Observing planetary nebulae can be challenging. However, using the skills you have learned in previous lessons, you shouldn’t have much difficulty locating most of the planetaries within range of amateur telescopes. And you will be able to see greater detail than you first imagined.

LOCATING THE OBJECTS

Planetary nebulae are the material ejected from very hot central stars. They tend to be very small with a high surface brightness. As a result, many can be seen in urban settings, a plus for amateurs who live within the city on clear nights when they cannot go to a dark site. In general, the ease at which a planetary nebula can be found will be determined by its size. Its size is dependent upon its distance from us.

Most planetaries are very small, between 10 and 25 arcseconds in diameter. I would still suggest using the most common technique for locating deep sky objects: use the lowest power eyepiece you have. These small planetaries will look similar to small, slightly out-of-focus stars. You will barely be able to notice the difference on the small ones such as the Little Gem or the Blue Snowball, so make sure you know the exact location from your star maps. Once you have found that blurry, starlike object, put in a higher eyepiece. Most will remain fuzzy, but bigger, while the background stars will remain small and sharp.

On the other end of the spectrum are the few large planetaries such as the Helix. They too can be challenging. Because their light is spread out over a much larger area, they tend to be faint, even with low power. Once you are sure you are looking at the exact location, continue to stare at that spot and use averted vision. You should then see it. Increasing power at that point can help to make the object more noticeable.

The planetary nebulae that are of mid-size — 50 to 350 arcminutes — are easy to locate at low power. Such objects as the Dumbbell and the Owl generally stand out in all amateur telescopes. The size of your main objective and the amount of power you can use with it will determine how much detail you’ll be able to see.

OBSERVING TECHNIQUES

The real goal in observing planetaries is seeing as much detail as possible. While the naked eye will never produce as much detail as time-exposed photographs, you will be surprised at the detail you can see. Use as much power as your telescope and viewing conditions will allow. That amount will vary from object to object.

You should be able to notice some color in many of the planetary nebulae. Some people’s eyes are more susceptible to color than others. Other planetaries have their own unique shape. Use both the high power and averted vision to try to locate depth in the structure of the object. Some even appear three-dimensional. Nebula filters can be very helpful in attempting to observe the different structure. Try any such nebula or light-pollution filter you have access to. It is the contrast with the background that allows you to see more.

Finally, all planetaries have a central star. Observing the central star has been a goal of many amateur astronomers. Unfortunately, most are too dim for the typical amateur telescope. Below I will list which ones are fairly easily observed. However, if you do have access to a scope with a large aperture, it is fun to try to find the more difficult central star.

SELECTED PLANETARY NEBULAE

I have included a table of the twelve most famous planetary nebulae. Each has been given a common name through the years. They are listed according to right ascension. Below I describe a little about each of them:

1. The Little Dumbbell is a smaller version of the more famous Dumbbell. It is regarded by many as the dimmest of all Messier objects. But I have always found it easy to locate, even in the city. It looks more like a slightly misshapen rectangle with no other detail.

2. The Eskimo, also referred to as the Clownface, shows its true features only in photographs. However, with good skies and high power, you can begin to notice some detail — like overlapping spheres. The central star is observable under perfect conditions.

3. The Ghost of Jupiter shows very little detail with amateur scopes. With high power and excellent seeing you do begin to notice that there is something more there than a circular glow.

4. The Owl looks like a nondescript, circular glow at low power. You can see a hint of a face when conditions allow for high power. But it takes a very large telescope to see the two dark owl eyes and the central star.

5. The Cat’s Eye has a central star in reach of many backyard telescopes. It takes a good night and patience to see it. If you are really lucky, you begin to notice how it got its name. Otherwise, you may be lucky just to see its bluish tint.

6. The Ring Nebula is the most viewed of all the planetaries. Its small smoke-like ring can be seen in just about any telescope. The more power you can use, the more structure in the ring you will see. But you will probably need to go to Yerkes to see the central star.

7. The Little Gem can be tricky to see in star-filled Sagittarius. Be content to recognize it in that it does look like a small, out-of-focus star. No detail here.

8. The Blinking Planetary does not blink at all. It’s an optical illusion. Your mind allows you to focus on the small, fuzzy nebula for only a short time and then allows you to focus on its central star for a short time. This process continues to alternate as you stare at it. But you can easily see the central star — off and on.

9. The Dumbbell does provide you with a lot of detail. Use different power and a nebula filter. It is bright, and both techniques help. Of all the nebulae, it appears closest to resembling its photograph — without most of the color.

10. The Saturn resembles an out-of-focus version of its namesake planet — at least in photographs. If you are able to use high power, it does appear to bulge on its sides.

11. The Helix can be downright elusive, even on good nights. Its low declination does not help, especially if the sky is light-polluted in that direction. But if you are at a dark site on a steady night, you can find it with patience. It looks like a larger version of the Ring.

12. The Blue Snowball looks exactly like that to me and nothing more. Put higher power on it and it resembles a bigger blue snowball. Nothing has allowed me to see anything else.

Congratulations!
You are ready for the Advanced Lessons