Facts about the Earth
The Earth is the third planet from the Sun. It is situated at the distance of about 93 million miles from the parental star. The Earth`s orbit is elliptical. The Sun, the Moon as well as all the stars rise in the East and set in the West due to the rotation of the Earth around its axis. The Sun and the Moon moving together create the eclipse, when the Moon stands between the Earth and the Sun we see a solar eclipse, at that moment the Moon passes in front of the Sun obscuring it. In the opposite case, when the Moon is between the Sun and the Earth, the Earth's shadow covers the Moon, and we observe a lunar eclipse.
The Earth is a rocky planet like Mercury, Mars, and Venus with a solid surface and the presence of mountains, valleys, canyons, plains, and etc. The Earth is the largest inner planet. Our planet has the highest density, the strongest surface gravity, and the strongest magnetic field among these four planets which is generated in its intracrustal sources. The Earth is different from other terrestrial planets as it contains the ocean which covers 70% of the surface. Of all known planets, only the Earth has the oxygen-containing atmosphere, extensive water oceans and most importantly — the biological life. (nineplanets.org)
Measurements of Light Pollution Effects on Stargazing
Light pollution greatly impedes the use of optical telescopes. The principle of the telescope is that it collects the light of the stars and other objects by using lenses or mirrors. In an urban area with high light pollution, telescopes collect not just the light of stars but more the light of lanterns, reflected and scattered by water vapor and dust that the air is filled with. In addition, light pollution reduces the contrast between celestial objects and the sky. This brings to nought many of the advantages of the telescope and forces astronomers to seek places away from urban settlement areas with their artificial lighting to dark, uninhabited places which are often uncomfortable, or to use filters that reduce the light pollution.Thus, light pollution seriously hampers not only observations of amateur astronomers but of astronomical observatories as well. Modern observatories are built far from large cities to avoid light and atmospheric pollution.
Depending on the size of the city, the level of light pollution can vary -- in my city there are clearly seen only the brightest stars in the sky.
Weather Conditions for Successful Stargazing
Of course, before starting observations, we must know the weather forecast. Modern methods of computer modeling of the weather provide a fairly high accuracy of the forecast for the next two or three days, and on the Internet there is satellite imagery of cloud cover over large areas in near real time. Comparison of weather forecast with satellite images allows predicting clear nights and avoiding annoying disappointments with sufficient degree of accuracy.
The atmospheric conditions for observations at the same site vary from night to night. The atmospheric turbulence leads to the fact that images of astronomical objects, visible through the telescope, have a blurring effect (indicator of the atmospheric turbulence is the twinkling of stars when observing them with the naked eye). If the atmosphere is turbulent, it makes sense to use lower magnifications, and then the distortion will not be so noticeable. If the atmosphere is calm, stars are almost not twinkling; the images in the telescope eyepiece are still and not blurred.
The atmosphere is more stable near the zenith than near the horizon, where a ray of light from an astronomical object passes a greater distance through the atmosphere. In addition, the stability of the atmosphere improves after midnight when most of the heat, accumulated by the Earth's surface during the day, dissipates into space.
The most important condition for the successful observation of dim astronomical objects is the transparency of the terrestrial atmosphere: absence of moisture, smoke and dust. All these substances scatter light coming from an astronomical object reducing its visual brightness. Also it is beneficial to conduct observations in anticyclonic conditions with high-level wind. The magnitude of the faintest stars visible to the naked eye says about the transparency of the atmosphere at night.
Therefore, for successful stargazing it is not enough to just have a cloudless sky and a warm season, it is extremely important to have a stable and transparent atmosphere, anticyclonic conditions, and to seek dark places, far from urban areas.
Works Cited
Nine Planets. “Earth Facts”. nineplanets.org. (n.d.) Web. Accessed on May 1, 2016 at <http://nineplanets.org/earth.html>
Teikari, Petteri. “Light Pollution: Definition, legislation, measurement, modeling and environmental effects”. petteri-teikari.com. September, 2007. Web. Accessed on May 2, 2016 at <http://petteri-teikari.com/pdf/Teikari_LightPollution.pdf > 19-20>
