how to see the milky way.
1.0 What is the Milky Way
2.0 Visible regions of the Milky Way
3.0 Where to see the Milky Way
4.0 The moon phase
5.0 How the Milky Way appears to the naked eye
6.0 Summary
0.0 Preface
The milky way galaxy is one of the most beautiful sights in the night sky, however the majority of people living in the developed world have never been able to see it.
This entry will aim to provide a guide on how to find the milky way in the sky, and what you can expect it to look like.
1.0 What is the Milky Way
The milky way is the glowing band of light that stretches across the night sky, the combined starlight of billi​ons of stars that form the galactic core and the spiral arms.
Because the earth is located inside a spiral arm, we're able to view the milky way in all directions, with the bright core region on one side, and the neighboring spiral arm on the other.
What people generally think of as 'seeing the milky way' is the view of the galactic core, the brightest region that represents our view inward toward the center of the galaxy. Looking toward this center, you'll the see the galactic core as a bright line across the sky. The reason why it appears as a line is simply because the milky way is very flat, much like a fried egg in shape, and because we are inside that flat disk, we therefore view it from side on.
2.0 Visible regions of the Milky Way
Because the earth is in orbit around the sun, throughout different times of the year the sun will block our view of various regions of the milky way. Because of this, the galactic core is only visible between the months of March - October approximately, with the best views coming in the months of June and July.
Likewise, the best views outward towards our neighboring spiral arm come during the months between November - February, with constellations like Orion and Taurus alongside this region.
Some other regions of the milky way are the great rift, the crux region, cygnus and scorpius. However, while these areas all make for nice photographs, the galactic core is by far the brightest and most visible to the naked eye.
3.0 Where to see the Milky Way
Finding an area where the night sky is dark enough to see the milky way can be challenging, especially with the ever growing issue of light pollution. A useful tool for finding dark sky locations is this light pollution map.
Anywhere brighter than orange (bortle 5 and up) will be too bright to see the milky way at all, and even the yellow regions will need perfect viewing conditions (latitude, humidity etc.) to see any milky way glow. Green and blue regions (bortles 3 and 4) are where you begin to see the milky way core, particularly if it's high in the sky. And once you reach a dark region (bortles 1 and 2) you'll get a clear view of the milky way. It's also important to ensure that the bortle regions surrounding you are dark as well, because if you're in a dark area, but you have to look through a bortle 5+ to see the milky way core, you won't be able to see much at all.
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Additionally not all latitudes will have the same view of the milky way, as the galactic core sits at around -30 degrees declination between the constellations of sagittarius and scorpius.
Because of this, latitudes around -30 degrees (the 30th parallel south) will see the milky way high in the sky, while latitudes greater than 60 degrees north will not be able to see the milky way (core) at all. The further north you are from the 30th parallel south, the lower you'll see the galactic core in the southern skies, and likewise the further south you go the opposite is true.
Elevation is also useful when viewing the night skies, as the higher up you are, the less atmosphere you'll need to look through to see the stars and milky way.
image 1: self portrait under the southern milky way
image 2: the milky way viewed from above (credit: NASA)
image 3: the galactic core (center of the milky way)
image 4: the bortle/light pollution scale (credit: Stellarium)
image 5: the night sky under a full moon
4.0 The moon phase
Another important thing to consider when attempting to find a dark sky location, is the moon phase. A full moon is so bright that it can turn a bortle 1 sky into a bortle 5+ sky, meaning the milky way won't be visible at all even from the darkest place on earth. Therefore, it's important to know the current moon phase and ensure that you're stargazing on a new moon night (or a few days either side). The application Stellarium is a useful tool for simulating the night sky for any given location and date.
5.0 How the Milky Way appears to the naked eye
The milky way is easily visible to the naked eye, however because most people have only seen the milky way through photographs, there is some confusion around what it actually looks like.
Our eyes contain two types of light detecting cells, rods and cones. The cones aren't very sensitive to light, but have great color detection, and as such are used for daytime vision. Rods however cannot see color, but are much more sensitive to light and therefore are used for night vision. The consequence of this is that humans can't see any color in the milky way, because it's the rod cells within the eye that are sensitive enough to see it.
See here for a more accurate edit of this comparison.
6.0 Summary
To summarize, the best way to see the milky way (core) is by travelling into the southern hemisphere during the months around winter (may - august), finding a location free of light pollution during the new moon, and then simply looking up after nightfall. A clear sky would obviously help too.
image 6: the night sky with no moon
image 7: the milky way to the human eye vs a camera