Basics of telescopes (Purchasing your first telescope - all you need to know)

If you do not want to watch 1.5hrs video, here is a good summary of important points: • Which telescope to buy? but it missing a lot of details that I go over in this video
This is the workshop I did for my local astronomy students club.
It is meant as a very basic introduction to telescopes for beginner astronomers. It is a first part in the series of "Introduction to Astrophotography" workshops.
There are can be few mistakes and misleading info in my presentation. So far I found:
1. In the list of telescope types I incorrectly state that "RASA" is the major class of reflective telescopes. In fact the major class of such telescopes is called "Schmidt", and RASA is just a version of Schmidt type telescopes (Rowe-Ackermann Schmidt Astrograph)
Please write in the comments of any inaccuracies you find, and I will make sure to correct them to avoid transfer of misleading information.
I start by explaining what is a telescope and how it works. Next I introduce most popular types of telescopes. I then proceed explaning types of optical imperfections and how they affect image quality.
I continue by sharing important environmental factors that affect telescope perfomance such as weather, light pollution, air turbulence etc and solutions to these challenges.
With this knowledge we then go and analyze what type of telescope is most suitable for a given task (visual, photography, planets, DSOs) for a beginner.