Astigmatism measurement
Astigmatism measurements vary a lot by time, lighting, what you've been eating/reading, phase of the moon, etc, etc. If you repeat one within .25 that's actually pretty good O_o.
Use the astigmatism fan. Best instructions from a quick search are https://www.slideshare.net/SeenaJose2/astigmatic-fan, though that's intended for optos so goes into a lot more detail and technology. 1. Find an astigmatism fan: https://duckduckgo.com/?t=ffab&q=astigmatism+fan&iax=images&ia=images
2. As you move it away from your eyes, lines in one direction (axis of astigmatism) will start to blur. As you keep moving it away, more lines will blur.
3. Measure the distance in cm at which the first set of lines starts to blur.
4. Convert cm to diopters as usual.
5. Then measure distance at which last set of lines starts to blur and convert as well.
6. One of those numbers (the first one?) is your CYL value. In which case the SPH value would be the second number minus the first. You might want to search around for more instructions on using the fan, and confirm that this guide is correct. It might not be, it is based on memory.