Planetary nebulas generally make great targets for washed-out astronomers. Most of them standout well even in light polluted skies because they are usually rather small and therefore have relatively high surface brightness. Their small size also means they are best seen using relatively high magnification which helps to darken the background and boost contrast. Finally, planetary nebulas respond very well to narrowband filters [2], even when observing in urban environments. (Image: Glenn Hitchcock and Bob Cowart/Adam Block/AURA/NOAO/NSF)

Famous planetaries like the Dumbbell Nebula (M27) and the Ring Nebula (M57) are well known to most amateur astronomers and are spectacular objects even in light-polluted skies. But regardless of season there are always planetary nebulas well positioned in the sky for urban observers. Here is a list of good planetaries for washed-out astronomers…

Unlike the Ring and Dumbbell Nebulas, most of the following planetaries are rather small. In fact, distinguishing them from stars can often be the most challenging part of finding them. These planetaries are less than a minute of arc in diameter, often much less. In general use magnification of at least 100x or 150x and look for a very distinctive color somewhere between blue and green. Here are some planetaries that I recommend to you.

 

NGC 2392

Known as the Eskimo Nebula, this planetary in Gemini rides high in the sky during winter and is easy to find. At magnitude 8.5 and about 40” across, NGC 2392 is quite bright and easy to find thanks to its distinctive green color. It takes magnification well, but it is hard to see the Eskimo appearance unless you have dark skies. The central star is magnitude 11, but hard to see due to the bright central nebula.

 

NGC 6543

The Cat’s Eye Nebula is located in Draco, allowing you to see it almost year-round. NGC 6543 is bright at magnitude 9.8. It’s only 18” across, so be sure to use sufficient magnification or you might miss it. NGC 6543 was the first planetary nebula to have its spectrum taken. It showed discrete emission lines, showing that it was made of gas, as opposed to an unresolved cluster of stars.

 

NGC 6210

This bright (magnitude 9.0) planetary in Hercules doesn’t have a cute name as far as I know. While it is quite small (15”), its distinctive baby-blue color gives it away, even at relatively low magnification (70-90x). Using higher magnification (150-200x) you can make out that it is egg-shaped. If you have a larger telescope, you might be able to see the magnitude 12.7 central star.

 

NGC 6826

This planetary in Cygnus has one of the brightest central stars in a planetary nebula. The planetary is magnitude 8.8 and the central star is magnitude 11. If you look at NGC 6826 directly, the bright central star overwhelms the eye and the nebula disappears. Shift your eye to use averted vision and the nebula pops into view. That’s why it is called the Blinking Nebula. Like other planetaries, NGC 6826 is blue-green, but the color is not as distinctive as some of the other planetaries.

 

NGC 7009

Located in Aquarius, this planetary is known as the Saturn Nebula because of two “handles” (ansae) which Herschel thought made it look like the planet Saturn. It is relatively bright (magnitude 8.1) and larger than most (40” x 60”). Like NGC 6826, the Saturn Nebula has a relatively bright central star (magnitude 11.5) and can display the “blinking” effect. I find the color is greener than most planetaries, most of which I think tend toward blue. While the planetary is relatively bright and easy to find, you are unlikely to see the “handles” from anything but the darkest skies.

 

NGC 7662

Known as the Blue Snowball, this planetary in Andromeda has a baby-blue color similar to NGC 6210’s color, but not quite as intense. This is probably because the Blue Snowball is over twice as large (37”) as NGC 6210 but has the same overall brightness (magnitude 9.0). The central star is variable ranging from magnitude 12 to 16. Magnifications of 150x or more reveal a bit of oval shape. At times I think I’ve glimpsed a darker hollow in the center, but I have never quite seen this clearly in light polluted skies, not even with narrowband filters.

 

IC 418

This planetary in Lepus stands out for its red color, which is rather unique among planetaries. It is relatively bright (magnitude 9.6) and quite small (12”). The color is quite subtle. The central star is relatively bright (magnitude 11.8) and rather blue, so the red tint of the nebula is best seen using high magnification (180x or more). IC 418 is known as the Spirograph Nebula because of the patterns seen in HST photographs.

 

NGC 2440

This planetary in Puppis contains what is believed to be the hottest known white dwarf, with an exceptionally high surface temperature of about 200,000 degrees Kelvin. At magnitude 9.9, NGC 2440 is relatively easy to find even though located relatively far south. It is small (16”), so at 100x it only shows up as a small smudge. At higher magnifications (200x or more) its elongated shape becomes clearer and you might even notice its bi-polar nature.

 

NGC 6572

This planetary in Ophiuchus is known as the Blue Racquetball. Particularly small (about 10” across), you really need to use significant magnification to clearly see its shape. It has an overall magnitude of 9.0, giving it a very high surface brightness due to its small size. I see the color as a very intense aquamarine.

 

NGC 6818

Known as the Little Gem, this planetary is found in Sagittarius, almost at the border with Capricornus. Most sources list it as magnitude 10.0, but I find it appears brighter than that and it is small (about 20”) but big enough to easily stand out from nearby stars. It has a very pretty and distinctive teal color.
 

 

Finding These

All of these planetary nebulas can be found in Sky and Telescope’s Pocket Star Atlas, in Sky Atlas 2000, or in any of the major star atlases. All of these planetaries are close to relatively bright stars, so you can star-hop to them even in light-polluted skies. They are all bright and distinctive enough in color that you can pick them out easily once you get them within your eyepiece field-of-view. But remember to use enough magnification (at least 75x), otherwise you might think they are stars and overlook them.

 

In a future article I’ll supplement this list with a list of planetaries that are more challenging to find and see, especially from washed-out skies.