Observing with Filters
This map of Mars shows south at the top and north at
the bottom, and represents the inverted view as seen through a
reflecting telescope. This map was computer generated by Daniel Troiani,
using all the data from the Mars Section of the Association of Lunar and
Planetary Observers, ALPO, as gathered during the 2001 apparition. This
map is intended to represent Mars as it might be seen through a
moderately sized telescope during the 2003 apparition. This map may be
found online at the ALPO Mars Section website:
www.lpl.arizona.edu/alpo Click on Image for Enlarged VIew.
Keeping an Eye on Mars
Mars is the only planet with a surface that can be plainly seen and
charted from Earth. For visual observers, the Martian atmosphere offers
more variety than any other Martian feature. Viewing with the human eye
is the most sensitive way to record features of planets. The human eye
and brain readily detect subtle patterns of light, shade, and color.
Because the eye records planetary features during successive brief
moments of atmospheric stability, an observer with a small telescope can
build up a detailed composite image of the planet in his mind.
Transferred to paper as a sketch, that subtle detail is preserved for
City lights don’t harm planetary observing, so you can observe Mars even
from New York City or Los Angeles! But you must allow your telescope to
reach outside temperature before attempting any critical observing, and
you must conscientiously work at educating your “observer’s eye” with
lots and lots of observing.
You will need good quality eyepieces, but you don’t need the expensive
wide-angle types. The standard Orthoscopics and Plossels the came with
your telescope are fine. If you have a binocular eyepiece available, you
will find that it makes finding small details much easier.
Filters and How they Work
A set of color filters is tremendously helpful when observing Mars.
Color filters increase contrast between areas of differing color, permit
you to separate clouds at different levels in the planetary atmosphere,
and reduce light scattered from a too-bright planetary image. All told,
they increase the sharpness of surface and cloud details you will be
trying to observe on the planet Mars.
A yellow filter brightens the ocher-colored Martian deserts and darkens
the greenish and brown features. Orange increases contrast between light
and dark features, penetrates atmospheric haze, and helps you see yellow
dust clouds. Red goes even further, yielding maximum contrast of surface
features and helping you see dust clouds.
Green, blue, and blue-green filters brighten atmospheric features and
darken the surface. Violet filters go even further, bringing out
haziness on the limb of the planet, small equatorial clouds, and clouds
over the poles.
Used intelligently, filters help you see more than you could any other
way. You can find glass filters from companies that advertise in both
ASTRONOMY and Sky & Telescope magazine, or obtain low-cost gelatin
filters from a camera store. Your filter set should include all of the
colors mentioned above, plus magenta to enhance polar cap contrast.
AAAA Mars Card
|The AAAA Mars Card is a concise way to learn the
essential information about Mars during the current favorable opposition
in August and September 2003. Just click on either image to down load our
PDF, print it off, and make copies for yourself and to hand out at your
own Mars Observing Events for friends and the general public!
Make the Photocopies!
have time to make copies? Let us do the work for you. We will make copies
at $10 per 100 postpaid, as many as you want, and send them to you via
USPS Mail! Order online through CCNow, our Online Retailer. Canadian and
overseas orders additional postage.
AAAA Mars Card:
100 for $10 ppd:
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Planning for the Public
In planning any special Mars observing activities for the
general public or the media, keep in mind that in late August
when Mars is closest (diameter about 25 arc sec), it will only rise
about 30 degrees above the horizon at midnight ... so not good for
"early evening" observing. However, this situation improves through September:
end of September, Mars will still be over 20 arc sec. in diameter, but will cross the meridian (a bit more than 30
degrees high) earlier ... about 9:30PM. This placement is somewhat
better for public programs.
As always, there is the danger of
planet-wide dust storms at this perihelion. Storm activity on Mars will
easily wipe out any surface features otherwise visible.
Society has proclaimed August 27, 2003, the date of opposition, as "Mars
Day". The Planetary Society has a goal of "half of the world's
population looking at, or thinking about, Mars" on Mars day. So please
circle this day on your calendar. Now is the time to start planning Mars
Parties in your local area.
This chart by C.F. Chapin shows the
relative positions of Mars and Earth for the years 1988 to 2003. The
last great opposition of Mars was 1988. On August 28, 2003, Mars will be
at its closest approach to Earth in recorded history, at a distance of
only 34,646,418 miles.
Click on image for