6 Main Window

The layout of the main window contains two primary areas: Tabs and Control. Each selected tab will show it’s associated control.

The top of the window shows the version of GS Server, how many connected applications exist, minimize, close buttons and Mount Type.

Connected Applications – shows how many applications are connected To GS Server. If you try to close GS Server when there are existing connections it will prompt you to confirm before closing. GS Server will exit on its own if the last calling application closes its connection.

Mount Type – shows either Simulator or SkyWatcher and is adjusted in the settings.

List of items in the Main Controls

Window Bar

CheckBox – Keeps the window on top of other windows. This is consistent with other GSS windows.

Mount Type – shows either Simulator or SkyWatcher and is adjusted in the settings. The simulator will use your selected highlight color as the background.

Connected Applications – shows how many applications are connected To GS Server. If you try to close GS Server when there are existing connections it will prompt you to confirm before closing. GS Server will exit on its own if the last calling application closes its connection.

Coordinates Bar

RA (Right Ascension) – the distance of a point east of the First Point of Aries, measured along the celestial equator and expressed in hours, minutes, and seconds. Double click on the value to swap between hours and degrees display.

Dec (Declination) – the angular distance of a point north or south of the celestial equator.

Azimuth – the direction of a celestial object from the observer, expressed as the angular distance from the north or south point of the horizon to the point at which a vertical circle passing through the object intersects the horizon.

Altitude – the distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object.

Local Hour Angle (LHA) – it is the angle between the meridian of the observer and the meridian of the object you are pointing at. This can be used to tell how far the object is before or after the meridian. Double click on the value to swap between Local Hour Angle and Local Sidereal Time. Local Sidereal Time equals the Right Ascension (R.A.) of the celestial coordinate of an object that is currently crossing the local meridian.

GoTo Control

Supports RA Dec and Az Alt GoTo. Right click in the GoTo Control to swap between coordinate systems.

Copy Button – Copies the current mount coordinates into the dropdown boxes.

GoTo Button – Tells the mount to move to the position defined in the dropdown boxes.

Sync Button – Takes the position entered and reset the mount to that location (Ra Dec only). Any syncs larger than 45 degrees in either direction from the current position will not be accepted.

Import Button – Select a .fit file to open and copies the RA and Dec from the .fit file into the dropdown boxes. This could be used as a manual plate solve where a plate solver validated the pointing location then you can load those coordinates from the image file.

Backlash Compensate

Used when guiding to account for slack within the axis gearing. If you are using the PHD backlash Compensate then there is no need to adjust this setting, leave the settings at 0. Review the video “Dec Backlash Adjustment” on the help videos page.

PPEC Control

This control is enabled or disabled depending on the capabilities of each individual mount. Clicking the Mount info button in the status bar will show if PPEC is supported for the mount.

PPEC (Permanent Periodical Error Correction) - Checkbox to turn on or off PPEC. The grayed-out timer will turn green when training is in progress. For more information see the PPEC section of this document.

PPEC Train – Checkbox to start the training process for PPEC

Buttons Controls

- Opens a separate window

Park Positions – List of available positions for parking. The default is two listings ‘Default’ and ‘Home’. Home is same position as the Home button. Default is a copy of the park position from previous versions of GS. If you never set the previous version park position, then Default will be set to the home position. Any applications requesting GS to park the mount uses the selected position at the time of the request. Adding and removing positions is done in the settings area of the Main tab. Park positions are defined and stored separately for equatorial, polar and Alt/Az mounts.

Park Button – move the mount to the defined park position defined within the setup settings. If mount is current slewing the button will stop the mount. Click again and the mount will park to the position in the dropdown.

Home Button– moves the mount to the initial home position which is typically counterweight down and the dec axis pointing to the pole. For Alt/Az mounts the home position is defined as Az pointing to North and the telescope tube horizontal. For polar mounts the home position is defined as Az pointing South (North for the southern hemisphere) and the telescope tube 5 degrees above horizontal. If the mount is currently slewing the button will stop the mount. Click again and the mount will move home.

Stop Button– Stops mount movement

Tracking Button – turn on or off the selected tracking rate to use. Will be automatically applied after a slew or goto. For Alt/Az mounts tracking will maintain a constant Right Ascension and Declination so that an object of interest remains in the center of the field of view. However, without a field de-rotator the field of view will appear to rotate about the center point. This rotation may be acceptable for visual observation or shorter exposure imaging but star trails will be visible on longer exposure imaging.

ReSync– Resets the mount axes encoder positions to either the home position or a preset park position. The home position for equatorial mounts is defined as Dec is pointing to the pole and Ra with the counterweights down. For polar mounts the home position is defined as Az pointing South (North for the southern hemisphere) and the telescope tube 5 degrees above horizontal. For Alt/Az mounts the home position is defined as Az pointing to North and the telescope tube horizontal.

When resyncing with a park position make sure the mount is turned on, connected, and in the desired park position. If not in the correct position, manually move the mount to the desired position and ReSync with that park position. For encoder accuracy be sure the manual position is as close to the park position as possible.

Flip SOP Button – for equatorial mounts moves the mount to the opposite side of the pier if allowed by hardware limits. Works in both directions. The button text is color accented when flip is allowed. An “On” badge is active when a flip is in progress.

For Alt/Az mounts moves the mount in the opposite direction to positions around the South azimuth direction pier if allowed by hardware limits. Works in both directions. WARNING: The mount will slew 360 degrees through North to reach the new position. Check that cables will not twist or bind.

For polar mounts moves the mount to the alternative RA/Dec position if allowed by hardware limits.

AutoHome Button – If your mount is equipped with auto home sensors then this button will assist in recovering the mount when it starts in a position that is not recognized as a park or home position. This would be helpful if the mount loses power and is then powered on and the axis positions are unknown. AutoHome will attempt to find each axis home sensor. It does this by moving each axis 5 degrees at a time towards the sensor for a maximum of 100 degrees. If it did not find the home sensor it will tell you at the end of the process. Once finished you will have the option to run it again for another 100 degrees search. If you’re using a side saddle you can enter an offset that will move the mount +90 or –90 degrees after home is found and AutoHome is complete.

For German equatorial mounts only: Your mount's AutoHome sensor may not be exactly at the 90° position due to manufacturing tolerances, which are typically a few degrees. The GEM AutoHome position is GEM counterweight down pointing to the celestial pole. This is the (90, 90) Ra/Dec position which you can check using the RaDec graphic. To compensate for small errors in the auto home sensor position:

• Click the Auto Home button
• In the "Sensor Position Adjustment" section:
  • Enter the actual Ra axis position where your home sensor is located
  • Enter the actual Dec axis position where your home sensor is located
• Click Start to commence the AutoHome function

To determine your AutoHome sensor position:

• Run auto home with default settings (90, 90)
• Note where the mount actually homes to
• If it's off by a few degrees, adjust the settings by that amount
• Example: Mount homes to (87, 91) instead of (90, 90)
  • Set Ra Sensor Position to 87.0 and Dec Sensor Position to 91.0

Click "Reset" to set the assumed the AutoHome sensor position to (90, 90) – counterweight down pointing to the celestial pole

For polar mounts only: If the auto home sensors have been moved from the default position these values must be set from the Settings page before starting AutoHome. The default value for both axes is 90 degrees (GEM counterweight down pointing to the celestial pole), and these values must only be changed if your mount has modified auto home sensor positions (e.g. EQ8 dual telescope polar mounts).

WARNING - If you slew greater than +180deg from home and loose power, when doing the auto home, instead of slewing in a negative direction to get back it will slew in a Positive direction and possibly twist or bind existing cables. It’s recommended to monitor the mount at all times while doing an AutoHome.

Scheduler Button – Allows a park to be scheduled at a future date and time. When checked it uses the currently selected Park Position, and the button will display “On” until the event is completed. It’s the user responsibility to ensure no other software is interfering or working the mount at the time the event is scheduled to run. This option is reset when GS server restarts.

Limits Button – Enables or disables tracking and horizon limits. The “On” badge is displayed when limits are active. Click the three dots to display the Set Mount Limits dialog (described below under Settings)

Hand Controller

Speed – 8 settings to control the speed of the hand controller buttons. All speeds are relative to the Max Slew Rate in settings.

Opens a separate or new window for the hand controller. You could open this then minimize the GSS application so you have more screen room for other applications

Open the hand controller options dialog

Open the pulse parameter dialog

Mode - Axes - Follow clockwise and counterclockwise directions of the axis. User would be able to set a flip switch for N vs S Hemi directions. Axis1 would be Ra/Az and Axis2 would be Dec/Alt

North (CW Axis2), South (CCW Axis2)
East (CW Axis1), West (CCW Axis1)

Mode - Guiding - Follow guiding directions in the same way guiding programs calibrate NESW with pulses for guiding. The following is defined by the ASCOM standard and would always apply. The user could not flip directions.

North (+ declination/altitude), South (- declination/altitude)
East (+ right ascension/azimuth). West (- right ascension/azimuth)

Mode - Pulse Enables pulse movement mode. The arrow keys operate in pulse mode. The pulse duration, interval between pulses and rate are user configurable.

Flip Dir – reverses the direction that the mount moves, swapping East and West / North and South

Anti-Lash – attempts to compensate for mechanical backlash errors in the mount when using the hand controls. Use the checkboxes to turn off/on the compensation for each axis. Best used at slower speeds when trying to use the hand controls to keep an object aligned.

E/W – Works when tracking is on and is based on the amount in the Backlash RA setting. If there is backlash in the RA axis each move east will move the lash to the wrong side. This will move the mount proportionally back to the west trying to remove the backlash so tracking will re-engage without having to travel the backlash distance.

N/S – Works when reversing the N/S direction and is based on the amount in the Backlash Dec setting. When the reverse direction is applied the compensation is applied before the actual move. This takes up the backlash in Dec before the reverse move is applied. Each reverse direction the backlash will be proportionally applied.

Direction Keys Off – If ticked direction keys are temporarily disabled whilst the mount is slewing. Otherwise, if clear, pressing a direction key whilst the mount is slewing cancels the slew.

Mouse lock. When you engage the lock you can then pick up the mouse and move to the mount where you can control certain movements. Left click this button and the mouse will lock and not allow movement of the cursor. A popup message will appear as a reminder it’s on. At the same time it enables the mouse buttons for the mount controls below. It’s recommended to have a 3 to 5 button mouse with a wheel.

• Press any keyboard key to stop or return the mouse cursor.
• Left or Right click for Dec or RA movements
• Center wheel to increase or decrease speed.
• Center wheel click to switch between RA or Dec control
• X1 button for Spiral Search “Out” command
• X2 button for Spiral Search “In” command.

Spiral Search.

The spiral contains dark points or dots that represent each GoTo coordinates. If no points exist then the next button movement ‘Out’ or clicking ‘New’ will create them. Right click on any point and a GoTo dialog will appear.

In – Executes a GoTo to the next inward point. Once at the center the button will do nothing. Available as a gamepad command.

Out – Executes a GoTo to the next outward point. Once at the end the button will do nothing. If no points exist they will be created on the first outward move. Available as a gamepad command.

Abort – Stops any GoTo movement but keeps tracking on. Available as a gamepad command.

New – Creates a new set of points or GoTo coordinates for the spiral. Available as a gamepad command.

Clear – Removes the points from the spiral

Calculate – Opens the dialog to calculate the needed width and height settings

All settings are entered in millimeters (mm). If searching with a camera enter the camera width and height along with the OTA focal length then click the Camera button. When using an eyepiece enter the field stop and OTA focal length and click the Eyepiece button. When the width and height are populated select accept to copy these values to the spiral window.

The search strategy is to create an invisible search box using the Width and Height as the field of view (FOV) size. Each point created on the spiral represents is a single FOV.

Width – The FOV width in seconds of arc

Height – The FOV height in seconds of arc

Use the Calculate button to assist in setting theses.

Limits On – When ‘On’ or check marked two limits will be imposed; 1) Meridian flips will not occur, so an ‘Out’ movement would do nothing if it required a flip. 2) Distance is a defined as the area around the spiral. Anytime the mount moves beyond that area the spiral will reset and no points will be defined. The distance is displayed at the top of the spiral and is the angular distance from the center of the spiral to its farthest point plus another 40%. Anywhere within this area you are free to move the mount how you want and the spiral will not reset.

Tips – As you move closer to the poles and away from the celestial equator the RA or Width movements will overlap exponentially. If you want Dec to overlap set the seconds of arc to a slightly smaller number.

How to calculate FOV in arc seconds

http://astronomy.tools/calculators/field_of_view/

The Field of View Calculator at Astronomy tools is probably one of the better online tools. For imaging mode simply enter the equipment information and calculate the Field of View.  Take the smaller of the 2 numbers in degrees and multiply it by 3600. i.e.  **2.01° x 1.37°**1.37 degrees x 3600 = 4932 arc seconds.  Enter 4932 into the Spiral Search Arc Seconds.

An alternative to the online tool for a sensor is it to do the calculation manually.  To do this, use the smaller side of the chip. (Width of chip in mm * 3460) / (focal length of optic train in mm) = arc minutes * 60 = arc seconds. i.e.  13mm * 3460 /  545mm = 82.5 arc minutes = 4951 arc seconds.

Another alternative for sensors is to take the smaller pixel size divide by focal length then multiply by 206.3 to get arc seconds per pixel.  Multiply that by the amount of pixels on the smaller side of the chip. At binning 1 use the following formula. i.e.  4.63um / 545mm * 206.3 = 1.75 arc seconds per pixel * 2822mm = 4945.8 arc seconds

For eyepieces use visual mode on the field of view calculator. Enter the equipment, take the field of view and multiple by 3600.  1.1°* 3600 = 3960 arc seconds. The manual formula is Scope Focal Length / Eyepiece Focal Length = Magnification.   Eyepiece FOV in degrees / Magnification = real Field of view in degrees.  Multiply that by 3600 for the arc seconds. i.e. 545mm / 10mm = 54.5 mag.  60deg / 54.5mag = 1.10091 * 3600 = 3963 arc seconds

Graphic Section

The 3 dots allow you to select one of the graphic modes for viewing; None, AltAz, RaDec, or 3D. The 3D model shows a German equatorial, polar or alt/az mount and telescope dependent upon the user selected alignment mode.

Warning – Some computers may not be able to display or render the 3D model correctly due to hardware or system limitations. Please check under the Options tab for the Render Capabilities number. Anything less than 2 maybe have these issues so use one of the alternative modes.

- Opens a separate or new window.

- Resets the position of the 3D to its default

- Saves the current 3D model position and view

3D Mode – There is also a Tab item in Options to turn on/off a separate 3D model control. Within the settings on the 3D tab you can select which 3D model to use. Right mouse click on the model to use the following shortcuts…

• Pan - Shift W, A, S, D or Shift Arrow keys or Mouse wheel click and hold.
• Pitch, Yaw - Right mouse click and hold and move
• Zoom – Shift Page Up, Page Down or Mouse wheel

Alt shows the elevation and will switch sides depending on E/W orientation. Az points north at 90 degrees and 180 degrees for southern hemisphere.

Ra/Dec: The Optics checkbox will flip the RA axis 180 degrees. View the RA axis as either the counterweight pointing down or the upward direction of the axis to the sky.

Bottom Status Bar – shows when the mount is in the Home or Parked position.

Status Lights – Parked, Home, Slewing, and Tracking are highlighted when active. If tracking is active and one of the axes has been commanded to move at a user specified rate the tracking status will pulse.

East / West – For German equatorial mounts East (pier East) where the mechanical Dec is in the range -90 deg to +90 deg. Beyond the pole West (pier West) where the mechanical Dec is in the range -180 deg to -90 deg or +90 deg to +180 deg

AzEast / AzWest – For AltAz mounts AzEast when motion is Eastwards from North and AzWest when motion is Westwards from North.

Normal / ThroughPole – For Polar mounts Normal where the mechanical Dec less than 90 degrees and ThroughPole where the mechanical Dec is greater than 90 degrees.

The indicator ring on the compass base of the 3D model shows the current state of the mount relative to the pier.

Errors Alert – Will turn red if an error is logged. This can be reset by clicking on it.

Warnings Alert – Will turn yellow if a warning is logged. This can be reset by clicking on it. Warnings can be caused by a variety of reasons from serial connections to the driver being asked for non-valid information. Check the session log for specific warning messages.

Connection – Is lit green when the mount is connected with a serial or Wi-Fi connection. Click for additional mount information.

Dependent upon the mount controller card firmware capabilities and version the values for some fields may not be available.

Monitor – Status of the internal Monitor. Will be lit green when active. See the Settings Control for more information about the Monitor.

Tracking Rate – one of the 4 icons will be displayed representing the selected tracking rate. Sidereal, Lunar, Solar, or King.

Axis Limits – is yellow when one or more of the axes reaches a limit such as passing too far past the meridian for a polar mount or setting the elevation too high or too low for an Alt Az mount. Warning – Axis limits will not stop the mount from moving and simply displays a warning light. It is up to the user to see that the mount is not damaged. Click the icon and you will be presented with a few options.

• Nothing – The mount will take no specific action
• Turn off Tracking – Tracking will stop
• Park – Mount will slew to the set park position.

Mount connection button. When connected Disconnect will be displayed. When disconnected Connect will be displayed. When connecting any errors will be logged and shown in a popup window.

Sky Watcher Settings

Click the 3 bars to open the settings for the Main Control.

Com Port – Lists available or active ports. It is up to the user to select the correct port for the mount. If you don’t know the mount port open or search for Device Manager and look in the ‘Ports (COM & LPT)’ section of the Device Manager.

Baud Rate – Rates from 300 to 230400 are available. Most mounts work at the default 9600 rate, USB at 19200.

Wi-Fi – Select the Wi-Fi method for connecting to the mount. A Wi-Fi enabled mount or SkyWatcher compatible Wi-Fi dongle is required. The Com Port list will auto populate with available Wi-Fi addresses.

USB – Select the USB method for connecting to the mount. The Com Port list will auto populate with available COM ports.

Mount Type – Choose between SkyWatcher (physical mount) and Simulator. The simulator will work in all alignment modes (Alt/Az, Polar and German Polar). The selected mount type will be used when an application attempts to connect to the server.

Equatorial System – Local or TopoCentric is the default but. TopoCentric is also known as JNOW. Other is set to apparent. The server will accept input and output to the display the coordinates selected.

Alignment Mode – German Polar is the default. Polar (fork) and Alt Az options are also available. The telescope must not be connected when changing the alignment mode. If necessary, reset the telescope position before (re)connecting. See Mount Types section for an overview of the different types.

Rates – Sidereal, Solar, Lunar, and King are present from the ASCOM standards. Clicking the 3 dots will confirm a reset to the default setting.

Max Slew Rate – speeds for the hand controller are a percent of the max rate. If you want slower movements change this to a smaller number.

Minimum Dec Pulse & Minimum Ra Pulse – Warning, it’s recommended you leave this set to 20 and only change after discussing issues and options on the support forum. This option is to refine guiding to a very small step increment. A correct setting is based on baud rate, guide rate, type of mount and settings in your guiding software. 20 milliseconds is the default and will work in almost all cases. A lower setting could cause poor performance depending on the capabilities of individual mounts.

Guide Rates – A percentage of the selected rates to use for guiding. The default 50% is a good starting point for guiding with applications like PHD2. Pulse guiding is not enabled for Alt/Az mounts.

Over Meridian Limit – degrees before or passed the meridian the mount can travel before running into a limit alert. Warning – limits will not stop the mount from moving and simply displays a warning light. It is up to the user to see that the mount is not damaged or is flipped when necessary.

Refraction – Adds the effects of light as it passes through the atmosphere to the coordinates.

Encoders – Turns on and off the internal mount encoders.

Alternating PPEC – This allows pulses from guiding software to not be truncated or cut when the mount implements PPEC. When the internal PPEC runs it’s been shown that some pulses may be randomly cut short because of the timing in PPEC changes. This problem doesn’t seem to exist for mounts using the ST4 or handbox interfaces only using an EQDir cable and the internal PPEC. The ST4 and Handbox interfaces implement a PPEC on/off strategy when dealing with pulses. This means that PPEC is turn off then the pulse is executed, then PPEC is turned back on. This strategy keeps PPEC from interfering with the pulses. Using this option emulates that on/off strategy. Any mount using the internal PPEC and an EQDir cable should consider turning this option on and evaluate its long-term affects. If not using the internal PPEC then there is there is no need to use this option.

Full Current – When you turn on the mount, by default the mount will track at half the watts/amperage. The full current option tells the mount not to track at half current and to use the full current. Full current is recommended unless you’re running off a battery and power consumption needs to be at a minimum.

GoTo Dec Pulse – A new alternative method when tracking and guiding. This turns pulses from guiding commands into a Dec GoTo command. It will slew like a normal GoTo which is different than the default pulse, which is based on the guide rate. GoTo slews are quicker and accurate. You can turn this on at any time even when guiding or tracking. If this option is turned off then guiding in Dec follow the normal guide rate and percentage. It’s recommended to use this option and evaluate it over the long term.

Sync Limits – When checked it enforces the mount cannot sync to targets that are greater than 30 degrees from the current position. It’s recommended to leave this checked as a safety precaution. Warning – When not checked the mount could sync to an object that is too far from its current pointing position throwing off the real axis positions to a point where the axis may end up colliding with the pier or something unintended.

Global Stop (esc) – Allows the escape key to stop the mount at any time. When check it works when the GSS window is minimized or is behind other windows. Be aware that global keys may also be hooked into to other programs that you may be running. Be sure to check if hitting the escape key will also affect them.

Advanced Set – Enables Skywatcher mount advanced control commands. These are more efficient and provide additional information. The mount capabilities are checked and, if advanced commands are not available this setting is ignored.

Park Positions – Click the + and – buttons to Add or remove park positions. Use the Set button to assign the current mount axes positions to the selected park position. You cannot edit or modify the name of an existing position, but you can reset its positions using the Set button. If you need to change a name it’s best to create a new park position and then remove the old one.

Observatory Location - Latitude and Longitude of your observatory is used to calculate local positions. Click the + and – buttons to Add or Remove observatory locations. Use the Set button to assign the currently displayed latitude and longitude to the selected observatory location. You cannot edit or modify the name of an existing observatory location, but you can reset its latitude and longitude using the Set button.

GPS – Reads a COM port for available NEMA sentences. Select GGA or RMC. GGA is the default and RMC does not contain elevation data. GS will retrieve the first found tag GNGGA, GPGGA, GNRMC, GPRMC. Hit retrieve again for another tag search. The time is also pulled for and compared against the local pc clock. Any discrepancies are displayed. If you ran GSS as Administrator you will see a checkbox to update the system time. Check your Windows system options for items that may change the time again like Internet Time Services. For viewing, guiding, and imaging a few seconds off isn’t going to matter.

CdC (Cartes du Ciel) – With the CdC server running you can connect to CdC and retrieve or send the observatory location information.

External Capabilities – Settings that tell external applications the capabilities of the driver.
Can Set Park – When checked this allows external applications to set the telescope Park position to the current telescope position. The default is checked.

Track After Unpark – When checked the telescope will start tracking immediately after unparking. Uncheck if this action is not required, for example when the mount might collide with a closed roll-on roll-off observatory roof. The default is checked.

Custom Gearing – If you have to replace any gears on your mount or changed the ratio then this will allow you to enter that information. Enter the total steps for Ra and Dec along with the total teeth count for each worm gear. The total steps divided by the total worm steps will give you the total worm teeth count. Only integers are allowed so only round down if the total worm steps are a fraction. Leave the tracking offset at zero until a drift test is done to determine if any offset is needed. The offsets numbers relate to a small percentage of Sidereal to apply along with the tracking rates when tracking. Also, the offset will only be applied if tracking is below 2x normal sidereal speed.

To use the custom gearing be sure to turn on the “Apply custom gearing” toggle button. Use the Connect/Disconnect button as all changes require a new connection to the mount. When the custom gearing is being applied the gear icon color will change to the selected accent color.

WARNING: Only enter the custom information if different gearing was put in the mount. Using the default gearing from SkyWatcher does not require the custom information. Entering invalid information can result unexpected results and possible harm to the mount. If you do not know what gearing is in the mount please use one of the support links at the end of this manual.

Set Mount Limits – German Equatorial

When a German equatorial mount continues tracking past the meridian the telescope will be below the counterweight and the telescope may collide with the pier.

The Limit Options dialog sets the action taken when the mount tracks past the meridian or below the horizon. The tracking limit, in degrees sets point when action can be taken. The available actions are

• Do nothing: the mount will continue moving. Only select this option if the mount position is being monitored independently and action will be taken to prevent damage
• Turn off tracking: the mount will stop tracking and remain at its current position
• Park: the mount will slew to the selected park position and stop all motion

The ASCOM Slews option enables automatic rejection of slew and go to actions (RA Dec and Alt Az) from external clients that would move the mount to an unsafe position below the horizon limit. This limit does not apply to user-initiated slewing from the Go To panel.

Set Mount Hardware Limits - Polar

Limits can be set for polar mounts to prevent excessive motion in either axis which may cause damage to cables. The setting dialog graphics show the mount axis movement limits.

The right ascension limit is symmetric about the home position – South in the Northern hemisphere and North in the Southern hemisphere. The angle of the canted polar pier determines the lower limit. The angle of cant is latitude dependent and this is automatically added on to the value of the lower limit. The upper limit is usually set to 90 degrees to allow the mount to be horizontal when pointing North.

The dual telescope can be oriented with the primary telescope on the East or the West side of the dual saddle. The usual position orientation is primary telescope on the East. Click the change button to swap the side. GSS must be restarted after changing the dual telescope side. For the Southern hemisphere the default side is West.

Set Mount Hardware Limits – Alt Az

Limits can be set for Alt Az mounts to prevent cable wrap around the azimuth axis and to prevent altitude axis collisions when close to the zenith. The setting dialog graphics show the mount axis movement limits.

The azimuth limit is symmetrical about the zero degrees position, i.e. North. The positions that can be reached by slewing either clockwise or counterclockwise are highlighted on the graphic

The altitude limit can be set to allow below the horizon motion. SkyWatcher Alt Az mounts typically have an upper limit of 75 degrees for the altitude axis.

Set Home Positions (Polar Mounts Only)

The home position, home park position and AutoHome sensor location can all be independently defined for Polar Mounts.

The home position is the mount position used by the “Home” button. It is specified using azimuth and altitude.

The azimuth is fixed at 180 degrees for observatory latitudes in the Northen Hemisphere and at 0 degrees for the Southern Hemisphere. The altitude can be set to any value between -30 degrees (i.e. below the horizon) and +30 degrees (i.e. above the horizon).

The home park position is the mount position used by the “Park” button when the “Home” park position is selected. It can be set to the GEM default position (RA = 90, Dec=90) equivalent to a counterweight down, celestial pole pointing configuration. The primary telescope is above the secondary. Alternatively, the home park position can be defined using Azimuth and Altitude coordinates. This option will only accept normal mount positions. Through pole positions are rejected.

Use the park positions dialog on the “Settings” page to manage park positions using RA and Dec position values.

The AutoHome function uses the AutoHome sensor to return the mount to a defined position. After this position has been reached the AutoHome function resets the axis values to the location of AutoHome sensor. Skywatcher AutoHome capable mounts such as the EQ8 series, are set to a “factory” default (RA, Dec) location equal to (90, 90), i.e. telescope pointing to the celestial pole with counterweight down.

The physical location of the AutoHome sensor can be changed for each axis. This requires a mount hardware adjustment, typically carried out for dual saddle mounts. The location can be at the default factory setting or a custom setting.

The AutoHome sensor location is specified using azimuth and altitude (c.f. home position). The azimuth is fixed at 180 degrees for observatory latitudes in the Northen Hemisphere and at 0 degrees for the Southern Hemisphere.

The altitude can be set to any value between -30 degrees (i.e. below the horizon) and +30 degrees (i.e. above the horizon).