one of the most surprising discoveries first telescope owners will find
is that images may appear upside-down or backwards depending on the type
of telescope. the first thought is the telescope is broken – when in fact
it is working perfectly normal. depending on the type of telescope images
may appear correct, upside-down, rotated, or inversed from left to right.
why is this? why would i want to see everything incorrectly? for astronomical
viewing, it is not important whether an object is shown correctly. in space
there is no up or down. besides, saturn is not something you see everyday
and you would not know if it was upside-down or not. a tree, building, person
or an automobile for example would be important to see correctly. when you
view an automobile upside-down, you recognize that this is not correct.
lets talk about the different types of telescopes and how the orientation
of the image is observed through them and what you can do to correct it
for land use.
refractor and cassegrain telescopes will produce an image that is upside
down when used without a diagonal. when a diagonal is used the image will
be corrected right side up, but backwards from left to right. it will look
like trying to read a sign in a mirror. there are special diagonals called
erect image prism diagonals that can correct the backwards image for land
newtonian reflectors will produce an image that is upside down and are not
recommended for land use. there are no ways to correct this with a newtonian
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