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Gazing in the night sky
May 4, 2016
5 minutes read

About 6 months ago, I picked up a new hobby: Stargazing. Starting off with just naked eyes, I quickly realized that there is actually quite a lot to see without any optical equipment. Sky Map and Stellarium are incredibly useful applications for a dilettante like me.

Dark adjustment

Before any stargazing session, dark adjustment i.e. dilating the pupils completely to improve night vision, is essential. I turn off all kinds of lights in the house and listen to podcasts for a while (at least 30 minutes). I go out to stargaze when the outside looks brighter than inside.

Avoiding the bright lights from neighbours can be a challenge though. Moon’s an issue as well.

Constellations

The apparent magnitude (m) of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth. The smaller the number, the brighter a star appears.
- Wikipedia

At the time I started, the most identifiable constellation was Orion. Betelgeuse, reddish orange star in Orion, very quickly became my favorite star. It gets the designation α Orionis even though Rigel is the brightest star in Orion (β Orionis). Betelgeuse’s apparent magnitude varies between 0-1.3, making it at times the brightest star in Orion. The star is huge - 630 times the radius of the sun. It was the first star (other than the Sun) to be imaged beyond a point source.

Taurus is another constellation that I observed in my initial stargazing period. It extends over a large area, so not as identifiable. But it is a host for a unique star cluster: Pleiades. The 5-6 bright stars in the cluster are a singular sight with naked eyes.

Canis Major also has a significance for me as the host for Sirius (the brightest star). Its relatively close, being only about 8.6 light years away.

There were some other constellations as well, but I haven’t paid them too much attention. Listing some off the top of my head: Gemini, Puppis, Hydra and Virgo. But I couldn’t identify them without Orion / Canis Major as anchors.

Moon

Moon’s the most noticeable and obvious site in the sky. At times, based on the shape of the moon’s bright portion, I’d try to visualize how the Sun, the Moon and the Earth are positioned relative to each other. The 22° halo around the moon is also nice to look at. To be honest though, I am always more interested in the Moon’s absence, since it impacts the visibility of stars significantly. It also damages my eye’s dark adjustment.

Planets

The first 6 planets are readily visible to the naked eye. Although, Earth’s little too close to have an astronomical perspective. Because planets are at a distance and visible as extend objects, they don’t twinkle. This makes it easy to differentiate them from stars. Even Betelgeuse twinkles.

March this year, Jupiter was at the opposition (Earth being roughly in between the Sun and Jupiter) and had its closest approach to us. Hence, it was at its brightest.

Venus is always very bright (3rd brightest after the Sun and the Moon), but is visible near the Sunrise and the Sunset (hence called the morning/evening star).

Mars and Saturn as of now are located nearby. Mars is bright reddish in color and Saturn is yellowish in color.

22nd January 2016 was a interesting day for planet watching. The 5 planets were all aligned for the first time in over a decade.

The path that the Sun and the planets take also point toward the flatness of the solar system. Feels nice to get some empirical evidence of this, against just having this told.

Artificial objects

A few artificial objects orbiting the Earth can be seen as well. For them, the sunset happens later (or sunrise earlier) than us, providing us with the dark background and enough contrast for the sunlight they reflect. The International Space Station (ISS), because of its size ends up being brighter than even Venus. This NASA’s site can be used to plan an ISS sighting.

Iridium satellites’ flares are also noticeable at times. There are ways to plan their sightings, but I haven’t done that yet.

Limiting Magnitude (LM)

In astronomy, limiting magnitude is the faintest apparent magnitude of a celestial body that is detectable or detected by a given instrument.
- Wikipedia

I like to calculate the limiting magnitude. This would give me an idea of the light pollution and what I should expect to see. I notice light pollution in Pune is (unsurprisingly) more than that in Jaipur. From these charts, I calculated the LM at Pune to be about 4.5. I came to doubt that when I eventually started using Stellarium. The naked eye LM at my place is roughly 3.5 - 3.8.

I should give using the charts another try. At the time, I had used the Tau (using stars in/near Taurus) chart which has a magnitude gap of 1.62 between 3 and 4 visible stars.

Wonders

Stargazing results in multiple interesting and unsettling thoughts:

  • When I see a star, the photons hitting my eyes are 1000s of year old. For example: Light from Betelgeuse travels for roughly 643 years to reach us.
  • I are literally looking at the past of those stars. But again, at these scales, the concept of present can be doubted. Einstein talks about the The relativity of simultaneity in his book.
  • The insignificance of the Earth’s and us with it in the universe.
  • We most probably aren’t alone.
  • How amazingly useful constellations are in navigating the sky.
  • How made up constellations are and the irrational significance humans give to them.

Telescope

After a month of naked eye stargazing, I bought a telescope (similar to this one but with better eyepieces) from a local provider. I’ll write about my observations with that over the next few days.

Edit
The post on my experience with a telescope has now been published here.


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