Configuring Mount Limits

Clicking the Configure... button in the Limits Monitor window will open the Mount Limits configuration window. This window has two tabs allowing you to separately configure the RA and Horizon limits and respective behaviours.

RA Limit Configuration

The RA Limit configuration tab is split into two aspects. The left-most area allows you to configure the left and right limits for the RA axis of the mount. The first time you open this window, both the left and right limits should be set exactly horizontal. If you want to change either of these limits, you should slew your mount to the position at which you want to set a limit and then click the Set Limit button (either left or right). The display will update to show your newly configured limit by moving the red line.

The terms "left" and "right" were used for the limits because they seemed more general than say "east" or "west", which would be different depending on which hemisphere you are in. In case it is not clear, the "left" limit is when the RA axis is slewed such that the scope would be on the left side of the mount looking at the mount from behind. For northern hemisphere users, the left limit is the western limit and is the one that controls when tracking will stop. If you are in the southern hemisphere, the left limit is your eastern limit and will control whether or not a counterweights-up slew is possible. The "right" limit is the opposite of the "left" limit according to the previous explanation.

Your western limit is used to detect when tracking should stop and the Limits Monitor window reports how long you have until this limit is reached.

Your eastern limit is used to detect whether a counterweights-up slew is possible. If you are trying to slew to an object that has not yet transitted the meridian, the normal behaviour would be to slew the RA axis to the western side which means that you'll need to do a meridian flip once the object does cross the meridian (or actually when your western RA limit is reached). However, if the object is sufficiently close to crossing the meridian such that an eastern RA slew could be achieved without violating your configured limit, then a counterweights-up slew will be performed. This will allow you to track objects across the meridian without needing to perform a flip and will be especially useful to imagers who want to track an object for longer without interruption.

The right hand side of the RA Limits configuration tab allows you to control what action should be taken when the RA limit is reached during tracking. The options are to stop, to park, or (in a future version) to perform a meridian flip and continue.

You can also configure whether counterweights-up slews are permitted or not. If you select the "Never" option, EQMac will not behave any differently than it used to. However, if you choose the Maximise Time Until Limit option, EQMac will intelligently decide whether it can gain more tracking time by slewing counterweights-up. This will only happen if your eastern limit would not be breached in doing so.

Horizon Limit Configuration

The Horizon Limits configuration tab allows you to define the position of your local horizon. The horizon view to the right plots the horizon with the horizontal axis representing azimuth starting at 0 degrees on the left and running through to 360 degrees at the right-hand edge. The vertical axis represents altitude and ranges from 0 to 90 degrees.

You can enter data for your horizon in two different ways. Either enter an Azimuth and Altitude manually in the list to the left of the horizon display, or you can slew your scope so that it points at the horizon and then click the Set Limit At Current Position button. In this way, you could slew to strategic points on your local horizon and click the button to accurately map your horizon. The software will interpolate between each point. You can change or delete any of the points in the list.

The default horizon (with no points) is a straight line at altitude 0 degrees.

Below the horizon configuration is an area to allow you to set the behaviour when the horizon is reached during tracking. You can set it to stop or to park.