A large part of what makes our apps so cool is their on-board star catalogs, deep sky databases, and image galleries. In our basic version, this is about 40 MB worth of data; in our Pro version, it adds up to more than 400 MB! Google Play should automatically download this additional data to your Android device along with the app. Similarly, data updates should automatically accompany app updates from Google Play.
The first time you launch SkySafari, it will ask you to install the database it has downloaded from Google Play. If the database was not downloaded originally, SkySafari may ask to download it. Make sure you do this over a Wi-Fi network! The database is up to several hundred MB in size, and may take 30 minutes or more to download, depending on your internet connection speed. Fortunately, you'll only have to do this once - the data is saved on your phone, and you don't need an internet connection to use it in the field.
PLEASE NOTE: SkySafari will not download the data over 4G networks, because this may incur unwanted network usage charges. Unlike Wi-Fi, 4G is not free!
If your phone absolutely, utterly, completely fails to download the extra data from Google Play no matter how many times you try, here is an alternative:
Download the data to your Mac, Windows, or Linux computer, by clicking on the appropriate link for your version of the app:
Connect your Android device to the computer where you downloaded the data with a USB cable. Mount your Android's SD card as a USB mass storage device on your computer, so it shows up as a removable disk drive. If you don't know how to do that, consult your Android device manual.
Copy the file you downloaded in step 2 to the following directory on your mounted SD card:
After the file has finished copying, unmount your SD card and unplug your USB cable.
Launch SkySafari. It should detect the file you copied in step 4, and ask if you wish to install the data. Click "Install." If you downloaded the wrong file for your version of SkySafari, or if the download was not complete, then you should see message saying that a corrupt installation was detected, and SkySafari will ask if you wish to try again.
PLEASE NOTE: You can run the app without the additional data - it'll just show naked-eye stars and planets, Messier objects, and none of the fancy deep sky objects or horizon panorama images. But everything else should work.
Most Android devices have slower OpenGL graphics hardware than equivalent iOS devices. Hence, SkySafari will run slower on those devices than it does on iPhones or iPads. However, SkySafari should still feel very "useable" on Android. Typical graphic refresh rates when panning around the sky chart should be upward of 10 FPS. You can show your refresh rate by turning on Settings > Appearance > Show Frames Per Second. If you're seeing performance significantly worse than 10 FPS, something else is wrong. Let us know.
We'll continue to work on performance in the future, even if Google has given us a platform which makes it more difficult! In the meantime, here are some things you can do to speed up SkySafari while panning/zooming:
Turn off the fancy horizon panoramas. Display the horizon as a transparent line, or use no horizon at all - in the Plus/Pro version, you can do this by using an Equatorial coordinate view (under Settings > Coordinates).
Turn off the Milky Way image (under Settings > Milky Way).
In general, the fewer things that SkySafari has to draw, the faster it will draw the sky chart. Panning across a relatively empty part of the sky, as in Draco or Bootes, will be a lot faster than panning across a very crowded starfield, as found in Sagittarius or Centaurus!