Plate Solving
Plate solving is AstroHelm’s pièce de résistance. Rather than relying on the notoriously unreliable compass and gyroscope, AstroHelm identifies your precise sky position by matching detected star patterns against a built-in star catalog — entirely on-device, in under one second.
How It Works
Section titled “How It Works”When your phone is steady, AstroHelm captures a frame from the rear camera. Foreground objects like buildings and trees are masked out, the image is de-noised, and stars are extracted. The resulting star pattern is then compared against the internal catalog to determine the exact pointing coordinates. The process repeats automatically every time the phone moves to a new position.
Plate Solve Status
Section titled “Plate Solve Status”The status indicator in the top-left corner of the app shows the current state at a glance:
| Indicator | Meaning |
|---|---|
| 🟡 Unsteady | The phone is moving — waiting for a stable frame |
| 🔴 Not enough stars | Fewer than 8 stars detected in the frame |
| 🔴 Solve failed | Enough stars found, but the pattern did not match the catalog |
| 🟢 (n stars) | Plate solve succeeded using n stars |
Troubleshooting
Section titled “Troubleshooting”Not Enough Stars
Section titled “Not Enough Stars”AstroHelm requires at least 8 visible stars to produce a reliable solution. Partial cloud cover, thin haze, or a bright moon can reduce the number of detectable stars. Plate solving will not work during the daytime, and may only work for parts of the sky during twilight depending on your location.
If you have a multi-lens iPhone, try switching to the telephoto lens. Its narrower field of view and longer focal length can improve star detection in moderately lit skies.
Solve Fails
Section titled “Solve Fails”Artificial light sources in the camera’s view — streetlights, illuminated buildings, car headlights — can be mistaken for stars during the extraction step, producing a pattern that does not match any known region of sky. Repoint the telescope to exclude bright artificial lights from the frame.