(c) Skyhound

Above is a sketch of NGC 2440 that I made at the eyepiece, overlaid on top of a SkyTools 3 Eyepiece View. 

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A Fantastic Planetary Nebula

I think this planetary nebula is among the finest in the sky. It is quite bright, which makes it fairly easy to find in any telescope, even though it is seemingly out in the middle of nowhere among the fainter stars of Puppis.

NGC 2440 doesn't always get the attention it deserves because has a very short observing window for northern hemisphere observers. It lies at roughly the same Declination as Sirius (which is about 14o to the west). Some may be tempted to look at it when low on the horizon, but it is well worth planning to observe it when at it's highest in a dark sky. From the latitude of Ohio, NGC 2440 barely rises above an altitude of 30o, and there is at most an hour or two per night to catch it at its best. At more southern latitudes it rises higher, but it is still just as important to catch it at its highest. For our friends in Australia, New Zealand, or South Africa it passes nearly overhead, which must be a real treat.  

The atmosphere is our enemy when it comes to observing. It dims our objects, lowers contrast, and blurs everything. All of these effects are magnified as we move closer to the horizon from overhead. For most telescopes, an object at an altitude of 30o makes for a comfortable and tempting target, but we are actually looking through twice as much air as overhead, which degrades our view. So the first thing we can do to get better views is to always observe objects when they are at their highest in the sky. The second thing is to keep going back again and again until we get one of those awesome nights when the sky is transparent and dark, or the seeing is very steady. This is particularly important for an object that never rises high in your sky. I keep a special observing list for these objects that require a special night, and break it out when such a night arrives. 

The first time I observed NGC 2440 in my 18-inch, I was surprised by how bright it appeared. It was brighter than the 11th magnitude listed in the catalogs of the time. The planetary was obviously non stellar at 100x and appeared as a tiny smudge. The best view came at 425x, where it appeared distinctly bipolar, as seen in my sketch on the right. At the heart of the nebula are two bright knots that nearly touch. The surrounding nebulosity stretches in the directions perpendicular to a line between the knots, and is brighter and extends farther to one side. I have seen sketches online that show even more detail. This planetary makes my personal list of favorites due to its interesting structure.

In smaller instruments NGC 2440 may appear as a mere smudge of light, but it is a feather in your cap to find it. In any instrument, use as much magnification as conditions will permit and averted vision to try to catch the two bright knots. 

How to Star Hop to NGC 2440 Quickly and Easily

I've always done the bulk of my visual observing via star hopping. Like many people, I often found it time consuming and frustrating. So when I set out to create SkyTools, one of my goals was to come up with a better way to star hop. What I ended up doing was inventing a whole new way to star hop, one that basically takes the hop out of it. The idea is to use context instead of motion. I start with a naked eye view of the sky, with my target marked at the center of a chart. I point my telescope roughly at that spot in the sky. Next I switch to the finding device, and a second chart that closely matches what I will see in the finder, with the same orientation, field of view, and limiting magnitude. I usually pick out an obvious asterism, like three brighter stars in a row, and look for that in the finder. Once I spot it, I center the telescope at the location marked on the second chart. Finally, I insert my lowest-power eyepiece and have a look through the main scope. Usually the object I am looking for is obvious, but for those troublesome tiny or faint objects, I look at a third chart that displays a close match to what I should see in the scope. As before, I find an obvious grouping of stars to orient myself, and then look at the spot marked on the chart. In some extreme cases, I have to center that spot, and switch to a higher-power eyepiece for the object to finally appear. 

When I first brought printed SkyTools charts to a star party, I was able to find tricky objects while people nearby were still fumbling with their atlases. I knew I was really on to something when I handed a chart to a nice couple with a new 8-inch scope. They had little experience, and had never seen a telescopic comet, yet they were able to navigate to it without difficulty.

Since that time, countless thousands of observers have been using SkyTools finder charts to quickly locate objects. The big advantage of these charts is that they are customized to your location, light pollution, current sky conditions, finding devices, telescope, and eyepieces, so that they closely match what you see. Sadly, I can't make a chart for everyone. For my example below I have chosen a pretty generic 8-inch Dob with a bullseye finder. For telescopes with a magnifying finder, SkyTools makes charts with three views, but this scope only needs two. The idea is to put everything you need to find your object either on your screen, or a single piece of paper.

Click/touch it to make it bigger. The idea is that the SkyTools Nightly Planner has already figured out the best time to observe NGC 2440 for you. You told it to make a chart, and it made the chart for that time of the night. So you go on out and observe near that time, starting on the left. Point your bullseye roughly where it is on the chart. Now, I have had people say that this is fine for a darker site, but what about a light polluted location where fewer stars are visible?

Above is the left side again, but now for a more suburban sky, showing stars to mag. 5. The trick is that you only need to be close to the right spot. You just have to be brave and point it as best as you can. Look at the shape of the triangle made with the bullseye, Sirius (alpha), and the star down to the left. Try to match that shape with your scope. Once you look in the eyepiece, you may have to move the scope a bit, but you will either see the nebula, or spot a grouping of stars that will help you hone in.

Download a pdf finder chart

Greg Crinklaw Amateur/Professional Astronomer and Developer of SkyTools 

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