Daily operation
In this chapter
- 5.1 Start-up and status checks
- 5.2 Location, date and time
- 5.3 Manual movement
- 5.4 Initial position and Home
- 5.5 GoTo and position synchronization
- 5.6 Tracking
- 5.7 Guiding
- 5.8 Meridian flips
- 5.9 Parking and shutdown
- 5.10 Switch between GEM and AltAz
5.1 Start-up and status checks
At each session, check attachments, counterweight retention, support stability, power cables and movement clearance. Changes to the imaging train can invalidate a previous clearance or protection setup.
- Connect the AHC with its joystick centered and start the mount.
- Wait for a green mount icon and plausible coordinate/state readings.
- Verify the physical arrangement matches GEM or AltAz mode.
- Check time/location, the safety settings available in the active mode (including EC HA Limit in GEM), AEB status and warning indicators.
- Unpark if required for normal operation, then complete the necessary Home and alignment checks.
Before the first GoTo or manual slew after power-on, update the mount's site/time and enable Tracking. Follow 5.6 Start-up and coordinate-limit initialization; Tracking ON alone does not establish coordinate-based protection.
An orange warning triangle means the mount has reported a limit or safety warning. Stop, inspect Settings > Safety & Limits and determine the cause before resuming.
Changing operating mode
Mode switching changes both the physical arrangement and the controller's operating mode. Follow 5.10 Switch between GEM and AltAz, including unloading, the recommended 90° saddle reorientation, AHC mode selection and the mount restart. A software selection alone does not complete the mechanical conversion.
5.2 Location, date and time
Correct location, date and time are essential to the mount's coordinate system. GoTo uses these data to determine where a target is in the sky. Meridian limits use the calculated hour angle, and Horizon/Overhead limits use the calculated altitude. An old observing site, incorrect date, time zone or clock can make these coordinates wrong: the mount may point incorrectly, stop unnecessarily or permit movement that the intended software limits should have blocked. Verify these data at the start of a session, after changing sites and after connecting an application that can update them.
Correct time and location do not protect against an incorrect plate-solving Sync. Sync changes the mount's pointing coordinates; a wrong solution or synchronization can make coordinate-based Meridian and altitude limits unreliable. Verify the solved field before applying Sync. EC HA Limit adds encoder-referenced RA travel protection, and AEB can provide a limited reactive response to abnormal loading. Neither corrects the coordinate error or replaces physical clearance and supervision.
Observing site
Set the site on AHC
- Open Settings > Location.
- Select Home, Observatory, Dark Site 1 or Dark Site 2.
- Enter latitude, longitude and elevation, or select Use GPS Location after a valid fix. Use Mount Location copies the values already stored in the mount.
- Press Save & Apply and verify the resulting location.
Set the site from Windows or KStars / INDI
- Windows / OnStep ASCOM: open the telescope chooser or application's driver setup, select the OnStep driver and open Properties as described in 4.5 ASCOM configuration. In OnStep Setup > Site Information, enter latitude, longitude and elevation using the field's stated sign conventions, then press OK to save. The reference panel labels latitude N is + and longitude W is +; do not copy a signed longitude from another interface without checking its convention. Connect and verify the location reported by the mount.
- StellarMate / KStars: open the INDI Control Panel, select the WARPDRIVE or LX200 OnStep mount driver, and open Site Management > Scope Location. Edit latitude, longitude and supported elevation, then press Set to send the values. Use Options > Configuration > Save if you also want to save the driver's configuration. Labels can vary with the installed driver version; verify the mount's reported values after applying them.
Choose the synchronization direction
When connecting N.I.N.A., decide whether the application's observing site should update the mount or the mount's site should update the application. Use the source whose values you have verified. N.I.N.A.'s location synchronization does not by itself confirm that the mount clock has been updated.
In KStars, Settings > Configure KStars > INDI > Time & Location Updates offers KStars updates all devices (KStars → mount) or Mount updates KStars (mount → KStars), with separate Time and Location controls. Some newer Ekos versions expose separate time/location source controls in the Mount panel. See the KStars INDI configuration guide. Check the chosen direction before connecting, so an old computer profile does not overwrite a correct AHC/GPS site or time.
Read back the resulting site and confirm the correct hemisphere. Saving a profile is not proof that the connected mount received its values.
Time source
In Settings > Date & Time, choose:
- GPS: wait for valid GPS data and use the controller's synchronization controls.
- NTP: use an internet-connected STA network; the controller synchronizes from network time.
- Manual: enter date, time and time zone, then apply them.
You can also set the mount time through the OnStep ASCOM setup panel or another ASCOM application that supports time updates. In the reference OnStep panel, Date/Time and Auto. set Date/Time on Connect control this behavior. Verify the computer's clock, date and time-zone settings before enabling automatic updates. Follow the installed driver's Standard Time / daylight-saving convention, and check the resulting UTC on the mount rather than assuming every interface handles seasonal time changes identically.
The OnStep ASCOM UTC Offset field uses the opposite sign to a civil time-zone value: it is the number of hours added to local time to obtain UTC. For a site at UTC+8, enter −8 (or −08:00, according to the field format); for UTC−5, enter +5.
This sign reversal applies to that OnStep ASCOM field. AHC's civil time-zone selector and the computer's time-zone setting use their own conventions; a UTC+8 site normally remains +8 there. Do not copy the ASCOM value blindly into AHC or an INDI field. Verify both local time and UTC after applying the settings.
Confirm the time zone for the actual observing site before synchronizing, including when using GPS or NTP. If Auto Timezone is enabled, verify its result rather than assuming the chosen offset is correct. Check both UTC and Local Time. For example, at UTC+8 a local time of 22:00 corresponds to UTC 14:00 on the same date. Keep date rollover in mind near midnight. A time-zone change must not be mistaken for an eight-hour change in UTC.
GPS synchronization
GPS supplies time and location data, but a valid fix does not by itself confirm the configured time zone. Open Settings > Date & Time, confirm the site's correct time-zone offset, and verify UTC and Local Time after synchronization. Check the result of Auto Timezone if enabled, including any applicable seasonal offset. Do not proceed to GoTo or Park with a wrong zone.
AHC uses direct satellite GPS, not A-GPS (assisted GPS). It must receive satellite signals itself. Give the controller a usable view of the sky and keep it clear of metal objects or enclosures that can block reception. Buildings, roofs and other obstructions can delay or prevent a fix; a Wi-Fi connection does not replace satellite reception.
The first fix after a cold start generally takes longer and may require 3–5 minutes, or longer with poor reception. Allow time for acquisition in a suitable position. Searching is not a valid fix; verify Fixed and plausible coordinates before using GPS data. With NTP, wait for NTP & mount synchronized. Time ready - waiting mount means the controller has time but has not finished updating the mount.
AP Wi-Fi alone has no upstream internet connection for NTP. Use GPS or manual time when operating directly on the AHC AP without an internet-connected STA route.
If your imaging software sends time/location at connection, recheck the mount after it connects. Choose one authoritative source and correct inconsistent values before GoTo or coordinate-dependent limits are used.
5.3 Manual movement
Slow motion can still snag cables or crush equipment. Keep hands clear and stop before uncertain clearance. A high-speed slew needs additional stopping margin.
Continuously monitor the mount during manual movement. If the connection fails before the release or STOP command reaches the mount, movement can continue until a configured limit or another firmware stop condition is reached. A collision can occur before that happens. Releasing an offline controller or disconnecting an application does not confirm a stop; do not rely on a timeout or AEB to stop safely. Confirm physically that motion has stopped and follow 6.7 Abnormal operation if it continues.
- Verify the mount's location and time. Before the first manual slew after power-on, enable Tracking and confirm the active state; read the coordinate-limit initialization warning.
- Open Motion and select a low speed, such as 2x, 4x or 8x, for a first direction check.
- Push the joystick briefly in the required direction and observe the telescope and cables.
- Release the joystick to request a stop of the joystick-initiated movement. Observe the mount and confirm that the manual slew has ended; ordinary tracking may remain active.
- Press STOP to abort motion when needed. Read the resulting tracking/motion state before continuing.
In Dashboard, joystick movement is available only when STICK is Active; tapping the card switches between Active and Locked. In Motion, the joystick is available for manual movement. F1 lowers the selected speed and F2 raises it on Dashboard/Motion.
Displayed directions refer to the controller's axis commands. The direction seen in an eyepiece or image also depends on telescope orientation and image inversion. Verify with a short movement.
5.4 Initial position and Home
Home is the mount's reference position. On WD-20EP, RA homing uses the absolute encoder and DEC uses an optical sensor. It is different from a user-selected Park location and from a target-coordinate synchronization.
In GEM mode, the default Home points the telescope toward the north celestial pole (NCP) in the northern hemisphere or the south celestial pole (SCP) in the southern hemisphere. The mount determines the hemisphere from the configured observing-site latitude, so verify the location before establishing the reference.
In the recommended AltAz arrangement, the default zero position points the telescope toward the north horizon: azimuth 0°, altitude 0°. The mount's mechanical latitude configuration is 90°. See AltAz zero position for the saddle orientation and conversion checks.
Return to Home uses the physical encoder/sensor references; Park uses the configured parking position and its coordinate/reference state. Although the factory-default Park destination is physically the same as Home, these are separate operations. In N.I.N.A. > Equipment > Telescope, Home and Park are distinct controls: use Home for a physical reference return and Park for the parking procedure. Home appears only when the connected driver exposes the homing capability; if it is unavailable, use AHC or the mount's front-panel button.
Return to Home
You can initiate the return from AHC > Motion > Go Home, or from the mount's front-panel Home button. For the front-panel button, hold it for approximately 0.5 seconds, then release it. The blue STATUS light becomes continuously lit while the Home operation is in progress. Do not keep holding: holding too long or pressing the button again cancels the return.
The mount's front-panel Home button commands physical movement. The AHC HOME navigation button returns to its main screen and does not command mount homing.
- Stop imaging and guiding and check that the entire Home path is clear.
- On AHC, open Motion and select Go Home, or use the front-panel 0.5-second press-and-release described above.
- Observe the actual return. Do not start another operation while it is in progress.
- Wait for completion and a stopped/Home state. Inspect both axes and the cable arrangement.
If homing is interrupted, do not treat the current position as a completed Home. Resolve the cause and repeat a controlled Home operation only when its route is safe.
Reset Home and encoder Home settings
Reset Home resets the mount's coordinate/reference state. It does not perform a physical Home return or save the RA encoder Home position, and is not a remedy for a telescope that is physically in the wrong place.
In AHC > Settings > Mount > Encoder, Save Current Home records the current RA mechanical position as the encoder Home zero/reference. This resets the stored RA Home reference used by subsequent homing and EC HA Limit checks. It is a calibration operation, not a routine pointing correction.
WarpAstron recommends performing this calibration after an accurate plate solve and a verified Sync, with correct location, date and time. Before saving, establish and verify the intended RA mechanical Home position using the supported calibration procedure. Saving at an arbitrary solved sky target would redefine RA Home at that physical position; the command does not calculate a Home offset from the plate-solving result.
- Verify the observing data and confirm that the precise plate solve and Sync represent the actual pointing.
- Establish and verify the intended RA mechanical Home position. If that position is uncertain, obtain the hardware-specific calibration instructions before proceeding.
- Stop tracking, guiding, homing and all other movement, confirm valid encoder status, then select Save Current Home.
- Supervise a subsequent Home return along a clear route, verify the resulting physical reference, and recheck the EC HA boundaries before relying on them.
RA ENCODER ANGLE displays the raw encoder angle and need not read 0° after saving Home. Clear Home Position removes the stored calibration and restores the firmware's configured fallback reference; it does not save the current position as zero.
Changing the RA encoder Home also changes the reference used by EC HA Limit. Do not save an arbitrary encoder position as Home or clear a valid Home calibration to make a warning disappear. Record the current settings and use the hardware-specific calibration procedure or support instructions if the reference is suspect.
5.5 GoTo and position synchronization
Do not view or image the Sun through unfiltered optics. A solar-rate setting or a software confirmation is not a substitute for suitable solar filters on every optical path and an appropriate observation procedure.
Choose and slew to a target
After powering on the WD-20EP, enable Tracking before commanding the first GoTo. This is part of the mount's start-up safety procedure. First update and verify location, date and time, then turn Tracking ON and confirm its active state. See 5.6 for the separate initialization requirements of coordinate-based limits.
Keep fingers, hands and all other body parts out of gaps that can close within the mount body or between the mount, telescope and tripod or pier. High-speed motion can close these gaps rapidly and cause serious injury. Check the full route, keep people clear, and never reach into the moving setup. Press STOP and confirm all motion has stopped before making an adjustment.
- Open GoTo on AHC and choose Solar System, Messier, NGC, IC Catalog or Named Stars.
- Browse the list or search by name, number, type or constellation. Check the displayed current altitude.
- Open the target details and review its altitude curve and current coordinates.
- Confirm time/location are valid and the complete movement path is clear.
- Confirm Tracking is enabled before the first GoTo after power-on.
- Press GoTo Target and watch the physical motion until it finishes.
- Verify the result through an eyepiece, camera or a plausible plate solve. If using the solve to synchronize pointing, verify the field and actually send Sync as described below.
Below Horizon means the target is below the configured horizon and GoTo is unavailable. Waiting Mount Time means the required time data are not ready. Resolve the cause rather than bypassing the check.
If there is no clear GoTo movement, first check whether Tracking has been enabled since power-on and whether the mount is receiving commands. Also check Park state, warnings and the reported target/motion state; a target close to the current pointing may require little movement. Correct the cause and confirm the route before retrying. Do not repeatedly send GoTo or disable limits to force movement; see 8.5 Movement and GoTo problems.
Synchronize a verified position
Use Settings > Mount > Sync to Target, or your control software's supported synchronization command, only after the actual pointing is established. A synchronization tells the mount which coordinates correspond to its present pointing; it does not perform mechanical polar alignment.
Check the target identity, solved field, coordinate frame and the software's expected coordinate convention. If a solve is obviously inconsistent with the sky or mount position, do not apply it. A wrong Sync can compromise subsequent GoTo and coordinate-based Meridian, Horizon and Overhead limits. EC HA Limit and AEB add protection within their stated limitations; they do not validate or correct a plate solve.
5.6 Tracking
After power-on, enable Tracking before the first GoTo or manual slew. Update and verify the mount's location, date and time first. Confirm the selected rate and the mount's actual tracking state before requesting movement.
In Motion, choose Sidereal, Lunar or Solar as appropriate, then use Tracking ON/OFF. Dashboard's STATUS card also provides tracking control in the reference interface.
Start-up and coordinate-limit initialization
If Tracking is forced on after startup before the mount's location and time have been updated, coordinate-based Meridian (GEM mode), Horizon and Overhead / Zenith protection is not yet active. Do not assume that saved limit values or a Tracking ON indication mean those checks have been initialized.
To establish these protections, update and verify the mount's location, date and time, then complete an initial GoTo, a verified alignment Sync, or an accurate plate solve followed by Sync to the mount. A solved image alone does not initialize the mount's pointing: the application must actually send the synchronization. Check that reported coordinates agree with the physical pointing and that the configured limits suit the setup.
Supervise the initial movement and check its full route physically; do not rely on these coordinate limits during initialization. Never apply a guessed or incorrect Sync merely to activate protection.
The recommended sequence is: update site/time → enable Tracking → perform a supervised GoTo or verified Sync → verify pointing and limits. A manual slew alone does not replace the GoTo/Sync step. EC HA Limit and AEB have separate encoder/reference and load-calibration requirements; neither validates the sky-coordinate solution.
Use Sidereal for ordinary stars and deep-sky targets. Lunar/Solar rates are intended for the corresponding targets, with any additional guiding handled by the observing setup. Confirm the selected rate and active tracking status after GoTo and after a restart or stop event.
If tracking stops unexpectedly, first check warning state, limits, power and control commands. Do not raise a limit before establishing why it stopped.
5.7 Guiding
In GEM mode, the RA encoder improves drive feedback, but it cannot correct slow tracking drift caused by a physically misaligned polar axis. Seeing and optical flexure also affect guiding. Aim for polar-alignment error below 2 arcminutes (2′) and follow the polar-axis stability checks, especially with heavy optical loads. Determine whether guiding is necessary from actual images, exposure duration and image scale. For AltAz operation, also consider the field-rotation limitation.
Pulse guiding through ASCOM/INDI
For ordinary computer imaging, use pulse guiding through the mount's ASCOM or INDI connection. The guide camera sends images to the computer by USB; the guiding application sends correction commands through the mount driver. A separate ST4 cable is normally unnecessary. First verify observing data, polar alignment, pointing and the Tracking start-up requirements.
Windows and PHD2
- Complete the Windows driver installation: CP2102 / CP210x VCP, ASCOM Platform and the OnStep Telescope ASCOM driver. Install PHD2 and the guide camera's supported driver separately. PHD2 does not replace the mount's ASCOM driver.
- Connect the mount's PC port by USB, power the mount from its DC supply, and verify the OnStep connection as described in 4.5.
- Create a PHD2 equipment profile. Select the actual guide camera and enter its pixel size, the guide optics' focal length and the mount's actual guide speed. With an off-axis guider (OAG), use the imaging telescope's effective focal length.
- In Connect Equipment, select the OnStep ASCOM telescope driver under Mount, then check its connection settings. Use the supported shared-driver arrangement if N.I.N.A. or another application is also connected; see multiple applications. For this pulse-guiding route, do not choose On-camera, which sends corrections through a camera's ST4 output.
- Connect the camera and mount in PHD2. Verify that mount coordinates and pier-side information are available, the selected guide rate agrees with the mount, and Sidereal Tracking is active.
- Focus the guide camera, take suitable dark frames, choose an unsaturated guide star and complete the calibration checks. Set the DEC flip option before calibration.
- Start guiding. Inspect RA/DEC corrections and RMS in arcseconds, then check actual imaging-camera star shapes. Once guiding is stable, connect the imaging application's PHD2 control for dithering and settling.
Equipment-selection details are in the PHD2 connection guide. Selecting an ASCOM mount connects guiding to the telescope driver; it does not automatically validate the mount's time, location or limits.
KStars / StellarMate and PHD2
For WD-20EP imaging with KStars / Ekos / StellarMate, this manual recommends PHD2 as the external guider. Ekos also has an internal guider. PHD2's calibration review, Guiding Assistant and logs provide a consistent workflow for checking this mount's guiding performance.
- Configure the mount in the Ekos equipment profile as WARPDRIVE, or LX200 OnStep when appropriate; follow 4.2. Add the required guide camera and start the INDI devices.
- In PHD2, select the camera and INDI Mount, using the same INDI server and the already-running WARPDRIVE / LX200 OnStep device. Avoid starting a second driver that independently opens the mount's serial port. If the camera uses a native connection instead, let PHD2 own that camera connection.
- Configure PHD2's equipment profile and calibration as above. Enable Tools > Enable Server so Ekos can control PHD2.
- Set the Ekos profile's guider to PHD2 and enter the PHD2 host and port. Use the local defaults when both run on the same computer; use the actual PHD2 host when they run on different computers. The PHD2 control endpoint is separate from the INDI server and AHC mount-command endpoints.
- With PHD2 configured and running, use Connect in Ekos's Guide module. Confirm calibration and guiding, then test dithering and settling before an unattended capture sequence. Run one guider at a time; do not let PHD2 and the Ekos internal guider issue competing corrections.
See the StellarMate external-PHD2 workflow. Application layouts and supported external-guider integrations vary by installed version.
PHD2 calibration and guiding checks
Obtain a reliable calibration
Calibration measures how guide pulses move a star in the guide image. A sound calibration is essential: in GEM mode, the measured RA and DEC directions should normally be close to perpendicular. Review PHD2's calibration details and warnings; do not accept a repeatedly poor result simply because guiding can be started.
- Choose the calibration field carefully. Use a clear field near the celestial equator and meridian, with sufficient altitude and safe mechanical clearance. Avoid calibrating near a celestial pole, where apparent RA movement becomes small. PHD2's Calibration Assistant can help select a suitable field. Do not cross an unsafe meridian boundary just to reach a preferred calibration point.
- Enter the real equipment values. Check guide focal length, pixel size/binning and the mount's actual guide rate. Use PHD2's calibration-step calculator to obtain a starting value. Recheck calibration after changing guide-camera orientation, guide optics, binning or guide rate.
- Adjust step duration according to the result. If the star moves in response to pulses but the calibration fails because travel is insufficient, increase Calibration step (ms) and retry in a suitable field. This increases each calibration pulse's duration. If movement is excessive and calibration completes in too few steps, reduce it. A longer step cannot fix an unresponsive connection, a disabled guiding output or a mechanical obstruction.
- Investigate non-orthogonal or inconsistent tracks. Check star signal, saturation, polar alignment, guide rate, cable drag and mechanical movement. Inspect whether both axes respond correctly. Do not use an orthogonality assumption or increasingly long pulses to conceal a bad calibration.
PHD2's calibration guidance and advanced guiding settings explain the step calculation, calibration warnings and review tools.
Guide-camera sampling and star quality
The guide camera's angular sampling, measured in arcseconds per pixel, affects how reliably small tracking errors can be measured. It is separate from the camera's exposure time:
Guide image scale (arcsec/pixel)
= 206.265 × pixel size (µm) × binning factor / guide focal length (mm)
For example, 3.75 µm pixels at 120 mm focal length give approximately 6.45 arcsec/pixel at 1×1 binning; at 240 mm, the same pixels give approximately 3.22 arcsec/pixel.
For a preliminary sampling check, use one-quarter of a guide pixel as an illustrative subpixel movement. This is close to the 0.2-pixel centroid-accuracy assumption used in an Open PHD Guiding community calculation, but it is not a measured or guaranteed guiding RMS. Convert the assumed movement to an angle:
Angle corresponding to 0.25 guide pixel (arcsec)
≈ guide image scale (arcsec/pixel) ÷ 4
With the examples above, 0.25 pixel corresponds to 1.61 arcseconds at 6.45 arcsec/pixel and 0.81 arcsecond at 3.22 arcsec/pixel. At 6.45 arcsec/pixel, a 1-arcsecond displacement is only about 0.16 pixel; a one-quarter-pixel assumption does not provide enough measurement margin for that target. At 4 arcsec/pixel, 1 arcsecond corresponds to 0.25 pixel, so 4 arcsec/pixel or finer clears only this preliminary check—not a prediction that the mount will guide at 1 arcsecond RMS.
Do not equate centroid measurement precision with final guiding RMS. PHD2's guide-log tutorial uses a 0.3-pixel displacement as an example of converting pixels to arcseconds; it is not a universal performance ratio. Actual centroid repeatability depends on star size and sampling, signal-to-noise ratio, seeing, exposure and whether multiple guide stars are used. Tracking, flexure and correction behavior also affect the measured RMS and imaging-camera star shapes. PHD2 cautions that guiding results may suffer when the guide image scale exceeds 2.5 arcsec/pixel; see its binning and sampling guidance. For a goal around 1 arcsecond RMS, choose finer sampling where practical, then validate the result in arcseconds using a guide log and the imaging-camera stars. PHD2's best-practices guide suggests about 1 arcsecond RMS as an initial target and assessing at least 15 minutes of guiding data.
Avoid combining large pixels with very short guide optics when aiming for reliably low RMS, especially with a finely sampled imaging telescope. Coarse sampling and undersampled stars can limit centroid measurement. PHD2 can measure subpixel movement, so one guide pixel is not a hard accuracy floor; there is no universal formula that predicts final guiding RMS from image scale alone.
Enter the correct pixel size, focal length and binning so the reported arcsecond RMS is meaningful. Keep stars well focused and unsaturated, use suitable dark-frame / hot-pixel correction, and evaluate guiding against the imaging camera's star shapes and image scale. A small pixel-based RMS alone does not demonstrate accurate tracking. See the PHD2 guide-camera and sampling discussion.
Cables and performance checks
Secure camera and power cables so they do not pull on the guide camera, telescope or mount. Leave controlled slack for both pier sides and the entire flip route, without loops that can catch on a knob or tripod. Cable drag can distort calibration and cause guiding excursions; increasing aggressiveness does not remove the physical cause. Stop movement before rerouting cables. See 3.8 Cable routing.
Once calibration is sound, use PHD2's Guiding Assistant to assess the setup and guide settings. Change one parameter at a time and keep logs. Check seeing, wind, focus, star signal, flexure and polar alignment before changing motor parameters. Encoder feedback is not a reason to copy another mount's PID or backlash settings. See 8.6 Tracking and guiding problems.
DEC output after a meridian flip
For the WD-20EP PHD2 profile, WarpAstron recommends checking Reverse Dec output after meridian flip in Advanced Settings (the brain button) > Guiding. Set it before calibration; changing the option clears the existing calibration, so recalibrate afterward.
This option controls how PHD2 adjusts its DEC calibration mapping after a flip. It does not initiate a flip, change the mount's mechanical limits or configure its encoder. The correct polarity depends on the installed mount firmware and driver behavior. Verify it with Tools > Calibrate meridian flip, or a supervised first flip followed by a check that DEC corrections return the star toward the lock position. PHD2's flip-calibration tool and DEC-flip setting describe this verification.
Make sure the ASCOM/INDI driver supplies valid pier-side information so PHD2 can adjust calibration at the appropriate time. If DEC errors grow after a flip, stop guiding, check pier-side reporting and the DEC option, then obtain a correct calibration before resuming. Do not try to overcome reversed corrections by increasing aggressiveness. Coordinate imaging-application flip scheduling with 5.8 and the Meridian limits.
ASIAIR and other guiding applications
Use the supported ASIAIR mount profile and connection, connect the guide camera, and enter the actual guide focal length. With an OAG or an integrated guide sensor using the imaging telescope, use that telescope's effective focal length. Check pixel size/binning where the application offers these settings, guide-star focus and signal, the mount's guide rate and active tracking.
Pay particular attention to Calibration Step, usually expressed in milliseconds. It is the calibration pulse duration, not the guide exposure or the Max RA / DEC Duration used to limit normal corrections. Choose it for the actual guide optics, camera scale and guide rate:
| Calibration behavior | Action |
|---|---|
| Star moves, but movement is too small to finish calibration | Check the field and guide rate, then increase the calibration-step duration. |
| Star moves too far per step or calibration has too few samples | Reduce the calibration-step duration and repeat. |
| No star movement despite pulses | Check tracking, the selected guide route, connection and permitted motion before increasing duration. |
| Poor RA/DEC directions or an unstable result | Check field selection, star quality, cables and physical setup; repeat a valid calibration before imaging. |
Do not copy a single calibration-step number from a different guide camera or guidescope. Recalibrate after relevant equipment changes, and verify calibration handling and guiding recovery after the first meridian flip. Use the exposure approach below when the application supports it. ASIAIR labels and available controls vary by version; consult the ZWO manuals for the installed product.
RA encoder and guide exposures
The WD-20EP's RA absolute output-axis encoder substantially reduces the transmission's periodic error. Strain-wave mounts with larger residual transmission errors often use guide exposures around 1 second to follow those errors. The EC-series output feedback allows a longer guide exposure to be tested, giving atmospheric seeing fluctuations more time to average out.
For WD-20EP, start by evaluating a 3-second guide exposure, then try 5 seconds if the star signal and residual tracking behavior allow it. Compare several settled intervals and the actual image quality. Longer exposures can reduce unnecessary corrections to seeing; shorten them if actual drift or disturbances require a faster response. 3 or 5 seconds are starting points, not fixed requirements or a guaranteed RMS. Guide exposure is separate from the imaging camera's exposure and the calibration pulse duration. See PHD2 guiding recommendations.
No separate encoder-versus-guider coordination setting is required. The WD-20EP encoder system is part of the integrated drive unit: the output encoder remains active while that drive receives guiding corrections. Normal guide commands and encoder feedback work together within the drive; they are not two independent corrections that need to be switched against each other. Keep the normal encoder configuration and adjust guiding through the guiding application's supported settings.
Output-axis feedback cannot measure atmospheric seeing, optical flexure or polar-axis misalignment. It does not eliminate the need for sound calibration, suitable guide-camera sampling, cable management or the polar-alignment checks at the start of this section.
Optional RJ12 / ST4 guiding
For equipment that specifically needs a standard RJ12 ST4 guide port, obtain the additional WarpAstron-compatible Type-C-to-RJ12 ST4 converter. Contact WarpAstron support or support@warpastron.com for compatibility, purchase and connection instructions. Use only the approved converter for the WD-20EP/AHC connector and pinout; a generic USB-C-to-RJ12 cable is not a substitute.
For most imaging setups, prefer the widely used USB-guiding workflow: the guide camera connects to the computer by USB, and PHD2 or another guider sends pulse-guide corrections to the mount over its USB ASCOM/INDI connection. This needs no RJ12 ST4 converter. Reserve the RJ12 route for equipment that requires it, such as a compatible dedicated solar guider.
If using RJ12 ST4 with PHD2, select On-camera and provide an appropriate Aux Mount connection for pointing and pier-side information when supported. Without those data, follow PHD2's manual calibration/flip procedure rather than assuming automatic adjustment. Do not let independent ST4 and pulse-guiding controllers send competing corrections.
5.8 Meridian flips
A GEM may change pier side to continue following a target safely. The imaging application's flip scheduling, the mount's meridian settings and EC HA Limit boundaries must work together.
An altitude/meridian setting or encoder limit cannot verify clearance for every accessory. Supervise the first flip after changing equipment or limit settings, and remain ready to press STOP.
- Check which system initiates the flip: mount behavior or the imaging application's sequence.
- Read the east/west meridian settings and understand whether the interface uses degrees, minutes or another convention. One hour of hour angle corresponds to 15°.
- Arrange the planned flip so ordinary meridian behavior occurs before the final EC HA boundary, with physical and stopping clearance.
- Check the complete telescope, counterweight and cable route on both pier sides.
- Supervise the first flip with the actual equipment configuration.
- After completion, confirm pier side, target position, tracking and guiding recovery according to the imaging workflow.
If a flip is refused, inspect Park/state, meridian window, altitude limits and EC HA Limit rather than repeatedly issuing GoTo. See Chapter 06.
5.9 Parking and shutdown
Park moves the mount to its stopping/stow position. Home establishes a physical reference. The factory-default Park position is physically the same as Home, but the commands remain distinct even when their destinations coincide. Check that the full movement route is safe for the installed telescope, counterweights and cables.
Before the first Park of the session, synchronize observing time and site, then plate solve and Sync the solved position to the mount. Confirm actual pointing and reported coordinates agree. Polar alignment aims the RA axis; Home establishes a reference. Neither alone confirms the current celestial coordinate solution required for the Park procedure. If the mount has been moved, restarted with an uncertain reference or mechanically repositioned, establish the coordinates again before commanding Park.
- Stop the imaging sequence and guiding.
- Confirm the expected Park position and its full movement route. If its destination is uncertain, do not issue Park until it has been verified.
- Select Park and wait for completion. Verify stopped/parked status and actual position.
- Disconnect control applications so they cannot restart movement. Shut down any mini PC powered through saddle Port B cleanly, then unplug its USB cable while the mount remains powered from DC.
- Support or reduce the load as necessary for power-loss holding. Switch off other saddle-powered accessories, then the mount and disconnect its DC input. The front-panel switch alone does not de-energize Port A/B; remove saddle power leads only after DC input is disconnected.
For the next session, check the physical setup before Unpark. Do not assume that a previously saved Park state still represents the setup if the mount was moved, disassembled or mechanically repositioned.
5.10 Switch between GEM and AltAz
GEM (German equatorial) and AltAz (altazimuth) use different axis arrangements and tracking coordinates. Complete the mechanical conversion, select the matching mode in AHC and restart the mount before commanding normal movement. Changing the software mode does not physically turn the latitude mechanism or reorient the saddle.
| Setup | GEM | AltAz |
|---|---|---|
| Mechanical latitude configuration | Approximately the absolute observing latitude, with the RA axis aimed at the appropriate celestial pole | 90°, with a level support so the azimuth axis is vertical |
| Recommended saddle orientation | Normal equatorial orientation | Reindex the unloaded saddle 90° so the telescope is horizontal at the default zero position |
| Initial reference | Verified GEM Home, then polar alignment and pointing checks | Default zero: telescope toward the north horizon, azimuth 0°, altitude 0° |
| AHC mode after restart | GEM | AltAz |
Stop tracking, guiding, GoTo, homing and parking. Disconnect applications that can command movement. Remove the telescope and attached loads before changing the coarse latitude range or removing saddle mounting screws. Keep the mount secured to a stable support, support the body or saddle while its fasteners are released, and switch off mount power for the mechanical work. Never loosen these fasteners with the telescope installed.
Mechanical conversion to AltAz
- With movement stopped, record the current mode, relevant limits and Park state. Remove the optical load and any counterweight load before releasing the latitude mechanism.
- Level the support. With mount power off, follow the coarse latitude procedure to select a range that includes 90°, then use the fine adjuster to reach that configuration. Keep the body supported; align the range-screw hole completely and fully secure the range screw and locks. Do not force an adjuster at its travel limit.
- For the recommended AltAz mounting orientation, mechanically reindex the unloaded dovetail saddle by 90° as described below.
- Check the saddle attachment and support stability before reinstalling the telescope. Route cables for the new arrangement and check the full altitude/azimuth travel, including clearance below and behind the telescope.
Reindex the dovetail saddle by 90°
The illustrated conversion uses the four M6 saddle mounting screws, not the two dovetail clamp knobs that retain the telescope. WD-20EP has internal connections to its powered saddle. Before removing any saddle screw, switch off and isolate mount power, unplug both external saddle cables, and check that the saddle can be reindexed without pulling, twisting or pinching the internal harness. If the saddle does not move freely or the harness path is uncertain, stop and obtain model-specific guidance from WarpAstron support. Never rotate it through repeated turns.
- Support the unloaded saddle and remove the four M6 saddle mounting screws with a correctly fitting manual hex key. Counterclockwise loosens a screw when viewed from its head.
- Carefully reindex the saddle 90° to the illustrated AltAz orientation while watching for cable resistance; align the mounting holes. Do not pull the saddle away from its internal wiring. Reorient it at its mounting interface; do not use a DEC motor command or change encoder Home calibration to imitate this conversion.
- Refit the original compatible M6 screws, start them by hand and secure all four evenly. Clockwise tightens a screw when viewed from its head. Verify the saddle cannot lift or rock before installing the telescope.
Do not force a screw into a misaligned hole or use a different screw length without confirming compatibility. If the saddle does not seat fully or the fasteners do not engage freely, stop and check the arrangement before adding the telescope or powering the mount.
Select the mode on AHC
After the mechanical work is complete and all fasteners are secure:
- Power the mount and connect AHC. Keep tracking off and do not start a GoTo, Home or Park while changing mode.
- Open Settings > Mount > Mode. Read Current to identify the mode presently in use.
- Select AltAz for the converted setup, or GEM when returning to equatorial operation.
- Tap Save & Apply. The Next Start value identifies the mode selected for the next mount startup.
- In the Restart Mount? dialog, tap Restart to restart the mount and apply the change. If you select Later, the current mode remains active until the mount restarts; do not operate the new physical arrangement using the old mode.
- Wait for the mount to reconnect, reopen Settings > Mount > Mode and verify Current now matches the intended arrangement. Recheck time, location and time zone after reconnecting.
AHC requires a connected, idle mount for mode changes; slewing, homing or parking must finish or be stopped first. A saved pending setting is not confirmation that the active mode has changed.
Default is a separate option labeled Config.h defaults (GEM + axes) in the reference AHC interface. It restores configuration defaults, including axis settings. Use GEM for an ordinary return to equatorial operation; do not treat Default as an interchangeable mode toggle.
AltAz zero position and first checks
With a level support and the recommended 90° saddle orientation, the default AltAz zero position has the telescope pointing horizontally toward the north horizon: azimuth 0° and altitude 0°. Aim toward true north rather than assuming an uncorrected compass reading is exact.
The two angles describe different things: 90° is the mount's mechanical latitude configuration; 0° altitude is the telescope's elevation above the horizon at the default zero position. Reindexing the saddle makes its mounting orientation agree with this expected reference.
- Verify Current: AltAz, a level support, secure saddle/telescope attachment and plausible time/site data.
- Check the physical initial orientation against the default north-horizon reference. If a Home return is needed, use the Home procedure only after checking its complete route, and supervise the movement. If the resulting orientation disagrees, resolve the mechanical arrangement or reference before normal GoTo; do not save an arbitrary encoder Home position to hide the discrepancy.
- Review the safety settings. In the reference AHC interface, EC/HA and Meridian are unavailable in AltAz. Review AEB, horizon/overhead limits and all other available protections separately; GEM settings do not by themselves establish safe AltAz travel.
- Inspect the complete motion route before any Home or GoTo. After verifying site/time, enable Tracking before the first manual slew or GoTo, then use short, low-speed manual commands and supervise the movement, keeping fingers out of pinch points.
- Verify pointing with the controller or control application's supported AltAz alignment/Sync procedure before normal GoTo or coordinate-dependent Park. Recheck tracking after the test; a level mount and north-facing initial position are not a complete pointing calibration.
Ordinary AltAz tracking changes both altitude and azimuth to follow a target, but the sky field rotates relative to a fixed camera. Consider that rotation when choosing exposure times and imaging equipment; changing mode does not make the setup equivalent to polar-aligned GEM tracking.
Return to GEM
- Stop all movement and imaging, disconnect command sources, remove the optical and counterweight loads, and switch off mount power before releasing mechanical fasteners.
- Support the unloaded saddle and reverse the 90° reindexing to restore its normal GEM orientation. Refit and secure all four M6 mounting screws.
- Follow the coarse/fine latitude procedures to restore the appropriate observing latitude. Aim the RA axis at the north or south celestial pole as appropriate; a latitude-range change must remain unloaded.
- Secure all fasteners, reinstall the telescope and any required counterweights, and recheck stability and clearance. On AHC, select GEM > Save & Apply > Restart, then confirm Current: GEM after reconnecting.
- Verify time/site, complete the Home checks, perform polar alignment, and follow the Tracking and coordinate-limit initialization sequence before normal operation. Establish verified pointing before Park. Recheck EC HA Limit, AEB and meridian settings for the restored arrangement, and verify the Park route before use.
Changing back to GEM does not replace polar alignment or validate a coordinate solution retained from the AltAz session.