Field of View Help

The settings in this view let you set the field of view width, centering, and display options. You can also display or hide the chart center coordinates and field of view while you are swiping or pinching the chart.

Field of View

Field Width Angle: Sets the sky chart's field of view width angle using a slider control.

The largest field of view SkySafari can display is 180 degrees, letting you see the entire sky at once. As the field of view increases past 90 degrees, the horizon becomes curved, due to the distortion caused by projecting the entire celestial sphere onto the flat Android screen.

If you hold your phone at arm's length, about 2 feet from your eyes, its 2-by-3 inch screen has an apparent size of 4.8 by 7.2 degrees. So, if you set the field of view width to 4.8 degrees (portrait mode) or 7.2 degrees (landscape mode), and hold your phone out at arm's length, the view on your phone should appear at the same scale as the real sky.

The smallest field of view SkySafari can display is 0.1 arcminutes, or 6 arcseconds - about the average size of the planet Mars as seen from Earth. One arcsecond is the best resolution a typical 8" backyard telescope can achieve under good observing conditions.

For comparison, the Sun and Moon appear about 1/2 degree (or 30 arcminutes) across. The smallest angle the unaided human eye can resolve is about 1/30th of a degree, or 2 arcminutes - about 1/15th the width of the full Moon. At its closest approach to Earth, the planet Venus appears about 1 arcminute across; Jupiter typically appears appears 45 arcseconds across.

Compass

SkySafari can use the compass built into your iOS or Android device to center the sky chart on the direction you're holding your phone. If your device does not have a compass, this option is disabled.

Tilt Up to Use: When turned on, you can tilt your Android Device upward to activate the compass and/or altimeter. Once activated this way, touch the screen anywhere to turn the compass off. Turn "Tilt Up to Use" off if you find that you're accidentally activating the compass too often, or if you prefer to activate it from the main toolbar.

iOS Users Please Note: for best results with the compass, turn your phone sideways to landscape mode.

On Screen Display

This items in this section control how the chart center coordinates and field of view are displayed at the top of the sky chart.

Show Always: When turned on, the chart center coordinates and/or field of view are always displayed at the top of the sky chart. When turned off, these items are only displayed when you swipe or zoom the chart, and will fade after you remove your finger from the screen.

Field Width x Height: When turned on, displays the sky chart's field of view in the upper right corner of the sky chart. If turned off, the field of view is not displayed.

Center Coordinates: When turned on, displays the sky chart's center coordinates in the upper left corner of the chart. If turned off, the chart center coordinates are not displayed.