Avalon StarGo + N.I.N.A.: Plate Solving & Centering – Error Analysis

Sep 22, 2026 · @Karsten
Short version

Slew & Center in N.I.N.A. never converged with an Avalon M-uno on the StarGo controller. The error stuck at around 45-60'. There were two consecutive causes, both from configuration, not a hardware defect: 

Wrong start position plus offset mode in NINA. The mount believed it was 115° off the actual position. NINA calculated this offset onto the target and sent a declination of −150°. The driver rejected this with “ASCOM driver error: unspecified”. 
Multi-star mode in the StarGo app. Each sync from NINA was incorporated into a pointing model as an alignment star. Two points close to each other resulted in a distorted model. Each GoTo then systematically ended for around 3.7 minutes in RA next to the target, while the position display reported “arrived”.

Solution: StarGo on Single Star, start from home position, maintain location only in the StarGo app (NINA: “Sync to application”), switch on Sync in NINA. NINA then centered to 20" in two passes.
Setup

component


Version/setting

Mount


Avalon M-uno, StarGo control, firmware 6.5.6

ASCOM driver


ASCOM.AvalonStarGo.NET.Telescope 7.1.2.6

ASCOM Platform


6.6.2

N.I.N.A.


3.2.0.9001 (.NET 8)

Plate solvers


ASTAP (blind failover active)

Optics/camera


400 mm focal length, ZWO ASI533MC Pro (3.76 µm)

Guiding


PHD2 (second ASCOM client on the driver)

Location


approx. 48° N, Central Europe

Power supply


15 V DC (corresponds to Avalon specification)
Symptoms in the order in which they appear

Each stage revealed a new symptom. If you only see the last thing, you're easily looking in the wrong place.

#


Symptom


Actual cause

1


ASCOM Device Hub: “Connection failed after 10000 milliseconds”


Connection to StarGo app; later solved directly with NINA and PHD2

2


NINA during centering: “ASCOM driver error: unspecified” (InvalidValueException, SlewToCoordinates)


Mount reported Dec −58° (below the horizon), real +33°; NINA offset gave target Dec −150°

3


Connection to the StarGo app breaks down (“RPC server is not available”)


NINA wrote the location into the mount (“Sync to telescope”)

4


Sync switch is missing in the plate solving panel


“No sync” was active in NINA

5


Slew & Center “creeps”: error remains at ~46–58', abort after 10 attempts


Multi-star model shifted each small GoTo by ~3.7 min RA
Cause 1: Incorrect start position and NINA offset mode

The mount reported RA 17:33 / Dec −58°. The plate solve found RA 23:15 / Dec +32°. That's 115° distance, and the reported position was below the horizon.

“No sync” was active in NINA. NINA therefore did not sync, but rather noted the offset and added it to the target. An offset of 115° became a target declination of −150°. There are no such options (the valid values ​​are −90° to +90°). The driver correctly rejected with ASCOM.InvalidValueException: unspecified. The log clearly shows the line:

Sync disabled - calculating offset instead to compensate ...
Slewing from RA: 17:33:26; Dec: -58° 34' 05" to RA: 11:50:23; Dec: -150° 09' 19"
ERROR ... SlewToCoordinates ... ASCOM.InvalidValueException: unspecified

Secondary finding: When the location was sent to the mount via NINA (“Sync to telescope”), the connection to the StarGo app was lost. The log then says “Unable to set mount latitude …” and shortly afterwards “The RPC server is not available (0x800706BA)”. The driver does not implement SiteElevation SET. So only maintain the location in the StarGo app and select “Sync to application” in NINA.

Fixed by: Entering the location correctly in the StarGo app, starting the mount from the home position and doing a sync. Then the sidereal time, altitude and azimuth were correct.

Cause 2: Multi-star model based on NINA syncs

Even after the position was correct, the "Slew & Center" routine still stalled at an offset of ~46 arcminutes. The StarGo app was set to "MULTI STAR" mode and displayed "2/24 Star Align." Every sync performed by NINA was added to the pointing model as an alignment star.

A multi-star model estimates errors—such as polar misalignment and axis tilt—based on these points. This process requires stars distributed widely across the sky. In this case, however, both points were located in the same field of view (Cygnus, Dec +31° to +33°). The result: the displayed coordinates were correct, but every GoTo slew landed off-target. The decisive test was a small manual GoTo followed by a plate solve:




RA (J2000)


Dec (J2000)

Initial position (Solve)


20:26:26


+33° 23' 44"

GoTo target


20:27:00


+33° 23' 21"

Driver reports afterwards


= Target


= Target

Actual position (Solve)


20:30:05


+33° 42' 30"

The commanded movement was ~30s in RA. The mount actually moved ~3m40s in RA and 19' in Dec. The same RA offset (−3m36s to −3m51s) appeared in every centering run. Manual slewing using the direction buttons, however, was accurate at both slow and fast speeds. This ruled out mechanical issues and power supply problems.

Resolved by: Setting StarGo to SINGLE STAR and restarting from the home position. Afterwards: Slew & Center improved from 4' 13" to 20" error over two runs.
Recommended settings

Slew & Center worked reliably with these settings.

Location


Setting


Reason

StarGo App → ALIGN


SINGLE STAR


A sync acts only as an offset, just as NINA expects

StarGo App → ALIGN


Enter location (Lat N, Long E) here only; select "SaveApply"


The app is the sole source for location data

StarGo App


Start from home position (N/S); select "Sync Home Posit."


The mount knows its position right from startup

NINA → Options → Equipment → Mount


Location sync: "Sync to application"


"Sync to telescope" causes the connection to drop

NINA → Options → Equipment → Telescope


"No sync" disabled


Otherwise, NINA calculates using offsets; large errors result in invalid targets

NINA → Imaging → Plate Solving


Sync ON, Reslew ON


With Reslew OFF, it only solves without slewing

StarGo App and NINA


Enter the actual elevation above sea level


A minor correction; the driver cannot import this value from NINA


For a true multi-star model, capture stars distributed strategically: East and West, high and low, and on both sides of the pier. As long as NINA centers via sync, "Single Star" is the more robust choice.
Diagnostic tips

The error messages alone were useless. The error was identified via the log by comparing "mount reports" with "plate solve finds." 

Open NINA log: Press Windows Key + R, enter `%LOCALAPPDATA%NINALogs`. Search the latest .log file for `CenteringSolver`, `Sync`, and `SlewToCoordinates`. This is where the actual target coordinates sent to the mount are listed. 
Do not confuse J2000 and JNow: NINA displays plate-solve results in J2000, while the StarGo driver calculates in JNow. In 2026, this accounts for a difference of ~1 min in RA and ~5–8' in Dec. Convert coordinates before comparing; otherwise, you might see errors that don't actually exist. 
Check sync: Set Sync ON and Reslew OFF, perform a solve, then check the StarGo driver window to see if RA/Dec jump to the solved position (in JNow). 
Check mechanics: Slew slowly and quickly using the directional buttons, performing a solve before and after the movement. If the solved position changes in the same way as the display, the clutches, motors, and power supply are functioning correctly. 
Check GoTo: Perform and solve a small GoTo (30'–1°) in NINA under Equipment → Telescope. If it lands off-target despite the display indicating "Target reached," the pointing model is the likely culprit. 
Plausibility: If the mount reports a position below the horizon or a consistent offset across multiple runs, the issue lies with the configuration or model, not the solver.