Since I was the one executing the design on the sewing machine, I did tweak some things and made the fabric and padding choices, but we were happy with the result, and I think my son is too!
In the picture above you can see the drawings and measurements my son sent. Mike made an actual "telescope" out of posterboard so we would have a model to work with and measure things by. The model is in the bag in these pictures.
I used some fun Star Wars fabric and poly stable stuff, double layered for the padding, which made it about 1/2 inch thick.
He needed something to store the lenses in too so I made an extra little case to store the five lenses, which are about the same size as a spool of Aurafil thread, so you can see in the picture below I used my full thread spools to measure the elastic holders and make them snug.
This little case is also double padded with stable stuff and fits down in the bag on top of the telescope before closing the drawstring -so it adds a little more padding to the telescope!
I don't think my husband will quit his day job and become a bag designer but it was fun to team up and work on this project together!