What Does PulseGuide() Do? I’m Confused.

PulseGuide() creates small incremental equatorial movements and is usually used to make fine adjustments to the mount in order to keep the target location centered.

The Direction parameter (see GuideDirections) determines in which equatorial coordinate and direction the movement is to be made, and the Duration parameter specifies the length of time that the appropriate guide rate set by the mount’s GuideRateRightAscension and GuideRateDeclination properties will be applied. Each call to PulseGuide() moves the mount in a single increment of GuideRate * Duration = Distance.

PulseGuide() always moves the scope on the equatorial coordinate axes (N/S/E/W) regardless of the mount’s AlignmentMode (which describes the mechanical construction of the mount).

Finally, PulseGuide() is asynchronus. If the mount supports it, an app may call for simultaneous pulse guiding in both RA and Dec axes.

Attention

Unfortunately some German Equatorial mounts make North and South movements in opposite directions depending on their Pointing State (flip state). Most commonly, the error is when the mount is “on the east” looking west (“flipped”), where the North/South directions are backwards. This is a result of the mount behaving like it’s using “guider cables” which just reverse the Declination motor.

Application developers will need to implement a Declination reversal option for German mounts that have the above described behaviour. Implement this by first reading SideOfPier and then depending on its value, reverse the guideNorth versus guideSouth parameter in the call to PulseGuide.

Magnitude of Move

Obviously the magnitude of the movement for a PulseGuide call is dependent not only on the given Duration and Direction but also on the mount’s guiding rates of movement as set by GuideRateRightAscension and GuideRateDeclination.

Important

The mount’s guide rates are not related at all to RightAscensionRate and DeclinationRate, which initiate and stop secular (long running) motions in RA and Dec. The RightAscensionRate and DeclinationRate methods enable a mount to track objects that move relative to the ‘fixed’ star background.