Bahtinov Mask Focusing Mask for Telescopes (for Outer Diameter from 125mm-180mm)

It does what a Bahtinov mask should at a great price point.

So I haven’t used it yet, take however many stars with a grain of salt. It’s a bit thin, but as described, the section that looks like a slotted triangle is solid on the first one to arrive. Will update, usually they are slotted and that may be an issue.

It is flimsy but you shouldn't be bending it. The size is what it says it is. Don't make the mistake of thinking it is for your telescopes diameter where it takes in light. Make sure you get a size a little bit bigger and smaller then your telescope

The mask arrived today and it appeared to be sturdy and well constructed. The edges were sharp, which provides good contrast for a sharp focus. The holding bolts were brass with a plastic coating to protect the telescope finish. The only problem I had was that one of the bolts was stripped and did not hold securely to the telescope. The bolt is inexpensive and fairly easily replaced, but I will have to do that. With that minor correction I would easily rate this as five stars. Update: ALL of the holding bolts were defective. They were not stripped, they were the wrong size for their nuts, and I've had to replace all of them. Other than that, it has been an indispensable aid for getting a precise focus for astrophotography.