What can I see with a telescope?

When an astronomy newcomer asks us: What can I see with a telescope? We usually choked. The truth is that the answer is not easy. If we answer without reflecting on, it is likely that we do not clear up our friend doubts and he goes away.

We have to answer with care and focus on three basic points: the scale, what you see and how you can see it.

Somebody that never has looked through a telescope does not know what he can see and, what even worst; he does not know the scale provided by a telescope. Recently, somebody asked me if he could see a whole constellation with the scope…

About the scale, we have to clarify that no… you cannot see a complete constellation but just a very small portion of it. As a reference, a telescope allows us see the portion of the sky equivalent to a small coin when we hold it with one hand and our extended arm. So, in general, we will see a really small part of the sky through our telescope

Now, we have to explain what you can see. Even with a modest amateur telescope, you can see a lot of things. It is a common complaint from a novel observer that he only sees white isolated stars. First, we have to suggest him to point to a bright star and see its appearance and how sparks due to the atmosphere turbulence.

It is needed to explain that the first step should be to observe some Solar System object since this observation gives you very appealing images. The Moon is a ‘must’. First you will apply low magnification and later with more magnification to see the surface details. Later, we can observe the Jupiter’s moons, Saturn´s rings, the Venus phase, etc.

Craters and mountains over the Moon should be one of our first observations.

Image credit: GalaxiesSoup.com

At this point, we have to warn our friend about the Sun observation and its dangers. The sun observation is possible but, at the beginning, the projection method must be used to avoid accidents. Never observe the Sun alone for the first time, an experienced amateur astronomer will guide you how to point the Sun safely. Take care not only of the main telescope tube but also of the finder which could burn something.

A characteristic of our visual system is that we are not able to see colours when the light intensity is very low. The low brightness of the celestial objects makes unlikely to see colours in the sky. However, there is one exception; double stars. On these stars, the contrast between them allows us observe subtle and suggestive colours. We have to propose him to visit some popular double stars such as Albireo in the Cygnus constellation, the delta of Orion or the double-double in Lyra. Gamma Volantis or Zeta Reticuli are good examples on the southern hemisphere. Our friend can find many other examples of bright double stars on the web.

Albireo. The best example of double star on the northern hemisphere. Credit: Tom Diana

Finally, we have to tell our friend what he can observe beyond the Solar System, what we call Deep Sky… and now the explanation becomes more complex.

Inside this deep sky category we can mention the following types:

  • Open Clusters.

    They are medium to low density star group. Usually, open clusters are easy to observe objects due to their bright. We will be able to count dozens or cents of stars. Some good examples of this category in the North hemisphere are the Pleyads, Beehive cluster, Messier M35 and the nice Double Cluster in the Perseus constellation. In the South hemisphere, we can found the Jewel Box in the Crux constellation as a good example of an open cluster.

Double open cluster in Perseus. Credit: UnderOakObservatory

  • Globular clusters. Much more compact than the open clusters avoiding to see space between the stars. These clusters have thousands to hundreds of thousands suns. Some good examples are Messier M13 in Hercules constellation or Messier M15 in the Pegasus, both for the North hemisphere observers. In the South hemisphere, Omega Centauri is the best globular cluster available.
 Double open cluster in Perseus ( Credit:UnderOakObservatory)

Wide field image of the Messier M13 Globular cluster. Credit: Álvaro Ibáñez

  • Nebulae. They are gas accumulations shining because the gas is ionized or due to the light of some close star which light the gas up. The sky offers huge nebulae and very small ones. They are elusive objects and with a small telescope is difficult to see many details but it is possible to see the famous Orion’s Nebula (Messier M42), the Ring nebula (Messier M57) or the Dumbbell Nebula (Messier M27) all on the North hemisphere. On the South hemisphere, the Homunculus nebula around Eta Carinae star or the Lagoon nebula (Messier M8) are good targets

Image of Messier M27 Planetary Nebula. Credit: GalaxiesSoup.com

  • Galaxies. They are the most distant objects. Much more than any of the mentioned above. The consequence of the distance is their faintness. Even through a telescope, they are very small and faint. We can only aspire to detect these fuzzy objects with our telescope. They are the most thrilling bodies we can see because we are seen objects at millions of light years of distance. The best example of galaxies is the Andromeda Galaxy, a galaxy similar to ours, the Milky Way. Another galaxies which are a ‘must target’ is the Messier M81 and M82 pair in the Ursa Major constellation.

M81 and M82 galaxies in Ursa Major. Credit: GalaxiesSoup.com

Another common question is about the use of our telescope to see terrestrial objects. The answer is ‘yes’, you can although depending on the optical system, the image can suffer some mirror effect; we could see everything upside-down or inversed the right to left when we point to something  on the ground. These mirror effects are not relevant for astronomical use but are very uncomfortable for terrestrial observation. We should ask our dealer for the optical accessory to correct this effect. For astronomy, we prefer not to mount any additional glass because whatever its quality the image always is always degraded.

In the South hemisphere, the famous Magallanes clouds can be seen with the naked eye. They are satellite galaxies of the Milky Way. Centaurus A is another relatively bright galaxy in the South hemisphere.

Finally, we have to tell our friend something about the images obtained with a telescope and warn him about the differences between the images he will be able to see through the scope and the images on the web or books. We must explain to him that those photographs are exposures of many minutes (even hours) while our eyes only integrate light during a fraction of second.

He could not see images as the ones depicted above but, for example, he will see the galaxies Messier M81 and M82 like this.

Realistic image of M81 and M82 galaxies through an amateur telescope. Credit: GalaxiesSoup.com

Another example about the views through an amateur telescope is the image you can enjoy when pointing to some Solar System planet such as Saturn and its rings.

Realistic image of Saturn through an amateur telescope. Credit: GalaxiesSoup.com

For a newcomer these views can be flavorless and not very promising. The observational astronomy has a very subtle beauty and it should be tasted slowly. It is important to learn and to improve our equipment bit by bit. It is impressive how you will learn to see fine details on faint images and how you will improve your skills to see more and more as you look through the eyepiece.

That said the views of a faint remote galaxy or the sparking stars on the outer halo of a globular cluster are astonishing.

If our friend put up all our speech we can conclude that, at least, he has patience enough to confront a demanding hobby as this is.