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How to See the Variable Stars With A Telescope?

Variable stars are crucial for testing our theories of stellar development, from bloated red giants nearing the end of their lives to binary stars engaged in deadly gravitational dances. They play a significant role in stellar astrophysics. 

However, extrinsic variables and intrinsic variables are the two basic categories of variable stars. Intrinsic variables are stars whose magnitude changes are brought on by internal physical processes in the star. For instance, many red giants, like Betelgeuse (Alpha () Orionis) or Mira, contract and expand over the course of months; as the star’s surface widens, it gets fainter; as it contracts, it gets brighter. Stars known as intrinsic variables undergo changes in magnitude as a result of internal physical processes. Many red giant stars, for instance, such as Betelgeuse (Alpha () Orionis) or Mira, shrink and expand over the course of months; as the star’s surface extends, they grow fainter; as the star shrinks, they become brighter. Eruptive variables are the result of violent changes to the star’s surface. For example, intense flare activity can brighten a star by six magnitudes. The novae and supernovae are more striking examples. 

What are Variable Stars?

Variable stars are a diverse group of celestial objects characterized by their fluctuating brightness, with over 52,011 known members and more being discovered regularly. These stars exhibit a wide range of variability types, including Cepheid variables, RR Lyrae stars, Delta Scuti stars, and eruptive variables, each with unique characteristics that influence their observability. The observability of variable stars is affected by factors such as their type, pulsation period, and luminosity, making them intriguing targets for telescopic observation.
When selecting a telescope for observing variable stars, several key attributes must be considered, including their brightness, variability, pulsations, and mass loss. The spectral type of variable stars is also crucial for telescope selection, as it helps determine the type of telescope needed based on the stars’ temperature and luminosity. The range of amplitude of variability for variable stars can vary greatly, from a few hundredths of a magnitude to several magnitudes, influencing the choice of telescope for observation.
Variable stars exhibit a wide range of brightness levels, from +4.8 to +12.6 magnitudes, with some stars showing small changes in luminosity and others displaying large variations in brightness. The period of variability for variable stars can range from 0.01 to 13 days, with observations typically lasting for an average of 141 nights across a time baseline of 218 days. The method used to measure the distance of variable stars involves observing their pulsation period and comparing it to their known luminosity, providing valuable information for understanding these enigmatic objects.
Mira variable stars, such as Betelgeuse, exhibit variability in brightness primarily due to atmospheric pulsations, expansion and contraction of outer layers, and irregular fluctuations in excitation levels. Studying these stars can provide insights into stellar evolution and pulsation mechanics, with telescope selection considerations including aperture size, filter compatibility, and specific observation needs. Delta Scuti stars, like Delta Scuti, are significant in the study of variable stars due to their short oscillation periods and location in the Cepheid instability strip, offering valuable information about stellar pulsations and evolution.
RR Lyrae variable stars, such as RR Lyrae, are essential for understanding the evolution of galaxies, serving as distance indicators for old stellar populations and providing insights into the structure and dynamics of galaxies. The study of variable stars, including Mira, Delta Scuti, and RR Lyrae stars, is crucial for advancing our knowledge of the universe and requires careful consideration of telescope specifications to observe and study these intriguing objects.
As of now, astronomers have identified more than 1 million variable stars, according to the American Association of Variable Star Observers (AAVSO). Variable stars aren’t rare or unusual, and it’s not uncommon for amateur astronomers to make interesting and useful scientific discoveries about them. The study of variable stars can reveal much about the nature, history, and future of stars, with many astronomers – both amateur and professional – actively involved in their research. Variable stars show that you don’t always need sophisticated and expensive technology to do useful and valuable science, as all you need is the ability to estimate the brightness of a star by comparing it to that of others.
Variable stars play a significant role in our understanding of the universe, with research into Cepheid variables helping determine the age of the universe and providing information on distant galaxies. Studies of Mira variables are important to our understanding of our Sun, while supernovae give us insight into how the universe is expanding, and cataclysmic variables help in understanding active galaxies and supermassive black holes.

How far are Variable Stars from planet Earth?

The distance of variable stars from Earth is approximately 4.25 light-years. The absolute magnitude of a Cepheid variable star can be used to determine its distance from Earth. The apparent magnitude of a variable star is affected by its intrinsic luminosity, distance from Earth, and any extinction of light caused by interstellar dust. Astronomers use the apparent magnitude to calculate the distance to a variable star using the distance modulus method. Factors such as eruptive events, thermonuclear explosions, instabilities in the star’s envelope, luminosity, and distance from Earth can cause fluctuations in brightness seen in the light curve of variable stars. The relationship between the apparent magnitude of variable stars and their distance from Earth is indirect, as astronomers use the apparent magnitude to calculate the distance using the distance modulus method.

Can you see Variable Stars with a telescope?

Variable star observing is ideal for observers with binoculars or small telescopes. You shouldn’t need anything larger than a 102mm refractor for objects brighter than 8 magnitude. To begin your observations you’ll need to print off a suitable variable star chart. Seeing conditions aren’t too important for variable stars, but you’ll want the sky to be free of haze and to avoid observing in strong moonlight. Once you have the variable star in the field of your telescope or binoculars, you’ll need to estimate its brightness. Don’t rush this – it’s really important that you identify the variable star in the field, so spend time checking that the stars in the field of view match up with those on your chart.

Quick Guide to Observe the Variable Stars.

The recommended aperture size for objects brighter than the seventh magnitude is 4 inches (102 mm). Pay attention to your impressions since red giants may appear brighter than they truly are. Aim the scope at the variable stars by positioning it in the finder’s center. For a closer look, choose an eyepiece with the lowest power and highest focal length. A 20 mm eyepiece or Barlow lens, for example, will perform better in this situation. Check the alignment of the finder scope if you are having trouble finding the variable stars.

How to find Variable Stars?

  1. The first step in beginning an observation of variable stars is to select a few.
  2. Starting with some variables that are simple to find is a smart approach. 
  3. Some require more frequent observation than others. Eruptive or dwarf novae can be seen on any clear night, whereas pulsating Mira-type stars should only be examined once a week (as their changes are sluggish).
  4. After centering it in the finder, aim the scope at the variable stars.
  5. When examining anything closely, use the eyepiece with the lowest power and highest focal length. For optimal results, use a 20 mm eyepiece or Barlow lens. Check the finder scope’s alignment if you can’t see any variable stars.
  6. Check your focus after you’ve located the variable stars.

Classification Of Variable Stars:

Eclipsing binary star

These two stars orbit one another and are aligned so that one of them passes in front of the other.

Cepheid variable

They expand and contract on a regular basis, such that they can be used as a distance measurement tool.

Mira variable

A Variable star that is erratic and semi-regular and lack a pattern in their brightness variation

Gamma Cassiopeia

Their brightness swings because of the material ejected near the equator from their rapid rotation.

8 Tips to observe the Variable Stars in the best way.

  • You must print off a good variable star chart before you can start your observations (more on this below)
  • For variable stars, seeing conditions aren’t all that crucial, but you’ll want the sky to be clear and avoid strong moonlight.
  • Record the date, time (in UT – Universal Time), your magnitude estimate, and the chart sequence of your observations in an astronomical notebook. The size and model of the telescope should also be noted.
  • It’s crucial that you identify the variable star in the field, so take your time and make sure the stars in your field of view correspond to those on your chart.
  • It’s generally preferable to start out using a low-power eyepiece. You should now be able to compare the stars you can see to the ones on your chart.
  • Find a good comparison star, ideally one of similar brightness, and note how much brighter or fainter the variable is in relation to it after you’ve found and confirmed your variable.
  • The Pogson step method is an effective way to accomplish this. With the aid of a comparison star, you may determine a variable star’s magnitude in increments of 0.1 magnitude.
  • Therefore, you would record it as “103 – 4” if your comparison star is mag. + 10.3 and you believe the variable to be four tenths brighter.

Which Variable Stars you can observe with a telescope?


  • Algol (Beta (b) Persei) is made up of three stars: Beta Persei Aa 1 and 2, and the fainter Beta Persei Ab.
  • The two blazing main stars, Beta Persei Aa 1 and Beta Persei Aa 2, eclipse one another and take around 10 hours to complete.
  • Algol’s magnification is typically about + 2.1, but every 2.9 days it drops to + 3.4. Consider observing it every clear night.

SS Cygni

  • SS Cygni is a dwarf novae that can be seen around the lovely double star 75 Cygni in the constellation of Cygnus, the Swan.
  • The star is roughly mag. + 12.0 while quiescent (in a state of inactivity), but during an outburst it can brighten to about mag. + 8.0.
  • Every 7 to 8 hours, SS Cygni experiences similar outbursts, therefore it should be seen anytime there is a clear night.

Chi Cygni

  • Chi (c) Cygni is a magnificent red giant of the Mira type that may be found at the base of the “Northern Cross” asterism in Cygnus, not too far from Eta (e) Cygni.
  • Chi Cygni can reach a maximum brightness of mag. + 3.5 over the course of around 400 days before waning to its lowest brightness of mag. + 14. Material from Chi Cygni is being ejected into space; this material will eventually coalesce to form a planetary nebula. If at all feasible, try to observe this star once per week.

V Bootis

  • Another stunning red giant can be found nearby Seginus (Gamma () Boötes) in Boötes, the Herdsman. Mag. + 7.0 to mag. + 12.0 are the ranges for this star over a 258-day period.
  • Studies of the light curve have revealed a secondary period of roughly 137 days, and the overall light curve during the early 20th century was somewhat different (the star may be transitioning from being a Mira-type star). Aim to do so once every week.

R Scuti

  • A notable example of an RV Tauri variable is this yellow supergiant star. Both Beta (Scuti) and the magnificent Wild Duck Cluster, M 11, are nearby.
  • This star’s light curve exhibits periods of deep minima and unusual’stand-stills,’ in which its brightness remains constant for extended periods of time.
  • Although many questions remain unanswered, it is believed that the star’s dynamics are to blame. Watch this star whenever you have the chance.


  • Draw a straight line from Aldebaran in the Taurus constellation to Cetus. Your best bet is a star map. Between Eta Eridani and Alpha Piscium, it’s around midway between them.
  • The brightest of the long-lived “red” variable stars, Mira is a huge, pulsating star that is also known as the beautiful Omicron Ceti. Despite the fact that its exact maximum is never anticipated, it has a duration of 332 days.


  • In the Northern Hemisphere, the Orion constellation is simple to locate in the winter. The star above and to the left of the Orion belt is called Betelgeuse.
  • The Orion constellation’s top left corner is where you can see this brilliant orange red star. The majority of people are unaware that this star fluctuates in brightness but only very slightly.
  • Over a period of around 6 years, its brilliance gradually increases and decreases. It is predicted that Betelgeuse will have a supernova explosion in the next million years. And it will be worthwhile to view. In fact, for a brief period of time, we should be able to see it throughout the day.

What telescope to see the Variable Stars?

Celestron NexStar 8SE, Celestron Astro Fi 102, Orion SkyQuest XT6 Classic Dobsonian are great telescopes to see the Variable Stars. A list of telescopes has more telescope options that can see the Variable Stars very clearly.

What size telescope to see the Variable Stars?

In fact, you shouldn’t use a telescope larger than a 4 inch (102 mm) aperture for objects brighter than the eighth magnitude. Also watch out for bias; red giants sometimes appear to be brighter than they actually are.

What magnification is required to see the Variable Stars?

It just takes a 50x magnification to see all of the variable stars. To observe the details, 150x magnification is preferable. 

Enjoying the Variable Stars? Here are other things to see with your telescope.

The wonders of the dark night sky can be seen through a telescope. Besides Venus, Mercury, asteroids, meteor showers, and other things in the night sky, you may see details of them with the same telescope you use to examine the variable stars. ‘How to See the Binary Star With A Telescope?’ can guide you to observe some double stars. You also can look at the  ‘List of things to see with a telescope’ which offers a summary of several night sky objects you can view using various telescopes.