I purchased a $39.95 Amscope and it was terrible! I could make out Dinos on my slide, but the image quality was very poor and smeared. I returned it and picked up a higher level Amscope that is excellent for what we are looking at everyday in our tanks. It uses glass optics and has fine/coarse tuning adjustments. It was only $89 on Amazon. He's the link...
https://www.amazon.com/gp/aw/d/B00AM5XB5O/ref=yo_ii_img?ie=UTF8&psc=1
I can easily hold my phone over my eyepiece and get excellent videos/pics...but, the digital screen on those listed earlier in this thread would be helpful. Just wanted to show a decent lower cost option for those wanting to quickly see what they are dealing with in their tanks!
Just played with my Amscope M150C... here's some pics I just took through the eyepiece with my phone... just to give an idea of the quality. And yes, I'm not happy to see so many dinos in my tank, ugggh.
I would like to find a phone holder that attaches to this eyepiece though... you do have to have a steady hand to get pics and videos.