The amount of noise reduction you get from stacking is the square root of the number of individual sub frames stacked. S/N = No. of Subs /sqrt(Subs)

Binning is when you merge adjacent pixels into one larger pixel. Most commonly in a 2×2 formation, where 4 pixels are combined through software to make one large pixel as shown in the figure below.

Because CMOS cameras all use software BIN during deep space shooting, image post-processing can also complete this process.

ZWO tutorial [here](https://astronomy-imaging-camera.com/tutorials/everything-you-need-to-know-about-astrophotography-pixel-binning-the-fundamentals.html#:~:text=Binning is when you merge adjacent pixels into one larger pixel.&text=Something you will notice when,signal-to-noise ratio.)

Binning when focusing or plate-solving helps to speed up the process!