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ITelescopeV3DeclinationRate Property

The declination tracking rate (arcseconds per SI second, default = 0.0)

Namespace:  ASCOM.DeviceInterface
Assembly:  ASCOM.DeviceInterfaces (in ASCOM.DeviceInterfaces.dll) Version: 3351c4f3fa64146a7efd5b51ed4591e32a0a5484
double DeclinationRate { get; set; }

Property Value

Type: Double
PropertyNotImplementedExceptionIf DeclinationRate Write is not implemented.
InvalidValueExceptionIf an invalid DeclinationRate is specified
NotConnectedExceptionIf the device is not connected
DriverExceptionAn error occurred that is not described by one of the more specific ASCOM exceptions. Include sufficient detail in the message text to enable the issue to be accurately diagnosed by someone other than yourself.

DeclinationRate Read must be implemented and must not throw a PropertyNotImplementedException.

DeclinationRate Write can throw a PropertyNotImplementedException.

This property, together with RightAscensionRate, provides support for "offset tracking". Offset tracking is used primarily for tracking objects that move relatively slowly against the equatorial coordinate system. It also may be used by a software guiding system that controls rates instead of using the PulseGuide method.


  • The property value represents an offset from zero motion.
  • If CanSetDeclinationRate is False, this property will always return 0.
  • To discover whether this feature is supported, test the CanSetDeclinationRate property.
  • The supported range of this property is telescope specific, however, if this feature is supported, it can be expected that the range is sufficient to allow correction of guiding errors caused by moderate misalignment and periodic error.
  • If this property is non-zero when an equatorial slew is initiated, the telescope should continue to update the slew destination coordinates at the given offset rate.
  • This will allow precise slews to a fast-moving target with a slow-slewing telescope.
  • When the slew completes, the TargetRightAscension and TargetDeclination properties should reflect the final (adjusted) destination.
  • The units of this property are arcseconds per SI (atomic) second. Please note that for historic reasons the units of the RightAscensionRate property are seconds of RA per sidereal second.

This is not a required feature of this specification, however it is desirable.

See Also