Need some help

I am thinking of getting a 16" dob with a pegasus mirror. The mirror has a chip and a 1 1/2 cm stress fracture in it as the picture shows. It was caused by a rock falling on it. The owner really doesn't want to give any type of warranty with this. Does anyone know if the fracture has a good chance of growing? Thanks for your help
Marty

Attached Image:

Hello Marty,

It's highly likely that the fracture will grow. Changes in temperarure of the mirror will provide the needed expansion and contraction, that will cause further stresses and growth of the current fracture.

Look at a car windshield that gets cracked by a rock. It's the temperature changes more than anything else that cause the cracks growth.

Clear Skys,

Preston