I'm just starting to get into astronomy later in life, and am using apps on my phone to locate various planets, stars, and other astronomical features to look at. However, the white light from the phone is a bit distracting (e.g., my wife might be using the phone to locate while I'm using the telescope or vice-versa).<p>For now we've been just using plastic, red filters over our screens. What I was wondering was two-fold under the presumption that there are no stupid questions :-)<p>First, do any stargazing apps combat this at all by actually only using the red channel? Or maybe there's an iOS/Android "plugin" or system setting that can act as a pixel shader emitting primarily only the red channel?<p>Second, I've found myself wondering if that would even matter, or if the screen would still be emitting white light regardless of any color channel filters being applied by the renderer?