Measuring the Cosmos: A Hazy Night with Lyra the Harp

Often, when amateur astronomers gather under the stars, the conversation turns to size and distance. We might say a planet looks incredibly tiny, or note that two stars seem to be sitting right next to each other. But how do you measure the sky? You can’t exactly hold a tape measure up to a constellation. Instead, astronomers use something called angular measure to describe how big or how far apart things look from our perspective on Earth.

To understand how this works, imagine the night sky as a giant, transparent sphere. We are standing right at the very center, looking out. Even though stars, planets, and galaxies are actually at vastly different distances from us, they all appear to be glued to the inside of this bubble. Astronomers call this the celestial sphere.

If you were to draw a line on the inside of this sphere that went all the way around the Earth and back to your starting point, it would form a perfect circle. Like any circle, this one can be divided into 360 degrees.

So, how big is a degree when you’re looking up at the night sky? A great reference point is the moon, which is about half a degree wide.* If you want something a bit bigger, look for the constellation Orion. The three famous stars that make up Orion’s Belt form a straight line that spans about three degrees across the sky.

Luckily, you don’t need high-tech equipment to measure these degrees; you carry a built-in ruler at the end of your arms.

If you extend your arm fully and hold your pinky finger up against the sky, your fingernail will easily cover the moon. That is because your pinky at arm's length measures about one degree of angular distance. If you see two stars that can just be hidden behind your pinky, they are roughly one degree apart. Need a larger ruler? Make a tight fist and hold it out at arm's length. The width of your fist from knuckle to knuckle covers about ten degrees of the sky.

But what happens when we look through a telescope at objects that are much smaller than a single degree? A typical backyard telescope only lets you see a tiny patch of sky at one time—usually one degree or less. To measure these miniature views, we have to break the degree down into smaller fractions.

Just like an hour is divided into minutes, a degree is divided into arcminutes. There are 60 arcminutes in one single degree. Since we already know the moon is half a degree wide, we can also say it has an angular size of 30 arcminutes.

For the truly tiny targets of the universe, like distant planets, even the arcminute is too large. For these, we use the arcsecond. Just as there are 60 seconds in a minute, there are 60 arcseconds in an arcminute. To put this in perspective, the giant planet Jupiter is only about 40 arcseconds across, and Saturn’s rings stretch to about that same tiny width from tip to tip. The tight spaces between double stars, or the diameters of distant star clusters and galaxies, are often measured in these tiny arcseconds.

The Target: Lyra the Harp

Now that we have our cosmic rulers ready, let's look at a fantastic summer constellation: Lyra, representing the ancient musical harp. Lyra is home to some of the most fascinating objects in the northern sky.

Vega: The Blue-White Anchor

The crown jewel of Lyra is Vega, one of the brightest stars in the entire night sky. At just 25 light-years away, Vega is practically a next-door neighbor in cosmic terms.† It shines with a brilliant, blue-white light and serves as a major landmark in the summer sky. While you don't need a telescope to appreciate its beauty, looking at Vega through an eyepiece can reveal just how intensely white and piercing its light truly is.

Epsilon Lyrae: The Double-Double

Just a short distance from Vega sits Epsilon Lyrae. To the naked eye, it looks like a perfectly ordinary, single star. However, if you point a pair of binoculars or a small telescope at it, you will notice something interesting: it splits into two distinct stars, known as Epsilon 1 and Epsilon 2.

As far as double stars go, these two are separated by a fairly wide gulf of about 3½ arcminutes.‡ But the real magic happens if you use a telescope with a lens or mirror at least 100mm wide. If you boost the magnification, you will discover that Epsilon Lyrae is actually a "Double-Double." Each of those two stars is itself a pair of incredibly close twins, separated by a mere 2.2 and 2.8 arcseconds, respectively.

The Ring Nebula (M57)

Deep within Lyra lies a ghost of a star: the Ring Nebula, cataloged by astronomers as M57. You absolutely need a telescope to see this one. Located about 2,300 light-years away, it is a planetary nebula—the glowing remains of a dying star that used to look a lot like our Sun.

When a sun-like star runs out of fuel at the end of its life, it swells into a red giant and gently sheds its outer layers into space. These expelled layers form an expanding shell of gas and dust, illuminated by the intensely hot, leftover core of the star—a white dwarf. Through a telescope, it looks remarkably like a cosmic smoke ring or a glowing donut suspended in the darkness.

Field Report: A Humid Night in the Backyard

To share with you how this all plays out in the real world, I stepped into my own backyard for a live observing session. The conditions were far from perfect. It was classic Southern weather—hot, sticky, and highly humid. Tenuous clouds drifted overhead, and the heavy moisture in the air scattered the local city lights, giving the night sky a washed-out, milky appearance.

Honestly, most astronomers would take one look at this "soup" and head back inside. But a bad night of astronomy is still better than a good night indoors, so I set up my gear anyway. I used three pieces of observing equipment: a pair of binoculars, a small 60mm refracting telescope, and a large 203mm reflecting telescope.

Looking up, the haze was so thick that I could barely see any stars in Lyra besides Vega. I could just barely catch a glimpse of a dimmer star, Sulafat, in the harp's frame, but the rest were lost in the glare.

Testing the Binoculars

I started with the binoculars. Vega looked decent—a steady, bright white beacon. I then swung over to Epsilon Lyrae. It was invisible to my unaided eyes, but I knew it was just two degrees (about two pinky-widths) away from Vega so it was easy to find in the binoculars. By leaning my arm against the backyard shed to steady my view, I could just make out Epsilon Lyrae as a double star. In cleaner, crisper skies, this would be an easy split, but on this night it took serious concentration.

Moving to the 60mm Telescope

Next, I targeted Vega with the small 60mm telescope. Through the eyepiece at 36x magnification, Vega was blazing. However, the thick air scattered so much light that the background sky appeared murky blue instead of black.

When I swung the 60mm scope over to Epsilon Lyrae, the low-power view clearly separated Epsilon 1 and Epsilon 2. They looked like two neat points of light. But could this little scope reveal the hidden doubles within those stars? I could see that one of the star pairs looked slightly oblong or egg-shaped, but the murky atmosphere prevented me from splitting them completely.

Unlocking the View with the 203mm Telescope

I moved to a bigger scope—a 203mm reflector. At a low power of 38x, the two main components of Epsilon Lyrae were beautifully sharp and widely separated. At this low magnification, however, the tiny 2.2 to 2.8 arcsecond secondary pairs were still hiding.

I swapped out the eyepiece to push the magnification up to 160x. Big difference! The atmospheric distortion was still there, but the greater light-gathering power of the bigger mirror succeeded. The separation between the secondary pairs of stars was unmistakable. I was clearly looking at four distinct stars arranged in two tight pairs. I remained at the eyepiece for some time just taking in the view.

The Verdict on the Ring Nebula

As for the Ring Nebula? Not in these conditions. The haze was so thick that I couldn’t even see the two stars I would normally use to "star-hop" my way to the nebula. A delicate, ghostly cloud of gas simply cannot compete with this humid sky glow. It was time for me to pack up the gear and call it a night on a very difficult, steamy evening.

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* All angular measurements, except for those regarding Epsilon Lyrae, are from Stellarium Mobile Plus, v1.15.0, by Stellarium Labs S.R.L. Accessed 7 June 2026, Google Play Store.

† All distances are from Stellarium Mobile Plus, v1.15.0, by Stellarium Labs S.R.L. Accessed 7 June 2026, Google Play Store.

‡ All angular measurements regarding Epsilon Lyrae are from Burnham’s Celestial Handbook, Volume Two, by Robert Burnham, Jr. 1978, Dover Publications, Inc., page 1131.

All graphics created by the author.