Photo by Marco Milanesi
Originally Posted On: https://www.astrojunkies.com/astronomy-basics/
Have you owned a telescope for years but never managed to actually see the Southern Cross with it, and let alone observing the Andromeda galaxy? Or, are you thinking about starting a backyard astronomy hobby but simply don’t know where to start?
If one of these is happening to you at this very moment, know that you are not alone. While stargazing can be a very fun and easy hobby once you get the hang of it, the first step towards astronomy can be a little overwhelming.
In fact, many newcomers to astronomy quit in frustration because they got lost at the beginning, and they have no success in finding the deep-space objects they had aimed to observe.
In this guide on astronomy basics, we will share the step-by-step advice of starting an astronomy hobby for beginners. By the end, you should have a clear picture to finally start your stargazing hobby and see Saturn, Sagittarius, and any deep-space objects you’d like to observe.
Without further ado, let us begin.
I. Astronomy Basics: Prepare for outdoor observing
First things first: have the right mindset and expectation.
Our Earth is part of the Milky Way galaxy, which is only one of more than 100 billion other galaxies. So, even NASA’s most sophisticated telescopes and technologies can’t fully observe all of these galaxies and the deep-space objects contained within.
So, as a beginner astronomer, you won’t be able to see them all (so don’t expect to). Your telescopes and binoculars will have their limits, but you can still see quite a lot of things. Even from your backyard, it’s possible to see a plethora of stars, planets, nebulae, galaxies, and even time-sensitive objects like comets flying by or asteroids.
One of the most important keys to achieving that, however, is to have the right preparations, as we will discuss below in this astronomy basics guide.
Astronomy Basics: Having the right gear
Yes, ideally you should invest in a telescope, but binoculars can be a ideal beginner’s telescope for several reasons:
- First, they have a wider field of view than standard telescopes. Telescopes magnify only a tiny part of the night sky and pinpointing the exact location can be difficult for beginners. Binoculars, on the other hand, show a pretty wide area right in front of you, so it’s easy to see where you are pointing.
- Also, binoculars are relatively affordable and widely available with pretty decent performance. A typical 7- to 10-power binoculars can improve your view as good as your regular amateur telescope while only costing less than half the price.
So, how should you choose your binoculars?
We’ve done a several articles here on the site about binoculars for astronomy. If you have some money to spend I would recommend checking out this article for a review of some higher end binoculars.
However, if you’re on a bit of budget, or just getting started into the pastime, don’t worry, there are still plenty of great options for quality astronomy binoculars on a budget as highlighted in this article.
If you’re looking to make a significant investment in a high-end set of binoculars, you can opt for modern image-stabilized binoculars like the Canon 10×42. These binoculars are a stargazers dream, but I warn you, the price is not for the faint of heart.
Even after you upgrade to a telescope, your binoculars will be an extremely useful tool. They are a great multi-purpose, long-term investment, so you might as well get a good pair.
In amateur and professional astronomy, red flashlights are used to see charts and view telescope settings, among other usages without limiting your ability to see at night.
Why do you need a red light instead of the traditional white/yellow flashlights instead? With a red light, we can maintain our eyes’ “dark adaptation” in nighttime stargazing. Dark adaptation is the state when our eyes gain improved ability to detect faint objects in dark conditions.
Our retina reaches the first stage of dark adaptation in quite a short time, around 30 minutes, and after that will get better in detecting faint objects.
However, when the eyes are exposed to bright light, the dark adaptation will be “reset”, and this is why we use dim red light, which our retina’s rod cells are least sensitive to. Even then, stargazers should close their observing eye when consulting using red lights to consult charts or change their telescope settings.
Nowadays, we have two options for star maps: using stargazing apps in our smartphones or computers or do it the old school way to get a star chart in book formor download and print them.
There are various star charts and stargazing apps for iOS and Android alike, many of them are free. Also, good star chart apps should offer night viewing mode that tints the screen red (see the red light section above).
Dealing With Dew
Dew is a very serious issue in backyard astronomy and stargazing (and photography), moist lenses will disturb your view significantly. Expensive Newtonian telescopes that have their mirror deep within the tube are mostly safe, but binoculars and cheaper telescopes are susceptible to dew issues.
There are several answers to deal with dew, namely:
- Always point the telescope or binoculars downwards between each observation
- Invest in larger dew caps or shields. Or you can make a DIY shield with accessible and affordable materials.
- Avoid bringing the telescope/binoculars from the cold into a warm condition, as the lenses will moist quickly. In such cases, wait until the lenses are moist free before you put your dew shield/cap on.
- Invest in dew heater bands like this one from Orion. They are usually the most effective measure to deal with dew and moist surfaces.
Have Enough Water and Snacks
Pretty self-explanatory, your body still needs enough nutrients to maintain your energy and stamina. So, make sure to take enough water and snacks of your choice with you. Since it’s going to be a late-night observation, avoid snacks with too high sugars/starches and calories. Also, you might want to pack hot chocolate or
Wear Appropriate Clothing
What you should wear will depend upon the location where you’d make the observation, and also the season. If it’s the winter in North America, then make sure to wear appropriate clothing. This should be based on common sense. Make sure you can be warm enough as you wait for the stars to come out.
Other Things to Take With You
Here are some other things you might want to prepare to start your stargazing project:
- Something to sit on such as a lawn chair, or viewing chair.
- Something to lie on, a blanket or a camping mat.
- A cover to protect your telescope. Useful if you start calibrating your telescope in the daylight and leave it there for hours.
- A compass and a star spotter app (i.e. Night sky on iOS and Android) to help you in finding your “target” star, constellation, or object.
- Your camera (or your phone camera), but make sure not to use any flash that will compromise your eyes’ dark adaptation.
- Since you’d need to make sure your eyes are not tired and can attain the dark adaptation properly, get audio-based entertainment if you want (podcast, a playlist of songs, etc.).
II. Astronomy Basics – Finding a Good Location
A huge aspect of astronomy observation is about finding an ideal spot, and it’s much more than simply finding a nearby spot with a clear, unobstructed view of the sky.
First, you have to make sure the area contains as little light pollution as possible, this can be very difficult if not impossible if you live in a city.
If you have a big enough backyard, it’s probably going to be enough and you can stand at the very rear. You can also try to go to the nearest park, or if you can go to the rooftop of the nearest buildings (or your apartment building), provided you have permission to access the rooftop.
Depending on your location, however, it’s possible that the sky might not be dark enough so it’s very difficult to spot stars, even on a clear night. In such cases, you might need to drive a bit and get to the countryside when there’s less light pollution.
Nevertheless, here are some important tips to follow when trying to find your best stargazing spot:
Find The North Star (Polaris)
Your first benchmark for a good stargazing spot should be whether you can find Polaris (the North Star), assuming you live in the northern hemisphere.
First, look up and give your eyes a few minutes to adjust and attain the dark adaptation. Without any light distractions, your eyes will adapt to the darkness incrementally and you’ll start to notice more stars in the sky. After your eyes have been properly adjusted, try to find the North Star.
First, try locating the Big Dipper, a bright section of Ursa Major that is easily recognizable—if not the most recognizable object in the northern hemisphere. Two of the Dipper’s stars line up with Polaris directly all year round, so it should be fairly easy to spot the North Star.
Know The Best Time
What is the best time to observe the sky? The answer will depend on many different factors. Here are a few tips you can use:
- Moon: in general, the time during the full moon is the worst time to observe the sky. The days before during, and right after the new moon is best.
- Season: different deep-sky objects and constellations are best viewed during certain months.
- Summer: in the summer, the hours of evening twilight and morning are longer, so there is only a short period in-between to view properly dark skies during the summer.
Find a Clear and Dark Location
It’s very important to find a place where buildings and trees don’t obstruct your view. You want to see as much of the sky as possible. If necessary, go to rural areas near you because those areas often have the lowest amounts of light pollution.
Also, it’s always a good time to know when it actually gets dark so you can plan your trip accordingly.
III. Astronomy Basics – Telescopes for Beginners
No guide on astronomy basics would be complete without reviewing the basic telescope types. Each telescope type has its own unique construction, features, and limitation. Therefore, it is very important to know the differences so you can decide which type is the right one for you.
We did a comprehensive article on astronomy telescope types you can check after you’re done here. In general, we can divide telescopes into three basic categories:
- Refractor type: refractor telescope uses lenses to bend light into focus
- Reflector type: reflector telescope uses mirrors that reflect light into focus
- Catadioptric type: or, compound telescope, which uses both lenses and mirrors to focus light
Along the way, you might stumble upon others types like Dobsonian, Newtonian, and Dobsonian. Most of these types would still be based on the basic three types. For example, a Dobsonian telescope is technically a type of reflector telescope.
Before we can these three different telescope types further, we have to understand these three important terms:
- Aperture: Aperture is the diameter of the primary lens or primary mirror. The primary lens is located in the front, while the primary mirror is the one located at the back of the tube. The larger the aperture, the more light the telescope collects, and so the more detail and magnification we can get. In amateur and hobby telescopes, apertures range between 2 inch to 16 inches (50mm to around 400mm).
- Focal Length: the length between the lens/mirror to a point where the light is focused by the lens/mirror. Shown as f.
- Focal Ratio: the ratio between focal length and the aperture. F5, for example, means that the telescope has a 5 focal ratio. You’ll also see other numbers like F8, F10, F12, F15, and so on. The higher the focal ratio is, the better you can see a uniformly good image across your field of view. On the other hand, telescopes with low focal ratio (F6 and below) will display the light at a steeper angle–compromising image quality.
As established, refractor telescopesutilize lenses to focus the light into an image. Refractors are usually longer than the comparable reflectors since the light must flow in a straight path through the tube until it reaches the eyepiece.
The Meade StarNavigator NG 102MM is a great entry level refractor telescope readily available at very affordable pricing on Amazon. Click here to check the last pricing on Amazon.
The larger the lenses, the longer the telescope has to be so it can properly focus the image. Also, large lenses are much more difficult and expensive to manufacture than large mirrors. This is why refractors available in the market usually are relatively small in focus.
Here are the pros and cons of refractor telescopes compared to the other two basic types:
- They require very little maintenance, great for beginners. For instance, you don’t have to collimate refractor telescopes (calibrate it so lights are actually parallel).
- Great contrast and sharpness. Again, great for beginners. This is because refractors don’t use a secondary optic like reflectors.
- The tube is 100% closed, so better protection against dust and humidity. This will also contribute to producing sharper images.
- Tend to be more durable, and small bumps won’t affect the optics as much as reflector telescopes.
- The eyepiece is located at the very end of the tube (in reflectors, the eyepiece is at the top), so it’s generally easier and more comfortable to view with.
- Can be expensive especially for beginners or hobbyists
- Refractor telescopes always suffer from chromatic aberration (the condition where different colors/wavelengths are not focusing at the same point).
- Refractors with large apertures can be very difficult to use because large lenses can be very heavy, and other factors
- Refractors can feature very long body, so can be hard to transport
2. Reflector Telescopes
Reflector telescopes use mirrors instead of lenses to reflect and focus light. The idea is that by reflecting the light within the telescope tube, we can extend the overall path of the lights and so it will focus.
This method will provide two main benefits. First, since the light doesn’t need to flow in a straight line, then the tube can be made shorter. Second, manufacturing large mirrors are much more affordable than manufacturing large lenses.
The Dobsonian telescope, “dobs”, is a classic example of a reflector telescope. In fact, for beginners, we recommend a dobs as your first scope because they are relatively inexpensive when compared to other telescope types for the size of aperture you get.
I recommend an 8 inch – 10 inch aperture so you can go after those deep-space objects. Otherwise, you’ll always be wanting to upgrade your scope. An 10-inch dobs will provide endless fascination when you open it up under clear, dark skies. Any bigger and it will become very cumbersome to travel around with.
This is why, I personally recommend the 10-inch Collapsible from Sky-Watcher. This has a truss-rod design that will allow you to collapse it down (versus a solid tube design). This makes it much more portable to take out with you.
So reflector telescope tend to give you more bang for your buck when it comes to aperture size. They also tend to be much cheaper than comparable refractors, but that’s not the only difference between the two. Here are the pros and cons of reflector telescopes:
- The biggest advantage of reflector telescopes is that they are constructed with mirrors instead of lenses. Mirrors won’t have chromatic aberration, a very common issue in any refractors.
- Simpler design, so they tend to be much cheaper to manufacture. Remember that more expensive telescopes aren’t necessarily better than affordable ones.
- It’s much more affordable to manufacture large mirrors, so you can get reflectors that have large apertures with a fairly reasonable price.
- Reflectors suffer from coma, a defect causing the focused image to look like a comet (hence the name) around the edge of the viewing field.
- Reflector telescopes are more susceptible to dew and air currents. When there’s a significant difference in temperatures between the mirrors and the outside mirror, we can get fuzzy images.
- Reflecting telescopes usually feature two mirrors (primary and secondary). The secondary mirror can obstruct light and so produce lower contrast.
- We have to collimate the two mirrors to keep then perfectly parallel. They can get out of alignment with improper handling and transporting.
- Mirrors require more maintenance than lenses and you’d need to clean them regularly and recoat them every few years.
3. Catadioptrics Telescope
Catadioptrics use the combination of lenses and mirrors to get the benefits of the two. As a result of this, we get a smaller and more portable telescope compared to reflectors or refractors of similar aperture.
This type of telescopes is made possible by utilizing a corrector plate, which folds the light path, and a curved secondary mirror to magnify the light within the tube.
There are many variations of catadioptrics telescopes, but the most popular ones are Maksutov-Cassegrains telescope (MCT) and Schmidt-Cassegrains telescope (SCT).
The SCT features a spherical corrector plate on the front of the tube, and two spherical mirrors (primary and secondary). The secondary mirror directs the light back through a hole in the primary mirror to the diagonal and finally to the eyepiece.
The MCT, on the other hand, is similar to the SCT excepts that it utilizes a thicker convex corrector plate instead of a spherical plate, and the secondary mirror is replaced by a chromed area on the back of the corrector plate to reflect back the light to the diagonal and eyepiece.
Our top pick in this style of telescope is the Celestron NexStar 6SE Telescope. This is a great scope for amateur astronomers of all levels.
For full reviews of these and other telescopes, check out our article Best Telescopes For Viewing Planets: Ultimate Guide.
Here are the pros and cons of catadioptric telescopes:
- The folded-path optical system allows a more compact size, shorter than what the focal length implies.
- When compared to other types with similar apertures, catadioptrics is always smaller, shorter, and lighter. So, easier to transport and store.
- The spherical mirrors and easily manufactured refractive plates and corrector lenses are actually much more affordable than traditional lenses and mirrors.
- As they increase in aperture, a catadioptric telescope become heavier significantly.
- Complex moving parts and when broken, harder to repair.
- Cardioptrics have an inherent limitation due to the central obscuration of the aperture, which is caused by the secondary mirror (or the replacement). This optical performance limitation, however, is relatively subtle.
Eyepieces and Magnification 101
Most telescope makers supply at least one (most of the time two eyepieces) so you can start observing right away with your new telescope. However, most of these free eyepieces are usually of pretty poor quality.
So, in most cases, you’d need to purchase a separate set of eyepieces. Typically you’ll get 5 or 6 of the same design with a wide range of focal lengths and magnifications.
You can use this formula to calculate magnification based on your eyepiece and telescope’s focal length specifications:
Magnification = Telescope Focal Length (mm) / Eyepiece Focal Length (mm)
For example, if your eyepiece has 30 mm of focal length and your telescope has 2000 mm f’, then you get 2000/30= 66.67x magnification or 66.67 power. Meaning, the object appears 66.67 times closer to you than they appear to your naked eye.
So, how much magnification and focal length would you actually require? Below is a quick summary for the focal range of your eyepiece compared to the stargazing purpose:
IV. Astronomy Basics – Observation Techniques
In this section, we will discuss some of the most important things to consider when making your first observation:
Field of View (FOV)
The field of view is, simply put, how much sky (or to be exact, celestial sphere) you can see. The average naked eye has a field of view of roughly 210 degrees. That is, we can see in front of us and a little to the sides.
In stargazing, however, a field of view refers to how much you can see through your telescope or binoculars (or the eyepiece).
Unless you are using a computerized telescope, you are usually star-hopping using a star chart to hunt your object. Knowing your field of view is very important when star-hopping, or else you might get lost looking for the next star to hop
In general, the larger your magnification, the smaller your field of view would be, and so the fewer objects you can see. On the other hand, if you are using too high magnification, your target can dominate your view, which is bad for star-hopping and the view might lose a lot of its visual appeal
Calculating Field of View Through Binoculars
Not all binoculars are marked with the field of view, but some do. When they do, it should look something like this:10/485 ft/160m.
Reading these numbers is pretty simple:
- The first number is the field of view in degrees, so 10 degrees
- The second and third number tells you that if you are observing an object from 160 meters away, you’d be able to see 485 feet of its height and width
If your binoculars only have two numbers (in this case, 485 ft/160 m), then you can use the first number to calculate field of view.
If the first number is in metric (i.e. 100 m), then divide it by 16 to get the field of view. In this case, it’s 100/16 = 6.25x
If the first number is in imperial measurements (i.e. 485 ft), then simply divide that number by 52.4, and voila. In this case, we get 485/52.4 = 9.25x
Calculating Field of View Through Telescopes
Telescopes function differently than binoculars since you can change the eyepiece (which affects total magnification). So, calculating your telescope’s field of view will involve several steps:
- Calculate magnification: we have discussed how to calculate your telescope’s magnification above, so refer back to the eyepieces section. To reiterate, it’s as simple as Telescope Focal Length (mm) / Eyepiece Focal Length (mm).
- Calculate the true field of view: your eyepiece should tell you the number that’s known as the apparent field of view value. To calculate the true field of view, simply divide the apparent field of view by the magnification.
For example, if your eyepiece has a focal length from 24mm, and will give you a magnification of 25x with apparent field of view of 60 degrees. Then the true field of view is 60/25=2.4x.
Note: not all eyepieces specify their apparent field of view. If you can’t find the number anywhere including online, then you can use 50 degrees in the calculation. It might not be accurate but usually suffice.
Magnitude, simply put, is a celestial object’s apparent brightness when viewed from earth. It’s not the true brightness of the object, which is referred to as luminosity or absolute magnitude.
Ancient astronomers like Ptolemy actually have used magnitudes in his star catalogs, with the brightest stars being the 1st magnitude, and the dimmest stars are the 6th magnitude.
In modern astronomy, the magnitude scale has been modified so now it’s much more precise. In today’s standards: the 1st-magnitude star is 100 times brighter than a 6th magnitude star (5 magnitudes difference = hundredfold brightness factor difference).
1m: brightness factor of 2.512
2m: brightness factor of 2.512 x 2.512 = 6.31
3m: brightness factor of 2.512 x 2.512 x 2.512 = 15.84
4m: brightness factor of 2.512 x 2.512 x 2.512 x 2.512 = 39.81
5m: brightness factor of 2.512 x 2.512 x 2.512 x 2.512 x 2.512 = 100
A difference of one magnitude equals a 2.512 brightness factor.
To put it in context:
- Our sun has -26.74 magnitude (negative magnitude is brighter than 0 magnitude)
- Our full moon has -12.74 magnitude rating
- Venus at its brightest has -4.6 magnitude
- The daylight sky with the naked eye has +3 magnitude
- The night sky with the naked eye has +6 magnitude
V. Astronomy Basics – Sky Measuring Techniques
Here, we will discuss two astronomy basics techniques that are very important for backyard astronomy beginners:
Measuring Night Sky With Your Hand
We’ll use the sexagesimal system to measure the sky with our hands. Sexagesimal is basically a numeral system with base 60. There are a total of 360 degrees in the celestial sphere, and each degree is divided into 60 degrees. Each arc minute is further divided into another 60 degrees.
When you look above the sky, you will see a total of 180-degrees of the celestial sphere (the other half is below the horizon). The point right above you is called the zenith, 90 degrees from the horizon.
You can easily use your hand to measure the sky by following these steps. First, hold your hand at arm’s length and close your non-observing eye:
- Make a first, your backhand should be facing you. The width of your fist is approximately 10 degrees. When there are two objects positioned on the opposite ends of your fists, then they are 10 degrees apart. Polaris and Dubhe of the Big Dipper, for example, should be around 3 fists apart, so 30 degrees angular distance.
- Open up your fist and stretch your little finger and thumb as far as you can. Keep the other fingers curled. The tip of your little finger and your thumb should be around 25 degrees (the angular size of the whole Big Dipper).
- Between the tips of your index finger and your pinky finger is roughly 15 degrees
- Your three middle finger spans about 5 degrees angular range
- Your little finger is about 1-degree wide
Remember to keep your hand at arm’s length throughout the whole process.
Using Your Hand To Find Your Latitude
For this purpose, stretch your hands to measure the angular size between the visible horizon and Polaris (North Star). Unfortunately, this method is only available is you are in the northern hemisphere since there’s no replacement to the Polaris in the southern hemisphere.
The angular degree between Polaris and your visible horizon = your latitude.
Another astronomy basics technique is star hopping. Simply put, star hopping, uses stars, asterisms, constellations, and other recognizable shapes in the sky to “jump off” to less recognizable objects or regions.
All you need to perform star hopping is a star chart and your red light torch (or star chart software in night mode). Also, you are going to use the above technique with your hand to measure angles between objects.
Here is how you do it:
- Find a constellation or asterism in the sky, and then locate the same object or group on your star chart. Now look for other recognizable patterns or stars on your chart, and locate them in the sky. Notice the relative scales, reverse the process and repeat.
- If you are a beginner, take your time with this as this will be a very important foundation for the rest of your astronomy career.
- Use pairs of bright stars that roughly align to your target object for directions. Remember, the key to star-hopping is estimating where to go and the distances.
VI. Astronomy Basics – Optional Equipment To Consider
Last but not least, here are some optional gears you might want to consider:
Ideally, you’d need two or three extra eyepieces to complement your current ones. Yet, exactly which two or three? The answer would depend on the focal length and ratio of your telescope, your budget, your current skill levels, and the object you’d want to see.
So, we won’t recommend any product here, but our advice is to match your eyepiece selection according to the several factors above. Check out our comprehensive article on eyepieces.
A Barlow lens can increases the effective focal length of any objective lens, effectively increasing the magnification. The basic idea is that two eyepieces and a Barlow can give you the versatility of magnification of 4 eyepieces in total.
We’d recommend Orion 1.25-inch 2x Barlow lens as an affordable and versatile option.
If you are going to use binoculars, bring a reclining chair with you. This will significantly add comfort to your back and arms.
If you are serious, however, consider a real astronomy chair especially if you are planning to use a refractor telescope (because of the long tube and relatively heavy build).
Folding Camp Table
A folding table so you can put your binoculars, star charts, and other equipment. Also useful to put your thermos, hot chocolate, coffee, and snacks.
If you are using a reflector telescope or any other type that needs collimation, then invest in a laser collimator. They are fairly affordable and help you save your valuable time significantly. So, you can actually use it to observe the sky instead.
We’d recommend the Meade Instruments Laser Collimator as an affordable option for your collimating needs.
VII. Astronomy Basics – End Words…
Astronomy, first and foremost, is about patience. While above we have discussed all the essential astronomy basics steps you’ll need to kick-start your astronomy career, not everything will work the first time. Be patient and know that it’s 100% okay to fail.
You are going to hunt some wonderful deep space objects and miss it, and hunt it again next time. This is perfectly okay. Remember that you need the attitude that in astronomy, the stars will not come to you: go to them instead, be humble, and be patient.