Easy to use - Collimation Tool for Newtonians Telescopes - 94183

I bought this tool in conjunction with a Celestron PowerSeeker 127 telescope. I used it almost immediately because I thought that it would help me align my external viewfinder with the actual optics. I was wrong -- the external viewfinder cannot be aligned with this tool. Rather, it is used to align the internal sets of mirrors. Once I really read about it and used it again, I was able to more accurately align the mirrors to get a crisper image (with almost no distortions or "halos" whatsoever).
Pros: ease of use
Cons: not sure if it made a difference

This review was written in the old system and had content requirements that are different than reviews written today.