TiltMap Pro

TiltMap Pro is a diagnostic tool for understanding what is really happening across your field. It measures star FWHM and shape in a grid of regions and turns that into visual maps and numbers you can use to tune backfocus spacing, tilt plates and sensor orthogonality before committing many hours to a target.

Quick Start (5-10 min)

Prepare a calibrated, focused image (lights + darks/flats already applied). Avoid extremely stretched images; a mild stretch is fine.
Open TiltMap Pro and load your image. For OSC cameras, use a debayered image if possible.
Choose an appropriate grid (e.g. 3x3 or 4x4 for typical APS-C/Full Frame sensors). More cells give more detail but require more detectable stars.
Adjust star detection thresholds if necessary so each cell has a reasonable number of stars.
Run the analysis. Review the FWHM map, numeric corner statistics and any tilt arrows/gradient indicators.
Optionally save the report or export maps so you can compare before/after mechanical changes.

Controls

Control	Default / Range	What it does	When to use
Grid (rows x columns)	3x3	Divides the field into sub-regions where stars are measured.	Increase for large sensors or rich fields; reduce if very few stars are detected.
Detection threshold / SNR	Medium	Controls how aggressively stars are detected in each cell.	Raise if noise is mis-detected as stars; lower in low-SNR fields to get enough samples.
Minimum stars per cell	10	Minimum number of valid stars required for a cell to be considered reliable.	Increase for very dense fields; decrease for sparse star fields or narrowband data.
Measure shape (eccentricity)	On	Computes an optional eccentricity/roundness metric per cell.	Enable when you suspect guiding, tracking or wind-induced elongation.
Normalize scale	On	Scales FWHM values to a consistent reference so maps are comparable between sessions.	Keep on for project-to-project comparisons; turn off if you want raw absolute values only.
Show tilt vector / plane	On	Fits a simple plane to FWHM variations and draws a tilt direction/strength indicator.	Use to get a quick sense of which corner to raise/lower when adjusting a tilt plate.
Export report	-	Exports FWHM, eccentricity and summary statistics (optionally as images and CSV).	Use before/after mechanical changes so you can quantify improvements.

Typical workflows

Pre-project field check

On a clear night, point at a moderately dense star field (not too close to the horizon).
Focus carefully, then capture a short stack or single calibrated exposure.
Analyze with TiltMap Pro using a 3x3 or 4x4 grid.
If one corner is significantly worse (higher FWHM, more ellipticity), adjust tilt/backfocus.
Repeat until the map is acceptably uniform, then start your real project.

Comparing before/after adjustments

Run TiltMap Pro on a "before" image and export the report.
Adjust tilt plate screws or spacing shims in small, documented steps.
Capture a new image and run TiltMap Pro again.
Compare the reports to see whether FWHM differences shrank or moved to a different corner.

Tips & notes

Use good seeing data where possible. Strong atmospheric blur can hide small tilt issues.
A small amount of variation across the field is normal, especially with fast optics or very large sensors.
Try to avoid dense nebulosity or the Milky Way core when diagnosing tilt; star fields are easier to interpret.
Do not over-tune. If all corners are within a small FWHM band and stars look good visually, it's usually "good enough".

Troubleshooting

No stars detected in some cells → reduce grid density, lower detection threshold, or choose a denser star field.
Insanely high FWHM values → check that the image is in focus and not heavily stretched or clipped.
Map looks noisy/random → increase minimum stars per cell or reject low SNR stars.
Tilt direction doesn’t match visual impression → verify that image is not rotated/cropped in a confusing way and re-check with a different field.

Updated 2025-11-15