With the release of the free iOptron Lite app for Android (the IOS version has been out for a while), we thought it’s time to explain what this package does, and how it’s different to the iOptron Commander program that loads onto a computer.

Commander Lite

Commander Lite is a free app, and is essentially a way of manually slewing your mount to different targets using just your phone, rather than a hand controller. Most iOptron mounts can use a wifi dongle rather than the handbox. Further, small mounts such as the SkyHunter, are often supplied without hand controllers.

First, the Commander Lite screen shows you where your mount is pointing (in terms of RA and Dec as well as Altitude and Azimuth). It also has a couple of movement functions: “move”, which simply moves the mount in either axis with no target, and “slew”, which slews your telescope to a named target, such as Alpha Centauri or Jupiter. While the slew function relates to a target, it is of limited use as there is no facility to teach the mount if the slew was inaccurate. Such an inaccuracy could be a result of poor polar alignment, an imperfectly levelled mount or an inaccurately set zero position.

I’ve added screenshots from my phone for the main screen, the move screen and the slew screen in Commander Lite.

There has been some mild criticism of iOptron for not providing more functions in Commander Lite. However, the app is not designed to be a fully-functional control mechanism for your mount. The manufacturer points out: “If you prefer a full function operation of the mount, please use a hand controller, iOptron Commander or planetarium software.”

As an example of one of these planetarium programs, I use the SkySafari planetarium app. SkySafari is not free, but depending on which version you want, it’s not very expensive. It is much more useful than the iOptron lite app, having a graphic star map visible on your phone. It also syncs on targets, which improves the app’s pointing accuracy in the vicinity.

Commander

Commander is a very different program, and runs on your computer, rather than a phone. It has two modes, a manual control (a little like Commander lite), and an ASCOM interface.

As you can see here, the Commander screen is more complex than those of Commander Lite.

In the manual movement section, you use the screen to control the mount directly. You can not only move and slew like with the Commander Lite app, but you can also sync to your target like SkySafari.

However, the main use for Commander is to allow other programs running on your computer to control the mount. To do this, Commander uses the ASCOM communications protocol, which is specifically designed to enable communication between astronomical equipment. It allows one program (I like to think of it as an “orchestra conductor”) to control any number of pieces of equipment, like your astro camera, focuser or filter wheel, as well as the mount.

While the orchestra conductor program (such as NINA, Voyager or SGP) is running, you don’t need to see the Commander screen, or even know it’s there. The conductor slews the mount to where it thinks the target might be, instructs the camera to take a photo, sends that photo to be “plate solved” (to identify where the telescope is really pointing), then instructs the mount to slew again based on any slew errors. Then the conductor uses all the other peripherals to get the images you want.

So the difference?

iOptron Commander Lite

• runs on your phone
• connects to your mount via wifi
• moves the mount using buttons on your phone
• slews to named targets assuming the mount is aligned

iOptron Commander

• runs on your computer
• connects to your mount via cable or wifi
• moves your mount using buttons on the computer
• slews to named targets and can synch following an inaccurate slew
• enables other programs to control your mount

Conclusion

At the most basic level, the differences between Commander and Commander Lite aren’t very significant. I can understand why the software developers decided to give the phone app the name Commander Lite. However, for phone-based control of my iOptron mount, I think that I would prefer to use SkySafari.

The more advanced features of Commander make it a powerful (and compulsory) tool for astronomers or astrophotographers who need a computer to control their mount, especially as part of a suite of equipment. At this level of use the name “Commander Lite” can be puzzling.