What size Telescope do I need? This is really the fundamental question regarding all things astronomy, and indeed has been the driving force behind the evolution of the telescope and the exploration of the stars ever since the Middle Ages.
What you really want to know is – What will I be able to see with my Telescope?
Obviously the moon and the Sun are the omnipresent objects in our skies, which we can see without the aid of visual magnification. Yes you can even enjoy a better view with a pair of hand held binoculars, which is interesting. But surely one of the most memorable sights that a child or adult can behold, is the first close up view of the moon and its mysterious surface, craters, hills and valleys. On a clear night the ever changing face of the moon provides endless entertainment – provided you have the magnified view provided by a nice telescope. And your first look at the details of the contoured surface of our nearest celestial neighbour will unlikely be easily forgotten. Now imagine that same feeling magnified each time you peer further and further into the heavens, and begin to unlock the mysteries of what other neighbours with which we share our solar system.
Why stop there? Have you ever been captivated by the stars beyond our small patch of sky? How about the Milky Way? Have you ever wondered about our own galaxy, and the fact that we are surrounded by thousands of the stars, just like our own Sun? And how about the other celestial objects? Believe it or not there are other entire galaxies, more or less like our own, globular clusters, emission nebulae, planetary nebulae, as well as comets, meteors and asteroids. All of these objects make up the scenery within the heavens, and if you are interested, might well be worth your time to explore further.
The Moon
The beautiful bright Moon has always attracted the interest of humans, being the most visible object in our night skies. Sometimes we get accustomed to seeing the full moon as an attractive orb, or maybe we have a glimpse through binoculars. However, once you have seen the incredibly detailed features on the moons surface, you can’t help but wonder in awe at the celestial forces that brought the Earth and the Moon together. Indeed, once you use the telescopic powers of magnification, you will be stunned and awed by the sheer clarity and beauty of the images, such that you may want to see more and more detail.
The Sun
Of course, don’t let us overlook the subject of studying the most obvious heavenly body – our Sun, the closest star. The Sun is a special subject and it can only be observed with a full aperture filter. For example you can buy a so called “daylight” filter which can be mounted on any telescope, and they won’t cost a lot of money. You can really get an interesting close up view of the Sun’s features through a simple daylight filter mounted on a modest telescope or you can enhance your view with any higher quality instrument.
The Planets
The 8 major planets that are easily observable – as long as you have the right sized telescope. As well as enjoying the wonder of exploring other worlds, some of the planets such as Mars, Jupiter and Saturn will reveal considerable details of their distant surfaces. You may even observe weather patterns, on these distant worlds, which is far more interesting than the weather on Earth. You can also see the moons of Jupiter, and there are several moons around Saturn, which are harder to see, but a rewarding experience. Not only will you be able to see Venus and Mercury, but you will notice their changing phases, which is an intriguing reference to the changing crescent shape as they orbit around the Sun. Neptune and Uranus will be visible , but don’t expect much detail, and they will only be slightly visible unless you have a very large telescope.
The Deeper Sky
Deeper sky objects are the collective name for stars, nebulae, star clusters and even other galaxies – all of the stellar objects that are outside our own corner of the universe. The difference between looking at planets and stars is that deeper sky objects do not necessarily become clearer with higher magnifications. What you really want is to have a large aperture telescope, since that is the method by which a telescope gathers the light and focuses the image for you to see. Another factor affecting our ability to observe an object in the Deep Sky is the darkness of the night, and the clarity of the air. If you try astronomy around bright street lights – you won’t get a high quality image due to light pollution. To enhance your viewing quality, you need to find an area away from bright lights such the ambient light levels are as low as possible and therefore don’t interfere with the faint light signals that reach Earth from the heavens.
What about Asteroids and Comets?
Asteroids are rocky objects that can be found in inner solar system, and you can find them with a decent telescope but even the largest asteroids appear no larger than simple stars. What makes them interesting is their movement relative to background stars, which can be noticed over a period of time as long as you watch carefully.
Comets are conglomerate bodies of ice and dust which are found in the outer solar system, which infrequently approach the Sun on their irregular orbital path through the heavens. At the beginning we can only see the nebulous envelope and a small bright nucleus inside (which is the actual body of the comet). As comets speed closer to our field of view, they become bigger, brighter and can develop an impressive tail of dust and gas, which is ejected from the core of the comet by solar heating as the comet approaches the Sun. Although the more famous comets become visible to the naked eye if they approach close enough to the Sun, viewing these incredible objects is always more special with a decent telescope.
So the fundamental question remains – What size telescope will I need?
Aperture sizes of 60 mm to 70 mm
A telescope with an aperture diameter between 60 and 70 mm will let you see the moon, the lunar lakes and craters, and the basic outlines of the larger planets. Don’t expect to be able to study surface features of distant planets, as you will obviously need higher powers of magnification. You also need to remember that your view can be impeded by the city or urban lighting, so it is best to find a dark area on a clear night.
Aperture sizes of 90 mm to 130 mm
If you are keen to explore a little further, here are some of the celestial objects you can study through a telescope with an aperture diameter of 90 to 130mm.
a) Within the Solar System:
– Look for sunspots and solar flares around the Sun (make sure you use a filter)
– the planet Mercury
– craters and other features in the Moon’s surface
– The polar regions of Mars and other surface features
– several additional clouds on Jupiter,
– Jupiter’s moons as they revolve around the super planet
– Cassini’s division in Saturn’s rings as well as some moons if you watch very carefully!
– Uranus and Neptune are only seen as very faint discs
b) Stars and beyond: You will be able to pick up many stars, including star clusters, emission nebulas, planetary nebulas, and galaxies. But you have to remember that most objects such as galaxies and nebulae will remain very faint patches of light.
Click Here for a review of telescopes around the 90 to 130 mm range (suitable for beginners).
Aperture sizes of 130 mm to 200 mm
A telescope with a 150mm aperture diameter will allow you to see planets such as Jupiter in great detail, and most other planets will seem clearer, and the surface of the moon will be remarkably detailed.
Here are some other celestial objects you’ll be able to see using a 150mm aperture:
a) Moon and planets: – craters, mountains, and other lunar features
– surface features on Mars,
– fine details of Jupiter’s clouds,
– fine details of Saturn’s rings
– comets and even some asteroids.
b) Deep Sky and beyond: Into the Deep Sky you will be able to see incredible details of galaxies, nebulae and more – be especially aware to avoid light pollution, for even better results.
Click Here for a review of telescopes around the 130 to 200 mm range.
Aperture sizes of 200 mm and above
Telescopes with aperture sizes greater than 200mm will provide incredible clarity and brightness. The advantage of using an aperture larger than 200 mm is the amount of light gathering power. So you won’t necessarily be able to see many more or different objects, but the detail provided by the larger telescope is the major factor. If you want to focus on the various galaxies or nebulae, the larger the telescope (ie larger aperture size) the greater the viewing area and therefore the likely to provide a clear and bright image.
These size telescopes will be more expensive than the smaller instruments, but the view is spectacular. Here are some other celestial objects you can see with a 200 mm aperture:
a) Moon and planets:
– You will be able to see all the secrets of the moon!
– surface detail on Mars, and the moons could be a special treat so long as you have pristine viewing conditions
– extra detail in Jupiter’s clouds
– views of the Triton (Neptune’s moon) if you are careful
– Pluto if you have excellent viewing conditions.
b) Stars and beyond: If you have pristine viewing conditions, you will be able to see a broad range of nebulae, galaxies, and star clusters with details that are simply not visible to smaller telescopes.
Summary
Far from being a hobby only for the wealthy investors, or only for the dedicated professional astronomers, we live in a fortunate time where every one can share in the wonder of the heavens. You can very easily take advantage of the technology available to us and create your own viewing facility in your very own home. For a relatively modest cost, you can set up a magnificent telescope in your own backyard to explore deep into the solar system and the stars beyond. Children especially will be amazed to see the planets and the stars using modest and easily affordable telescopes.
