What Do Astronomers Observe With Telescopes [The Objects]

Astronomers use Telescopes for increased visibility. They enable Astronomers to view objects that just would not be possible with the naked eye. But what do Astronomers actually observe?

Before we look at what Astronomers view and monitor in space, it’s important to know why they use Telescopes in the first place.

Why Do Astronomers Use Telescopes?

Telescopes do not just provide magnification. They actually collect light that our eyes are unable to.

This includes light frequencies including radio, microwave, infrared, ultraviolet, x-rays, and gamma rays.

As our eyes are considerably smaller than that of a Telescope Lens, we can only collect a small amount of light due to the small surface area.

Telescopes on the other hand enable us to collect light of massive areas.

And why is this light important? Because, it is light that enables us to actually see things in Space and the Universe. A lot of stars, planets and objects emit light. This is how actually we see them.

In this way, telescopes enable Astronomers to see finer details, with much more clarity.

Beyond just what they can show, telescopes enable the ability to record observations.

They can be used to take pictures (also known as Astrophotography). When you compare this to just the naked eye, you would have to draw and sketch what you see which is impossible to decipher if it is actually real or not!

What Do Astronomers Observe With Telescopes? 

Now you know why Astronomers need to use a telescope, you can start to get an understanding of what they can observe.

Simply speaking, they can view anything that emits light.

This is a very basic answer, and you may be wondering what kind of objects even emit light, to begin with.

Generally, here are what Astronomers primarily use telescopes to see: the Moon, the Planets of our Solar System, the Sun, Deep Sky Objects, Comets, Stars, Light pollution, Novae, Supernovae and Satellites.

Now, there are a number of factors that dictate what an Astronomer can observe, and the level of detail they can then see their objects with:

  • Size/Quality of Telescope Used.
  • The observing location (sky darkness and cloud overhead)
  • Astronomers Skill/Knowledge or Experience.

Looking specifically at the Telescope, there are two main components that dictate how much it will be able to show.

The first is the “Aperture”. This is the diameter of the lens of the telescope and this is the component that defines how much light the scope collects.

Consequently, the resolution is highly reliant on this piece.

The second is the “Optical Quality”. This is basically the ability of the scope to show unaltered image.

Telescopes are available in a range of sizes. At a very basic level the larger a telescope the more it will be able to see.

As such, prices fluctuate depending on the size of the telescope and the quality of instruments used to build it. At a high level here are the options.

  1. Low-End (Small – Prices ranging from $50-200). These are typically portable telescopes intended for casual viewing by Astronomy Beginners and kids. They tend to be 70-80 mm Newtonian reflector telescopes or 50-80mm refractor telescopes. What you can see with these telescopes are more limited.
  2. Mid-Tier (Medium Sized – Prices ranging from $200-$500). These are typically 150 mm Newtonian reflector, 80-100mm refractor or a 90-130mm Maksutov Cassegrain telescopes.
  3. High-End (Large – Prices from $550+). These telescopes include 200-300 mm reflectors, 120-150mm refractors or a 200-250 mm Schmidt Cassegrain.

This is a pretty vague overview, because the price of a telescope can vary tremendously due to other factors like (accessories or equipment included, the quality of the mount etc).

Beyond this, different objects require optical requirements.

If Astronomers want to see the Moon, the planets or stars it is usually best to have a smaller scope that has a higher quality.

So for example, a 80mm refractor tends to be better than a larger 150mm reflector that has poor optics.

If an Astronomer wants to focus on deep sky objects then the opposite holds true.

A cheaper 150mm reflector tends to be better than a high end 80mm refractor for this task.

Below you will see what objects are available to observe for an astronomer, and the type of scope that is required for that observation.

The Moon

The Moon

The Earths Moon is one of the easiest objects to observe in the night sky for an astronomer.

Even with low magnifications and smaller telescopes it looks equally impressive. By using a larger and better quality scope, astronomers will be able to zoom in on the various parts of the moon with better clarity.

It is using a more premium scope that craters and mountains can be more closely studied.

The Planets

Planets of our Solar System

There are a total of 8 planets that make up our Solar System. Each of them can be observed from Earth with a Telescope.

Due to the relative distance to each of them, it is only with Jupiter, Saturn and Mars that you can see the finer surface details.

Additionally, if an astronomer was to observe one of these planets, they would be able to see the planets own weather conditions – including clouds, dust storms the famous rings of Saturn.

Interestingly, Jupiter and Saturn have several moons that rotate around their gravitational pull.

By using a mid-tier telescope, it is possible to witness the phases of Venus and Mercury.

Due to their relative distance from the earth, regardless of the telescope used, Neptune and Uranus tend to look small with traces of blue and green disks.

Pluto is very hard to see, more-so when in the periphery of the Milky Way. If an astronomer was to succeed, it usually shows as a dim star.

Beyond having sufficient Aperture and Quality Optics, for astronomers to see greater detail and clarity on planets – the telescope will need to be well collimated and cooled.

Then there is what astronomers refer to as the “seeing” (the turbulence in the atmosphere) If there is too much, the image becomes distorted.

So to be able to observe the finer surface detail of the planets, astronomers need the right atmospheric conditions and a high-spec, well-collimated and cooled telescope.

Deep Sky Objects (DSOs)


Deep sky objects (also known as DSO) is the blanket term for Galaxies, Nebulae and clusters of Stars.

These are referred to as ‘Deep Sky objects’ because they are effectively beyond our solar system.

If an astronomer wanted to observe Deep Sky Objects, they do not necessarily need to worry too much about the magnification of their scope.

Instead, their main concern is the aperture of their telescope, because the priority is getting a lot of light.

Outside of the Astronomers control is the sky darkness, which is obviously something that has to be understood.

In a period of high sky darkness, not even the most expensive, powerful telescope can dis cipher a view.

Most Deep Sky Objects appear faint and it is unusual to see much detail on them.

Where the astronomer is based (known as the observing location) is another important factor when looking at deep sky objects.

With very dark skies and where the milky way is very bright – a large 250mm telescope typically shows around 5000 deep sky objects.

If the Milky Way is barely visible, which is typical if a telescope if used in the suburbs, it is common that only 2000 deep sky objects are able to be observed.

By observing in an area with pollution (like in cities) the deep sky can only be observed with limited success, less objects and less clarity.

The most distant galaxies are even more susceptible to light; the more pollution, the less the chances of being able to see them.

Double Stars

Double Stars

Many of the stars that can be seen in the sky are actually not singular. Many are in fact double, triple or more.

Some even have different colors! Telescopes are an effective way of seeing these nuances.

Even the smallest and cheapest scopes allows the observation of Star Doubles. The larger scopes with the higher spec, will enable you to see the star relationship more clearly.

By viewing Double Stars over a period of time (typically months, sometimes even years) pairs are likely to change position in relation to one another.

Astoroids and Comets


Asteroids consist of rock and occur within the inner Solar System. They are likely to look like stars when observed through a telescope. However, it is within their movement that they can be distinguished.

Comets on the other hand, consist of ice and are relatively small. They occur in the outer Solar System.

It is when they align or venture closely towards the sun that they become visible. Initially, their coma (also known as the nebulous envelope) and a tiny bright “star” inside (also known as the nucleus) that can be noticed.

When Comets come closer to Earth, they look larger and shine brighter. It is sometimes possible to see a tail of dust and gas coming off of them.

The Sun

The Sun

Looking directly at the sun should never be attempted with a telescope. Instead, a special component called a “Full Aperture Filter” must be worn. These come in two different varieties: H-alpha and a Daylight Filter.

The H-alpha is a device that is placed onto a solar telescope, whereas the filter can be mounted onto any telescope.

When observing the Sun it is best to have a smaller aperture and a higher optical quality. The reason for this is that in the day – turbulence in the atmosphere prevents larger telescopes from being able to draw upon their full power.

Other Objects


As an astronomer becomes more experienced, so does there ability to observe more objects. Variable Stars are one example of this. They change over time, and become brighter as time goes by.

Novae and supernovae are the culmination of explosions of stars in the distance. These occur randomly and if the time is right, can be observed using a standard telescope.

Another event which requires the right time to see are Occultations of stars. It is only possible to see these from specific locations on Earth.

Another object to observe are Earth orbiting satellites. The most commonly sited satellite is The International Space Station due to its size (largest satellite).