# Star Trail Stacker

A browser-local astrophotography workspace for star trails, registered deep-sky integration, fixed-ground nightscapes, explicit dual-alignment comet stacks, Planetary SER stacks and RAW calibration masters. It exposes its decisions, produces 16-bit PNG and signed Float32 FITS output, and uploads nothing.

Contact-Availability: false
Reserved-Address: support@startrailstacker.com
Canonical: https://startrailstacker.com/

- [Star Trail Stacker — trails, nightscapes, deep sky and SER](https://startrailstacker.com/) — Build star trails, registered deep-sky integrations, fixed-ground nightscapes, Planetary SER stacks and RAW calibration masters in your browser. Finds aircraft and satellite trails a matched filter alone misses, and shows the measurement.
- [Why a plain lighten stack loses your faintest star trails](https://startrailstacker.com/star-trail-stacking/) — Why a plain lighten stack loses faint trails when sky brightness drifts, measured on three instruments with the method, range and limits.
- [Star trail stacking on a Mac, honestly compared](https://startrailstacker.com/star-trails-on-mac/) — Sequator and StarTrails.de are Windows-only. What actually runs on macOS and Linux for stacking star trails, what each one does and does not do, and where this tool fits.
- [Why star trails come out dotted, and the arithmetic that fixes it](https://startrailstacker.com/why-are-my-trails-dotted/) — Why exposure intervals make dotted star trails, how the gap is computed from EXIF in seconds and pixels, and how to prevent or repair it.
- [Removing aircraft and satellite trails without losing the meteors](https://startrailstacker.com/remove-aircraft-and-satellites/) — How a matched filter finds the dashed trail an aircraft leaves under a sky full of stars, why sigma rejection removes your meteors along with it, and what a real removal actually changes — measured on a licensed observatory sequence.
- [What your lens does to the frame, measured before anything is changed](https://startrailstacker.com/what-your-lens-does/) — A 14 mm lens moves the edge of your frame by tens of pixels, and the displacement changes sign twice. This reads the measured coefficients for your own lens and tells you the number, in pixels, without resampling anything.
- [Bringing out faint structure without inventing any](https://startrailstacker.com/bring-out-faint-structure/) — Wavelet sharpening separates a picture by scale, so the structure can be lifted without lifting the noise it sits in. What that does to a real telescope frame, what it deliberately leaves alone, and why the Float32 file never changes.
- [Does drizzle help your night, or just make a bigger file](https://startrailstacker.com/does-drizzle-help-your-night/) — Drizzle raises resolution only when your frames landed on different parts of the pixel. This measures that from your own sequence and tells you either way, including on a real observatory set that was dithered and still refused.
- [What it can read, and what has actually been through it](https://startrailstacker.com/what-it-can-read/) — Every file type Star Trail Stacker accepts, what it does with each, and which of them a real file has been through rather than only a test fixture.
- [Taking the result into Lightroom, Photoshop or PixInsight](https://startrailstacker.com/into-lightroom-and-pixinsight/) — Which of the two files this tool writes to open where, what signed and unclamped means for a 32-bit FITS, and the one mistake that quietly ruins a deep-sky integration.
- [What it refuses to do, and the words it uses](https://startrailstacker.com/what-it-refuses/) — Every refusal this tool can put on your screen, what each one means, what to do about it — and a glossary of the terms it uses while doing it.
- [Your first star trail, from the night to the finished file](https://startrailstacker.com/your-first-star-trail/) — What to shoot, what to hand over, what the tool decides for you, how to read what it says it did, and which file to open next.
- [Fixed-ground nightscapes, and the foreground this tool will not invent](https://startrailstacker.com/fixed-ground-nightscapes/) — How the sky and the ground are built as two separate products from a fixed tripod, what the two ground methods actually do, and the reconstruction this tool refuses to attempt.
- [Registered deep-sky integration, and the eight-frame refusal](https://startrailstacker.com/registered-deep-sky/) — Mean, exact median or sigma-clipped mean over registered Lights, why sigma clipping refuses fewer than eight frames before reading a file, and what the 32-bit FITS carries out.
- [Comet stacking, where every scientific decision is yours](https://startrailstacker.com/comet-stacking/) — Star, comet and composite stacks from one set of Lights, why this module detects nothing and chooses nothing, and what marking every nucleus actually buys.
- [Planetary SER stacking, and the three things it insists you choose](https://startrailstacker.com/planetary-ser-stacking/) — Lucky imaging from one uncompressed SER capture: the header it validates first, the region, reference and Best-X choices it requires, and every refusal it can raise.
- [Calibration masters, and the groups it will not mix](https://startrailstacker.com/calibration-masters/) — Building reusable master darks and flats in the browser: how compatibility groups are formed, why they are deterministic, and what a refusal looks like when two frames do not belong together.
- [About Star Trail Stacker](https://startrailstacker.com/about/) — Who made this, what it deliberately does not do, where the measured numbers come from, and why nothing you open in it is uploaded.
- [Privacy — Star Trail Stacker](https://startrailstacker.com/privacy/) — What this site processes, what it stores and what it sends. There is no upload endpoint.
- [Terms — Star Trail Stacker](https://startrailstacker.com/terms/) — What this tool promises, what it does not, and who owns the images you stack with it.
- [Contact — Star Trail Stacker](https://startrailstacker.com/contact/) — Current support-email status and what to record when a sequence will not stack.