Nothing can show you just how far out of collimation you are as well as the OCAL. And within 5 minutes of unpackaging, uploading the program and entering the SIN code data and switching my OCAL on it showed me I was Miles away and would have never reached collimation.
I have a 6" F4 imaging newt which shipped from Britain and came with the focuser tube off due to travelling, and its never been right since the day I bought it. I tried my best with cheshire and laser but every picture showed imperfections I could never resolve. My eyes are not the greatest but this OCAL did my seeing for me and as a result brought my odd shaped stars back into the glowing balls I was looking for and allowed me to start calibrating all the other little details not noticed due to bad secondary positioning. A simple process to achieve when you employ this handy well rounded tool.
laser collimators and Cheshire's are great up to a point but if you want to be certain, Buy an OCAL, even if I never need to use it again it was worth every penny Thanks to AstronomyPlus!

Purchased this for my 6” RC. Not sure if I did it correctly and lousy weather this winter so no way to tell though it does focus on the tree down the street.

Have been using a Cheshire eyepiece to collimate my 6" GSO RC, supplemented by unfocused bright star images. But as I get older, the eyepiece is more difficult to use. The OCAL camera replaces the Cheshire and provides an image on my PC screen that serves the same purpose. If anything, it is easier as I can see the screen while adjusting the secondary mirror screws -- so a faster and possibly more accurate adjustment. Two criticisms -- I did not find the video tutorial info helpful (a problem for a beginner); and under the same conditions, the image is not as bright as the Cheshire eyepiece. Overall a useful tool.