My question is, if you go to a CP4 just for this purpose, HOW LONG would your (particular) smartphone run its intended Planetarium program just to operate the AP mount, until the phone battery died, especially when severe cold drains the battery even faster?
You can operate the AP Keypad even at –20C with a “gloved hand”, but smartphones require a warm bare finger to operate its touch screen for the Planetarium program to operate the mount. I don’t think frostbitten fingers work well on smartphone screens.
Besides, there has been recent discussion on how to keep a smartphone from going to sleep after a brief interval of “user response” inactivity. I don’t think there was a good solution other than running a background program that continually pings the WiFi, as if it were a user input. I would hope that a planetarium program would do that, when you put the phone down or into a packet, while observing the skies.
Before deciding on a move to CP4, strictly for WiFi access from a smartphone app, perhaps as a “practical test”, you might want to run the intended smartphone Planetarium (display only) program outdoors on the back porch, on a cold winter’s night, and see how long the program keeps running, and how long the phone battery lasted. This would give you some idea of “real field use” under tough conditions, before you decide on a CP4, only for this purpose ... and also, whether you might actually need a new smartphone with a lower drain, longer lasting battery charge – which will probably cost as much or more than a CP4 upgrade.
However, if the smartphone works, you should still let your present AP mount Keypad tag along on field trips, just in case the smartphone dies. At least, with the Keypad as a backup, you won’t have to pack up in early.