I bought the Observer Pro app after seeing it recommended here, so I could map my horizon but when I access the Local Horizon mapping menu, the "Measure" feature is greyed out, I can't access it.
My phone being an iPhone 5S (iOS12.4.6), I thought that it may be to old even though Sky Safari Pro works fine on it, I tried my iPad Air 2 (iOS 13.4.1) but same thing, "Measure" is greyed out. Is there anything that I am missing or was the app developed for the latest iPhones and iPads?
I have other apps that make use of the magnetometer (compass), GPS, and Augmented Reality via the camera and all work without any issues. I have sent an email to the developer last week asking if there was something special required to be done, but no reply.