I use the yellow one
it works a treat. Don't be fooled by the not being square issue ive had some really bogus info before and i went around in circles trying to make sure everything was square. My Feather touch focuser does not have adjustments to "square" the focuser either so it cannot be that important.
I have found if you do a flat you can see where the center of the light cone is impacting your sensor.
if you have used the cats eye kit and have lined up the astrisims.... its right pretty simple
