I've had two colonoscopies, both without sedation. Just in case I let them put in an IV and let just saline run in, so if sedation were suddenly needed, it could be given essentially instantly. It wasn't on either occasion.
During the exam I was able to watch what the doctor was seeing through the 'scope on a TV. Frankly, the whole procedure was a complete bore. I could see my colon increase in diameter when air was pumped in. There is not a lot to see otherwise.
Incredibly, near the end of the exam the doctor turned the end of the 'scope into a "U" and looked backwards at my anus... from the inside. I could see the 'scope entering me. Really weird.
During one exam, the doctor found a small polyp and put a clip on it and cut it off. I covered my eyes during that part. I felt ono pain.
The two preps were somewhat different. The first time, there was nothing but liquids the day before. At 2pm I had to take 4 Dulcolax pills. At 6pm, I had to start drinking GoLytely... a glass full every 15 minutes. About 7, I felt the Dulcolax starting to work. I was actually pretty constipated and had done nothing in advance of the prep. Big mistake. The time from the start of the cramps to having to go was perhaps 15 minutes. There was no time for the poo to get soft and the Dulcolax forced the big, hard poo out.
Very uncomfortable. The lesson is don't be constipated at the start of a bowel prep. For the next couple of hours I was sitting on the toilet, pooing and drinking the GoLytely.
Even after all the prep there were flecks of poo visible in the 'scope during the exam. Fortunately the colonoscope had provisions to wash out and drain this stuff.
I'm inclined to think the olde time preps were probably more thorough. For example, the Fleet preps were a dose of castor oil, Dulcolax pills, and a large volume soapy enema.