The phrase astronomical telescope is used to mean three quite different things, and separating them explains a good deal of the confusion in this market: an instrument built for the night sky, a professional research instrument, and a marketing word printed on a box.
What actually makes a telescope astronomical
It is optimised for faint objects and high magnification rather than for daylight convenience. That means the largest practical aperture, no erecting optics in the path to cost light, eyepieces in standard astronomical sizes, and a mount that holds still at high power rather than one that pans smoothly for video.
Professional against amateur
Professional instruments are research equipment: metres of aperture, permanent buildings, instruments rather than eyepieces at the focus, and observing time allocated by committee. None of it is buyable, and the word professional on a consumer telescope box is marketing rather than a category. The best amateur instruments are excellent and are not professional ones.
The toy end and how to spot it
Boxes leading with magnification, tripods that flex, plastic focusers and obsolete 0.965 inch eyepiece fittings. These are astronomical telescopes by name and are not usable ones. The specification that sorts them from real instruments is aperture, which is why this index publishes it beside every price and refuses to print a price without it.
Where the real line falls
Somewhere around a 70mm refractor or a 76mm reflector on a mount that settles in a couple of seconds. Below that, instruments exist and are toys. The cheapest genuine instrument in this index prints $79.95 and states its 76mm aperture and 300mm focal length on the same page as the price.
Questions people ask about telescope
What is an astronomical telescope?
One optimised for faint objects and high magnification rather than daylight use, with no erecting optics and a mount built for stability at high power.
What is a professional telescope?
Research equipment at observatories, not a consumer category. On a consumer box the word is marketing rather than a specification.
How do I spot a toy telescope?
It leads with magnification, has a flexing tripod and often a 0.965 inch eyepiece fitting. Read the aperture instead, which is the number that decides what it can show.