can do to increase the sturdiness of the mount, or replace it. consider making one as i did on the Inexpensive Tripod page.

Use High Power Eyepieces

You'll need to magnify quit a bit to see mars, in excess of 100x. Better if closer to 200x or more. Any given telescope can only perform well at maximum magnifications of 50x per inch of objective diameter. Consider this when choosing a telescope. You can find a large range of suitable eyepieces at SHOP.COM .

A Clock Drive is Nice

A clock drive is not necessary. Better to have a solid mount than a clock drive. That being said, it is more relaxing to be able to sit comfortably and have a clock drive keep the planet steady in the field of view.

Consider Filters

Don't be disappointed at the few details you see at first. Planetary observing takes persistence even on good nights. The atmosphere is rarely completely clear. Rather, clearing occurs now and again. You need to be watching to enjoy the benefit.

If you wish, get a drawing tablet and make some sketches. I've made a few and described my technique at Mars 2003 Opposition page.

You can even try some photography if you choose. Mars is a difficult target, however. You need to photography through your telescope at high power. Even then, Mars will make a quite tiny image on film or CCD. Still, it is possible as you can see by my photo shown on the Mars 2003 Opposition page.

If it's a winter opposition, you may get your best views. Sometimes cold winter air gives extraordinary images. You'll need to be out awhile to see the most fleeting details, so dress warmly.