As for the reflection issue - no I don't have any timed schedule but what I have done, not visible on the photo, is placed a large black book behind it, close the curtain in the evening and just hope. I am not expecting great results but am just experimenting. I am figuring that at only one image per hour each image will be only 1 24th of a second so things like that may get smoothed out. It is still going and I will see if the camera, my curiosity or my wife's irritation causes it to stop first. As for battery packs - interesting and I don't know. I have charged my iPhone from my drone's battery before but never tried the power pack option for a camera. I was advised to buy extra batteries but haven't yet - it is something I considered for a trip to photo the northern lights (thinking that the cold would sap battery power quickly) but due to same sad news about one of my daughter's health I have postponed that trip so don't need to think about it.
I will let you know what the tree looks like either way just for the fun of it. Hope you got yours at the weekend and are having fun.