Refracting telescope and Reflecting telescope

For each inflection point
Clearly identify (give a name to) the inflection point

Describe the product as it existed at this inflection point

Discuss major change(s) that occurred to result in this product
Describe the reason(s) for the change with respect to relevant factors,

Relevant factors could include any or all of the following: dimensions of value, type of innovation, source of innovation, externalities, emergence of a dominant design, contextual factors.