TheSkySearchers

Hi guys. Super beginner here. Just got my Nexstar 6SE. Tried collimating, i think i might have loosened the screws too much , secondary mirror fell off when I tilted it back. I didnt realise it had come off loose. Just peeking into it I dont see anything wrong with the primary mirror. I havent disassembled or anything. Does this mean I can just put the secondary mirror back on (assuming I can do it myself)? Or once the secondary mirror hits the primary mirror then I am screwed??? I dont see any scratches or break or anything.

I think you might have to pull the corrector plate off to reattach the secondary,orientation of the corrector is critical, most should have an alignment mark and some don't. some minor scratches to the optics isn't going to degrade the performance, what you really don't want is chips or cracks, typically if it's a chip on an edge you can mask it with black paint to reduce any stray light bouncing off .

If the secondary has fallen off of the mounting then you will have to remove the corrector plate to re-attach it.
Pay attention to the orientation of the corrector plate to the tube (mark them) so the plate goes back in the same location/ orientation.
There should be a mark already on the tube, corrector and secondary (usually at 3 o'clock when facing the front of the telescope) they all need to be aligned correctly.

Just to add a bit to the above good advice. The corrector plate is not some sort of a plastic protector; it is an optical component of your scope. It was aligned at the factory in the correct orientation to the mirrors. In other words, when reassembling the scope, you are not just trying to fit things back together mechanically, you have to carefully align the parts in their initial orientation. If there is no mark, or you can't see it, make sure to carefully mark the position of the corrector plate before removing it.

Edited to clarify that the corrector plate is not plastic of any kind. It's optical glass. On my first SCT, I just assumed it was there to keep dust out of the OTA. Ignorant me, but that was a long time ago. Fortunately, I never thought to remove it and hence mess things up, but it could have happened oh so easily.

There are several guides on the Web about cleaning SCT optics that show how to mark / remove / replace a corrector that might be helpful. Some use blue painters' tape for registration points on the corrector.

Technique starts around 2:45:

https://www.youtube.com/watch?v=e66yIuD3cMk