Between 24 and 26 February, I put in two hours solid grinding (still with #120 grit using 1/3 strokes). At this stage, I’m trying to shorten the focal length of the mirror, so that the end result will fit in the boot of my car. There’s no point in making a telescope that isn’t practical enough to get used, after all.
Frustratingly, after these two days, I’ve measured precisely zero progress. I’ve used both the spit test to measure radius of curvature and feeler gauges to measure the sagitta, and both tests show no progress whatsoever. ROC remains stubbornly at 220 cm’s. I’m not sure if the #120 grit cuts slowly enough that I’m simply being too impatient, or if there’s something wrong with my strokes but either way this is not good enough.
So I will try extending to longer strokes again (as in the first stages) to deepen the curve. Once I’ve reached ROC = 210cm, I’ll resume the proper strokes and restore the nice spherical shape I’ve got now. And then, finally, I start with the finer grit.
Only problem: I’m not sure if this is the smartest thing to do. Comments? send advice to firstname.lastname@example.org