Eyepiece Cheat Codes: Binocular astronomy

One of the common pieces of advice for amateur astronomers who are just starting out is to get binoculars. The reasons are that you can get a decent pair for less than a mediocre telescope, they are intuitive, compact, and easy to use, they help you learn the sky, and they will be useful no matter how experienced an observer you become. In addition, you can also use them for nature viewing, sports, and many other situations.

The main drawback to binoculars is that they don't magnify as much as telescopes and you can't change that magnification, at least for handheld binoculars. There are larger binoculars and  binocular telescopes that do both, but these tend to be very heavy and very expensive.

A second complaint is that it's difficult to take advantage of them fully for astronomy because holding them introduces shakiness and fatigue. Try keeping your hand on a telescope while you observe with it and you see how much it degrades the image.

But the beauty of binoculars are manifold. They allow you to use both of your eyes. They are eminently portable. They are uncomplicated: just point and focus. They have a wide field of view. They are inexpensive for the quality you get. They are widely available in many different size and magnification combinations. They are versatile. They are the ultimate "grab-n-go" astronomy gear.

Astroboy cartoon by Astronomerica.

Mounting binoculars

Besides learning how to hold it steady, you are going to get better views by mounting your binoculars in some way. For lower powered binoculars like 7x35 or 7x50 you can keep them pretty steady handheld, but once you get to around 10x50, even with a steady hold, you will still not get the good views that you would get if you mounted them. Also, any binoculars get tiring after holding them up with your arms for a few minutes.

For those reasons, many astronomers mount their binoculars. Most use a photo tripod or a monopod, but this limits the freedom of movement somewhat and certainly makes it uncomfortable to observe high in the sky, where the sky is usually darkest and most transparent. You can observe sitting down, but not in a reclining chair without difficulty. The best uses of a tripod are for objects lower in the sky, which is often the southern summer Milky Way for North American observers, and comets, which are often close to the Sun and visibly at their best shortly after sunset or before sunrise. I find a tripod very limiting overall.

Another option is the parallelogram mount. These are commercially available or you can build your own. I built one from plans in Astronomy magazine years ago, and while it worked okay, it was bulky and heavy. You have to adjust it if you move your chair to look at a different part of the sky. Commercial options are somewhat limited lately, and they are relatively expensive. Because I have to travel to observe in a darker sky, I don't have much room left after the Dobsonian telescope and other gear is loaded, so I don't want another big piece of gear and a tripod to mess with.

Some people don't bother with mounting and buy image stabilized binoculars instead. I've tried them and they're okay, but I get a bit dizzy using them. They are also quite expensive. You still have the fatigue of holding them up, and they are generally heavier than the same size non-stabilized binoculars.

My own preference is to build and use the compact, simple, and inexpensive Bino Body Mount (left), which you can use to observe anywhere in the sky (best up high) in a zero gravity chair for maximum flexibility and comfort. This lets you keep your elbows down by your side and transfers most of the weight to your shoulders directly, rather than through your eye sockets and arms. It preserves the freedom of motion of handheld binoculars and you can get views so steady that only your heartbeat is discernible.

What other equipment do I need?

Binoculars are the only essential equipment. There are many articles and videos about choosing binoculars. Generally, the higher the power the narrower the field of view. The larger the objective lens, the fainter and finer detail you will be able to see.

My recommendation is 7x50s if you are in the first half of your life and just beginning. They are easier to hold steady, have a wider field, lower power, big exit pupil (second number divided by the first, i.e., 50/7=7.1mm exit pupil) that young eyes can fully take advantage of. I recommend 10x50s, 15x70s, or 20x80s especially if you are older or interested in viewing more than starry vistas and want to locate individual objects like smaller star clusters, globular clusters, some nebulas, galaxies, and the like. These are the binoculars I recommend for my binocular audio guides "Space Walk Among the Stars."

But you'll really improve your observing and comfort with a reclining chair. A zero gravity chair is best because, unlike most other recliners, you don't need to manipulate the arms with both hands to change the reclining angle. Instead, you just transfer your weight between your feet and shoulders to change the angle, or altitude. The only drawback is the same as any chair: you have to get up and move it to view a different part of the sky. This leads some DIYers to build rotating platforms for their chairs. I recently built one, although I haven't got it quite right yet.

Left: Reader Mike (Telescope Guy) using his homemade rotating chair mount with his Bino Body Mount. Can't get much better than that!

For cold or cooler nights, besides dressing appropriately, a blanket laid on the chair will help insulate you from the cold air between the underside of your chair and the ground. I like to use a cheap moving blanket, but any blanket will do.

Unless you are just casually scanning the sky only, you will need some type of star chart, planisphere, or app. I use an app (Sky Safari Pro) with night vision turned on. Some will argue that this little bit of red light still disturbs your night vision, but I haven't found that to be the case unless I am observing in a super dark location, which doesn't happen very often. You'll have the same issue if you use a dim red flashlight and a paper chart, which to me is way too fussy for observing with binoculars. Even if  you don't have a specific observing list in mind, it's nice to be able to look up something you spotted to see what it is. I just attach my phone to the arm of my chair so I know where it is and it doesn't end up on the ground.

If you observe where dew is prevalent, you can add a pair of USB dew heaters made for camera lenses and power them with a phone power bank, which I recommend you carry in a pouch around your neck. If it's really dewy, and I've experienced this, or you are sweating from setting up, you can use a small battery operated pocket fan to clear the eyepiece lenses periodically.

What to look at

Well really, the sky's the limit. You can look at anything you want. But some things are too small and dim and are best left to telescopes.

The "Space Walk Among the Stars: Binocular Edition" audio guides are a great way to learn different areas of the sky and what objects are there. I suggest that you start with them.

Besides the Space Walks, here is a list of the types of objects you can view well in binoculars, with some examples for Northern Hemisphere observers. It's difficult to simulate the binocular view for each, other than adjusting the scale and dimming it down some from images, which I have done just to try to give you an idea of scale and brightness. But images just can't capture the sparkling beauty, color, and contrast with the sky that stars show visually. You'll find that these objects will appear much more entrancing in your binoculars, and you may end up staring at them longer than you expect. 

I've compiled an observing list of all the named objects below plus a few more, except comets and asteroids, in .skylist format for Sky Safari Plus and Pro. Download to your phone or tablet and import into Sky Safari Pro or Plus. Do this by emailing the .skylist file to yourself, open the email on your device, download it, then select the file, select "open with" and choose Sky Safari. You'll get an acknowledgment that it was imported. The list will show up as "Imported List" followed by the date and time. You can rename it in Sky Safari. 

1. Comets. I think brighter comets are best viewed in binoculars. The really good ones require a large field of view, larger than most telescopes, the tail shows best, and they're easiest to find quickly in binoculars. These tend to be brightest, with the longest tails, when they are closest to the  Sun. Therefore, low in the west in the evening and in the east in the morning is where you'll often be looking. The window for best viewing in these situations is often fairly short, so you want to be able to hop out before or after work or school and catch them.

Above: Comet C/2023 A3 (Tsuchinshan-ATLAS) by Kevin Gill, via Flickr, CC by 2.0.

2. Star fields. One of the truly amazing sights in amateur astronomy is getting out to a dark sky and just scanning the Milky Way with binoculars. Sometimes that's all I do, and I may not even set up my telescope. Binoculars (and the unaided eye in a dark sky) are the best instrument for these wide field vistas. A wide field refractor can be great, too, but being able to lie back, using two eyes, and the freedom to move around the sky easily with an orientation matching your unaided eye are huge advantages for binoculars. Check out M24, the Small Sagittarius Star Cloud, the area around Sadr in Cygnus, and the Belt of Orion for some standouts.

Above: Simulated binocular view of a star field in Sagittarius (adapted from Aladin Lite)

3. Open star clusters. There are many larger and brighter open clusters that are easily visible in even small binoculars. Some of the best are the Hyades and the Pleiades in Taurus, the Double Cluster (NGC 869 and 884) and M34 in Perseus, M35 in Gemini, IC 4756 in Serpens (Cauda), M44 (the Beehive) in Cancer, M23 in Sagittarius, M7 in Scorpius, NGC 752 in Andromeda, NGC 7209 in Lacerta, NGC 6940 in Vulpecula, M46 in Puppis, and NGC 2360 in Canis Major. Many globular clusters can also be spotted in binoculars, but they invariably look like little fuzzballs unless you have very large binoculars.

Above: M35 in Gemini. (Astrophoto Andy, via Flickr, CC by 2.0, brightess/contrast adjusted, cropped and rotated)

4. Asterisms. These are groups of stars that form patterns even if they may not be actual gravitationally bound clusters. You can probably find your own by scanning the sky, and many of them are best seen with the naked eye (Big Dipper or the Plough in Ursa Major, the Backwards Question Mark in Leo, the Keystone in Hercules, the Teapot in Sagittarius), but a couple of the most famous ones for binoculars are the Coathanger (Collinder 399) in Vulpecula, and Kemble's Cascade in Camelopardalis.

Above: The Coathanger asterism. Simulated binocular view.

5. Nebulas. You need a darker sky to view most nebulas in binoculars. Some of the brightest are the Orion Nebula (M42), which will show up even in bad light pollution, the North American Nebula (NGC 7000) and the Veil Nebula (NGC 6992 and NGC 6960, etc.) in Cygnus, the Helix Nebula (NGC 7293) in Aquarius, the Lagoon Nebula (M8) in Sagittarius, and the Dumbbell Nebula (M27) in Vulpecula. If you're in a really dark sky, you might also be able to pick out dark nebulas, which are clouds of obscuring dust that make it seem like there is a ragged black hole in the star field.

Above: The Helix Nebula, NGC 7293. Simulated binocular view adapted from Aladin Lite.

6. Galaxies. Most galaxies are relatively small objects, and some of the smaller but brighter ones can be seen in binoculars. The bigger, brighter ones are the Andromeda Galaxy (M31) in Andromeda, M33 in Triangulum (need a pretty dark sky), and NGC 5128 in Centaurus (if you're far enough south).

Left: Galaxy M33. Simulated binocular view adapted from Aladin Lite.

7. Interesting stars. Many double stars, variables, and colorful stars are good for binoculars. A very steady hold with 10x or higher binoculars will split the colorful double Albireo. Any stars with reasonably close magnitudes with a separation of about 30 arc seconds or more are fair game for binocular observation. You might do better or worse, but that's about the practical limit for most people with 10x binoculars.

Above: Double star Nu Draconis (Kuma). Although this simulated binocular view adapted from Aladin Lite makes it look very difficult to split, at 62.3 arcseconds separation, mounted or steadily held 10x50s can do half that.

8. Asteroids. Asteroids look like stars except they appear to change position over a matter of hours or days, depending on the magnification you are using. Binoculars can be used to view stars and asteroids to approximately 11th magnitude, depending on your sky, your binoculars, your observing experience, and the density of the star field. Here's a list of 25 asteroids that are often viewable in binoculars. Magnitudes of asteroids do vary as they orbit the Sun, so sometimes you can catch dimmer ones during a favorable apparition. Sketch their position from one night to the next to verify you have the right "star." Apps like Sky Safari Pro let you do a canned search on the night's brightest asteroids. I looked at tonight's list, and there are 14 asteroids brighter than 11th magnitude, however not all of them are well placed in the sky to view at any given time.

Above: Asteroids vary tremendously in shape and size. This diminutive walnut-shaped asteroid, Dinkinesh, shows a typically irregular shape. Only the largest asteroids become somewhat spherical, and they are some of the brightest, consistently visible in binoculars, unlike this dinky guy. (NASA/Goddard/SwRI/Johns Hopkins APL/NOIRLab/Brian May (yes, the Queen guitarist)/Claudia Manzoni). This is a parallel view stereogram. How to view.

9. The Moon and planets. All eight planets can be spotted in binoculars at different times of the year. You won't see any details (except for Earth!), but Saturn looks oblong when the rings are tilted and you can see up to four of the moons of Jupiter, depending on where they are in their orbits. The Moon supposedly shows 100 craters in binoculars, but I haven't counted, and I think it would drive me crazy trying to sort out the ones in the southern hemisphere. Larger objectives may blow out your vision on the Moon. I can't take the full Moon in my 15x70s without some kind of filter.

Above: Jupiter will show up as a tiny disk with no detail. Up to four moons can be seen, depending on their positions in orbit around the planet. Simulated binocular view.

While some people may observe the Sun with proper filters on their binoculars, I don't recommend it because you are looking in its direction and you can be blinded if you pull the binoculars away from your eyes even momentarily.

Technique

Advanced binocular observers often say you can get steady views and reduce fatigue with proper handheld technique (the way you cup your hands around the binoculars and rest them on your eye socket bone structure, etc.), but most people intuitively gravitate to a technique that works for them. That's the beauty of binoculars. But you still won't get the steadiest views without some kind of mounting (see above). 

Some people also say that they rest their arms on the chair arms to steady the view. Well, I don't know what kind of chair they are using, but for every chair I've ever used, the arms are way too low for that and I end up scrunching way down so my head is where my butt should be. Not comfortable or healthy!

Most multipurpose binoculars have a center-focus wheel that you turn with one or two fingers to focus both eyepieces at the same time. This allows you to quickly refocus for terrestrial viewing and is best if your binoculars are not strictly for astronomy. They will have a diopter adjustment on the right eyepiece that allows you to turn a ring to adjust for the inevitable difference between how your two eyes focus. 

Right: The diopter adjuster ring is usually on the right eyepiece. In the case of these 8x42s, adjustment marks are molded into the rubber armor just below the ring. This binocular also has eyecups that adjust by twisting them in or out for the desired eye relief, great for glasses wearers or to get just the right eye placement.

To use the diopter, first find a bright star field, close your right eye, and use the main focus wheel to focus for your left eye only. Stars should be pinpoints, or at least as small as you can make them. Then, close your left eye and using only the diopter ring, focus for your right eye only. Then look with both eyes and tweak the adjustment as needed.

Left: My 15x70s have individually focused eyepieces.That's true with many larger binoculars made for astronomy or long distance viewing only.

For astronomy, many binoculars focus each eyepiece individually, because once you are focused at infinity, you shouldn't need to refocus. You just turn the ring on the outside of each eyepiece and you shouldn't need to mess with it again. In my experience, individual focusing eyepieces hold their focus better and prevent my obsessive-compulsive tendencies from causing me to be continuously tweaking focus, so I like them better for astronomy.

When viewing a specific object, first look at it or the area with the unaided eye, facing it straight on, then without moving your face or gaze, bring the binoculars up between your eyes and the object. If you consistently have your binoculars too high or too low, make the adjustment until you typically have them right on the object each time. With practice you'll find objects more reliably this way, although it can still be frustrating even with practice. Don't get bent out of shape if you can't find something the first time. You can always scan around and compare the view to a chart to see where you are. Especially in a dark sky, it's easy to get lost among the stars. But that's kind of the point, isn't it!

Reducing glare

Unfortunately, we often have to observe with lights around us, not just skyglow. You can set up some screens or other objects to block out the lights (I'm working on an article for a DIY light screen), but you can't always block all of them. Even in a dark sky there's usually some light somewhere and the general glow from parts of the sky or the Moon.

Above: The Bino Bandit glare shield.

I find the Bino Bandit binocular glare shield to be a worthy investment, despite the relatively high cost for what it is. I've tried making something similar and failed miserably. It's made of neoprene and has two holes in it that stretch over your binocular eyepieces. You can get rubber eyeguards, but the Bino Bandit blocks the light from all angles. In addition, it leaves a little more air around your eyes so the lenses won't fog up as easily, and works with eyeglasses. It's easy to switch it from one pair of binoculars to another. I find it great for daytime viewing, too.

Using filters

Filters have limited use for binoculars, but they can help on certain nebulas. The problem is that they are designed to be fitted at the bottom end of the eyepiece, but with binoculars they must be threaded in front of the eyepiece, if the binoculars even have threaded eyepieces. This degrades the view, but can still help in some cases. I wouldn't buy a filter just for binocular observing, but if you have one for your telescope you might try it out.

If your eyepieces aren't threaded, you can try holding a filter between your eye and the eyepiece, which is not easy to do. A 2" filter is easier. 

Left: A UHC (Ultra High Contrast) type filter on one eyepiece will enhance a bright nebula, and the non-filtered eyepiece will still give you the full star field: the best of both worlds.

If you do have threaded eyepieces, use a UHC narrowband filter and thread it on one of them. This will give you a filtered view that enhances the nebula but dims down the stars in one eye, and gives an unfiltered, fully illuminated view in the other eye. 

I find a UHC filter helps on the larger and brighter binocular nebulas such as the North Ameircan Nebula, the Helix Nebula, and some of the brighter summer southern Milky Way nebulas. I don't have an OIII filter, but you might try that on the Veil Nebula or Helix Nebula if your sky is relatively dark. I can usually see the Eastern Veil from a Bortle 4 or 5 sky without any filter.

The quest for perfection

As with any pursuit, amateur astronomers wonder, "What would perfection look like?" With amateur astronomy most people realize nothing is perfect, yet there is an underlying current of constant comparison of equipment to see what is the "best." I'm sure if you are an experienced observer you can tell the difference, however slight, between a high end eyepiece, for example, and a value eyepiece, maybe somewhere in the mid-range. But how much does it really matter? If a little coma, for example, bothers you that much, maybe you're looking in the eyepiece for the wrong things.

Connoisseurs

Like wine, some people have cultivated a finer sense of the subtle differences between high end astronomy equipment and the rest of it, which the majority owns and uses. The most prolific posters online often tend to be those who fall into the former category. The result ends up being a constant chase by the rest of the group to try to keep up with "the best," even if it sometimes really doesn't matter, or is even detrimental, to the enjoyment of the hobby.

Above: Diamond by Nikilok, CC by 2.0.
Right: Wine taster by William Lawrence, CC by SA 2.0, cropped.

I remember when I attended my first astronomer gatherings and star parties how I was a bit put off by the emphasis on discussing equipment versus what we were looking at in the sky. I gravitated towards those individuals who were quietly observing while others spent most of their time discussing this or that mount or eyepiece. Now I understand. I believe this is because a lot of technical and engineering people are attracted to a scientific hobby like amateur astronomy. It's also because people just tend to compare themselves to others. We're in competition even when we don't need to be. I guess it's in our DNA.

It's a different facet of the hobby that most of us do at some time partake, but often the main purpose gets lost in all the focus on equipment and the manipulation thereof. Truthfully, it's a lot easier to blog or v-log about equipment because there's an endless supply of material and it's easy to comment about it. I'm guilty of that myself. After all, that's what we use to do our observing.

Tell me what you want

It goes off the rails somewhat when someone is convinced they have to have something because others have it and they gush about how good it is. It's fear of missing out (FOMO), of course. I read about how great the new line of Houdini eyepieces are, and I try to find reasons why I should buy one. A new telescope is praised as such a great value that everyone should have one. You can't stop it, but you can resist it.

What do you really want out of amateur astronomy? For some, there's certainly a component about getting the best equipment, the largest scope in town, etc. I think the majority of us just want to observe the night sky because we find it fascinating and mindblowing. What do you need for that?

Above: Montparnasse trainwreck, 1895, Public Domain.

Now tell me what you need

Actually, very little. The most important thing is a clear, unobstructed sky, hopefully without a ridiculous amount of light pollution. That's becoming more difficult to find. Another thing is time. You have kids, you start school, you take a new job, and all of a sudden you have no more time for astronomy. Health. An understanding family. A safe place to observe. You can't buy your way past those hurdles.

You can, however, buy your way into dissatisfaction or disillusionment with the hobby. It's easy. You just bought this telescope, but now you're thinking a bigger one would show you more. Maybe you buy the bigger one and you're happy as a clam. 

But maybe later in the back of your mind you're thinking how much easier it was to observe with that little telescope, and you're sorry you sold it. So you buy another one to replace it. And another one because you don't have one of that type. And...

You're encouraged because you see all the online people with their ever-growing lists of equipment under every post they make. Your eyepieces are breeding in their box, which now no longer holds them all. 

Eventually nothing is enough, you give up, and you admit you're addicted to buying things. You've become a consumer more than an observer. But you comfort yourself with the thought that now you are an "expert," having tried most everything that's out there! You decide to start your own social media channel and monetize it all to buy more stuff.

By CusterDome, Public Domain

There's nothing wrong with wanting good equipment. It makes observing more enjoyable. It's when the reason for consuming is more about FOMO than it is about making the experience better for you that the problems arise. What can you do?

Dance with the one that brought you

Get out and observe. Try going out with just a chair and a pair of binoculars. Or even just a chair. Do you still enjoy that? Try taking your old small scope out and seeing what you can observe with it. Do you still know the constellations, or have they missed you? Get back in touch with what got you started in the first place. Do some outreach, if you're so inclined. 

When you do that, you'll get a lot more enjoyment out of that big Dob you bought because you're actually using it for what it was intended: to give you a great look at the sky. And maybe you can share that with others.

Dancing under the Moon by Yusuf Gönenli, CC by 2.0.

Learning to use your first telescope

The internet is bursting at the seams with telescope reviews, which is why I try not to add to that. However, it is harder to find some comprehensive advice regarding what to do when you get that package in the mail, put it together, wait two weeks for the sky to clear (the "curse" of buying a new telescope), and are ready to start observing.

Learning the telescope

Of course you will be eager to start observing, but before you put your new telescope outside under the stars, make sure you read the instructions, whether included with the telescope or found online. Put it together properly and understand what each part does. If you don't, you might end up frustrated that you can't find anything or wondering why everything just looks like a blob.

DO NOT start tweaking collimation, if your telescope allows it, until you know what you are doing. I can't count how many times beginners go online saying they can't see things well in their telescope and because they've heard about collimation they immediately think that's the problem and hopelessly screw up the telescope's alignment. Most telescopes are reasonably well collimated out of the factory and won't be out of alignment so bad that it will even be noticeable to a beginner. They also tend to hold collimation extremely well, so while it's something you will need to learn to do eventually, it's not something I recommend a beginner start messing with. That's a rabbit hole you don't need to go down when you are starting out.

Tripod and/or mount

Steady views are good. Most inexpensive telescopes that beginners buy, except for Dobsonians, tend to be undermounted, giving shaky and frustrating views. That's why advanced amateurs, especially imagers, spend gobs of money on big heavy mounts and tripods. The tripod is the three legged stand that holds the mount, which holds the telescope optical tube assembly (OTA). The mount provides movement in two axes, either in altitude and azimuth or right ascension and declination. Either system allows you to point the telescope tube anywhere in the sky.

Hopefully your telescope's mount is reasonably sturdy. If not, it's not the end of the world. You simply wait a few seconds after touching it (moving the tube to an object, focusing, etc.) for the vibrations to die down. If it's windy and you have a shaky mount, try to get behind a car or the side of a building to minimize the effect. Or just wait until it's not so windy. 

Left: The Explore Scientific FirstLight 102mm refractor, with main parts labeled.

A far greater impediment to observing is if the mount is difficult to move smoothly. This is where Dobsonians shine. You simply push the tube where you want it to go. I recommend putting one hand up on the lip of the aperture and the other near the back of the tube. This gives you more precise control and leverage.

Right: A Dobsonian reflector, such as the Apertura AD8, is a simple design that maximizes aperture and stability per dollar spent.

For tripod-mounted scopes, a lower quality mount will really become an issue when you try to move the scope to center an object and track it manually. Some just aren't designed well or are cheaply manufactured, making these operations incredibly frustrating. This is why I like slow motion controls. These are semi-flexible cables with a knob on the end that you turn to allow you to move the scope in finer increments than by just pushing the tube around. 

Main optics

Telescopes work by collecting as much light as possible using a larger aperture than the pupil of your eye. Refractors do this using a set of lenses. Reflectors use a large parabolic-shaped mirror. Catadioptrics (Schmidt-Cassegrains, Maksutov-Cassegrains, for example) use a combination of lenses and mirrors to create a light path that folds back upon itself. The larger the aperture, the more light the telescope collects. 

By concentrating and focusing this larger amount of collected light into a spot roughly the size of your pupil, a telescope allows you to see dimmer objects and more detail in even bright objects like the Moon or Jupiter. You look through an eyepiece inserted into the telescope where the light comes to focus. The eyepiece contains multiple lenses to magnify the image. In short, the telescope collects and concentrates the light, the eyepiece magnifies it.

Redirecting the light path for comfortable viewing

If you have a refractor or catadioptric ("cat") telescope (like a Schmidt-Cassegrain or a Maksutov-Cassegrain), you will first insert a diagonal, usually containing a mirror tilted at 90 degrees, and insert the eyepiece into that. The diagonal ensures that you have a comfortable position for viewing high up in the sky. If your scope comes with a 90 and and 45 degree diagonal, use the 90 for astronomy and the 45 for terrestrial viewing.

Because the diagonal is usually held in by a couple of thumb screws, you can rotate it to position it more comfortably for viewing. This will change the orientation of the view in the eyepiece, like tilting your head, but you learn to know which way is which after a while. There's no law saying you have to have it set vertically and look straight down into the eyepiece.

A reflector has a diagonal of sorts, too, but it's built into the upper part of the telescope tube. It's called the secondary mirror, and like the mirror diagonal, it's a flat mirror that redirects the focused light path 90 degrees so you can view in a comfortable position, either on the left or right side of the front of the tube.

Generally, a refractor or catadioptric will mirror-reverse the view. A Newtonian reflector will simply rotate it 180 degrees. Understanding directions in your eyepiece will help you make sense out of what you are seeing compared to a chart or image.

Changing magnification

Eyepieces, what some people call "lenses" (or "oculars" for the more esoteric term), are how you change magnification, or power. Except for specific eyepieces with a rotating barrel that actually are zoom lenses, each eyepiece will give you a fixed power depending on its focal length and that of the telescope. You change magnification by changing eyepieces. 

The standard eyepiece barrel diameter is 1.25". However, many telescopes have 2" focusers, allowing for larger eyepieces with 2" barrel diameters. Most of these come with a 1.25" adapter so you can use both, or you can buy one.

Magnification (or power) = telescope focal length / eyepiece focal length. So a 750mm focal length telescope with a commonly included 25mm eyepiece will give you 30 power (30x)—magnifying 30 times what your unaided eye sees. Place the eyepiece in the focuser or diagonal, making sure it's seated all the way in, and use the thumbscrews to clamp it tightly so it won't fall out. It doesn't matter how it's rotated. 

It's best to remove an eyepiece before you move the telescope to prevent it from falling out if the thumbscrews aren't tight. Get in the habit of frequently checking the tightness of all thumbscrews for eyepieces, diagonals, and finderscopes. After 30+ years with no incident, I recently had an 8x50 finderscope fall from the upright tube of my 10-inch Dobsonian onto the cement floor of the garage. Surprisingly, no damage, but it does happen. (Most finderscopes have a tab on one side of the base of the bracket, however the ones I've seen are always toward the back, where they don't help to prevent the finderscope from sliding out on a reflector, as mine did. Makes more sense to me to have the tab in the front, but it's a refractor thing.)

Taking a seat

Although I stood the first dozen or so years when observing with a telescope, I highly recommend finding a good seat and sitting while you observe. You will be more comfortable, you will get a steadier view, and you won't tire so quickly.

The longer the tube of your telescope, the more variation there will be in the height of the eyepiece as you view objects around the sky. You can get by with a stool or chair for a shorter tube, and for telescopes that use a diagonal you can rotate it to make up some of the difference, but longer tubes such as larger Dobsonians will require an adjustable chair. 

You can decide later if you want to spend the money on a commercially available observing chair, such as the Starbound, Vestil, Catsperch, or build your own. Some people also buy and use drum thrones with varying degrees of success. 

I built my own Denver Observing Chair, a popular option, for my 10-inch Dobsonian but I often use a collapsible stool for my 6-inch tabletop Dobsonian and 102mm Maksutov-Cassegrain.

Right: My homemade Denver Observing Chair that has served me well for over 20 years.

Finding objects

Your telescope should have some sort of finderscope, either what amounts to a tiny refractor mounted on the main scope that magnifies the view or a red dot or red circle finder that projects a dot or circle on a tilted glass or plastic surface and makes it look like the dot is projected onto the sky with no magnification. In either case, it is absolutely critical that you align the finder with the telescope. The finder has a low power (in the case of a red dot, 1x) and wide field so it's easier to find objects than looking directly in the main telescope.

Before searching for anything, focus your finderscope if you have one. This is usually done by loosening a ring near the objective lens and screwing the lens housing in or out, then retightening the ring. Also put your lowest power/widest field eyepiece in the telescope's main focuser and focus on any random stars. Focusing tips are covered later in this article.

Above: Simulated view of the field for the Owl Nebula, M97, in an 8x50 straight-through finderscope on a Dobsonian telescope in a light polluted sky. The view will be rotated 180 degrees from the naked eye view, which matches the view in the eyepiece.

Left: Screenshot from Sky Safari Pro showing the 8x50 field of view, rotated to roughly match the finderscope view above. You can customize the field of view to match your own equipment, which helps to match what the chart is showing to what you are seeing in the finderscope and eyepiece. The small circle around the planetary nebula symbol is the eyepiece filed of view. You can see how much more difficult it is to find something in the eyepiece without first centering it in the finderscope.

Sometimes the labels and other clutter can obscure some of the stars, so be careful. Zoom the screen in and out to see what might be hidden.

Below: Simulated view of the same field for the Owl Nebula, M97, in a red dot finder, also in a light polluted sky. The brightest star in both views is Merak, or Beta Ursae Majoris, magnitude 2.3. The view is the same as your naked eye view, with fewer stars visible than in a magnifying finderscope. 

In neither finder will M97 be visible, so you need to aim based on the location in relation to the star patterns from a star chart and what you can see in the sky. Without the magnification of a finderscope, the red dot loses a lot of precision, so it's critical that you use the lowest power/widest field eyepiece that you have once you are pointed in the right general direction. 

Sometimes, especially if the object is very dim and you may not recognize it right away, it's better to start by pointing the red dot at the nearest bright star, Merak in this case, then switching to the eyepiece and starhopping your way to the object by comparing the star patterns in your eyepiece to those on the chart. This sounds simple, but it's often difficult to be sure exactly where you are pointing, and it's easy to get lost along the way. It still happens to me all the time. It takes practice and, even with experience, patience.

It's easiest to do the finder rough alignment in the daytime. Find a distant fixed object, like the top of a telephone pole. Put your lowest power eyepiece in (the one with the highest mm number) and center the object in the telescope. Then, without moving where the scope is pointing, look in the finder and use the little thumbscrews on the side of it to put the same object in the center or crosshairs. Do this a couple of times, even using a higher power eyepiece for more accuracy, until you are sure they match.

Each time you go out observing, check the finder alignment on a bright object like the Moon, Jupiter, or a bright star, something you'll be certain you are pointed at. First in the main telescope, then in the finder and adjust the finder as needed.  Then when you use the finder to locate an object, it will show up in the main telescope eyepiece. Depending on how accurate the alignment is and how well you positioned the object in the finder, you may need to look around in the main telescope eyepiece a little to find it. Use low power when searching. You can always switch to higher power later.

Some telescopes have a go-to computerized mount, which requires battery power and must be leveled and aligned prior to observing. These aren't as foolproof and simple as they sound, and they often don't work right. They will have tracking, though, which keeps an object more or less centered in the eyepiece. These usually come with a hand controller or are controlled via an app. 

Another computerized navigation system is a variation of a push-to configuration, where an app guides you with arrows to manually push the telescope to the location of an object. Again, this must be aligned or calibrated. The Celestron StarSense app is a good example. It takes pictures of the sky and matches them to an internal database. A freeware push-to app is AstroHopper, which requires frequent recalibration but otherwise is a good alternative to pure starhopping or expensive commercial push-to systems.

Focusing

The basic rule for focusing is to slowly turn the focusing knob, or the focuser itself in the case of the helical focuser found on many tabletop telescopes, until the object gets as small and sharp as it can be. If it does so, but then gets larger and fuzzier as you keep turning the knob, then you know where the point of focus was and that you have passed it. Just go back slowly and find it. You may have to tweak the focus in very small increments back and forth until you get the best focus possible for the seeing conditions. Usually you will have to let the scope vibrations settle after each tweak. This is normal unless you have an exceptionally sturdy mount. If your telescope has a dual-speed focuser, you can use the smaller knob for fine focus adjustment, much the same for focusing as slow motion controls on a mount are for centering and tracking objects with more precision.

Stars should look like points in low power. However, in high power, you may begin to see the "Airy disk," which is the tiny disk of light that the star is spread out into due to the optics in your telescope, its size dependent upon the aperture of your telescope. Dimmer stars will still look like points in high power, but the brighter ones should look like tiny disks surrounded by a thin circle or two, called diffraction rings. This is what you want in a well focused and collimated telescope.

Above: If you look closely, the Airy disks and diffraction rings of the two brightest stars are visible in this simulated high power telescope view. Too often Airy disk images are blown way up in scale so you don't know what you should be seeing.

What if things don't look sharp?

Assuming thin clouds aren't obstructing your view and your focus is the best it can be, then by far and away the likeliest culprit is atmospheric turbulence, or what astronomers call "poor seeing." This is what causes bright stars to "twinkle." The seeing changes based on your location, night to night, and even minute to minute. Some places in the world frequently have very good to excellent seeing, or steadiness. Examples in the United States include much of the western U.S., as well as Florida. The northern, eastern, and midwestern U.S. are often under the jet stream, meaning nights of very good or excellent seeing are rare. 

Below: Jupiter and its Galilean moons in good seeing (L) and bad seeing (R). (Jupiter images by TheWitscher via Flickr, CC By 2.0, modified to simulate seeing conditions in eyepiece.)

You'll get used to knowing what's good and bad seeing through experience. When Jupiter, Saturn, or the Moon look like they are sitting in the bottom of a clear flowing stream, you have very poor seeing. Stars will look like undulating blobs. The view will shimmer and boil as waves of thermals pass in the atmosphere. You may not be able to make out a bright star's sharp Airy disk or diffraction ring in high power. Every object will just be a moving mess. 

Don't give up just because the seeing isn't great. It's not uncommon to have very brief moments when the air steadies out despite bad seeing. It might only be a split second every few seconds, but you can see a lot in those short bursts of good seeing.

Extended objects like galaxies and nebulae are less obviously affected by seeing, so if you have a very clear night but poor seeing (a common combination), go for those types of objects. 

At the other extreme, excellent seeing means you see stars as steady points or Airy disks, bright planets seem to be much larger than you remember and show a lot more detail to an experienced eye. You can see tiny craterlets on the Moon, the shadows are sharply defined with no double-edges, and you see little or no shimmering.

Seeing is also affected by thermal currents within the tubes of some telescopes, mainly reflectors and catadioptrics. Refractors not so much, if at all. This is why you will see some Dobsonian owners with fans installed to blow air through the tube, or "cat" owners who wrap their tubes in Reflectix or other insulating material. It's all to make sure the scope design is not contributing to poor seeing. In the former case, they are trying to cool the mirror down to ambient temperature or remove thermal layers inside the tube. In the latter, they are trying to slow down and distribute the cooling so there are no big temperature differentials or plumes inside the tube to cause poor seeing. 

In most cases. setting a reflector or "cat" outside for an hour or so before observing will help, but it's not always possible, given your situation. Just be aware that it may take time for the scope to "settle."

What about collimation?

Rarely is it the case where collimation, the alignment of the telescope's main optics, is so bad that it spoils the view as much as bad seeing. There are tools you can use to check and adjust collimation, but you're better off leaving those alone until you can recognize what is bad seeing versus bad collimation. With bad collimation, you'll often see one side of an object always fuzzier than the other. Stars may look asymmetric, like little bumblebees. On nights of excellent seeing you will still have a "soft" view that you can't quite focus. But don't assume it's bad collimation until you've ruled out bad seeing, poorly made optics, or even the nature of the type of optics. 

For example, a "fast" reflector with a small focal ratio, for example f/5, will normally show "coma" at the outer edges of the field, an abberation that makes stars near the edge look like comets. Same with achromat refractors and "chromatic abberation," where you may see blue or yellow color fringing along the edges of bright objects at higher powers, an indication that the focus is going to be a bit soft. These abberations are inherent in the design. Because most everything in life is a compromise.

Learning the sky

Using a telescope is like driving a car. You can learn to drive it, but if you don't know where to go or how to get there it won't do you much good. Even if you have a go-to telescope, the equivalent of an autonomous-driving car, knowing what you want to see, when is a good time to see it, and knowing what to look for are important for enjoying your observing.

Many experienced amateurs recommend buying a book to start learning. That's fine if you are a book-learner, but with so much information available on the internet, with options to ask questions and interact with other people, I wonder if starter books aren't a little obsolete. With younger people especially, I don't think learning from a book is a very appealing process. I think it just depends on the individual.

I did start with some books, but most of my actual learning came from simply getting out and observing, and then reading about the objects I saw. Back then, the charts in the book were most important for me, but with charting apps that's changed. Unlike paper charts, apps are flexible, can be zoomed in and out and filtered and manipulated however you want. So many nights I wished my paper charts went deeper than what they showed. And don't get me started on trying to find the right chart late at night for the area I wanted to observe!

Start with things that are easy to find: the Moon, the bright planets, M42, the Orion Nebula (winter), or M8, the Lagoon Nebula (summer), and brighter star clusters. 

We measure the brightness of celestial objects primarily by "magnitude," with higher numbers meaning dimmer, and lower numbers, including negative numbers, meaning brighter. The magnitude scale is reverse logarithmic, therefore a difference of five magnitudes is 100 times brighter or dimmer and each difference of 1 magnitude is about 2.5 times brigher or dimmer. 

Venus varies from magnitude -3 to almost -5. The bright star Vega is a reference at magnitude 0.0. The limiting magnitude of the unaided eye (dimmest you can see) in a transparent, dark sky is around magnitude 6 or 7. A typical 3-inch (80mm) telescope can reveal stars to about magnitude 12. A 6-inch (150mm) to about 13.5 magnitude. An 8-inch (200mm) to about magnitude 14. This doesn't sound like much of a difference, but it makes a big difference in what you can see when so many stars and deep sky objects are at these threshold levels for seeing details, or just seeing them at all.

Extended objects like larger nebulas and some more diffuse galaxies will appear dimmer than their listed magnitudes might indicate, in which case we say they have "low surface brightness." This is one of the reasons a larger aperture that collects more light can show many deep sky objects better than smaller ones. 

Once you are familiar with using the telescope and have seen some of the brightest objects, observing the rest of the Messier Objects is a good next step. Some of them are more challenging than those in the much larger NGC catalog, but the rest are some of the biggest and brightest. Be realistic in what you try to observe, but once you gain experience, don't be afraid to try for something normally just out of reach if you have a great sky. That's part of the fun of observing!

Navigating the sky

Learn how to navigate with your telescope, depending on what assistive equipment it has. Regardless, learn how to starhop. This means comparing the patterns of the stars you see in your finder or eyepiece with those on a chart and moving the scope to the object you want to see. Unless your go-to or push-to system is really precise and functions flawlessly every time (ha!), you will still need to recognize star patterns and be able to hop to the object from where your navigation system takes you. Knowing how to starhop will also ensure you can continue observing even if your electronic system fails or runs out of power—not an uncommon occurrence.

Observing

Don't expect deep sky objects to look anything like the images you see online or in books. Your eyes, even with the help of a telescope, can't gather as much light or see most of the wavelengths represented in images. So most objects will be white or gray and look rather like dim fuzzy blobs or patches, if you can glimpse them at all. Star clusters on the other hand, at least the ones your telescope can resolve into individual stars, will look like sprinklings of beautiful points. 

Once you learn how to observe and spend 10 minutes or more viewing an object, very subtle detail will eventually start to reveal itself on clear and steady nights. Learn to appreciate what you are looking as much as how it looks.

Except when viewing the Moon or bright planets, let your eyes get accustomed to the dark, which takes about 20-30 minutes for full dark adaptation. Use a dim red light when you need light.

As you observe more, you will learn what different objects look like, what to expect, what to look for, and how to improve your observing skills. Astronomerica has articles on using averted vision, understanding distances and directions in the sky, observing the Moon, observing the brighter planets, and observing galaxies, to name a few. The internet has a huge amount of resources.

Modifying and tweaking

Even a high end telescope may require some modification and tweaking by the user, if only to customize it to your own satisfaction. Inexpensive telescopes will almost always require some modifications to get the most out of the equipment, so expect that and don't be afraid to experiment. 

Right: I added the right angle bracket and 6x30 finder to my 6-inch tabletop telescope. I also added the light-blocking craft foam, a hose clamp and extra long focuser thumbscrews to improve the helical focuser. These are all reversible mods.

However, don't start making changes until 1) you're sure you are going to keep the telescope, to avoid return or warranty issues, and 2) you've tried it as is and determined there is a modification that you can do yourself that will likely make it better. Mods for specific telescopes are abundantly available online, often offering multiple options to solve common problems. The safest mods are those that can be undone to return the scope to its original condition.

Don't rush to upgrade

Once you're comfortable with all of the above, then you can think about upgrading. Or not. You really don't need a lot of gear to see a lot. You mostly need clear dark skies, good seeing, time, patience, enthusiasm, and experience. You can't buy that. 

Unless you are missing a critical piece of gear or it just doesn't work, upgrading equipment should be the last thing on your list. You might find yourself buying a lot of stuff you don't need, won't use, or will have to rebuy once you determine what items you really want or need after observing for a while.

The important thing is to get out under the stars.

Observing with bad vision

I've worn glasses for about forty years, and my vision has been getting progressively worse, as it usually will. It has stabilized in recent years, but now without my glasses, everything is a blur. I started out with hyperopia (farsightedness) which was joined later in life by astigmatism (irregular curvature of the cornea or lens) so, close or far, it's now all blurry. About 15 or 20 years ago I decided to try contact lenses, and now my typical observing session requires I put them in before going out. I don't wear them regularly, only while observing.

(Image by JSB Co. via Unsplash.)

Vision correction

There are nearly as many degrees and kinds of bad vision as there are observers. Most bad vision can be corrected at least to the point where observing is possible, and the telescope focuser takes care of any basic refractive errors in your vision. That's my case. While I have +6.5 and +7.0 corrective lenses that also help correct for astigmatism, the correction is not perfect. Nevertheless, for me progressive lenses correct enough for me to get through life. I don't recommend trying to use progressive lenses at the eyepiece.

Contacts don't do quite as well for me but they work better at the eyepiece. Although I have toric lenses, the astigmatism is still pretty strong, and I've gotten used to the idea that my views of astronomical objects are not going to be ideal—one of the reasons I don't spend a fortune on eyepieces! I have what's called monovision contacts. My left side focuses at about three feet to infinity and my right side focuses around reading distance. It takes some getting used to after wearing glasses, but within half an hour or even less I'm fully functional. 

(Star images rendered from AladinLite.)

Glasses on

Some people just observe with their glasses on. This requires you to have eyepieces with long eye relief, such that you can have your glasses in between your face and the eyepiece lens and still see the whole field of view, or at least most of it. 

Eye relief is the distance in millimeters from the closest your eye can get to the lens to the furthest point you can pull it back and still see the entire apparent field of view (you can see out to the circular edge of the eyepiece field). For eyepieces with very short eye relief, usually in the smaller focal lengths, this may be the same distance, and your eye has to be almost touching the lens. This can force you to strain and your eyelashes will deposit oil on the lens. 

When using glasses, this point may be closer to the eyepiece than you can actually place your eye, and in that case you will never be able to see the full field of view. Eye relief that is too long may require you to move your head around to catch the sweet spot and can be equally frustrating as the view blacks out when you move your head slightly out of position. Eye relief is also dependent upon the shape of your eye socket and your glasses.

I have yet to find an eyepiece with enough eye relief that works with my prescription, and I have progressive lenses anyway, so I don't wear my glasses when looking through the telescope. I can, however, use various binoculars with long eye relief.

Observing without glasses. Notice how close the eye can get to the lens, making longer eye relief unnecessary to be able to see the full apparent field of view of the eyepiece, which in this case is 82 degrees, nice and wide. Contact lenses require no additional eye relief.

Observing with glasses on. Compare to previous image, noting the much greater distance from the top surface of the eyepiece to the observer's eye. Long eye relief when wearing glasses is critical to being able to see most or all of the eyepiece field of view. This Astro-Tech UWA 10mm eyepiece has only 10mm of eye relief. Not long enough for eyeglass wearers, who need a minimum of about 17-20 mm.

(Images by Astronomerica.)

According to Don Pensack's 2025 Eyepiece Buyer's Guide, eyepieces currently available range in eye relief from a mere 1 to 3 mm for the Harry Siebert Optics Planesphere series to a whopping 46 mm for the Masuyama 60mm 2-inch eyepiece. The caveat on any eye relief figure is that the numbers often only count the measurement from the glass surface not including additional inset or eyecup. So if anything, the effective eye relief may be shorter than the advertised eye relief. This thread from Cloudy Nights discusses some of the better eyepieces for eyeglass wearers. Scroll to post 14 to bypass some rather less useful posts.

Glasses on and off

Another way to cope is to use your glasses when reading a chart or looking up at the sky and then taking them off each time you put your eye up to the eyepiece. This may work especially if you have a relatively mild prescription and maybe only use glasses for reading. For us hardcore Magoos (link provided for younger folks who have no idea), this is fraught with danger. 

(Superman image by DC Comics)

Let me relate my experience in that regard. Before I switched to contacts, I thought I would just swap my glasses on and off when observing. While annoying, this did work to some extent. Until one night, when I placed my glasses atop the roof of my car. They slid off with the heavy dew, and here I was with no way to search for them. Oh, I had a red light, but everything was blurry. I was afraid to move, but I took one step in the direction I thought would be away from the glasses and, you guessed it, heard and felt a sickening crunch underfoot. I managed to drive home that night using an older pair of glasses I had kept as a backup, but that was it for me, and I got contacts shortly thereafter. 

If it works for you, go for it, but be careful. Sometimes I still do use this technique (with my backup glasses!) when I'm just out for a quick look in the backyard or I'm taking a quick look in my solar scope. I recommend velcroing a soft case to your scope or table so you can slip the glasses in there, rather than trusting to a pocket that could contain who knows what that could scratch your lenses or just laying them on a table. I've tried keeping them on eyeglass retainers around my neck but the constant bumping and scraping as I leaned over the telescope was annoying and made me worry about scratches.

No glasses

You might be lucky enough to still be able to read or look at the sky without your glasses and still see reasonably well. In that case, just put your glasses away and use your uncorrected eyes. I did this until the stars just started looking like fuzzy blobs and I was straining to read charts with a magnifier in the dim red light of my flashlight. A man's got to know his limitations, and I had reached mine.

Contact lenses

For me, contacts are really the best solution. With my monovision lenses I can read reasonably well up close, I can drive, I can see the stars reasonably well when I look up, I can see pretty well with any eyepiece, and I've gotten used to using one eye for each. Another benefit is at public star parties, where I can focus an object in the telescope and know that people with reasonably good vision will get a decent look. But a tweak of the focuser will work for most people with uncorrected vision issues, other than astigmatism. I usually encourage people to take off their glasses to observe and just refocus, as long as they don't have bad astigmatism.

There are a few downsides, though. Especially if you don't wear them often, contacts can be itchy, scratchy, and blur out sometimes, especially as your eyes get tired. I sometimes struggle to get them to stay in at first, although other times they just slide right onto my eyeballs and stick. I've had them get stuck under my eyelid when I rubbed my tired eye, and I've even put two in at once, thinking the first one didn't stick and had dropped on the floor. 

Or maybe you just don't like touching your eyeball? Ewwww! (Image by Moist.acuvuehk via Wikimedia, public domain)

I always take a second pair of contacts with me in case I get a tear in one, it just feels crappy, or I somehow lose one out of my eye. Also bring eyedrops to rewet them if they get too annoying. The lens solution bottle won't help unless you want half the bottle all over your neck and down your shirt. Trust me on that one.

Televue DIOPTRX

Televue makes a device they call DIOPTRX that can help with mild astigatism. It looks like a filter with a fold-down eyecup attached that you can thread onto a variety of Televue eyepieces. I've read some accounts that all say it works well. If your astigmatism is relatively mild, but bad enough that correction would make it worth the cost, and you have Televue eyepieces, you might want to check it out.