Paramount GEM User Guide
102 | P a g e
When the Paramount is positioned at the home position, the mount’s mechanical orientation is always
identical (to about one arcsecond or so). In the northern hemisphere, this position points very near hour
angle 0 and declination 0. For a mechanically perfect imaging system, the telescope would be pointing to
a position on the celestial sphere at the intersection of the meridian and the celestial equator.
Provided the base of the mount is fairly close to level, and the altitude of the polar axis matches the
observing site’s latitude, TheSky Professional (configured with accurate location, date, time, and time zone
settings) can be used to slew the mount to the computed position of an object (usually a star or other
bright object) on the celestial sphere.
Once the telescope has been slewed to the object, the mount’s mechanical azimuth axis (not the
telescope’s position) can be adjusted until the object is centered in the eyepiece. This technique relies on
the home position and the computed equatorial coordinates of an object to approximately align the
mount’s polar axis to the celestial pole.
The rough polar alignment method can be performed during the daylight hours by slewing to a planet,
bright star or even the Moon or Sun (provided the proper solar filters are used). Another advantage to
this technique is that the celestial pole need not be visible.
Note that while the home position is mechanically fixed, the telescope itself will not necessarily precisely
point to hour angle 0 and declination 0. This is mostly due to optical and mechanical non-
perpendicularities. For this reason, the rough polar alignment method should be deemed a “rough” not
a “precise” polar alignment technique.
After performing a rough polar alignment, use TheSky Professional’s Tools, Accurate Polar Alignment
command to achieve exceptional polar alignment .
Step-By-Step Rough Polar Alignment
To begin a rough polar alignment, from TheSky Professional, click Tools, Rough Polar Alignment and follow
the step-by-step instructions. Note that the Rough Polar Alignment window can be resized larger to make
the graphics larger and easier to read.
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