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Methods and techniques for the astronomical application of binoculars
Apr 11, 2018

Do not think that only astronomical telescopes are suitable for astronomical observations. Even a pocket-sized 10X25 binocular can collect dozens of times more light energy than the eye and can see more dark objects than the naked eye. And its light, large field of view, and low price are unmatched by astronomical telescopes. For an amateur with a professional astronomical telescope, handheld binoculars still have an irreplaceable position. The most popular hand-held astronomical binoculars at home and abroad are 7×50, because his exit pupil is relatively large. When observing nebulae, comets and other objects, the surface brightness is high, while the multiple is low, the field of view is larger, and the target is found. More convenient. In an excellent observation environment, 150,000 stars can be seen through it. Even in a city with serious light pollution such as Shanghai, many stars can be seen. There are still 10×70 telescopes with such large pupil diameters, but I am afraid I will use a stent. If your pupil is less than 7mm, you can choose 10x50, 15x70, 20x80 higher magnification. For star clusters, dense double stars, and observing targets such as galaxies with very small viewing distances, the multiples can be higher, such as 20×60. If used for lunar and planetary observations, telescopes with higher magnification are more effective. In general, telescopes with more than 6 times can see the craters on the moon's surface (when the observations are best at the moonside, the craters will not be noticeable due to the light at the full moon). Jupiter’s satellites can also be seen clearly. More than 15 times you can see Saturn's aura, high-power binoculars need to be observed with the support, but doing this observation is not the strength of binoculars, it is best to use astronomical telescope.


Star clusters, nebulae, and galaxies

Now, more and more astronomers are keen to observe deep-sky objects such as clusters, nebulae, and galaxies, and see this as an effective way to train their observational skills. Binoculars are more suitable for this task than telescopes with similar calibers. One of the items that most motivates observers to work hard and can always appreciate the fun of observation is to find Messier objects as much as possible. Of the 109 Messier objects, more than 80 out of a total of 109 Messier objects can be observed with a 7×50 binoculars, and some of them are very dim. You can use them to test your observation skills. . Before and after the vernal equinox every year, the Sun is in Pisces. At the same time, apart from the thirst-shaped globular cluster M30, all Messier objects can be observed on the same night. The foreign astronomers vividly call this the Messier celestial marathon. Race." With a binocular with a diameter of 80 mm or more, it is perfectly possible to observe about 100 Messier objects at night, that is, to use smaller binoculars to enjoy more than half of Messier objects overnight. It is also very interesting. Observations should be made on a sunny, moonless night before and after the vernal equinox.


Double Stars and Variable Stars

Observing clusters, nebulae, and galaxies must have a clear, dark sky background in addition to suitable instruments. Astronomers who live in the city are oblivious to the effects of light pollution, and they rarely observe these objects. However, it doesn't matter. There are two kinds of celestial objects that are much less affected by light pollution. They are binary stars and variable stars. Observing binaries is a challenge to the quality of binoculars and the observer’s eyesight. Many astronomical books published in China have binary star catalogs, such as "Star Map Handbook" and "Astronomer Observation Manual". You may find your own observations. The results are not the same as those described in the star list, such as distinguishing between binaries that are considered to be indistinguishable by binoculars, or observing colors not mentioned in the star catalog. In fact, it is not surprising that no two people will make the same description of the same celestial body. With the improvement of observation skills, the details of celestial bodies will become more and more obvious. The color of double stars is a good example. Many double stars are pure white for the first time. As the experience grows, they will find that each of the two stars has its own different color. Slight defocusing will make the color of the binary more visible. Like the bright planets, usually the most hazy weather is suitable for observing binary stars because the atmosphere is very stable and the double stars are most easily discerned. Astronomers provide variable observation observations, which are also helpful for studying such objects. The estimation of the brightness of variable stars is not as difficult as most people think, because the human eye has a strong resolution to the light and darkness of light. The accuracy of visual metering can be as good as 0.1 stars by comparing with standard stars of known brightness in the vicinity. When observing the variable stars, the exact time for estimating the magnitude should be recorded. The variable-variable observers are accustomed to using the Julian date, and the Julian days can be found in the “Astronomical Almanac”.


New stars and comets

Finding new celestial bodies is also very suitable for binocular observation projects. The new celestial bodies here mainly refer to new stars and comets. This is a very meaningful job, and it requires not only the observers to have the appropriate instruments but, more importantly, determination and perseverance, plus a little bit of luck. The discovery of each new celestial body is the result of hundreds of hours of work by the observer near the telescope. To find a new star, there is only a 50 mm diameter binocular. Magnification can be slightly higher, but do not exceed three times the caliber (centimeters). In addition, a good star map is also needed. It is better to search for new stars using hand-drawn star maps than to use photo star maps because the variable stars are all marked in the hand-painted star maps, so that it is possible to avoid changing the brightness of a star. It is mistaken for a new star. The "new celestial body" may also be a bright asteroid or a Uranus or a Neptune before and after the Red Sun. We must carefully observe whether it has relative motion with the surrounding stars, and check the "Astronomical Calendar" of the year to confirm that it is not a celestial body in the solar system. , report this finding to an astronomical agency. Statistics show that the new stars appear on both sides of the galactic plane10. Within the scope of the survey, especially from Cygnus to Sagittarius along the Galaxy, the highest rate of occurrence. Finding a new comet must have a binocular with a caliber of at least 80 mm, and the location of the observation should be far away from cities, factories and mines. In spite of these harsh conditions, finding a comet is still the most enthusiastic activity for astronomers. There are many articles in the article “Astronomy Enthusiasts” that introduce the search method. We will not repeat them here.


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