Most people who get their first telescope will spend their first nights looking at the Moon. And the Moon is certainly a worthwhile target. But it is the planets that usually draw their attention next.
This guide will be about observing Venus, the second planet from the Sun, and the third brightest object in the sky. When Venus is in the sky it is brighter than any star.
However, Venus is not always in the sky. As it orbits around the Sun, moving behind the Sun, it moves out of our view.
Venus, like Mercury, is closer to the Sun than Earth. The result of this is that it is never far from the Sun, from our vantage point. In fact, it is never more than around 47 degrees away.
On average, Venus is about 67 million miles from the Sun. Earth’s orbit averages about 93 million miles. Venus’ year is 224.7 Earth days vs. Earth’s year of 365 days. So Earth and Venus can be very close or very far apart as we travel around the Sun.
At its farthest distance from Earth, when we are on opposite sides of the Sun, Venus is about 162 million miles away. However, every 584 days the orbits of Earth and Venus place us at our closest positions, about 25 million miles apart. That is closer than we ever get to Mars, our other neighbor planet.
When To See Venus In The Sky?
Venus is covered with clouds which are highly reflective. To the naked eye, in binoculars, and in a telescope it appears as a bright ball. It shines brighter than any star in the sky.
However, because of these clouds, you won’t be able to see the venus’s surface. And Venus has no moons to observe.
The fun thing about observing Venus is that Venus goes through phases, similar to the phases of our Moon. You can observe these phases and track them as Venus and Earth travel along our respective paths around the Sun.
In 2019 Venus was visible in the morning. Early in the 2019 calendar year, it reached around 25 degrees when it was easily viewed before sunrise. However as we proceeded into May Venus dropped lower and lower to the Horizon each day, being very near the horizon at sunrise by the end of May. After that it became difficult to view as it was too close to the Sun, to safely view. It then proceeded around the other side of the Sun.
Come September Venus will return as the evening star. However, hold off trying to use your telescope till December when you will have a better separation from the Sun, as the Sun sets. It will be higher and higher in the sky as the months proceed, meaning further and further from the Sun as we proceed through to May 2020. So plan your Venus viewing for this period.
A great way to plan for viewing Venus is to use one of the Planetarium programs. My favorite is Stellarium. This application can be downloaded for Windows, Linux or Mac OS and it is free.
It is also available for smartphones and tablets for a very small charge. You can find it in the app store.
Another fun tool is to view Venus on Google Maps. Yes, they have the planets in Google maps. Who knew?
You might expect that you would be able to watch Venus transit across the face of the Sun frequently, but that is not the case. The plane of Venus’ orbit is 3.4 degrees off from Earth’s plane of orbit so these transits of Venus across the face of the Sun happen very rarely.
The last transit was in 2012 which was a huge event within the astronomy community. Unfortunately, I will not be around to see the next one which will occur in 2117. But perhaps you will be around to see it. I hope so.
The picture is a screen capture from the Stellarium program I referenced earlier. It depicts the sky on February 10, 2020, just as an example so I can explain how to find Venus.
Notice that the direction we are facing is 180 degrees, or directly South. There is an orange line shown across the image, the Ecliptic line. This is the path across the sky traveled by the Sun, Moon and all of the planets. Notice that Venus is shown on the Ecliptic.
The Ecliptic is always along the southern sky. So, if you are looking for Venus or any of the planets, watch the path traveled by the Sun and Moon and you will know where to look. Now it is just a matter of knowing when to look and were on the Ecliptic to find them.
Again, I will encourage you to download Stellarium and install it on your computer. Play with it and learn to use it. If you search on YouTube you will find plenty of videos on how to use Stellarium.
What Equipment Do You Need to Observe Venus?
Because Venus is so bright, you can easily see it with the naked eye even in very light polluted areas. And you can see it with binoculars.
The best way is with a telescope. Even a small telescope, say 60 mm in aperture, can show you Venus and allow you to see it go through its phases. I would recommend using a magnification of 50X or higher while observing venus using a telescope.
I have found the use of a Moon filter can be helpful. This is like putting sunglasses on your eyepiece. The filter screws on to the bottom of the eyepiece. Of course, as the name suggests, the primary use of this filter is for observing the Moon.
Moon filters come in a variety of densities. The number provided with the filter indicates how much light passes through. I typically use a 25% moon filter for viewing Venus if all I see is a bright ball of light rather than the disk that is the planet.
Venus is so bright that the image in the telescope eyepiece can be of a white ball, but if you tone it down with a moon filter you can reduce that glare and begin to see the disk of the planet and the phases.
The Astronomical League has a planetary observing program that includes Venus.
A fun exercise would be to follow Venus through its phases, keeping a notebook of each night’s phase, where you observed Venus in the sky and include a drawing of the phase. Record what time you observed and what equipment you used. If it is a telescope, include the aperture, focal length, what eyepieces you used and what filters, if any.
Venus is a great target for new observers. It is easy to find if you know when and where to look. It can be observed naked eye or with binoculars, but it is best observed with a telescope. It can be fun to watch as it goes through its phases. And it can be an easy introduction to keeping observing reports and sketching what you see in the eyepiece.
Enjoy observing Venus!