Things that are not true
None of these are invented by bad people. Each one is a true thing stated in a misleading place, or a good rule applied where it does not hold.
"675× magnification!"
Useful magnification is capped by aperture at roughly 2× the aperture in millimetres — about 120× on a 60 mm telescope, an exit pupil of 0.5 mm. Past that the image gets bigger and worse: the same light spread over more area, and an exit pupil so small that floaters in your own eye start to show. On most nights the atmosphere caps things lower still, around 200× — on a 200 mm, an exit pupil of 1 mm — whatever the instrument.
Why it persists It is the only number on the box that can be made arbitrarily large without spending anything, and it is technically true as arithmetic.
It will look like the picture on the box.
The human eye has almost no colour response at low light levels, so nebulae and galaxies appear grey — sometimes faintly green. The photographs are long exposures, often in false colour, often from space. What you actually see is a faint grey shape, and it is genuinely thrilling, because those photons left their source before there were people.
Why it persists Box art sells telescopes. This single mismatch is the biggest cause of instruments abandoned after two weeks.
Buy the biggest you can afford and grow into it.
The best telescope is the one that gets carried outside. A 200 mm that needs two trips and lives behind the lawnmower is used four times a year; a 130 mm by the back door is used forty. Aperture only counts when it is pointed at the sky.
Why it persists Aperture is the one thing that is genuinely, measurably better — so it is easy to advise, and it ignores everything else about a person's life.
GoTo means you don't need to learn the sky.
GoTo needs an alignment on two or three named stars before it will find anything, which means knowing at least a few stars by name. It also fails in ways that are hard to debug in the dark. It is genuinely useful under a light-polluted sky where star-hopping has no signposts — and it is not a substitute for knowing where you are.
Why it persists It sounds like automation, and the alignment routine is not mentioned until the manual.
There's no point owning a telescope in a city.
Light pollution does almost nothing to the Moon, the planets, double stars or bright clusters. Saturn's rings look identical from a city centre and a mountain top. What a bright sky takes away is faint extended things — galaxies and nebulae — and it takes those away almost completely.
Why it persists Both halves get told separately, and neither half is the whole answer.
Any cheap telescope is fine to start with.
Optics at the bottom of the market are usually acceptable; the mount is what fails. A tripod that shakes for five seconds after you touch the focuser makes an instrument unusable, and no amount of enthusiasm survives it. Spend on steadiness before aperture, and on aperture before magnification.
Why it persists Mounts are invisible in photographs and absent from specifications.
One thing that is not a myth
Never look at the Sun, or point any telescope or pair of binoculars at it, without a certified solar filter made for the purpose, fitted over the FRONT of the instrument and fastened so it cannot slip or blow off; check the filter before each use. Eyepiece-mounted solar filters, exposed film, welding glass and smoked glass are not safe. Unfiltered sunlight through even a small telescope causes permanent blindness in less than a second, painlessly. Cap or remove the finder before you start. With children, an adult is there every time.