Does The Astronomer's Knife work offline?
Yes. The Astronomer's Knife is a single HTML file that runs entirely in your browser. No internet connection required after download. Your data never leaves your device.
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The Astronomer's Knife
Ten sky tools — offline, portable, permanent
Science & ResearchKnife 17 of 50
$39
One-time purchase · Instant download30-day money-back guarantee
$39
What it does
The Astronomer's Knife puts ten essential astronomy tools into a single HTML file that works offline, forever. Tonight's Best analyses your location, date, moon phase, and weather to recommend the best objects to observe right now. The interactive Sky Map renders your local sky in real time. A Celestial Events calendar tracks eclipses, meteor showers, conjunctions, and oppositions. Calculate moon phases with visual displays, track the sun's position and arc, compute sunrise and sunset times for any location, convert between Julian and calendar dates, browse 88 constellations with detailed guides, calculate stellar magnitudes and distances, and find planetary positions with visibility data — all without an internet connection. Your observations stay on your machine.
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INCLUDED TOOLS — 10 TOTAL
\Tonight's Best
\Sky Map
\Celestial Events
\Moon Phase Calculator
\Solar Position Tracker
\Sunrise & Sunset Calculator
USE CASE 01\Dark Sky Session Planning
\Julian Date Converter
\Constellation Guide (88)
\Magnitude & Distance Calculator
\Planetary Position Finder
USE CASE 02\Astrophotography Timing
USE CASE 03\Constellation Tour Guide
USE CASE 04\Remote Observatory Scheduling
USER'S GUIDE
Download PDFFull documentation with detailed instructions for every tool.
DELIVERYSingle HTML fileDownload instantly after purchase
PRIVACY100% localYour data never leaves your machine
OWNERSHIPOne-time purchaseNo subscription, no recurring fees
PRO TIP
The file works in any modern browser — Chrome, Firefox, Safari, Edge. Save it to a USB drive, email it to yourself, or keep it in your cloud storage. It will work anywhere, anytime, forever.
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$39. Yours. Forever.
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OTHER PRODUCTSIs The Astronomer's Knife a subscription?
No. The Astronomer's Knife is a one-time purchase of $39. No monthly fees, no renewals, no price increases.
What is included in The Astronomer's Knife?
The Astronomer's Knife bundles 10 science & research tools into a single HTML file: Tonight's Best, Sky Map, Celestial Events, Moon Phase Calculator, Solar Position Tracker, Sunrise & Sunset Calculator, and 4 more.
Where is my data stored?
Entirely in your browser's local storage. Nothing is uploaded, transmitted, or tracked. You can export your data as JSON at any time and import it on another device.
Which browsers and operating systems does The Astronomer's Knife support?
Any modern browser — Chrome, Firefox, Safari, Edge — on Windows, macOS, Linux, ChromeOS, iOS, or Android. The same file works everywhere.
Can I try The Astronomer's Knife before buying?
Yes. The interactive demo on this page is the full knife running in an iframe. Try every feature in your browser, no signup required.
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