🔭 Updates an earlier post to include recent changes and new information.
As an amateur astronomer, I use desktop planetarium software to plan viewing sessions and keep track of the planets and Moon. There are many products available for all computer platforms and smartphones. A Google search yields links to many sources. I downloaded and use the open source Stellarium on my desktop computer. It can be customized to your location and is free. For Android and Mac phones and tablets, I like SkySafari. It isn’t free but is inexpensive.
Online planetarium sites are popular and offer many features. Below are highlights of some I find interesting. Each has multiple features, a unique look and feel, and different levels of detail. They can help satisfy your curiosity about astronomical events.
I have included only a few select sites and links since so many are available. I welcome reader questions or reviews about using these tools or others you find helpful.
This popular site offers a wealth of sky viewing options. It is simple and very easy to use. Your first visit to Heavens Above should include Configuration to change your viewing location using the link in the left sidebar of the site. There is no need to register or login. Type in a city. Click Search. If you wish, drag the red marker to be more specific. Click Update at the bottom. Bookmark the site for return visits. Heavens Above will remember your location for future visits.
Also at the left sidebar are links to many other tools. The Interactive Sky Chart is set to your location and time. Date and time are adjustable above the chart.
After returning to the home screen, I suggest clicking on ISS under 10 day predictions of satellites. It will give you viewing opportunities to see it pass overhead.
Eyes on the Solar System
From JPL at NASA, this is a powerful simulator. It is accompanied by rich graphics and top of the line accuracy. Eyes on the Solar System requires a download. It is useful to me when following a special space mission. NASA adds features which the program downloads as an update. If you are reasonably proficient with astronomy and technically comfortable, this is a great resource.
There are helpful Tutorials. For best results, I advise using them. Or, jump in and start exploring the Solar System on your own. Try out the controls. You won’t break anything. Explore the planets and their moons. Bookmark the Eyes site and check back for new features, tours, and news. Their menu choices are updated as needed.
First time I opened the Planetarium for In-The-Sky, it recognized my location and local time and gave a sky map for it. The controls are simple and adjusted easily. Dominic Ford runs it from the UK. It is worth a look.
Motions of the Moon
Our nearest heavenly body is the Moon. The animation Dial-a-Moon from NASA shows the geocentric phase, libration, position angle of the axis, and apparent diameter of the Moon throughout the year. Enter a date to see the Moon as it would appear then. You don’t need to change the time entry. If you do want to change it, Universal Time UT can be found here for your location.
The most obvious change in the Moon is the sequence of phases which occur during each orbit. This animation accurately shows the level of detail possible in a computer simulation. The shadows and features are based on the global elevation map developed from measurements by the Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter (LRO).
The Moon’s orbit is not circular. It appears a little larger during the time it is closest to Earth. Watch the size vary in the videos below as the Moon goes through the phases during each orbit. It keeps the same side facing toward us. Notice the wobble, or libration. There is a lot going on in the videos. Stop them at any time. Drag the slider in the player. View full-screen for best effects. Follow this link for my detailed explanations of each of the Moon’s motions.
The northern hemisphere version…
The southern hemisphere version…