The vertical axis is now showing the "Excess Noise" (%) in your final stacked image, and, the horizontal axis is still showing the Exposure Time used for your images. Excess Noise is the amount of noise above the noise in a single image with an exposure lasting your entire imaging session. Of course such an image would saturate nearly all the stars, but, it would have the lowest noise. The graph shows that Excess Noise increases as the Exposure Time gets shorter. To get the Excess Noise down it looks like an exposure of somewhere around 150 seconds would be a good choice. Hopefully it won't saturate too many stars.
This second graph is for your
As you can see the narrow filters require longer exposure times to reduce the Excess Noise. Exposures in the 400 to 600 sec range look appropriate (maybe 400 for
I'm very glad we worked on this. I like this new way of presenting the results better. Much easier to determine how Exposure Time affects Excess Noise.
Hope this helps,
Steve