Terms

Version and effective date: 2026-11-07. The terms, the Engine Licence and the privacy policy carry the same version.

Who we are and how these terms apply

Star Trail Stacker is provided by Vitali Bibikov, a sole proprietor (JDG) registered in CEIDG, NIP 5213977371, REGON 522636099, trading as AIErudit, Warsaw, Poland (registered in the Polish business register CEIDG; email support@startrailstacker.com) (“we”, “us”). These terms and the Engine Licence form the agreement between you and us for using the site, the Studio, its accounts and its processing code. If they differ on the processing engine, the Engine Licence applies. The privacy policy explains how we handle personal data; it is not part of the agreement.

You accept these terms and the Engine Licence by ticking the box shown before your browser first downloads the processing engine, and again before you create an account. We keep a record of the version you accepted and when. If software acting for you accepts these terms, starts a run or uses the site, you are bound as if you had done so yourself. If you do not accept them, do not use the Studio or create an account.

To create an account you must be at least 16 or have the permission of a parent or guardian. These terms are offered in English. You can save or print this page; earlier versions are available on request.

Accounts and plans

Every currently released stacker tool works without an account. An optional account, with Google sign-in, keeps settings and working nights you choose to save. You may sign out or delete your account from Your account. No paid plan or charge is offered now; any future paid feature will state its price and terms before you choose it. The plans page shows prices planned for after the beta; pressing a button there only counts your interest, starts nothing, charges nothing and asks for no card.

Your images

You keep every right you had in the photographs you open here, and in the stacked image the tool produces from them. Photographs are not uploaded, and no licence to your work is asked for. Subject to the rights in your source material, you may sell, print and publish your resulting photograph.

Data you choose to save to your account, such as settings and working-night snapshots, is stored so that we can provide that feature. You allow us to store it and return it to you for that purpose only.

You are responsible for having the right to use the images you stack.

Ownership of the site and its code

Except for material identified as third-party material, the site software, compiled browser code, processing workflows, user interface, original text, illustrations, documentation, datasets created by the site owner, model weights and other original site content are copyright © 2026 Vitali Bibikov, a sole proprietor (JDG) registered in CEIDG, NIP 5213977371, REGON 522636099, trading as AIErudit. All rights are reserved. No ownership right is transferred by visiting or using the site.

This includes the processing engine we wrote, in every form and number of parts in which it is delivered. Delivering it to your browser is a licence to run it under the Engine Licence, not a sale or a transfer of a copy. Anything these terms or the Engine Licence do not expressly permit is reserved. No right to use the Star Trail Stacker name or logo is granted.

Third-party components and reference material remain the property of their respective owners and are governed by their own licences and notices. They include LibRaw, zlib and libjpeg in the RAW decoder, the Rust standard library compiled into our WebAssembly, ONNX Runtime Web, Leaflet, protomaps-leaflet, tz-lookup and the lens database derived from Lensfun. They are not ours, they are not part of the processing engine, and they are licensed to you under their own licences, listed with their notices and source on the credits and licences page, including the LibRaw licence and corresponding source archive. Nothing in these terms or the Engine Licence restricts a right that a third-party licence gives you.

Limited permission to use the tool

Vitali Bibikov, a sole proprietor (JDG) registered in CEIDG, NIP 5213977371, REGON 522636099, trading as AIErudit grants you a personal, limited, revocable, non-exclusive and non-transferable permission to run the publicly available tool through startrailstacker.com on photographs you are entitled to process. This permission includes commercial use of your own resulting photographs. It does not grant a licence to the site, its code, content, model weights, design, documentation or datasets. The processing engine is licensed only under the Engine Licence. To use it in any other way, ask us about a commercial licence.

Prohibited use

Except as Rights the law keeps for you allows, and unless we give prior written permission, you must not:

• copy, mirror, republish, redistribute, sell, sublicense or host the site or a substantial part of it;
• extract, scrape or systematically collect its code, text, images, documentation, weights or structured content;
• download, save, record or export the processing code, WebAssembly or model files, other than copies your browser or device makes automatically while you use the site or copies we ask you to make for support;
• extract the WebAssembly modules, worker code or any other part of the processing code from your browser’s memory, cache, storage, developer tools or network traffic, or reconstruct it from the parts in which it is delivered;
• reverse engineer, decompile or disassemble the delivered browser code, or derive source code from it;
• deobfuscate the delivered browser code or reverse its minification;
• translate or port the delivered processing code, WebAssembly or model files into another language or product, or create a program that reproduces their expression, including from code obtained by decompilation;
• load, embed or execute the site's code, WebAssembly or model files from another website, domain or application;
• run the processing code outside a browser session on startrailstacker.com, for example in a command-line runtime, on a server or in a packaged application;
• modify the site into a competing or derivative product or service, or use its code to create one;
• submit, paste or upload any part of the processing code, or a capture of the requests that deliver it, to an AI model, code assistant or analysis service;
• circumvent access, origin, rate, robots, rights-reservation or other protective controls;
• use any site material for text-and-data mining, dataset construction, embeddings, retrieval corpora, or machine-learning or AI training, fine-tuning, distillation or retraining; or
• use any site material to evaluate or benchmark a machine-learning or AI system.

These restrictions apply to automated and manual collection. They do not limit an exception or user right that applicable law makes mandatory and that cannot validly be excluded by contract. They do not stop you from writing independent software that does not copy our code, and nothing in these terms restricts honest reviews, comparisons or benchmarks of the tool or its results that you publish.

Automated access and AI agents

In these terms, an “automated agent” is software that, without each action being started by you in real time, operates the Studio, loads the processing code, or retrieves, stores, analyses or transmits it. Bots, crawlers, scrapers, scripted or headless browsers and AI agents that act on your behalf are examples. Unless we agree otherwise in writing, you must not use, or instruct or allow, an automated agent to:

• sign in, operate the Studio, or start or control processing;
• call our API other than through the site's own pages in your browser;
• retrieve, store, analyse or transmit the processing code, WebAssembly, model files or the requests that deliver them; or
• collect site material in breach of the prohibited uses above or our robots and rights-reservation rules.

This section does not restrict assistive technology you use to perceive or operate the site in real time, including screen readers, magnifiers, voice control, switch access and AI-based description or voice tools, as long as it is not used to extract the code. Nor does it restrict ordinary browser features such as translation, reader mode or a password manager. Search engines may index public pages as our robots rules allow. If you need an automated or accessible route that this section seems to block, ask us.

Notice to operators of automated agents and AI services. You are not authorised to access the Studio, the API or the processing code with an automated agent, whether or not a user asks you to. This does not apply to search-engine crawlers that fetch the scripts and styles needed to render and index public pages, as our robots rules allow, and that do not keep or reuse the code for any other purpose. We may block other access and may withdraw any authorisation by notice.

Technical protection measures

We use technical measures from time to time to control access to and use of the Studio, the API and the processing code and to detect automated use. Measures may change; where they process personal data, the privacy policy describes them. You must not, and must not help anyone else to:

• avoid, bypass, disable, deactivate or impair any such measure;
• share or transfer a session, token or other credential issued for your browser, or use one outside the browser for which it was issued; or
• remove, alter or obscure a copyright notice, licence notice, identifying mark or other rights-management information in the site or its code, or distribute code from which it has been removed.

Our code may carry notices and identifying marks that do not change what it does with your images. We may use them, and the records we keep about our builds, as evidence that code found elsewhere was copied from this site.

Security research

Good-faith security testing is welcome if you report what you find to us through the contact page before disclosing it, do not access other people’s data, do not degrade the service, and do not publish or redistribute our code.

Text-and-data-mining reservation

The rights holder expressly reserves all rights for text and data mining, including the reservation contemplated by Article 4(3) of Directive (EU) 2019/790. The machine-readable declarations in TDMRep, ai.txt and the tdm-reservation tag on every page communicate the same reservation for all site material. Our robots rules leave public pages open to crawlers, and keep AI-training crawlers and user-directed AI fetchers away from the code and the Studio. Allowing a crawler to fetch a page is not a licence to mine it or train on it.

Rights the law keeps for you

Nothing in these terms or the Engine Licence excludes or limits a right that applicable law gives you and does not allow a contract to remove. Where the law of the European Union, the United Kingdom or another country gives a lawful user of a program a mandatory right, that right applies within the conditions the law sets. Such rights can include: observing, studying or testing how the program functions while running it as permitted; correcting an error that prevents it from working as described; and decompiling it strictly to obtain the information needed for interoperability with an independently created program.

Please report an error to us first. We will correct errors we can reproduce within a reasonable time, and you may correct one yourself only if we do not. We will provide information needed for interoperability free of charge within 30 days of a request, made through the contact page, that describes the independently created program. Information obtained by decompilation may be used only for that interoperability, may not be given to others unless that is necessary for it, and may not be used to create a program substantially similar in its expression.

What the tool promises

That it does what these pages say it does: it equalises each frame’s background before the lighten blend, it computes the gap-fill radius from your EXIF, it repairs small persistent bright defects, and it masks long thin single-frame streaks. In Deep sky it registers every included Light, integrates it with the selected mean, exact median or sigma-clipped method, and exports the result as a display-stretched 16-bit PNG and signed, unclamped 32-bit Float32 FITS. In Comet mode it uses only the nucleus marks, shared reference and arm decisions you supplied to produce separate star-aligned, comet-aligned and composite PNG/FITS pairs; it does not promise automatic comet detection. In Planetary it applies the explicit ROI, reference and Best-X choices to one admitted SER, refuses a failed global translation instead of substituting identity, and exports only an all-selected-frame valid crop. The measured results quoted on this site come from the real data named on the about page, and the limits of those measurements are stated there rather than hidden.

What it does not promise

Apart from what is stated under What the tool promises, and to the extent the law allows, the tool is provided as it is, with no warranty of any kind. It may fail on a file format it has not met, run out of memory on a large sequence, or produce an image you do not like. It makes no promise about any particular result on your data: the measured comparison spans three instruments and four nights, and your night is none of those nights. If you are a consumer, this does not affect the statutory rights you have where you live, including any right that digital content or services conform to the contract.

Keep your original files. This tool never modifies them — it only reads them — but no browser tool should be the only place a night’s work exists.

Availability

There is no service-level promise. The site may be unavailable, may change, or may stop. Once the worker and any RAW decoder needed for the current session have loaded, that processing can continue without uploading photographs; a fresh or uncached session still needs the site to be reachable.

Features, limits, access conditions or pricing may change. Any paid offer will identify its price and additional purchase terms before an order is placed; these terms alone do not create a charge.

Liability

We are liable without limit for intent and gross negligence, for fraud, and for injury to life, body or health. For slight negligence we are liable only for breach of an obligation essential to the agreement, and then only for foreseeable damage typical of this kind of agreement. Otherwise, because the tool is offered without charge, we are not liable for slight negligence. Nothing here removes any right you have as a consumer that cannot be removed by agreement, and statutory liability that cannot be excluded is unaffected.

Names

Sequator, StarStaX, StarTrails.de, Siril and aerotimelapse.com are named on this site only to compare them factually. Those names belong to their owners and this site is not affiliated with, endorsed by or connected to any of them. Startrails Creator and Starry Landscape Stacker are named on the Mac comparison page on the same terms.

Ending your permission

Your permission to use the tool, including the Engine Licence, ends if you materially breach these terms or the Engine Licence. Where a breach can be put right, we will first tell you and give you a reasonable time to do so, unless it involves copying the code or getting around a technical measure, or unless notice would put the service, other users or our rights at serious risk. We may also end your permission for another valid reason with reasonable notice, or by ceasing to offer the tool. You may stop using the tool, and delete your account, at any time.

When your permission ends, you must stop using the processing engine and delete any copy of it you hold outside your browser’s own cache, and we may close your account and block access from you or the tools acting for you. Images you have produced remain yours.

The sections on liability, enforcement and governing law and courts continue to apply after your permission ends. The sections on ownership, prohibited use, automated access, technical protection measures and rights the law keeps for you, and the Engine Licence’s list of what you may not do, continue to apply to any copy, capture of the requests that deliver it, decompiled output, translation or adaptation of our code that you made or obtained while these terms applied.

Enforcement

We take copying of our code seriously and we will enforce our rights. If we find our code, or code copied from it, used or published outside startrailstacker.com without our permission, that can include notices to the hosts, stores and platforms involved and court proceedings, in which a court may, depending on the law that applies, order the use to stop, award damages or an account of profits, order copies delivered up or destroyed, and award legal costs. Report suspected copying through the contact page. If we do not enforce a term at once, we can still enforce it later.

Governing law and courts

These terms, the Engine Licence and any dispute about them are governed by the law of Poland. Courts in Warsaw, Poland (the common court competent for our place of business) have jurisdiction, except as stated next.

If you are a consumer, you keep the protection of the mandatory rules of the country where you normally live, and you may bring proceedings in the courts there; we may bring proceedings against you only in those courts. Whatever law governs these terms, claims for infringement of our intellectual property rights may also be brought where the infringement takes place, under the law that applies there.

Changes, transfer and severability

We may change these terms and the Engine Licence for legal, security or service-change reasons. A new version number will identify the change. If a change affects your rights or the engine licence and you have an account, we will tell you before it takes effect and ask you to accept it, and you may close your account instead. When a new version changes the terms or the Engine Licence, we will ask you to accept it before your next run or sign-in, and we will not start a run until you do. Otherwise, the version published when you use the site governs that use. Changes never apply to a dispute that has already arisen.

We may transfer this agreement to a successor that takes over the service; your rights will not be reduced by the transfer. If a court decides that part of these terms or the Engine Licence is invalid or unenforceable, the rest remains in force.

Questions

Support is available by email. Use the contact page for the address and guidance. Legal notices may be sent in writing to the postal address above.