Next message: Brooke Clarke: "Re: Avoiding collision."
Andrew, an achromatic lens, be it a telescope, a microscope, binocular, or
camera lenses, means that the lenses are corrected for chromatic aberration
(partially true). It means that the colored fringes you see around a bright
object over dark background are held to a controlled level. An apochromatic
lens is more corrected and more suitable for the more critical aplications,
wich doesn`t necessarily means that you need it.
As to the other question, most simple binoculars will enable you to see
some Jupiter`s moons. The selection of a telescope is not trivial, and will
depend mostly on other factors, not magnification. The most important factor
is quality of construction, and you better stick to Zeiss, or Takahashi if
you can spare the money. The russian Intes is a much cheaper alternative
with high quality. Then come the Meades and Celestrons, wich have models for
all budgets. You won?t regret having any one of these. Then comes the choice
of the diameter of the objective. If you want to see the moon and planets,
where light gathering capacity is not an issue, you may look into a small
refractor or Maksutov. But if you want to see deep sky objects such as
nebulas and galaxies, you need a large diameter objective, say a minimum of
200 mm.The refractors become too expensive in these sizes, but you have a
choice of Maksutovs, Cassegrains and Newton reflectors. Also, don?t forget
the mount. The telescope orientation must compensate for the earth`s
rotation, and the telescope mount should do this. You have a choice of
mounts to do the job, depending on the size and weight of your telescope. In
short, I recomend you find the local astronomical club, see the plethora of
equipment choices, get some eyes on experience with them, and then make your
choice. Jose Almeida.
-----Mensagem original-----
De: Navigation Mailing List [mailto:]Em
nome de Andrew Corl
Enviada em: segunda-feira, 6 de outubro de 2003 18:46
Para:
Assunto: Achromatic Telescope
I was recently reading the journals of Lewis and Clark. They mention
taking several telescopes with them on their voyage. Further research told
me that one of the telescopes was an "Achromatic Telescope." Could anyone
tell me (or refer me to a website) what this type of telescope is. If there
are plans available for this I would appreciate that link as well. I am
mainly interested in being able to see the moons of Jupiter (gives you an
idea of the magnification I am looking for).
Andrew
