Over the past few months, I have been engrossed in capturing images for my latest astronomy book and this has generally meant targeting faint deep sky objects like galaxies and nebulae.
While looking for these deep space objects, I have felt somewhat comforted as, every night without fail, I get to see the beautiful sight of a red star-like object rising in the east to greet me. This is the planet Mars and on the April 8 it will rise just as the sun sets and be visible all night.
"Opposition" is the official name that astronomers give this event and it comes from the fact that Mars and the sun are located at opposite points in the sky. These oppositions of Mars occur every two years, so this month is a great time to observe the red planet. So, dust off your telescope and let's take a closer look.
It is easy to find Mars at the moment, in the hours that follow sunset take a look low in the east and you will be able to easily spot it next to the bright blue/white star Spica in the constellation Virgo.
Spica is 261 light-years away, which means it took light from Spica 261 years to travel through interstellar space to reach us. By contrast, the reflected light we'll see from Mars on April 8 will be just 5.16 minutes old because it is so much closer -- only 93 million kilometers away, or 5.16 light-minutes from Earth.
The distances between Mars and Earth during opposition vary; in 2012 it was a little more distant at 100.7 million kilometers, but in 2018 it will be offering us views that we have not seen since 2003 when it will be just 57.6 million kilometers away.
While Mars is easily visible to the naked eye about 7 degrees to the north of Spica, to really get a good view you will need a telescope. Magnifications need to be at least 200x to be able to see some of the surface details of the planet and that means ideally you will need a telescope that has an aperture (diameter of main mirror or lens) of at least 10 centimeters.
With a setup like that, you will be able to see the polar caps of Mars that are made up primarily of carbon dioxide ice. You may also be able to glimpse the region in the southern hemisphere of the planet known as Syrtis Major, a large area of dark subsurface rock that is poking up above the red dusty surface material of the planet.
Just north of the equator is the large shield volcano known as Olympus Mons and, while it is a challenging object to spot, it is easier to detect clouds that often form around its summit.
To maximize your chances of getting a good view, set up your telescope during the afternoon so it can cool down; thermal currents in the tube can significantly affect what you can see. Also aim to observe the planet when it is nice and high in the sky, which will mean you are looking at it through less atmosphere.
It is worth investing in a set of filters for your eyepieces, too, as this can markedly improve your view although the choice of filter is very much one of personal preference. Filters are usually described by their Wratten Number (named after their inventor) and their color. My preference is to use a #82A Light Blue filter to enhance detail in the polar caps; a #12 Yellow filter to help to detect clouds; and a #23A Light Red to enhance surface detail. But do not be afraid to experiment with others.
If your telescope is smaller than about 20 cm (or 8”) then steer clear of the darker filters, otherwise the view of your red planet close encounter will be too dark to enjoy.