Eyepiece cheat codes: Angular distances in the sky

In a previous post, we looked at cosmic distances and how they are measured. In this post, we'll look at angular distances as objects appear in the sky, and how to apply this to your observing. For this we use a system of degrees, minutes, and seconds of arc.

There are many resources on the internet that describe this system, so I'll only cover the basics. What we're interested in as visual observers is being able to translate numbers given to us in an app, article, or data source to what we see in the sky, especially in the telescope.

Because there are 360 degrees in a circle, the sky as we see it is always half of that, or 180 degrees. We are standing on the other half, as if we are standing in the middle of a globe. The zenith is 90 degrees overhead, so if the altitude of Jupiter is 45 degrees for our location at a given time, it will be halfway up the sky and good for observing if it's clear with steady air (seeing). At 20 degrees, things are a bit low and murky, subject to poor seeing and probably horizon light glow. 

Left: If we are using an altitude-azimuth mount like a Dobsonian, a degree in altitude is the same no matter how high we point our scope because all the circles of altitude are the same size. Think of these as lines of longitude.

But only if the scope is horizontal and pointed at the horizon is a degree of azimuth the same distance as a degree of altitude, because it's the only full diameter horizontal circle. As we point the scope higher up in the sky, the circles of azimuth, similar to lines of latitude, get smaller as we approach the zenith, so the apparent distance in the sky for the same number of degrees of azimuth is shorter. The higher we point the tube of the telescope, the smaller the arc it describes as it swings in the same number of degrees of azimuth.

As a result, we use a standard angular measurement of apparent distance essentially equal to degrees, minutes, and seconds of arc equivalent to any altitude circle (like a meridian of longitude, or our azimuth circle at the horizon only—essentially both great circles), regardless of what direction we are moving in, and we call them degrees, arcminutes ('), and arcseconds ("). 

Practical application

Left: At the scale of the unaided eye and binoculars, we usually use degrees. 

An easy rough estimate can be done with your outstretched hand.  

1 degree is about the width of your pinky 

5 degrees is about the width of your three middle fingers 

10 degrees is about the width of your fist 

20 degrees is about the width of your outstretched hand. 

This can vary considerably depending on the size of your hands and length of your fingers, but it's close enough for rough estimates. You can check how your own hand measures up by looking up the distances between bright stars that fit these measurements using an app such as Sky Safari Pro, Stellarium, or Cartes du Ciel.

When looking in binoculars or a telescope, your best bet is to know the field of view (FOV), or diameter of the portion of sky that you can see in your particular instrument, measured in degrees for binoculars and widefield eyepieces, and in arcminutes in higher power eyepieces. This will be fixed in non-zoom binoculars and will change depending on what eyepiece you use in the telescope. This is called the "true field of view" (TFOV) (or "actual field of view" in Stellarium), as opposed to the "apparent field of view" (AFOV), which is the angle of  "wideness" of your view based on the optics you are using. 

Left: The circle represents the true field of view (TFOV) in typical wide angle 10x50 binoculars. This diameter represents about 6.5 degrees of angular distance in the sky. (Chart adapted from Cartes du Ciel).

Left: The circle represents a true field of view (TFOV) of 35 arc minutes, or a little over half a degree in the sky, that is viewable in the combination of my 10-inch GSO Dobsonian with a particular 13mm focal length eyepiece. The apparent field of view (AFOV) for this particular eyepiece is 57 degrees. (View of globular cluster M13 adapted from Stellarium)

Left: A simplified diagram showing the apparent field of view (AFOV), which is determined by the lens configuration of the eyepiece and the eyepiece field stop or opening usually at or near the bottom. This does not change if you put the eyepiece in a different telescope. Manufacturers and vendors will state the AFOV in the specifications for the eyepiece.

Some eyepieces have a narrow AFOV because of their design, and it's like looking down a tube, whereas others have a wide, sometimes very wide, field of view, described as like looking through a "porthole" or on a "spacewalk," where you can't see the interior edge of the eyepiece, the field stop, at all without peering into the eyepiece almost sideways.

To recap, the AFOV is the apparent angle of wideness that you experience, but the TFOV is the actual angular measurement of distance in the sky that you are able to see, and that is what we're more concerned with here. Knowing this makes it easier to compare what you are seeing in your binoculars or telescope to your chart or unaided eye view.

Calculating TFOV in the telescope

TFOV must be calculated for each combination of telescope and eyepiece. You can use a variety of methods to calculate TFOV, with varying degrees of accuracy:

The easy calculated method

This method gives you a rough estimate because it is dependent upon the manufacturer specs being exactly correct, which is not always the case.

AFOV (provided by manufacturer or vendor) / MAGNIFICATION = TFOV (in degrees; multiply this by 60 for arc minutes)

Example: 60 / 30 (*see below for this calculation) = 2 degrees or 120 arc minutes

The published AFOV is often not completely accurate but usually fairly close.

*Magnification is calculated as follows:

FOCAL LENGTH OF TELESCOPE (in mm) / FOCAL LENGTH OF EYEPIECE (in mm)

Example: 750 / 25 = 30x

Both of the focal lengths above are provided by the manufacturers or vendors and are usually marked in millimeters somewhere on the telescope near the focuser and on the barrel of the eyepiece. 

The more precise calculated method

This method relies upon the manufacturer or vendor to provide the field stop diameter. Unfortunately, aside from Televue eyepieces, these are not easy to find (check out Don Pensack's 2025 Eyepiece Buyer's Guide, which lists many, or it can be calculated or measured with calipers). If you have it, here is the formula:

EYEPIECE FIELD STOP DIAMETER / TELESCOPE FOCAL LENGTH x 57.3 = TFOV (in degrees;  multiply this by 60 for arc minutes)

Example (for the Celestron Xcel-LX 24mm eyepiece pictured above and a 750mm focal length telescope):

25 (provided by manufacturer) / 750 = .033 x 57.3 = 1.89 degrees or 113 arc minutes

The drift method

This one must be done in the field with the telescope - eyepiece combination for which you wish to find the TFOV. Rather than go into the details, David Knisely provided an excellent description in this post from the Cloudy Nights forum. He also provides descriptions of some of the other methods.

The app or chart method

This one is also accomplished in the field and is another rough estimate. Again, With the telescope - eyepiece combination for which you wish to find the TFOV, locate any two easily identifiable stars that just fit on the edges of a full diameter of the eyepiece field of view, and measure the distance between those stars in the app. This is inherently inaccurate because you have to eyeball it, but it will give you a number close enough for casual observing.

Using TFOV in starhopping

Fortunately, apps like Sky Safari Pro, Stellarium, and Cartes du Ciel let you specify the custom TFOVs for various combinations of telescopes and eyepieces. Once you've set those up, it's easy to starhop around by moving the background behind the TFOV indicator in the app and seeing how far you need to move from one object to another in the telescope. 

For example, "I need to move two-and-a-half fields of view in my 750mm 6-inch telescope using the Celestron Xcel-LX 24mm eyepiece (1.89 degree TFOV as calculated above) to get to M13 from Zeta Herculis." (Chart adapted from Cartes du Ciel)

Once you're comfortable with this, your navigation skills will improve immensely.

Eyepiece cheat codes: Becoming a Lunatic

Most of us probably live in light polluted urban or semi-urban areas. My home usually exhibits a Bortle 8 sky at best (no hope of seeing the Milky Way and only the brighter constellations visible on a good clear night). We eagerly await the period around new moon so we can get somewhere darker and do some deep sky observing: galaxies, clusters, nebulae, hoping that we might have some clear nights.

We've all probably observed the Moon when it was up. But have we really observed it?

I am by no means an accomplished lunar observer, primarily because for many years, like many of us, I waited for new moon to do my observing. Now that I'm unable to get out to a darker sky as often, I have developed a new attitude toward our little rocky satellite, and I've discovered that lunar observing is pretty damn B A D A S S.

Having a 6-inch reflector as my current "go to" scope, I can't see many of the smaller features that someone with a 12-inch with consistently excellent seeing might see. Yet, given my limitations, I've found lunar observing to be something I look forward to as much, and sometimes more, than deep sky observing. 

[Want some Pink Floyd on YouTube to accompany you while you read this post? Click here.]

Catch the excitement

When I was much younger, the race between the U.S. and the Soviet Union to put spacecraft and eventually people on the Moon was exciting for the general population, and even more so for space nerds like myself, whose favorite movie then (and now) was 2001: A Space Odyssey. Say hello again to HAL 9000.

Now, with spacecraft once again landing on the Moon, some of that excitement is returning. Where are the landing sites? Where did the Apollo astronauts land? What are the various features visible in small telescopes? Can I see the flag on the Moon? (No, a flag is much too small to see in a backyard telescope. Buzz Aldrin saw the Apollo 11 flag blown over upon ascent from the lunar surface, but the other five flags planted in the Apollo program are still standing, although they may be quite faded and deteriorated from the ultraviolet light and temperature extremes. See this LROC explanation and this NASA evaluation for further discussion of the flags on the Moon.)

Above: The Apollo 11 landing site viewed by the Lunar Reconaissance Orbiter Camera showing the Lunar Module (LM) just left of center and several instruments left by the astronauts. The image is roughly 225 meters across, or about 738 feet. In comparison, an 8" telescope will only resolve details as small as about seven times the width of the image, or about a mile across, or half an arc second in perfect seeing. With a good Moon map, however, you can identify the general location of the various spacecraft landing sites. (NASA/GSFC/Arizona State University)

Get started being a lunatic

I recommend starting your lunar observing by simply perusing the surface, especially along or near the terminator—the line demarcating sunrise or sunset, where the shadows highlight the relief of the various features. Don't worry about names until you get curious. What is that crater with the long bright rays? How about that one with the straight radial line inside it? What is that U-shaped valley by that bright crater? What is that long cliff-like feature? How about that gap in that huge mountain range? Discovering these features on your own and then looking them up on a Moon map is part of the fun.

The ever-changing shadows

One of the many great things about lunar observing is that the view is continuously changing as the Sun's light marches across the Moon, with the terminator highlighting new vistas every night. One rule of thumb is that the period between new moon and full moon, centered on first quarter, will place the Moon best for observing in the evening sky, and the nights centered on last quarter will place the Moon best in the morning sky. First quarter in the first part of the night, last quarter in the last part of the night. In the evening, you'll be seeing sunrise marching across the Moon. In the morning, sunset.

You can look up the rise/set times and current phase of the Moon on many websites, including Time and Date. There are also many apps available, such as Moon Phase Calendar.

The importance of good seeing

With lunar observing, we really want to see detail as sharply as possible, with little to no blurring by the atmosphere. A night with steady air, or good "seeing," will yield more detail than a night of poor seeing when the Moon looks like it is rippling, undulating, or just plain fuzzed out. How do you know when the seeing will be good? Well, if you're like me and live under the jet stream, it won't happen very often that you get excellent seeing. But usable seeing can often be had. 

Check apps or sites like Astrospheric or Clear Dark Sky (R.I.P, Attilla Danko) for seeing predictions for your location, understanding that they are just predictions. Other factors can affect seeing, especially from urban locations where heat rising from streets, driveways, and roofs can turn an otherwise good night of seeing into churning soup. If your telescope needs some cool down time, typical for reflectors or SCTs, try to set it outside for at least 30 to 60 minutes and use a fan or insulation to reduce internal tube currents.

Charts and Moon map apps

While my favorite charting app, Sky Safari Pro, shows lunar features when zoomed in, I find it difficult to see in night mode, with the features just too dim. Since I do most of my observing of the Moon from home, I can hop indoors and check out the excellent (and free) Virtual Moon Atlas, which I highly recommend if you have a Windows or Linux operating system.  Once you set it up, it will show you where the terminator is currently, you can turn labels on or off, zoom in to an astonishing level of detail (thanks to Lunar Reconaissance Orbiter Camera imaging), look up information about various features, and even orient the view to match your telescope's. There are other apps available that you may prefer. Try Moon Globe for iPad, or the online Real Time Map of the Moon. 

Left: Virtual Moon Atlas showing the phase on a particular date and time and set up for a 180 degree rotated image with south up and astronomical west to the left, as seen in a reflector. The Moon is about 31 arc minutes in diameter, or half a degree as seen from Earth. On the other hand, the Earth is about 2 degrees in diameter as seen from the Moon.

Note that when describing directions on the Moon, we use the convention of east being toward Mare Crisium, the circular dark plain just below center near the left limb in the image. This conforms with how terrestrial maps work, and is opposite from directions described for the night sky and deep sky objects. The idea was that lunar explorers would not get confused by "backwards" maps of the surface, compared to terrestrial maps. The crater Copernicus is on the terminator just below center.

Right: Zooming in on the crater Copernicus, which is about 58 miles in diameter. 37 mile-wide Eratosthenes is the crater in the lower left. The image is about 3.5 arc minutes wide.

Left: Zooming in further into the interior of Copernicus. This image scale and detail is beyond the capability of most backyard telescopes. The image is about 25 arc seconds across.

The central peaks are almost 4,000 feet high, ,while the crater wall at left is about 13,500 feet high. The detached part of the central peak just to the right of center is about 9 miles wide, or about 7 arc seconds in the telescope.

Lunar features and naming conventions

Features on the Moon are labeled in Latin (and you thought it was a "dead" language!). These are based on names first proposed by Giovanni Battista Riccioli, an Italian astronomer and Catholic priest (hence the Latin) who lived in the 1600s. His Moon maps were drawn by Francesco Maria Grimaldi, his colleague and fellow scientist/priest. They both have large walled plains, close to each other on the western limb, named after them. Many features, mostly craters, have been named since then. For more on naming, see the Smithsonian Magazine's How are Places on the Moon Named?

Some of the main types of features include:

Mare ("sea"): the expansive darker, smoother basaltic plains formed from molten rock that can be seen with the unaided eye. Examples: Mare Tranquilitatis (where the Apollo 11 astronauts landed), Mare Crisium, and Mare Imbrium.

Left: Mare Crisium (Virtual Moon Atlas. South is up.)

Sinus ("bay"): A smaller plain similar to a mare. Similar smaller "maria" include Lacus ("lake") and Palus ("marsh"). Examples: Sinus Aestuum, Sinus Iridum, Lacus Lenitatis. 

Left: Sinus Aestuum, with craters Eratosthenes below center and Copernicus at right edge (Virtual Moon Atlas. South is up.)

Crater: 95% of named features on the Moon are craters, almost all of which were caused by the impact of meteors or asteroids. They are named after dead scientists and explorers. Examples: Copernicus, Tycho, Clavius.

Left: Clavius, amid many other craters in the lunar southern hemisphere. This was the home of the fictitious moon base in the movie 2001: A Space Odyssey (Virtual Moon Atlas. South is up.)

Mons/Montes ("mountain/mountain range"): These can be individual mountains or massive mountain ranges. Examples: Montes Apenninus (named after the Apennines on Earth), Montes Alpes (named after the Alps on Earth), Mons Piton (named after a peak in the Canary Islands).

Left: Montes Apenninus (Virtual Moon Atlas. South is up.)

Vallis ("Valley"): Usually, but not always, named after a nearby crater. Examples: Vallis Schröteri, Vallis Alpes, Vallis Rheita.

Left: Vallis Schröteri. The deep crater to the left is Aristarchus. The valley's end points to the crater Herodotus. (Virtual Moon Atlas. South is up.)

Rima/Rimae ("rille/rilles" or narrow channels): These were mostly formed by lava flows, collapsed lava tubes, or grabens caused by the sinking of the surface between faults. Examples: Rima Hyginus, Rima Cauchy, Rimae Ariadaeus.

Left: Rima Hyginus. Crater Agrippa is in the upper left. (Virtual Moon Atlas. South is up.)

Rupes ("scarp" as defined by the IAU, but actually a fault looking like a huge cliff): Examples: Rupes Altai, Rupes Recta, Rupes Cauchy.

Left: Rupes Recta, the "Straight Wall,"  on the southeast edge of Mare Nubium (Virtual Moon Atlas. South is up.)

Dorsum/Dorsa ("ridge/ridges"): Tectonic features found in maria, these "wrinkle ridges" are long, thin folds formed by the cooled and solidified edges of lava flows. Examples: Dorsum Heim, Dorsa Smirnov, Dorsum Zirkel.

Left: Dorsa Smirnov, curving vertically down the center. The crater Posidonius is at bottom left. (Virtual Moon Atlas. South is up.)

Advanced lunacy

If you really want to get into all the details of the Moon's orbit, phases, libration, etc., check out NASA's Scientific Visualization Studio. 

For more ideas on lunar observing, and what others are looking at, see The Association of Lunar and Planetary Observers (ALPO) Lunar Section.

If you don't mind logging your observations in detail, you might consider joining the Astronomical League and trying out their Lunar Observing Program, which contains features to view with the unaided eye, binoculars, and a small telescope. Even if you don't log your observations to get the certificate, this gives you a list of prominent lunar features to observe.

Welcome to the lunatic asylum!

Eyepiece cheat codes: Observing galaxies in small telescopes

When it comes to faint fuzzies, you either get it or you don't. A lot of people don't understand what the point is to look at these things that all just look like very faint grayish white blobs. Why not just look at images? If I have to answer that question for you, you probably should stick to imaging or stay on the sofa. 

Smaller telescopes, those about 10 inches or less, excel on open star clusters and some of the brighter objects in the sky, including some of the larger galaxies like M31, M81 and M82, and some of the brighter nebulas, like M42, the Orion Nebula, M8, the Lagoon Nebula, and M17, the Swan or Omega Nebula. But most galaxies tend to be faint fuzzies in the eyepiece, like my sketch of NGC 4762 below. 

The joy of searching for faint fuzzies 

A big part of the fun of starhopping is the hunt. Winding your way from a bright star through an interesting star field usually yields new discoveries that you wouldn't get if you just punched in an NGC number and your scope slewed right to the object. 

While I often jump from one object to another object in a different part of the sky, sometimes I like to relax a little bit and just get to know a specific area of the sky. I find little clusters, double stars, interesting asterisms, and other objects that I wouldn't otherwise observe. 

Push the limits

Usually where there's one galaxy, there are others. Many are out of reach of small telescopes, but there's a surprising number that can be seen, especially in a good sky. While there are calculated limits to what you can see in a particular aperture and sky, I recommend you take these only as guidelines. I've often seen objects that were supposedly beyond the limits of my telescope's capability. It's fun to push these limits. In my experience, the galaxies and details listed here can be seen with a 10-inch telescope and often smaller apertures in a reasonably dark, transparent sky with decent seeing and no Moon in the sky. (Image: A gravitationally lensed galaxy cluster imaged in the infrared by the James Webb Space Telescope. NASA, ESA, CSA, STScI, Vicente Estrada-Carpenter-Saint Mary's University.)

When I was much younger and I only had a 4.5 inch reflector, I spent some time looking for really faint objects. I saw some of them and others I could never find. But I learned about my telescope's capabilities and my own. I also began learning the sky, and I'm still learning and relearning it.

I remember seeing all five members of Stephan's Quintet, a tight group of very faint galaxies ranging from 12.6 to 14.0 magnitude near the larger galaxy NGC 7331 in Pegasus, with my 4.5 inch. Back then my eyes were better, and in a larger scope nowadays I have trouble seeing even a couple of the members. That helps me to understand how my eyesight has changed, and how the sky is getting brighter.

Above: Difficult but not impossible for small telescopes: Stephan's Quintet in Pegasus. (Fort Lewis College Observatory, CC-by-NC-SA 4.0)

Even looking at brighter galaxies, if you spend some time on them, not just taking a casual glance but spending 10 to 30 minutes, or even more, really examining them, you might surprise yourself how much detail you can actually see. 

Things to look for

When you first look at a galaxy, you might think to yourself, well, it is indeed just a faint fuzzy blob. Nine times out of ten, though, if you spend some time really looking at it, you'll start to notice there is more to it than first meets the eye. This is when you become a true observer. 

(Image: Astronomer Vera Rubin in her last year as an astronomy major at Vassar College, 1948. Rubin later found the first evidence to support the theory of dark matter through her study of the rotation of galaxies. Vassar College Archives and Special Collections)

Here are a few things to look for that will help you discern details you never thought possible to detect. 

• What shape do you see? Round, oblong, oval, thin, cigar-shaped, pointed ends, etc.
• What is the directional orientation of an elongated galaxy (for example, northwest to southeast)?
• What is the core of the galaxy like: stellar, slightly brighter, dramatically brighter, diffuse, etc.?
• Is there a central bulge?
• Do the arms taper to a point or are they stubby?
• Which points are likely foreground stars and which might be brighter parts of the galaxy (or even a supernova)? Good seeing and sharp focus can help you sort them out.
• What are the edges like: do they fade out slowly, are they ragged, sharply defined, etc.?
• Do you see any mottling, clumpiness, or variations in brightness across the galaxy?
• Any dark lanes or sudden cutoffs of brightness?
• Is one side of the galaxy different from the other or is it symmetrical?
• Can you detect any hint of spiral structure?
• Any nearby galaxies or other interesting objects in the neighborhood?

Tips and Tricks

• Most galaxies within range of small telescopes cannot be seen at all without using averted vision.
• Only the brightest central part of a galaxy may appear in the telescope compared to images, which aggregate the faint light of the outer arms or halo that is invisible to the eye. Features such as star clouds or supernovae may appear to be well outside the boundaries of the visible galaxy.
• Make a note of which direction is west, which will always be the direction an object drifts without tracking. This helps you orient yourself and describe a galaxy through sketching or taking notes, if you keep an observing log.
• Large, bright galaxies do well with lower power, but don't be afraid to try higher power for additional detail—it dims the galaxy but increases the contrast, similar to using a filter.
• Small, dim galaxies may not even be visible until you increase power, but tracking them can be difficult in high power if you are tracking manually, especially with a sparse star foreground. 
• Get a good look at the star field in low power and make a mental note of certain star patterns that you can use as markers if you get lost or you bump the scope. Pay special attention to those east of your target, which will come into view as your target drifts out of the field of view to the west. Use them like breadcrumbs to find your way back. Also make note where your finderscope is pointed.
• A zoom eyepiece is great for finding just the right power to see a galaxy best.
• Try sketching a few galaxies until you get a feel for how to make note of the visible features and can assemble them to form a complete picture in your mind.
• Some galaxies have a pretty bright listed magnitude, but have low surface brightness, in other words the brightness is spread over a larger area, so they may not be as easy as the magnitude would indicate.

The character of a galaxy 

The "tuning fork" diagram of galaxy morphology devised by Edwin Hubble and refined by Gérard de Vaucouleurs (Antonio Ciccolella / M. De Leo, CC BY 3.0):

Galaxies are classified by shape and activity. I've never really gotten into all the specifics of this, but in general, there are spiral galaxies, which include barred spirals like the Milky Way, there are lenticular galaxies, there are elliptical galaxies, there are irregular galaxies, and there are galaxies with active nuclei that can take any shape. 

Now do some observing

The following are some representative galaxies that show up well and often show some detail in 4 to 10 inch telescopes. Aperture is king when observing galaxies, so use the largest telescope you have access to. Even in very small apertures, just trying to spot as many of these as possible is an interesting observing project. These are visible at different times of the year. The darker and more transparent the sky, and the better the seeing (steady air), the more you will see. The images are included to give you an idea of the type of galaxy and features you can try to look for, but imaging chips and computer processing tremendously exaggerate all the features, color, brightness, etc.

Link to a Sky Safari Observing List for the galaxies listed below:

Astronomerica-Galaxies for Small Telescopes

This is in the Sky Safari .skylist format. Download to your phone or tablet and import into Sky Safari Pro or Plus. (See The Lumpy Darkness Blog for an explanation of how to do it.)

Spirals 

Spiral galaxies, the most common type of galaxy, can take on many different appearances, based on the angle from which we're viewing the galaxy. Because these are generally flattened discs with central bulges, the viewpoint can really affect their character, as well as how easy or difficult they are to see. 

Interesting edge-ons

I love thin edge-on spiral galaxies, as do many observers. There's something fascinating about seeing that thin slash against the darker background. Small telescopes can be used to see many of them well and appreciate their character. Here are a few.

M104, the Sombrero Galaxy in Virgo; look for a stellar core, the sharp edge of the dark lane on the southern edge of bright central area and the much dimmer glow on the other side of the dark lane (8.0 mag)

(NASA/Hubble Team/Hubble Heritage/Keith Noll/Kevin M. Gil, CC BY 2.0, via Wikimedia Commons) North is up.

NGC 4565, in Coma Berenices; look for the central bulge and the thin dark lane using high power; can you determine where the tips of the arms end? (10.4 mag)

(Brucewaters, CC BY-SA 3.0, via Wikimedia Commons) North is to the lower left.

NGC 891, a large but surprisingly dim and ghostly edge-on in Andromeda; look for the full needle shape and vague clumpiness, which may only come to you after extended observation, south-southwest arm easier; a 12th mag star just on the other side of the core complicates the observation; the dark lane requires larger apertures (10.8 mag but very low surface brightness)

(C.Howk (JHU), B.Savage (U. Wisconsin), N.A.Sharp (NOAO)/WIYN/NOIRLab/NSF, CC BY 4.0, via Wikimedia Commons) North is to the upper left.

NGC 5907, a large, thin splinter in Draco; look for subtle detail in the center area in larger scopes; if you have a wide field eyepiece, see if you can fit spindle-shaped galaxy M102, to the west-southwest about 1.4 degrees, in the same field (11.1 mag)

(KPNO/NOIRLab/NSF/AURA/Brad Ehrhorn/Adam Block, CC BY 4.0, via Wikimedia Commons) North is to the right.

NGC 4216, nearly edge-on, within the Virgo Cluster (11.0 mag)

(Adam Block/Mount Lemmon SkyCenter/University of Arizona, CC BY-SA 3.0 US, via Wikimedia Commons) (NGC 4222, 13.9 mag, upper left, and NGC 4206, 12.8 mag, lower right) North is to the upper left.

NGC 3501, a tough one for the larger apertures in Leo not far from NGC 3507; a very faint slash in a sparse field that gives your eye a better chance of picking it up in averted vision now and then (13.6 mag)

(ANAKLO, CC BY-SA 4.0, via Wikimedia Commons) North is up.

NGC 2683, in Lynx, nearly edge-on; look for a flattened nucleus, almost double-lobed, faster dropoff in brightness on the northeast arm (10.6 mag)

(ESA/Hubble & NASA, CC BY 3.0, via Wikimedia Commons) North is to the lower right.

NGC 4631, the Whale or Herring in Canes Venatici; try around 110x, look for much smaller and dimmer dwarf elliptical galaxy NGC 4627 (The Calf, or Pup), and while you're in the area, find the Hockey Stick, NGC 4656/7, a 9.6 mag disturbed barred spiral (9.8 mag)

(Adam Block/Mount Lemmon SkyCenter/University of Arizona, CC BY-SA 3.0 US, via Wikimedia Commons) North is up.

NGC 4244, in Canes Venatici; enjoy the thinness, you won't make out much else, check out NGC 4214 nearby (see below) (10.2 mag)

(Ole Nielsen, CC BY-SA 2.5, via Wikimedia Commons) North is up.

Face-on or nearly face-on spirals 

Some brighter face-on spirals offer the challenge of getting hints of the spiral structure and knots of star formation and nebulosity in darker skies with good transparency and seeing. A 10-inch will show the following details, but you may be able to pick them out with smaller apertures, depending on your sky.

M51, the Whirlpool Galaxy in Canes Venatici; look for the smaller galaxy, NGC 5195, as well as hints of spiral structure (8.4 mag)

(Todd Boroson/NOIRLab/
NSF/AURA/, CC BY 4.0, via Wikimedia Commons) North is to the left.

M61, a barred spiral in Virgo; look for a stellar nucleus and a semicircular dark lane just east of the nucleus, as well as a bright knot on the north side (9.7 mag)

(KPNO/NOIRLab/NSF/AURA/
Adam Block, CC BY 4.0, via Wikimedia Commons) North is to the left.

M101, the Pinwheel Galaxy in Ursa Major; large with low surface brightness; look for a condensed core and non-uniformity to the surrounding glow; you may be able to pick out some of the brighter emission knots such as NGC 5455 out near the south edge of the galaxy, looking starlike in lower power, NGC 5447 and NGC 5450, which are right next to each other about the same distance from the core as NGC 5455, but toward the southwest (7.9 mag)

(NASA's Scientific Visualization Studio - KBR Wyle Services, LLC/Scott Wiessinger, University of Maryland College Park/Jeanette Kazmierczak, Public domain, via Wikimedia Commons) North is up.

NGC 3184, in Ursa Major; look for a brighter but non-stellar core, with hints of structure in the galaxy's outer glow (10.4 mag)

(Sloan Digital Sky Survey, CC BY 4.0, via Wikimedia Commons) North is up.

M83, in Hydra; best framed in low power; look for a very bright core that dominates the galaxy and hints of shading and structure in the arms; outer area suffers greatly from light pollution, 10.7/11.7 mag double star (8" separation), Herschel 4599, just on the southeast edge of the outer arms of the galaxy (7.6 mag)

(NASA Goddard Space Flight Center from Greenbelt, MD, USA, Public domain, via Wikimedia Commons) North is up.

Oblique-view spirals

M31, the Andromeda Galaxy, is a classic obliquely-viewed galaxy, tilted somewhat from edge-on, northwest to southeast; look for the two satellite galaxies, M32 and M110, a dark lane on the west side of the nucleus, and possibly a fainter dark lane outside of that, as well as NGC 206, a knot of nebulosity far out on the southwest arm (3.4 mag)

(Steve Fung, CC BY-SA 2.0, via Wikimedia Commons) North is to the right.

M33, the Pinwheel Galaxy in Triangulum, very large; spiral structure not discernible, but look for many clumpy areas, including the HII region NGC 604, which looks like a very faint galaxy way off to the northeast of the core, seemingly outside the galaxy (5.7 mag)

(Alexander Meleg, CC BY-SA 3.0, via Wikimedia Commons) North is to the left.

NGC 2903, barred spiral in Leo, oddly not a Messier object; look for north-northwest to south-southeast elongation, impression of a bar, nucleus area somewhat broken up, mottling and clumping, including star cloud NGC 2905 just outside a slightly dark lane to the northeast. (9.0 mag)

(Adam Block/Mount Lemmon SkyCenter/University of Arizona, CC BY-SA 3.0 US, via Wikimedia Commons) North is to the upper left.

M81, in Ursa Major; look for oval shape, stellar core, and possibly hints of a soft spiral structure including darker lane southwest of the core (6.9 mag). Also check out nearby M82 (see below) while you're in the area.

(KeithSteffens, CC BY-SA 4.0, via Wikimedia Commons) North is to the lower left about 7:00.

Lenticulars

Lenticular galaxies occupy a spot in between ellipticals and spirals.

NGC 4026, edge-on lenticular in Ursa Major; look for a big bright central bulge that houses a supermassive black hole and well defined pointy ends to the arms, especially the southern arm (10.7 mag)

(Sloan Digital Sky Survey, CC BY 4.0, via Wikimedia Commons) North is up.

NGC 1023, edge-on barred lenticular in Perseus; look for nearly stellar round core (that also houses a supermassive black hole) (10.4 mag)

(NASA, ESA, and G. Sivakoff (University of Alberta); Image processing: G. Kober (NASA Goddard/Catholic University of America), Public domain, via Wikimedia Commons) North is up.

NGC 4762, edge-on lenticular in Virgo, look for a stellar core within an elongated central area (11.1 mag)

(ESA/Hubble & NASA, CC BY 3.0, via Wikimedia Commons). North is to the upper left.

Irregulars, Peculiars, etc.

NGC 55, in Sculptor; look for a fat slash, trailing off more on the eastern end, giving it a comet-like or minnow-shaped (without the tail) appearance, clumpiness and mottling toward the center, especially on the southern edge (7.9 mag)

(ESO, CC BY 4.0, via Wikimedia Commons) North is up.

NGC 4214, a dwarf barred irregular in Canes Venatici; the bright northwest to southeast bar makes it look a bit like an edge-on with a halo around it (10.2 mag)

(Ole Nielsen, CC BY-SA 2.5, via Wikimedia Commons) North is up.

NGC 4449, an irregular starburst galaxy in Canes Venatici; look for a brighter elongated mass in the center but no real core, splotchy mottling and a bump off the south end, fainter outer rectangular glow as if it were a fat edge-on that someone snipped the ends off (10.0 mag)

(KPNO/NOIRLab/NSF/AURA/John and Christie Connors/Adam Block, CC BY 4.0, via Wikimedia Commons) North is to the upper right.

M82, starburst galaxy in Ursa Major, close to M81; look for a pinched dark intrusion or lane cutting laterally, or diagonally through the center, brighter pinpricks in the central area, and irregular, mottled arms on both sides (8.4 mag)

(N.A.Sharp/NOIRLab/NSF/AURA/, CC BY 4.0, via Wikimedia Commons) North is up.

NGC 5128, in Centaurus, if you are far enough south to see it well, closest radio galaxy, also designated Centaurus A; look for a dramatic thick dark lane separating the glow into two lobes, making it look like a tall, skinny hamburger, much brighter southern lobe (6.8 mag)

(ESO/IDA/Danish 1.5 m/R. Gendler, J.-E. Ovaldsen & S. Guisard (ESO), CC BY 4.0, via Wikimedia Commons) North is to the upper right.

NGC 4490, Cocoon Galaxy in Canes Venatici, starburst galaxy just finishing an interaction with the smaller NGC 4485 (the pair designated Arp 269); look for a fat, elongated oval with pointy ends, well condensed but mottled core, small round satellite galaxy NGC 4485 to the north (9.8 mag)

(Adam Block/Mount Lemmon SkyCenter/University of Arizona, CC BY-SA 3.0 US, via Wikimedia Commons) North is to the upper right.

Ellipticals

In terms of visible detail, ellipticals are the plainest. Other than shape and degree of condensation to the core, there's not much to see. I recommend doing some research before you observe them so you can just appreciate what they are. I've only included two here that have a little more to offer, being in close proximity to another galaxy and a bright star, respectively. Have at it.

M60, in Virgo; look for the smaller and much dimmer spiral galaxy NGC 4647 just off the northwestern edge of it (8.8 mag)

(Adam Block/Mount Lemmon SkyCenter/University of Arizona, CC BY-SA 3.0 US, via Wikimedia Commons) North is to the upper left.

NGC 404, "Mirach's Ghost" in Andromeda; challenging observation because it is so close to the 2nd magnitude star Mirach, Beta And, hence the name; look for it about 7 arcminutes to the northwest by putting Mirach just outside the field of view (11.2 mag)

(Ole Nielsen, CC BY-SA 2.5, via Wikimedia Commons) Mirach is the bright star below center, NGC 404 is the much smaller object up and right from Mirach. North is up.

Active galaxies (Seyferts, Quasars)

NGC 3079, an edge-on Seyfert in Ursa Major, showing a fat cigar shape; look for subtle mottling and asymmetry in larger apertures (11.5 mag)

(KPNO/NOIRLab/NSF/AURA/Jeff Hapeman/Adam Block, CC BY 4.0, via Wikimedia Commons) North is to the lower right.

M77, a barred spiral, the prototype Seyfert in Cetus; look for the bright active nucleus and compare it to the nearby 11th magnitude star just to the east-southeast (8.9 mag)

(KPNO/NOIRLab/NSF/AURA/Francois and Shelley Pelletier/Adam Block, CC BY 4.0, via Wikimedia Commons) North is to the lower right.

3C 273, first quasar identified and the brightest, in Virgo; just look for it, you won't see any detail, just a starlike point, but you'll be looking at probably the farthest object you may ever see in your small telescope, at 2.4 billion light years (12.9 mag)

(Giuseppe Donatiello, Public Domain, via Wikimedia Commons.) The quasar is indicated by horizontal tick marks. North is up.