Why is there a "grid" overlaid in the viewer when viewing a subframe, but not when viewing a stacked file. It changes when zooming. See attached.
Hi, When using flats I always get the message: "Warning flat pixel colour values differ too much. Use white light for OSC flats!!. Will compensate accordingly." This happens whether I use an LCD panel and white t-shirt, or EL panel or Skyflats. Why would this happen? Should I be concerned?