Paramount GEM User Guide
26 | P a g e
5. Slew the mount to a nearby star. The mount should slew back to this star; that is, it should return
to the same position in the eyepiece, video, or CCD detector. In practice, there may be small
pointing errors that are introduced by mirror flop, or slight differences in time, so the star may
not be in the same position, but it should be very close.
Note that during the process of polar alignment, you will be required to synchronize the mount several
times (each time the mount is adjusted to a new altitude and/or azimuth). For permanent installations,
once the mount is sufficiently aligned with the celestial pole, it should not have to be synchronized again
unless the optical tube assembly or the telescope’s physical mounting changes.
Portable setups must be recalibrated using the Portable Recalibration option, as described in TheSky
Professional User Guide.
TPoint Calibration
All mounts are mechanically imperfect; TPoint, used by virtually every professional observatory on the
planet, is the ideal software to correct the repeatable mechanical errors that degrade pointing and
tracking. TPoint also corrects errors that have nothing to do with the mount, such as errors caused by
atmospheric refraction and tube flexure (where the telescope behaves exactly like a coiled spring as it
tracks across the sky).
As every mount is imperfectly different, TPoint needs mount-specific pointing calibration data. Pointing
calibration involves slewing the telescope to various positions in the sky, then recording the known
coordinates and the actual position the telescope ended up at each position.
TPoint uses this data to intelligently generate the optimal pointing model (called a Super Model) for the
telescope system. The model is comprised of geometric and harmonic terms that define how the
telescope behaves and calculates the root mean square (RMS) pointing metric.
A rigid system comprised of a Paramount mount atop a solid pier or tripod, with a well-mounted telescope
that has a fixed mirror system should produce RMS all-sky pointing accuracies of 15 arcseconds or less.
With ProTrack, a pointing model based on 100 or more pointing samples on the same system should
produce 5 minute or longer unguided photos with round stars.
Use TheSky’s Automated Pointing Calibration feature (TheSky, Telescope, TPoint module, Calibration
Run, Automated Pointing Calibration) to collect the pointing calibration data for your imaging system.
See TheSky Professional User Guide for details about TPoint calibration.
Verify Mount Initialization
When connected to a Paramount, the Sky Chart provides feedback to help verify the mount has been
initialized correctly and identifies the regions near the meridian that have unique behavior when tracking
or slewing. These two regions are described below. If these regions are both centered on the meridian,
then the mount has most likely been properly initialized.
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