there are two major groups of instrumental mounts : The alt-azimuth and equatorial. The first usually equip
all small initiation instruments. Easy to implement, intuitive
to use and requires no special knowledge. However, with these
mounts, it is also easy to find an object to lose because it
is obliged to act on both axes to follow. The altazimuth mounts
will therefore used only as visual (the DOBSON telescopes are
part of this category). When one team an evolving astronomical
instrument, it immediately switches to the second family, the
equatorial. Fitted with polarfinder or not, they can be set so
that we can follow a star by acting only on one axis, the time
axis (the second, the declinaison, being used for tracking corrections).
This time axis,
if it is equipped with a stepper motor controlled by an electronic
quartz rigorous can practice without embarrassment astrophotography.
The famous setting that allows the equatorial mount to develop
its full potential in monitoring quality to compensate for the
Earth's rotation is called the station establishment.
I practiced this
setting each night early for a little over ten years on a German
mount polarfinder. So this is the mount type that I know very
well the process which I have detailed the main phases in the
The quality of
the stationing on a German mount polar finder for an observer
in the Northern Hemisphere is directly influenced by the position
of the north celestial pole relative to the stars as it is to
match a pattern lasered in the viewfinder with the actual position
of the pole star whose validity is not definitive.
The long precession
extending a cycle of 41,000 years causing a steady movement of
the celestial North Pole among the stars. In this long circular
course, the representative of the celestial pole star changes
repeatedly over the millennia. In this perspective, we can deduce
that the celestial north pole was incarnated once, around 3000
BC, the Thuban star in the constellation Draco. Then, in a slow
slide that lasted 5000 years, North Celestial Pole is now close
to the pole star.
The annual value
of the displacement is 50.290966 arcseconds per year or 1 arcdegrees
every 72 years. This movement is not harmless because it means
the German equatorial mount polarfinder is actually becoming
obsolete in the space only two decades !
a german mount||