Deep Sky Observing: The Astronomical Tourist

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Lemmon SkyCenter. Where else can you find a dark-sky destination that offers updates from those involved directly in the Phoenix Mars Lander Mission? This Smithsonian Institution Observatory is located on Mount Hopkins, with a visitor center at the base of the mountain, about thirty-five miles south of Tucson. The Visitors Center is open Monday through Friday, offering an extensive collection of exhibits and an outdoor patio with two spotting devices, a power telescope, and wide-field binoculars. These tours last about five and a half hours and include a stop for lunch, which visitors bring for themselves.

Be sure to check the details about the tours because they are not for everyone because of their length, the altitude and exertion required. What a great idea to offer one more opportunity to enjoy the same night skies that allow professional astronomers to do there on Mount Hopkins. Of all the destinations in the Southwest, the Grand Canyon is probably the most well-known. It attracts eager visitors from around the world, but few stay long enough to see the other view, the one that lies above the grandeur of the Grand Canyon. Staying overnight and actually getting outside after dark is one of the most awe-inspiring experiences that this priceless treasure of North America has to offer.

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If you make this more than a daytime stop, you can be one of those privileged to visit the Grand Canyon that is a premier dark-sky destination. Once a year stargazers get the opportunity to join in the fun at the Grand Canyon Star Party. Just register, make your housing arrangements and plan to bring the family to enjoy a Grand Canyon dark sky adventure on the South Rim. Not to be outdone, the North Rim now has its own star party. Nevertheless, it does attract stargazers from around the world.

Their dark sky sites are only ten minutes from downtown Sedona. He uses a wide range of instruments during a tour, including large astronomical binoculars and telescopes from small refractors to his large home built telescopes. What more could one ask for from a bed and breakfast inn? Want a double dose of astronomy? This small, only two guest rooms, but very special bed and breakfast inn, offers guests a beautiful and comfortable place to stay, along with astronomy programs and dark-sky viewing from its own observatory, modern telescopes, space binoculars and a brass planetary refractor.

In addition to breakfast, with advance reservation, your host will also cook dinner for his guests. But, be sure to spend some time outdoors, enjoying the magnificent views and the wildlife strolling across the landscape. The hill-top setting is perfect for stargazing. Guests receive a discount on the nightly astronomer-guided night sky viewing sessions.

This small inn offers four themed rooms with private bath. Breakfast is served and a kitchen is available so that guests may prepare other meals for themselves. Travelers looking for a destination to enjoy the beauty of the universe and world-class bird watching can rent a private home in Arizona Sky Village. This rental includes access to both the Community Observatory and Birding Station. Apparently, they take their name, Stargazing for Everyone , very seriously because they do seem to have programs for all groups and all ages.

Their astronomy "field trips" reach more than 75, stargazers every year. Stargazing for Everyone hosts activities that range from free public events at local parks to presentations for corporate groups. Schools, Scouts, and homeschoolers can learn about the universe and telescopes.

Observing Secrets of Deep-Sky Objects Revealed

This technique is called averted vision. You'll be using it almost all the time when deep-sky observing. Avoid placing the object very far on the "ear side" of your center of vision; it may fall on the retina's blind spot there and vanish altogether. In practice, finding how far to avert your vision is a matter of trial and error.

Not enough and you don't get the full benefit; too much and you lose the ability to resolve details. Your peripheral vision is highly sensitive to motion. Under certain conditions, wiggling the telescope makes a big, dim ghost of a galaxy or nebula almost pop into view. When the wiggling stops, the object disappears again into the vague uncertainty of the sky background. But under other conditions, just the opposite technique may work, especially with objects that are both faint and tiny. According to Colorado astronomer Roger N.

Explore deep-sky delights |

Clark's book Visual Astronomy of the Deep Sky, some studies indicate that the eye can actually build up an image over time almost like photographic film — if the image is held perfectly still. But in the dark, claims Clark, it's a different story. A faint image may build up toward visibility for as long as 6 seconds if you can keep it at the same spot on your retina for that long. Doing so is quite contrary to instinct, because in bright light fixating on something tends to make it less visible with time.

Long exposure times might possibly be one reason why an experienced observer sees deep-sky objects that a beginner misses. Perhaps the veteran has learned, unconsciously, when to keep the eye still. It also may help to explain why bodily comfort is so essential for seeing faint objects. Fatigue and muscle strain increase eye motion. Conventional wisdom holds that low magnification low power works best for deep-sky viewing. After all, low power concentrates an extended object's light into a small area, increasing its apparent surface brightness the amount of light hitting a given square millimeter of your retina.

But, as Roger Clark has documented, this assumption is usually false. High powers should do better on many faint deep-sky objects. The reason is subtle but important, so we'll go into some detail. Unlike a camera or other purely mechanical lens system, the eye loses resolution in dim light. This is why you can't read a newspaper at night, even though you can see the newspaper, and even though your large nighttime pupil should theoretically resolve the letters even more sharply than in daylight. This is almost the size of the Moon as seen with the naked eye. So, details in a very faint object can be resolved only if they are magnified until they appear tens of arcminutes across.

In many cases, this can require using extremely high power! Why does the eye work this way? The explanation lies in how the visual system has adapted to cope with night. Photographic film records light passively, but the retinal nerve system contains active computing power.

Sketches of Astronomical Objects

In dim light, the retina compares signals from adjacent areas. A faint source covering only a small area — such as a small galaxy in the eyepiece — may be completely invisible at the conscious level.

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But it is being recorded in the retina, as evidenced by the fact that a larger galaxy with the same low surface brightness is visible easily. In effect, when rod cells see a doubtful trace of light they ask other rods nearby if they're seeing it too. If the answer is yes, the signal is passed on up the optic nerve to the brain. If it's no, the signal is disregarded. When an image is magnified by high power, its surface brightness does indeed grow weaker.

But the total number of photons of light entering the eye remains the same. A photon is the fundamental particle of light. Experiments show that most people can detect as few as 50 to photons per second. It doesn't really matter that these photons are spread over a wider area; the retinal image-processing system will cope with them. At least within certain limits. A trade-off is needed to reach the optimum power for low-light perception: enough angular size but not too drastic a reduction in surface brightness.

What does all this mean for deep-sky observers? Simply that it's wise to try a wide range of powers on any object. A judiciously chosen, high-quality zoom eyepiece makes this a breeze. You may be surprised by how much more you'll see at one power than another. A long-focus telescope is simply more likely to be used at high power!

Map of Dark Sky Protected Locations

It's also more likely to have high-quality optics, because "slow" mirrors and lenses are easier to manufacture well than "fast" ones. Left: We're accustomed to beautiful color images of the Orion Nebula M But most deep-sky objects manifest themselves in shades of gray at the eyepiece right. Deep-sky objects disappoint beginners not only by lacking obvious detail, but also by lacking the brilliant colors recorded in photographs.

In order to show us color, a deep-sky object must have a high enough surface brightness to stimulate the retina's cone cells — and the list of deep-sky objects this bright is short. The brightest parts of Great Orion Nebula M42 qualify, as do some small but high-surface-brightness planetary nebulae. The ability to see color in dim objects varies greatly from person to person, and surprises may occur.

Averted vision is not the way to look for color. The cones are thickest in the fovea, so stare right at your object. In this case, the lowest useful power should work best. A large telescope aperture is especially advantageous for those who seek to see color in deep-sky objects. Persistence pays. Using a premium mm 4-inch telescope, Stephen James O'Meara has seen hundreds of deep-sky objects from the Big Island of Hawaii left.

Every deep-sky observer, even those with computer-pointed telescopes, will appreciate highly detailed star charts such as those in Uranometria If you know exactly where a faint deep-sky object is supposed to be located in your telescopic field of view, you will be able to detect objects about a magnitude fainter than you could otherwise see with certainty. That's about like increasing your telescope's aperture by 60 percent.


A inch becomes a inch. Alternatively, a portable computer at the telescope can display the very detailed and flexible star-charting software available from many sources. Red cellophane over the screen will save your night vision. When you pour all your concentration into examining a deep-sky object at the very limit of vision, does it get even harder to see after 10 or 15 seconds?

Does the sky background brighten into a murky gray? Diagnosis: you're holding your breath without realizing it.

Low oxygen kills night vision fast. An old variable-star observer's trick is to breathe heavily for 15 seconds or so before trying for the very dimmest targets.

And keep breathing steadily while you're looking.