Finding the Ring Nebula (M57) with a 114-150 mm Reflector

When and where to look

The Ring Nebula is best placed in August and September, when Lyra stands high in the evening sky for northern observers. From 35° N it passes almost overhead, reaching 88° at its highest. From 50° N the maximum altitude is 73°, which is still comfortable. From 35° S it only reaches 22°, so it stays low in the north and you need a clear northern horizon.

Observe when Lyra is as high as it gets. That usually means the hours around the time the constellation crosses the meridian, which is the imaginary line running from north to south through the zenith. The higher the object, the less atmosphere you look through, and the more stable the image.

Northern hemisphere

Face roughly east to south-east after dusk in late summer. Vega, the brightest star in this part of the sky, will be high up. Later in the evening it moves toward the zenith and then into the west. If you are at 35° N, you may need to tilt your head back or use a diagonal to avoid awkward positions at the eyepiece.

Southern hemisphere

Face north. Lyra sits low, and Vega will look noticeably lower and more orange-white than it does for northern observers, because of atmospheric reddening. At 22° maximum altitude, trees, roofs and the suburban glow near the horizon all matter. Pick a spot with a clear view to the north, and expect the nebula to appear dimmer and softer than it would from a high-latitude site in the north.

Preparing the telescope

A few minutes of preparation make the star-hop smoother.

• Let the reflector cool outdoors for 20 to 30 minutes so the mirror reaches air temperature. A warm mirror produces tube currents and a smeared image.
• Align the finder in daylight or on a bright star. Check that the finder and the main telescope point at the same spot at about 50x.
• Choose a low-power eyepiece for the search. A 25 mm eyepiece in a telescope with a focal length of 650-900 mm gives a field of roughly 1° or a little more, which is ideal for this hop.
• Keep a higher-power eyepiece ready, giving around 100x to 150x, for the confirmation and detail stage.
• Have a red light for reading a chart. White light ruins your dark adaptation in seconds.

If you use a star diagonal, remember that it may reverse the view left to right. A simple Newtonian reflector gives an inverted image, with north and south swapped, but not mirrored. Confirm how your telescope shows the field before you trust a chart.

The star-hop from Vega

Lyra is small. Its pattern is a bright star, Vega, with a compact parallelogram of four fainter stars trailing off to one side. The Ring Nebula lies between the two lower stars of that parallelogram, Beta Lyrae and Gamma Lyrae.

Step 1: Identify Vega

Vega is the brightest star in the area and is easy to recognize even in a suburban sky. Point your finder at it and center it. This step also checks your finder alignment.

Step 2: Find the parallelogram

From Vega, look about 6° to 7° away. That is roughly the width of a fist held at arm's length, or slightly less. You will see a small parallelogram of four stars. Two are brighter and two are fainter. From a suburban sky they should all be visible to the naked eye, although the fainter ones can be a little tentative under bright skies.

The two stars at the end of the parallelogram farthest from Vega are the ones you need. They are Beta Lyrae and Gamma Lyrae. Gamma Lyrae is the one closer to Vega's side of the pair when viewed in the sky; Beta Lyrae is slightly farther along toward Cygnus. Each is a moderately bright star, easy to see in the finder.

Step 3: Move to the midpoint

Place Beta Lyrae and Gamma Lyrae in the same finder field. They are about 2° apart, so they fit comfortably in a finder with a field of 5° or more. In a 6x30 finder, they will be separated by roughly half of the field. Center the finder on the line between them.

Step 4: Shift slightly toward Beta Lyrae

The Ring Nebula is not exactly at the midpoint. It sits on the line connecting the two stars, a little closer to Gamma Lyrae than to Beta Lyrae. Nudge your telescope a short distance, about a third of the way along the line from Gamma Lyrae toward Beta Lyrae, if the midpoint does not show it. In practice, you will search a small region about 1° across along the line.

Step 5: Use the low-power eyepiece

Look through the 25 mm eyepiece. Beta Lyrae and Gamma Lyrae may both be inside the field, or one may sit near the edge. Scan slowly along the line between them. You are looking for a faint, slightly out-of-focus star, with a small fuzzy glow that does not sharpen when you adjust the focus.

Confirming you have arrived

At low power, the Ring Nebula is a little compact and a bit gray. It is easy to pass over, so use several checks.

1. Check the focus. Stars snap to sharp points. The nebula stays slightly soft, because it is a tiny disk rather than a point.
2. Check the geometry. The target should sit near the midpoint of the line between Beta Lyrae and Gamma Lyrae, a little nearer Gamma Lyrae. In a 1° field, you should see one of the two stars off to the side while the nebula sits alone in a sparse area.
3. Increase the magnification. Switch to 100x or more. The fuzzy dot should expand into a small round or oval disk. With a size of 1.3′, it is small, but at this power it is clearly not stellar.
4. Try a nebula filter. If you have one, thread it into the eyepiece. The surrounding stars dim, and the disk usually keeps its brightness better, so it stands out more clearly from the background.
5. Use averted vision. Look slightly to one side of the disk. This uses the more sensitive part of the retina and can help you see its shape.

If the field does not show a nebula, retrace the route. It is common to overshoot by one finder field, or to follow the wrong pair of stars in the parallelogram.

What you will see

The Ring Nebula has a magnitude of 8.8, which is within reach of a 114-150 mm reflector. In practice, you will see a clearly visible, small round or oval disk. It is not a sharp ring in most small telescopes under suburban skies. The disk looks a little grayish, and the shape may appear slightly elongated.

Expect the following

• At 50x to 70x: A small, soft gray patch that looks distinctly different from the surrounding stars. This is the confirmation view.
• At 100x to 150x: A larger oval disk. With steady air and good dark adaptation, you may see that the center is slightly dimmer than the edge. Do not expect a bold hole.
• With a nebula filter: The disk becomes easier to see against a suburban background. The filter does not make it larger or brighter, but it improves contrast.

The central star is far too faint for a telescope of this size, so do not look for it. The classic ring structure is often said to be visible in larger instruments, and a 114-150 mm reflector may show only hints of it on a night with steady air. Be honest with yourself about what you see, and record exactly that in your notes.

Suburban sky effects

Streetlights and skyglow reduce contrast, but the Ring Nebula is compact and relatively bright for its type. This is why it survives suburban conditions much better than larger, more diffuse nebulae. Shield your eyes from nearby lamps with a cloth or an observing hood, and wait several minutes for your eye to adapt before judging the view.

Making the most of the session

Once you have found the nebula, spend time on it rather than moving on at once. A few minutes of careful viewing reveals more than a quick glance.

• Tap the tube gently to make the object appear to flicker. Motion helps the eye detect faint shapes.
• Alternate between averted and direct vision, and note which view gives the clearest outline.
• Compare the nebula with nearby stars at the same magnification, to appreciate its apparent size.
• Try a slightly higher power if the air is steady, and a lower one if the image shimmers.

Nearby targets in the same session

Beta Lyrae and Gamma Lyrae are both worth a brief look as part of the route. Beta Lyrae is a bright star in a multiple system, and a moderate magnification can reveal faint companions. Keep this as a short side trip. The nebula is the main goal.

Troubleshooting

• You cannot find the parallelogram. Start again from Vega, and sweep roughly 6° toward the lower part of the sky, away from the brightest nearby stars. Use binoculars to confirm the shape.
• The finder view seems too crowded. A narrow finder field can make it hard to see patterns. Start with the naked eye, then binoculars, then the finder.
• The disk looks like a star. Your focus may be slightly off, or the magnification too low. Increase power and refocus carefully.
• The view is murky. Check for dew on the corrector or eyepiece, and make sure the mirror has cooled.
• You are in the southern hemisphere and the view looks weak. The low altitude is the cause. Observe when Lyra is highest, and avoid nights with a hazy northern horizon.