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“Anyone who does not … gaze up and see the wonder … of a dark night sky filled with countless stars loses a sense of their fundamental connectedness to the Universe.” -Dr. Brian Greene

Credit: How to Photograph the Milky Way:A Complete Guide | Expert Photography

Introduction

You don’t always need a telescope to get started with astronomy, not even a smaller one. All you need to do is look up and experience the heavens above. On a clear, dark night, thousands of stars could be seen with naked eyes. Stand beneath the starry background and listen to the Universe conversing with you while the stars play the soothing melody. This, not just sounds overwhelming, but is an unparalleled experience.

What do you see when you look up? Or to frame it the other way- What can you see when you look up? The answer might be the Moon or the Evening Star, assuming that you are viewing the sky shortly after the sunset. The answer could also be the Stars, the Planets (the five planets visible to the naked eyes) or maybe even the satellites like the ISS, if you are viewing the night sky. Let us explore this further and learn a bit better.

Dark Adaptation

Before going out and looking up, make sure your eyes are adapted to the dark. On entering a dark room, you cannot see anything at first. But slowly things become visible and you get a dark vision. This happens due to the expansion of the pupils in our eyes. Due to this increase in size, they are capable of collecting more light and hence giving us a dark vision. Same is the case with our eyes when we go out to observe the night sky. At first, only the bright objects are visible but as the pupils expand and are able to gather more light, even the faint stars become visible. This is the dark adaptation.

It is advised not to use a normal flashlight during the night sky observations because the bright white light will cause the pupils to contract and hence lose the dark adaptation. Instead, a red flashlight can be used because it is not as bright as a normal flashlight and won’t affect the dark adaptation of our eyes.

Objects in the Sky

What objects can you see in the sky depends on the following major factors:

  1. The time of observing
  2. The place of observing
  3. The sky conditions

There are a few objects that are visible just after the sunset like the Moon, the Evening Star- Venus or satellites like ISS, HST etc. There are days in a month when the Moon is not visible and that is the best time to chase the stars. If you observe the sky for a few hours after the sunset you can see the stars appearing- the brighter ones first and then the dim stars as the night falls. On a clear, dark sky you can see thousands of stars, some of the five planets visible to the naked eyes- Mercury, Venus, Mars, Jupiter, and Saturn and some of the Deep Sky Objects (DSOs) like the Pleiades Star Cluster, Hyades, Andromeda Galaxy, the two Magellanic Clouds etc. Also, the objects depend on the time of the year when you are viewing the sky. The Summer skies are different from the Winter skies and the Monsoon Skies.

The sky above your head is different from the sky beneath your feet. To frame it better- the sky looks different from the northern hemisphere as it looks from the southern hemisphere. The objects visible in the night sky vary with locations. For example, Polaris- the North Star is visible only to the folks living in the northern hemisphere while the Crux- the Southern Cross is visible only from the Southern Hemisphere. The Small and the Large Magellanic Clouds (DSOs) can be seen only from the places which are towards the South.

Time and location decide what objects can be seen, but how bright and how better will they be seen depends on the sky conditions. Sky conditions include various factors, namely, the weather, the artificial light pollution, and the Moon. If the sky is cloudless then you can see more stars and objects than seen in a cloudy sky. If the sky is hazy then only the bright objects are visible but they too appear dim. It is always better to observe the sky away from city lights because the light pollution hinders the view for faint stars and objects. Similarly, the moonlight makes it nearly impossible to view the stars and various other DSOs which are otherwise visible to the naked eyes. So, clear, dark night skies are the better ones to observe and enjoy the beauty of this infinite Universe.

Now, since, we have talked about the factors which decide your view of the night sky, let us categorize these objects and learn to differentiate between them.

Categorizing and Differentiating

The objects that can be seen with naked eyes are the Moon, the five planets, the stars, the satellites and a few DSOs. The Moon can be distinctly identified but it is difficult for the beginners to differentiate between planets, stars, and satellites. If you see any object then answer these two questions in a yes or no:

  1. Is the object twinkling?
  2. Is the object moving across the sky?

The combination of the answers to the above questions will help in deciding whether the object is a planet or a star or a satellite. If the object is neither twinkling nor moving then it is a planet. If the object is twinkling and not moving then it is a star. And if it is not twinkling and moving then it is a satellite. And what if the object is moving and blinking lights? Are they aliens, who have come to visit you in their spaceship? Have they come to abduct you? No need to worry, it is then an airplane. But you never know, so, always look up.

To differentiate among the five planets, you need to observe carefully. But before this you need to know whether they are visible during the night you have planned your observations for or not. If yes, then here are a few points that can help differentiating among them. The one that appears pinkish-red is Mars. If there are two planets close to each other- one very bright and other a bit dimmer- both showing yellowish tint, they are Jupiter and Saturn respectively. The one which is possibly the brightest of all the ‘non twinkling’ dots is the Evening Star Venus. There are times in a year when Venus is seen in the pre-dawn skies and is called the Morning star. It appears whitish. Mercury is a bit difficult to find because being the smallest, it is usually dimmer than the other planets.

Not just planets, you can also view some DSOs with naked eyes. Some of them are the Pleiades (M45); Hyades; Double Cluster — NGCs 869 and 884; Beehive Cluster (M44); M7; Coma Berenices Star Cluster (Melotte 111); Andromeda Galaxy (M31); the two Magellanic Clouds; the southern open cluster IC 2391, and Omega Centauri globular cluster (NGC 5139).

In the parentheses, are the catalog designations of these Deep Sky Objects. NGC stands for New General Catalogue, M stands for Messier Catalogue, and IC stands for Index Catalogue.

Credit: Orion, Jupiter and Pleiades from Cape Espichel | Miguel Claro Art Science Photography

The features of these DSOs cannot be identified through naked eyes. However, you can differentiate between various DSOs. The Star Clusters usually look like a dense patch of stars in the sky. Galaxies like the Andromeda Galaxy appear as a fuzzy blob in the sky. The two Magellanic Clouds are the satellite galaxies of the Milky Way and appear like a fuzzy patch of stars in the southern sky.

Where to look?

Now, that is a difficult question because you cannot always know the positions of these objects in the sky. So, there are Sky Maps and Planispheres to assist you. Sky Maps are the maps of the entire night sky which basically gives an idea of what all we have in our night sky. However, the Planisphere is a much handy tool, since sky maps are huge and cannot tell what is visible for the particular night. A planisphere is a simple handy tool which shows a map of the stars that are visible in the night sky at any particular time. By rotating a wheel, it shows how stars move across the sky through the night, and how different constellations are visible at different times of year.

Though Planisphere is a simple handy tool, it still requires a bit of practice before you can use it comfortably. However, there are various open source, free web and mobile apps which can show the live view of the entire night sky. Moreover, the planisphere cannot show the satellites that are passing above us but the websites and mobile applications can. They are really easy to use and it is highly suggested to use them in Night Mode. The Night Mode turns everything on the screen in the shades of red, black and grey which is not bright and hence your eyes will remain adapted to the dark.

Credit: Night Mode | Stellarium Web

Two of the open source websites are stellarium-web.org and theskylive.com. The free mobile applications are Star Chart, Sky Safari, Sky Map, Star Walk 2, Sky View, SkEye etc.

Patterns among the Stars

Constellations are the regions of the sky which have a star pattern in them, usually representing some animal or mythical figure. As a beginner, it is difficult to make up constellations without any help. However, there are few patterns which are easily identifiable like Orion, the Big Dipper, Cassiopeia, Cygnus, Scorpius etc. Nonetheless, the stargazing applications can be a great help. Just point your phone at the sky and easily identify the constellations. Sky Maps can also be used for this purpose.

As a practice exercise, you can try identifying and making up these constellations by tracing them with a green laser pointer.

What’s More?

Apart from all the objects and constellations that are visible in the night sky, the best treat is the Milky Way Band. On a dark, moonless night, our galaxy, the Milky Way, extends a spectacular band across the sky.

Credit: Florida Milky Way Astrophotography | BGPictures

The best time of the year to observe this band is from July to September. Many DSOs can be found across this band.

Another surprise in the bag are the meteors. As the sky gets darker, you may see a streak of light. This is a meteor or a shooting star, a fragment of rock that burns up in a blaze of heat and light as it plunges from space into Earth’s atmosphere. Throughout the year, there are various meteor showers going on in the night sky which put up a spectacular show of cosmic fireworks. These meteors can be reddish, bluish, greenish, whitish or yellowish in color depending on their composition.

A Homework Exercise

Now, you probably know that there is so much that you can do without a telescope or a pair of binoculars. So why wait? Plan your observation now using stargazing apps. Decide the date, mark the hour and experience skies with your eyes.

References

[1] “The Eyes Have It – Deep-Sky Observing Without Equipment.” Sky & Telescope, 12 Nov. 2018, skyandtelescope.org/observing/deep-sky-naked-eye/.

[2] Rao, Joe. “When, Where and How to See the Planets in the 2020 Night Sky.” Space.com, Space, 1 Jan. 2020, www.space.com/39240-when-to-see-planets-in-the-sky.html.

[3] Shanahan, Jesse. “The Best Free Stargazing Apps Of 2018.” Forbes, Forbes Magazine, 11 May 2018, www.forbes.com/sites/jesseshanahan/2018/05/09/the-best-free-stargazing-apps-of-2018/.

[4] Stellarium Web Online Star Map, stellarium-web.org/.

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Manreet

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