500 Rule: Max seconds = 500 / (focal length x crop factor). Simple but less accurate.
NPF Rule: Accounts for pixel pitch and aperture for sharper stars.
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About Star Trail
Star Trail solves a specific problem that comes up daily for anyone dealing with this task: doing it once, fast, without an account. The goal was to keep the path from "open the page" to "get the result" as short as possible. No mandatory account, no cookie wall, no upsell at every step. It is one of about a hundred utility tools that share the same philosophy: do one thing, do it well, get out of your way.
When you'd reach for Star Trail
You're on a public or shared machine and don't want to leave traces of what you're working on.
Travelers, contractors, anyone working from a friend's computer.
Nothing is uploaded, nothing persists if you're not signed in.
You're cleaning up a folder of files that accumulated over a project and need to standardize them.
Designers, writers, and developers wrapping up deliverables.
Drop each file in, copy the output, move on.
You're hitting the daily limit of a paid SaaS and need a backup option for a single quick job.
Marketers and ops people whose primary tool is metered.
Stay productive without burning credits.
You need to handle a one-off task right before a meeting and don't have time to install anything.
Anyone working remotely on a borrowed or restricted machine.
Open the page, get the result, paste it into your doc — under a minute.
Frequently asked about Star Trail
- Is Star Trail really free?
- Yes — Star Trail is free for unlimited personal use, with no account required and no watermark on the output.
- Can I use Star Trail commercially?
- Yes. The output of Star Trail belongs entirely to you, with no licensing restrictions.
- Will Star Trail change my original file?
- Never. Star Trail only reads your input file and produces a new output file.
- Do I need to create an account to use Star Trail?
- No. Star Trail works without any signup. We only ask for an email if you decide to subscribe to a paid plan.
- Does Star Trail work on mobile?
- Yes, Star Trail is fully responsive and tested on iOS Safari and Android Chrome.