How to Open the Sky Chart

The main Sky Chart page is located in SkyandTelescope.com's Observing area. You can get to it from anywhere on the site by selecting Interactive Sky Chart from the navigation bar running down the left side of your screen.

Or you can bypass the Sky Chart page and go straight to the applet from the Home page via a graphic that looks like this:

Click this graphic. You will see a black screen for a moment. You may also see a message saying, "Please wait while Sky & Telescope's Interactive Sky Chart loads...." The applet may take several minutes to download, especially if you connect to the Internet using a telephone line and ordinary modem rather than a high-speed connection such as a cable modem or DSL service.

If you haven't previously set your default observing location, the first thing you will see when the Sky Chart opens is the Choose Location screen. Enter your observing location in only one of the three sections available for this purpose: USA or Canada, World by City, or Worldwide by Latitude & Longitude. Then click the corresponding SUBMIT button. (If you run into trouble at this stage, see the more detailed instructions in How to Change Your Location and Time Zone.)

Once you've specified your location, the Choose Time Zone screen will appear. Select the appropriate time zone from the pull-down list. If daylight saving time is currently active in your area, check the small box to the right of the words Daylight Saving Time. Then click the SUBMIT button.

The Interactive Sky Chart should now appear on your screen, showing the sky visible tonight from your location at 9:00 p.m. local time:

On the right side of the screen you'll see a circular map of the constellations labeled ALL-SKY CHART, with a green, four-sided frame near the edge labeled WEST. The part of the sky inside this frame appears at a larger scale in the rectangular window labeled SELECTED VIEW in the upper left corner of your screen. Under that you'll find Location and Date & Time displays. This page is known as the Combined View.

The All-Sky Chart's center represents the part of the sky directly overhead. Its circular edge represents the horizon all around you, as if you were standing in an open field and turning around in a complete circle. Compass directions are labeled around the horizon/edge.

A star that's plotted on the map halfway from the edge to the center, therefore, can be found about halfway up the sky — halfway from horizontal to straight up.

The Selected View shows about as much sky as you can take in at once with your unaided eyes; the field of view is about 50 degrees wide by 40 degrees tall. Compass directions are abbreviated along the bottom, and two markers partway up the right edge of the window indicate your viewing altitude, from 0 degrees at the horizon to 90 degrees overhead.

If you cannot see the bottom or part of the side of the sky chart, resize your desktop to 800 x 600 pixels (or larger). To do this on a PC running Windows 95 or higher, go to the taskbar at the bottom of your screen and click Start > Settings > Control Panel > Display. On the Display Properties screen, click the Settings tab and move the Screen Area bar until it says "800 by 600 pixels." Then click OK. You'll get a pop-up window that says, "Windows will now resize your desktop;" click OK. Once your display is reset to the new size, another pop-up window will ask, "You resized your desktop, do you want to keep this setting?" Click OK again.