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29 August 2003

Mars 2003: Some Tips for the Curious

by Paul Curtin

This year Mars will be closer to Earth than it has been for about 100,000 years and it won’t come closer until August 2287. Even if you are not normally a Mars watcher this should be an exciting event. It is a great opportunity for amateurs to capture the public’s imagination and perhaps increase interest in matters scientific in your community. The following are suggestions for jump-starting an observational program of this intriguing planet. My hope is to encourage readers to view Mars at opposition and, once hooked, continue observations beyond the end of the year.

Finding Mars

Mars has been in Aquarius since early June and will remain in that constellation until mid-December. It moves into the night sky in August and can be found due south at midnight, continuing to rise earlier each night (thus becoming increasingly friendly to those of us who actually need sleep) as the year progresses. From August 1 until October 1 Mars appears to loop backward in Southern Aquarius. This seemingly retrograde motion is observed when Earth, with its greater orbital speed, chases and overtakes the outer planet in the months near opposition.

Provided you have a clear view south from your observing spot Mars will be easy to pick out well into December. Nothing in the sky will rival it for brightness and color so do not despair if you are unfamiliar with the night sky. See Mars Observers Guide or Observers Handbook 2003 for detailed positional information. Sky and Telescope and Astronomy also provide monthly planet finder charts.

A rare opportunity for all telescope owners

Mars is not an easy astronomical object. Unlike Jupiter or Saturn it is usually a tiny, featureless disk in the small telescope and it can be deeply disappointing to the beginner expecting to see the same degree of detail immediately apparent when viewing the larger planets. Observers embarking on a serious observational program are often (quite rightly) advised to seek the largest precision instrument available. At opposition however, even the standard 2-inch refractor can show the polar caps and some dark features. The bottom line is this: if you have a telescope, any telescope, now is the best chance to use it. I would be interested in hearing from readers regarding their experiences observing with small telescopes.

When observing, use a lower magnification first and accustom yourself to the disk and larger features. Take some time before moving up to maximum magnification and don’t be surprised if the intermediate powers give superior views as many small scopes come with high power eyepieces beyond their resolving limit.

At the Eyepiece

The quality of your telescope is not the only variable to consider when observing. The condition of the atmosphere and the state of the observer are likewise of great importance. Try to observe as often and as long as possible, but don’t overtax yourself. The physiology of the eye, glare, fatigue and thermal conditions will force you to modify the telescope focus quite often. Be patient: for those used to microscopy the need to wait for that perfect moment of clear seeing may be frustrating. Wait until Mars has risen as high as possible to avoid thermal effects and blurred telescopic images. Wind and wobbly telescope mounts can often ruin an otherwise productive observing session. If possible, place your equipment in an area protected from the breeze. With Mars, as with all scientific observations, try not to be misled by your expectation of what should be visible. Anticipation may lead you to miss the details of a dust storm or other transient event or to imagine something that is not there: don’t forget the canal fiasco!

There are a number of discrete features observed on Mars. Most are apparent in white light but filters can be helpful in bringing out details. Always acquaint yourself with the object in white light before employing filters. For those who wish to use filters the suggested Wratten numbers are given when relevant.

The polar caps can be glimpsed even in small telescopes. The length of the Martian year and the eccentricity of its orbit result in much greater seasonal temperature variation that that experienced on Earth. These seasons are marked by the ebb and flow of the caps. The receding edge is often uneven and the fragmentation of the caps is the subject of intense observation. The dark bands left in the wake of the cap are best seen with green filters (W56, 57). Dobbins, et al. describe observations of the polar ‘hood’ and note that these cloud-like apparitions vanish when viewed in red light (W25, 25A) whereas the caps themselves remain visible.

Dark and light areas were observed and sketched quite soon after astronomers first turned telescopes to the heavens. Huyghens drew the familiar form of Syrtis Major as long ago as 1659. One should attempt to identify the albedo features but beware that their shape can change over time and can appear radically different (or be entirely absent!) as a result of dust storms. Orange (W21) or red (W25) filters can help increase contrast. See Bone or the June 2003 and July 2003 issues of Sky and Telescope for maps of these features. Dobbins, et al. contains a detailed discussion of seasonal and non-periodic changes.

Clouds, transient phenomena, and dust storms, such as those that bedeviled the opposition of 2001, can be both challenging and frustrating. Blue-white and white clouds can be seen best with a green filter (W58) whereas orographic or W-shaped clouds show best with blue (W38) or violet filters (W47, 38A). These filters also allow one to observe the phenomenon known as the violet clearing. Usually the deep blue/violet filters allow one to see nothing on the planet except the polar caps. Occasionally however, there is a clearing through which surface features are seen. Localized dust storms, appearing often around the Martian summer solstice, are called ‘yellow clouds’. Yellow filters (W12) can show these in more detail. For more on transient events see the recent Sky and Telescope articles.

Record Keeping

Anyone interested in more than casual viewing should keep careful records of all observations. A good record should include the date and time of observation in Universal Time, a description of equipment used including the magnification employed, an estimation of the ‘steadiness’ of the atmosphere and a sketch of features observed. These last two items deserve special comment for newcomers. It takes some practice to quantify how clear and steady the viewing is: a number of books noted below suggest schemes for doing this. The system you choose is less important than the need to stick to one method and maintain consistent, comparable notes over time. With regard to sketches even poor draftsmen such as myself are able to make a positive contribution provided the drawings are true representations of what was actually seen. Drawing also helps the eye develop a sensitivity to fine detail and though your first attempts may (or may not) be meager your technique will rapidly improve. Price suggests using pre-inscribed circles of about 2 inches diameter, Bone provides a template that can be copied and used as the basis of your records. Even for the occasional observer a completed sketch is a tangible memento of a once in a lifetime event.

More detail on technique and planetary characteristics can be found in the brief bibliography below. I look forward to comparing notes with Mars observers later in the year. As the commercial said, "try it, you’ll like it", and if you do the opposition of 2005 is just around the corner.

Bibliography

Bone, N. Mars Observer’s Guide: a practical handbook for amateur astronomers. Toronto: Firefly Books, 2003.

Dobbins, T. A., Parker, D., Capen, C. F. Observing and Photographing the Solar System. Richmond, VA: Willman-Bell, 1992.

Encrenaz, T., Bibring, J.-P., Blanc, M., The Solar System. Berlin: Springer-Verlag, 1995.

Gupta, R. (ed.) Observer’s Handbook 2003. Toronto: University of Toronto Press, 2002.

Lowell, P., Mars. Boston: Houghton, Mifflin and Company, 1895.

Moore, P. (ed.) Practical Amateur Astronomy. London: Lutterworth Press, 1975.

Muirden, J. The Amateur Astronomer’s Handbook. New York: Thomas Y. Crowell Company, 1974.

Murry, B., C. (ed.) The Planets. Readings from Scientific American. New York: W. H. Freeman and Company, 1983.

Price, F. W. The Planet Observer’s Handbook. Cambridge, UK: Cambridge University Press, 1994.