Although there are thousands of astronomical objects worth observing in the night sky, all astronomers, both amateur and professional alike, will tell you that they have their own personal favorites. These might include lingering early memories, such as the first sighting of the Milky Way‘s largest globular cluster, Omega Centauri, or the first splitting of a difficult binary star system, such as observing the double star Albireo in Cygnus, whose brighter yellow star presents a striking contrast to its fainter blue companion. Whatever the case may be, the following list looks at ten celestial objects most astronomers agree are worth a second look.
The Moon
It is possible to spend a lifetime observing the Moon, and still discover something new every time you observe it. The play of light and shadow, the amount of illumination, and the libration of the Moon can sometimes obscure some features, but bring them sharply into focus at other times. A good time to observe the Moon is during daytime when it is visible, and quite often, you will discern details that are not visible at night.
The Moon is an excellent training ground for new observers since many features become visible only under certain illuminations, but also because using the correct magnification is important for seeing different features. High magnification is not always the best option, so use the Moon to practice using different magnifications under different conditions before you venture further into the solar system and beyond. One thing is certain, though, you will keep coming back to the Moon!
The Planets
Mars
Finding the planet Mars is one of the most rewarding experiences any novice stargazer can enjoy. While it first may look nothing more than a small reddish disc, with a bit of practice even a small 4″ telescope can reveal tantalizing surface features on Mars, such as the Red Planet’s darker regions and its polar caps, whose appearance changes with the Martian seasons.
If you don’t have a go-to scope, Mars offers an excellent opportunity to learn your way around the night sky, since during certain times of the year it is easy to confuse Mars with Antares located in the constellation Scorpius, which is a giant red star.
Venus
The planet Venus also displays phases, just like the Moon, and although it may sometimes be difficult to obtain a fine focus on Venus, with good optics and some practice with the fine focus control, it is possible to view the phases of the planet as its illumination from the Sun changes. Venus may not offer much visible detail other than its phase, but you will want to see it again and again.
Jupiter
The King of the Planets always offers a rewarding viewing experience, since the detail in its colorful bands is forever changing. Fine detail becomes easier to see in larger amateur instruments, but even modest equipment can reveal the main equatorial bands and the four Galilean moons as they move around the gas giant.
Of particular interest is the Great Red Spot on Jupiter, which is visible during good seeing conditions with modest equipment when the storm is facing Earth. Once you start tracking the movement of the Spot, you will want to return to Jupiter for as long as it is visible. See how well you can follow this enormous storm as Jupiter rotates.
Saturn
Credit: NASA Hubble, licensed under CC BY 2.0
When Saturn’s rings are tilted with respect to our line of sight, the planet offers one of the most spectacular sights in the entire solar system. Even modest equipment, such as a 4″ telescope, will reveal the splendor of the ring system.
The rings change their apparent inclination as Saturn and Earth move around the Sun, and at certain times they become extremely difficult to see when viewed almost edge-on. The main rings are extraordinarily thin compared with their enormous width, so Saturn can look dramatically different over the years as our viewing angle changes.
Star Clusters
Pleiades Star Cluster (M45)
Also known as the “Seven Sisters”, this famous open cluster in the constellation of Taurus contains more than 1,000 known stars, although only a handful are usually visible without optical aid. The cluster is dominated visually by hot, young blue stars that formed at roughly the same time.
It is best viewed at low magnification because higher magnifications reduce the field of view and can cause much of the cluster to be lost from sight. Long-exposure photographs also reveal striking blue reflection nebulosity produced as the stars illuminate interstellar dust through which the cluster is currently passing.
Galaxies
The Andromeda Galaxy (M31)
At around 2.5 million light-years from Earth, Andromeda is the nearest large galaxy to the Milky Way and may present you with your first real test in finding a faint deep-sky object. As with other colorful objects, photos of the Andromeda Galaxy reveal far more detail than can be seen visually. In a telescope, it generally appears as a large, fuzzy glow with a brighter central region.
However, the real reward will be in having found it in the first place. One way to locate this large spiral galaxy is to find the Great Square of Pegasus first and use it to navigate into the adjoining constellation of Andromeda with a good star chart or atlas. Once you have it in sight, you can appreciate that you are looking across roughly 2.5 million light-years of space at another great spiral galaxy.
Nebulae
The Orion Nebula (M42)
Because Orion lies across the celestial equator, it is visible from both hemispheres and is one of the most recognizable constellations in the entire sky. The Hunter’s Belt consists of three prominent stars, while below it lies Orion’s Sword.
The middle region of the Sword contains the Orion Nebula, which is visible to the naked eye under reasonably dark skies and becomes a spectacular cloud of glowing gas through a small telescope. At a distance of roughly 1,300 light-years, it is one of the nearest major star-forming regions to Earth and contains the young stars of the Trapezium Cluster.
The Ring Nebula (M57)
The Ring Nebula in Lyra is a classic planetary nebula and makes a rewarding target for a small telescope. It is located between the stars Sheliak and Sulafat in Lyra and initially appears as a tiny, slightly fuzzy patch.
Increasing the magnification once you have located it can make its distinctive ring-like shape easier to recognize. The Ring Nebula is generally seen visually as gray or gray-green rather than displaying the vivid colors captured in long-exposure photographs. Enjoy the sight; the search will have been well worth the effort!
The Crab Nebula (M1)
Also known as M1, being the first item in the Messier catalog, this nebula got its name from Lord Rosse, whose 19th-century drawing gave the object a crab-like appearance. The Crab Nebula is actually the expanding remnant of a supernova observed in 1054.
Chinese astronomers recorded the appearance of this brilliant “guest star,” which became bright enough to be seen during the daytime. Today, the much fainter nebula can be found in Taurus near the star Zeta Tauri. Under a dark sky it can be detected with a small telescope as a faint, hazy patch, while larger apertures begin to reveal more of its irregular structure.
There are many more…
The few objects on this list represent a minuscule fraction of what is visible with an amateur instrument, but all of the above items have their own particular challenges. However, challenges are only stepping stones, and as you learn the sky and develop your observing skills, you will eventually start to “discover” other treasures on your own. Enjoy the journey!