There is a popular belief that to make an astronomical discovery, you must have a large telescope. Well, at least 1 meter in diameter. Or even better – Hubble or Webb. Astronomy is one of the few modern sciences in which amateurs without professional education and professional equipment can make a significant contribution, and even numerous discoveries. With very modest instruments, amateur astronomers can solve problems that large telescopes do not have time for. So, what is available for small scopes?
What is a small telescope?
One of the main parameters of a telescope is its aperture, the diameter of the main mirror or lens, as this determines how much light it collects. What aperture should an instrument have to be classified as a “small” telescope? There is no definitive answer to this question. Speaking of professional optical astronomy, telescopes with a diameter of up to 1 meter can be safely classified as small, and sometimes instruments up to 2 meters are included.
In amateur astronomy, the standards are much different. Typically, small amateur telescopes are 114-150 mm in diameter. Up to 250-300 mm are considered medium, and anything larger deserves the title of large amateur instruments. In some cases, amateurs manage to get an aperture of up to 600 mm, although with such a diameter, the telescope can be classified as professional.
However, in the context of this article, by “small” we will mostly mean amateur instruments of various calibers, focusing mainly on diameters of 150-250 mm. Surprisingly, sometimes even telescopes with an aperture of 100-120 mm can also produce excellent scientific results.
From small to large and vice versa
Almost always, a beginner in amateur astronomy sooner or later concludes: “I need a telescope, at least a small one on a budget”. And often this dream comes true – either in the form of a simple homemade instrument or as a purchase on the secondary market, or, if the financial situation allows, it is realized in the purchase of a completely new instrument. Oh, that incredible, exciting first meeting with the first instrument! The long-awaited observations of the Moon, planets, brightest galaxies, star clusters, and nebulae begin.
Having seen the very limited list of objects available for small amateur instruments, a novice amateur feels that he or she wants something more. Most often, this “something more” is either a transition from visual observations to photographic observations or the purchase of a telescope of the next level. In general, this is understandable: a larger aperture collects more light, so it will show fainter objects and with better detail. Astronomy enthusiasts even have a term called “aperture fever”. This “disease” manifests itself in the form of an irrepressible desire to buy or build telescopes of larger and larger diameter. It is not treated on an outpatient basis.
Visual observing enthusiasts in pursuit of more powerful telescopes at some point find that the latest instrument they have purchased is too heavy to take outdoors or travel under dark skies. And at this point, they often return to smaller diameters that will be more mobile, or, conversely, build a private observatory for the “main caliber”.
Astrophotography enthusiasts are faced with the fact that, in addition to the telescope tube itself, they need a high-quality mount (a structure that holds the telescope and allows you to point it at a selected point in the sky), and the budget increases dramatically. Add to that a special astronomical camera, and you have a very expensive hobby.
But some astronomy enthusiasts have more ambitious desires than just to see or photograph something new for themselves. They want to do something useful for their favorite science. Natural questions arise: “What can I observe or photograph with the instruments I have that will help professional astronomers?” and ”Is it possible to make an astronomical discovery with my equipment?”
It turns out that even very small telescopes can be quite useful. Observations through them provide a potential opportunity to contribute to science by collecting additional data that scientists can use in larger-scale research. And under certain conditions, in the right hands, an amateur telescope can become a tool for impressive discoveries. So, as counterintuitive as it may sound, size does not matter.
If size does not matter, what does?
Several points need to be addressed. First of all, it is necessary to set an adequate task for the available instrument and observation conditions: away from the lights of civilization, any telescope will show much more than in the city. Modern astronomy is at a qualitatively different level than it was a few centuries ago, largely due to the widespread use of photography. However, visual observations remain valuable in certain cases, which we will discuss later.
Amateur astronomers aiming for scientific discoveries often prefer photographic observations, which are certainly much more convincing in the scientific community than visual ones. In addition, images taken with modern CCD or CMOS cameras capture much more and more accurately than the human eye. Nowadays, in almost 100% of cases, discoveries made by amateurs are based on photographs. Depending on what objects or phenomena the observer wants to focus his or her efforts on, he or she chooses the appropriate camera, selecting the optimal field of view, resolution, sensitivity, and so on.
A less obvious but more important factor is the choice of mount. As already mentioned, a mount is a device that allows you to control the position of the telescope. Photographing the sky, especially at long exposures, requires compensation for the Earth’s rotation. Fortunately, modern equatorial mounts are mostly quite capable of handling the task of tracking the same object throughout the night. When choosing a mount, you need to pay attention to its load capacity – it must match the weight of not only the instrument itself, but also additional devices. These include the camera, as well as (often) a small additional telescope guide with its simpler camera, which allows for greater accuracy of the mount.
Finally, processing the images requires both a computer and specific software. The choice of programs depends, again, on the task at hand. Some allow you to process the images in such a way that previously invisible, faint details become brighter and clearer. Some are designed to search for moving “specks” – comets and asteroids. Some help to measure the brightness of objects very accurately and detect previously unknown variability.
A powerful armada of variable star observers
One of the simplest, yet most rewarding tasks that can be performed with amateur equipment is the monitoring and discovery of new variable stars. These are stars whose brightness changes over time. Moreover, the causes of these changes can be extremely diverse: from eclipses in binary star systems to sudden outbursts, from pulsations to large-scale dark spots.
The problem is that the number of even officially registered variable stars has already exceeded 10 million, and very, very little is known about most of them. However, variable stars are the source of the largest amount of information about stellar masses, evolution, and the formation and “life” of stellar systems in general. Certain types of them give scientists clues about the expansion of the Universe and the development of entire galaxies.
Professional telescopes cannot cover such a large number of objects with observations. And even more importantly, they cannot provide a long-term study of these stars. And certain effects can only be seen on the scale of decades or even centuries! This is where numerous amateurs with their small telescopes come in. They observe both already known variable stars and discover new ones, and a telescope with a diameter of 150-200 mm and a decent astronomical camera is often enough for this purpose. The largest community that unites amateurs and professionals who are fond of variable stars is the AAVSO (American Association of Variable Star Observers), which has existed for more than 100 years. The American Association of Variable Star Observers has long been an international organization, and anyone who wants to contribute to the study of variable stars can join. The AAVSO maintains the largest catalog of variable stars to date and has the largest database of their behavior.
Some variable stars are so bright that they can be observed with the smallest amateur telescopes and even with the naked eye. You can also add information about the discovery of new variable stars here.
The AAVSO regularly publishes the most relevant variable stars, in particular, offering to support parallel space telescope observations from the Earth. For example, in May 2025, they recommend T Coronae Borealis, EV Lacertae, V5856 Sagittarii, RW Cephei, and many, many others.
Among the recent discoveries of variable stars made by amateur astronomers with their telescopes is TYC 3161-926-1, which pulsates with a period of 81 minutes. It was discovered by Italian Tommaso Dittadi, who used a telescope with a diameter of only 254 mm.
In pursuit of supernovae
One very special class of variable stars is supernovae. They are always huge cosmic catastrophes that often end in the death of a star. Unpredictable and extremely bright, supernovae can emit almost as much light as an entire galaxy in a short period! This is why they can be seen from millions of light-years away. But it is precisely in these catastrophes, for example, that heavy elements are born – the ones that make up everything around us, and us.
Today, several automatic surveys continuously scan the starry sky and allow for the rapid detection of supernovae. They include the Zwicky Transient Facility (ZTF), the All-Sky Automated Survey for SuperNovae (ASAS-SN), the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), and this is not a complete list. Competing with such systems is becoming more and more difficult, but some amateur astronomers are succeeding.
And here it is impossible not to mention one of the most famous “supernova hunters” of our time, the Japanese amateur Koichi Itagaki. He has already made at least 190 discoveries. One of his most recent discoveries is the supernova SN 2025fvw, which erupted in the galaxy NGC 5957 on March 26 this year. How does he do it?
Koichi Itagaki has his observatory in Yamagata Prefecture, where several small telescopes are located, from very small ones to the “main caliber” 600 mm in diameter. Every clear night, these instruments take pictures of thousands of galaxies. The new images are compared with the old ones, and from time to time, new sources of radiation appear in the images – distant supernovae! Sounds a bit like the work of gold miners, does it not?
By the way, supernovae are not Koichi Itagaki’s only passion. He is also known as the discoverer of comet C/2009 E1 (Itagaki) and at least three asteroids.
How amateurs discover new nebulae
One of the most interesting and exciting areas of amateur research is the search for new nebulae. Most often, these are either planetary nebulae (the ejected shells of stars similar to our Sun) or supernova remnants. And in fact, this task is precisely an amateur one, since the unknown objects of these classes are exceptionally faint and often very large in angular size. Large professional telescopes are simply not suitable for such tasks, if only because they almost always have a tiny field of view.
Usually, the discovery of new nebulae takes place in one of two scenarios. In the first scenario, an amateur takes a picture of a well-known object, such as a galaxy, cluster, or nebula, but to obtain an image of impressive detail, he or she accumulates tens of hours of exposure, often using specific filters. When the images are processed and combined into the final photo, it may turn out that the image contains a faint, previously unseen structure. This way, an ordinary astrophoto can unexpectedly reveal a discovery.
The second scenario is a targeted search for new nebulae. Amateur astronomers carefully study existing automatic sky surveys, looking for faint hints of new structures. When they come across something new, they start shooting, accumulating precious photons for sometimes hundreds of hours! For such projects, astrophotographers often organize themselves into creative teams to observe in parallel with several instruments, which allows them to obtain the final image faster.
And here I would like to introduce you to a recent discovery by a group of amateur astronomers led by Marcel Drechsler. They found a huge supernova remnant, G115.5+9.1, which the authors of the discovery nicknamed “Scylla”. But not far from it, an additional reward was hidden – a previously unknown planetary nebula! It was nicknamed “Charybdis”. What a combo for a dedicated group of astro-amateurs. The most amazing thing here is that only 85 and 106 mm diameter telescopes were used for the survey!
Comets – on the verge of possibilities
The hunt for new comets is now in much the same situation as the search for supernovae: automatic surveys are often ahead of observers with small telescopes. Most often, the role of amateurs in the study of comets is limited to monitoring their brightness, coma diameter (cometary atmosphere), and tail length. But some enthusiasts can be called a “rapid response team”. They follow discoveries when comets are still at the “suspected” stage and are the first to take pictures of these distant, faint objects.
The task of the amateur in this case is to measure the position of the comet as accurately as possible and to determine whether the new object has a coma. If so, it is a comet. Otherwise, the newly discovered object should be classified as an asteroid.
Nevertheless, sometimes luck smiles, and some amateurs manage to discover a comet. A recent example is the achievement of Martin Mašek, who discovered comet C/2024 Y1 (Masek) on Christmas night using a 300 mm telescope. Although Martin is technically a professional astronomer, comet hunting is his hobby, not his main specialization.
Summarizing all of the above, we can say that in astronomy, any data collected carefully and thoroughly can be useful to professionals. Maybe you will be the lucky one who will be the first to notice the long-awaited outburst of a repeated new T Coronae Borealis. Or maybe your efforts will help the world learn about a previously unknown planetary nebula. The main thing is to choose the task that suits your equipment.
