Elusive Mercury (lower right below the Pleiades) sets in the twilight in this wide-angle shot. Taken with a Canon 18-55mm f/3.5-5.6 EF-S Zoom IS lens working at 23 mm of focal length with a single 20-second exposure at f/4 at ISO 1600 with a Canon Digital Rebel XS (1000D) on a fixed tripod.

The first planet from the Sun was named after the Roman God Mercury, messenger of the Gods. His swiftness was portrayed by his winged sandals, and the planet may have been named after him because it moves quickly in the sky. Mercury was also the god of traders, travelers and thieves.

Mercury is the closest planet to the Sun, and the smallest (excluding Pluto now that it is not officially a planet anymore), with a diameter of 4,879 km (3,031 miles) compared to the Earth's diameter of 12,742 km (7,917 miles). It orbits the Sun in a highly elliptical orbit with perihelion at 46 million km (28.5 million miles) and aphelion at 69.8 million km (43.4 million miles).

It takes 87.969 Earth days for Mercury to orbit around the Sun (what we consider to be one Mercury year) and 58.646 Earth days to rotate once on its own axis (what we consider to be one Mercury day). Mercury is tidally locked to the Sun much as the Moon is to Earth. But instead of it rotating on its own axis once for every orbit around the Sun as the Moon does around the Earth in a 1:1 resonance, Mercury's resonance is 3:2. It rotates three times on it's own axis for every two orbits around the Sun.

Mercury's brightness and size can vary greatly depending on where it is in its orbit in relation to the Earth. Its apparent magnitude can vary from -2.3 to 5.7. It's apparent size can vary from 4.5 to 13 arcseconds. As with Venus, the other inferior planet orbiting the Sun inside the Earth's orbit, Mercury can exhibit interesting phases from gibbous to crescent. Mercury is at its largest size near inferior conjunction when it is a thin crescent. At greatest elongation Mercury is nearly 50 percent illuminated, but only 7 - 8 arcseconds in diameter, and at an elongation of 18 to 28 degrees from the Sun.

Mercury can be a difficult target for photography. Because it is the innermost planet in the solar system, orbiting close to the Sun, it never has an angular separation of more than about 28 degrees from the Sun, and usually it is a lot less than that.

To observe or photograph it when the Sun is below the horizon, Mercury will never be very high in the sky. This means that we will be looking through a lot of atmosphere, which not only dims the brightness, but also makes the seeing worse.

In the northern hemisphere, Mercury can best be seen in the evening sky in the spring after sunset, and in the morning before sunrise in the fall. In the southern hemisphere, Mercury can best be seen in the fall in the evening, and the spring in the morning. This is when the ecliptic is at its steepest angle to the horizon, putting Mercury at its highest elevation above the horizon when the Sun has set or not risen yet. Mercury reaches its greatest elongation 22 days before and after inferior conjunction with the Sun.

Mercury can also pass in front of the Sun in a solar transit. This century, transits of Mercury occurred in 2003 and 2006, and will occur again in 2016, 2019, 2032, 2039, 2049, 2052, 2062, 2065, 2078, 2085, 2095 and 2098.

Mercury is the only other planet besides Mars to show a solid surface. It is heavily cratered like the Moon, so it is possible to capture detail on the surface with excellent optics and technique, and under good seeing. This is very difficult however because of its small size and because it is usually viewed low on the horizon where the seeing is bad.

Mercury can, however, be viewed in the daytime with the Sun up, if done with extreme caution. Placing the Sun behind a building is a good idea when attempting to view Mercury during the daytime because you are going to be trying to photograph it without a safe proper solar filter.

Mercury is seen here in a crescent phase in an image taken during the middle of the day at 1:02 p.m. when it was at an elongation of 17.9 degrees from the Sun. Mercury had a diameter of 7.8 arcseconds and a visual magnitude of 0.1 at the time of the photo. Taken with a Canon T2i (500D) and a 130 mm f/8 triplet apochromatic refractor. The sky appears black because of the exposure used with a red #92 wratten filter inside the camera body. The camera was used in 640x480 movie crop mode at 60fps and the best frames from 3 minutes of video were selected and stacked in AutoStakkert!2, from which the red channel was extracted in Photoshop for this image.

Mercury can be found in the daytime by following it up in the morning out of the twilight before the Sun rises, or by using a properly initialized and synced Go To telescope.

To shoot Mercury in the daytime, try using a red filter to darken the sky.

Since Mercury can be very bright while it is a crescent, it is easy to overexpose when shooting in a telescope. If you want to get the correct phase of Mercury at high magnification, shoot test exposures and bracket down to shorter shutter speeds. A crescent can end up looking like a gibbous phase if greatly overexposed. Check the phase of Mercury in a planetarium program or in WinJupos or with the UNSOs Apparent Disk of a Solar System Object web app.

Tips for Photographing Mercury

• Mercury never gets farther from the Sun than about 28 degrees, so it is a tough planet to shoot. If you shoot it when it rises before sunrise, or when it is still visible after the Sun has set in the evening, the seeing will usually be poor because of its low elevation.

• Mercury is also relatively small, so its apparent size never grows that large either. It is largest near inferior conjunction when it is a thin crescent, but it will also be very close to the Sun at this time, so extreme caution must be exercised in shooting it then.

• Mercury will appear half illuminated at greatest elongation. This is when you will probably have the greatest chance of recording detail on the planet if the seeing allows. When it is a largest as a crescent, most of the surface detail is unilluminated. When the surface is most fully illuminated as it approaches superior conjunction, it is farthest away and smallest.

• Try shooting Mercury in the daytime around noon when it is high in the sky, this will improve the seeing compared to shooting it when it is low on the horizon. Use a red filter to darken the sky background. Use Go To to find the planet. Be exceptionally careful that you do not accidentally point the scope at the Sun without a safe solar filter on the scope.