Hi, I'm fairly new here, but I've been a browser for a while. I thought I would post this for anybody struggling with this finder scope.
I have an Celestron Evolution 8 and it comes with the red dot finder, which as you probably know, does your back in after a while and is not the most accurate of devices So I decide to change it and bought a Celestron 93781 Illuminated RACI Finder Scope. Anybody who has one of these will know what an absolute poor design the frame and control of this scope is. To the point it simply doesn't work for the most part. Here is a solution for you that will make the scope an absolute delight to use. It'll cost you a little bit, but it's so worth it.
1. Take the scope apart so you just have the scope itself and not the frame. Take off and ditch the crappy rubber ring too (what were they thinking).
2. Buy one of these... (dovetail base)
3. Buy one of these... (guiding scope ring kit)
Attach the dovetail base to your scope. Assemble the ring kit and place your finder scope in it, and slide it into the dovetail and make sure it's all tightened up.
ALL problems with the spring screw thing and any problems aligning will completley vanish. Once I did this, it took me less than a minute, and very easy to align during the day. It has a much broader aligning bandwidth, if you like, Why Celestron didnt use this approach in the first place, i will never know, but this approach turns it into an extremely high quality finder scope with no problems at all. I use a 3 point setup, so i still have my red dot finder for initial set up, which i do during the day on a distant object, then use the celestron for aligning the stars when it gets dark. So, so simple and has taken the pain of alignment away... quite literally