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Observing Tips
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"At length, by sparing neither labor nor expense, I succeeded in constructing for myself an instrument so superior that the objects seen through it appear magnified nearly a thousand times..." Galileo Galilei (1564 - 1642) Italian astronomer |
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* Night Adaptation One of the first tips you should know about observing the night skies is to adapt your eyes to the night sky. As you know, when you walk inside a dark building after being out in the sun your eyes need a short bit of time to adapt to the low light conditions before you can see well. The first few seconds are bad, then you gradually see more and more in the next few seconds. The greater the differences from light to dark, the more time it takes. The same is true when going outside at night to observe the night sky. Since some of the objects that you want to observe are extremely faint it's going to take much more than a few seconds for your eyes to adjust. Most amateur astronomers allow 15 to 30 minutes for their eyes to adapt. Once your eyes are adapted to the dark, avoid looking at any lights or your pupils will dilate again. So how can I read my charts?, or see my eyepieces and filters?, you may be wondering. The human eye doesn't loose its dark adaptation under red light. Therefore the trick is to use a red flashlight. Most places that sell telescope accessories will sell red beam flashlights. Or you can make one of your own. Simply take a regular flashlight and wrap a piece of red cellophane over the end and secure it with a rubber band. Or you can paint the lens of the flashlight with red nail polish. * Telescope Cool Down This is as simple as it sounds. Before observing for the evening, bring your telescope outdoors for a period of time to allow it to cool down. This can be anywhere from a half-hour to an hour, depending on how cool (or cold) it is outside. If you don't allow your telescope to cool down you will see the heat diffraction through the telescope as you try to observe. Images will be wavy or blurry. The same thing can occur if you set up your telescope on concrete or a paved area, or pointing your telescope over the top of a nearby building. The heat waves from the day will rise off the pavement or rooftop during the evening. You're better off setting up on a grassy area. * Light Pollution Light pollution can come from many sources. The glow of a city, a neighbor's porch light, the glow from a full moon. The more of it you can avoid, the more objects in the night sky you will be able to see. Try to do your observing from the darkest spot that you can find. A little bit out in the country is always better, far away from city lights is even better still. The ideal spot would be a small island in the middle of the South Pacific. (If you have a spot like this, call me, I'll join you.) If you're in the city or suburbs try to avoid setting up where streetlights or other light sources are anywhere in your line of vision. Your best nights will usually be during a new moon. There are no "magic" filters that block out light pollution. Some people say that they have had fairly good luck with a broadband eyepiece filter, but personally I never noticed any difference. A narrowband eyepiece filter will help some, but only when observing nebula. You can find a small review on these filters here at the top of the page: Opinions/Mini Reviews page 4. The only other hint I can give you is when light pollution is heavy, do most of your observing near the zenith where you are looking through less atmosphere, instead of near the horizon where the atmosphere is thicker. You can easily notice how the sky looks darker at the zenith than it does at the horizon.* Planisphere and Star Charts To get the most out of your observing sessions use either a planisphere or star charts. A planisphere is nice to orient yourself with the current position of the sky relative to Earth. You move the dial to the current month and time, hold it in front of you with the direction you are facing pointing down on the planisphere, and simple as that you should have a good reference to the sky above. All the main constellations are drawn out, and some of the Messier objects are on there too. These are good to use with any telescope, but they really come in handy when observing with binoculars too. Of course for more detail you want a good set of star charts. There are many out there to choose from. How detailed you get depends on your telescope. If you have a small telescope that can't see many faint objects you don't need a complicated set of charts that shows stars at faint magnitudes. If you have a large scope you don't want a set that won't show everything you are capable of seeing. A great beginners atlas is "Norton's Star Atlas & Reference Handbook" which shows all stars down to 6.5 magnitude. For the next level I recommend "SkyAtlas 2000.0" which shows stars down to 8.5 magnitude. There are a few versions of this one. I have the Deluxe version that you can read about here: Opinions/Mini Reviews page 6 third one from the top of the page. The best one out there for really showing the faint stars is "Uranometria 2000.0" which shows stars down to 9.75. This book is the granddaddy of them all, and it comes in 2 volumes. One for the northern hemisphere, one for the southern.If you're the type who would rather download star charts and print them out here is an excellent web site. Sky Maps.com not only lets you download a free chart each month, you can also order any of the above atlases, planispheres, astronomy software, and much more. You can find them here: http://skymaps.com/* Miscellaneous Tips * Use adverted vision while trying to observe faint objects. When you look straight at the object you are using the rods in your eyes. When you look slightly away you are using the cones in your eyes, and the cones are more light sensitive than the rods are. Keep going back and forth from direct vision to adverted vision. * Be comfortable! Dress warm in cold weather. You're not going to want to see much if you are shivering from the cold. It's better to have a little extra clothing that you can remove if you get too warm than not have enough. Remember it's always cooler at night, especially when you're standing around not being very active. (This doesn't apply to owners of large dobsonian telescopes who work up a sweat just setting up their telescopes.) * Bring a snack and something to drink when you go to a viewing location away from home. Yeah, this might be common sense, but you're more likely to stay a bit longer and enjoy your stay more if you have something to drink and munch on. A thermos of hot drinks is nice on a cold night. This goes back to the "Be comfortable" statement, as does the next one.... * Bring a chair to sit on while observing if you have a telescope that's low to the ground so that you don't have to spend the evening bent over. An adjustable observing chair works great, but an adjustable drummers stool works just as good and it's cheaper too. For dobsonian telescope owners a better suggestion than a chair is to build a base for under your telescope to raise it up. Seems to me I saw plans to build one somewhere on the Internet, but I just can't remember where. Hmm.... where was that? * Use a small table (such as a folding table) to hold your charts and accessories. This helps greatly. Make sure it's sturdy enough to not be knocked over too easily. I just use the tailgate of my truck, which works just as good as a table. The advantage here is... nobody has knocked over my truck.... yet. * If you are observing with binoculars bring a reclining lawn chair. Your comfort level will improve dramatically because you're not straining your neck looking up. Not only that but if you're lying back you will be able to hold the binoculars much steadier. * Another good binocular tip here.... When observing with binoculars that are hand held, hold them near the objective ends, not the eyepiece ends. You will be able to hold them much steadier.
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