Stonyhurst disks are useful for accurately drawing sunspots from a projected image.
A few of the members having been to my talk about observing the sun during the summer where I showed a drawing I had done on the at that time with the latitude of the new cycle spots, and I mentioned the Stonyhurst discs I had used and how I had printed them on overhead projection foils. As requested, the discs have been included so that members could download them and print them to paper or whatever they preferred.
I have attached the Stonyhurst disc set and my own faint and dark grid for solar projection and marking sunspots. I have adjusted all the Stonyhurst discs and the solar projection grids to be the same size when printed of 6 inches. This should make it easier for members to print out and use. The solar data can be obtained from the BAA handbook for each day of the year.
Select and download the disks
By Ken Kennedy