Which tool should I start with for observation planning?

Start with Solar Insight Pro to find sunset and golden hour times. Then check MoonSync to see if the moon will interfere with your session. Finally, use the Twilight Calculator to find when the sky becomes truly dark.

Do I need an internet connection to use these tools?

No. All astronomy tools run entirely in your browser using client-side JavaScript. After the page loads, every calculation is performed locally.

How accurate are the calculations?

Solar and twilight calculations use the algorithm from Meeus' Astronomical Algorithms (1998) with precision to ±1 minute. Sidereal time follows the IAU 2006 precession model.

Is my location data shared with any server?

No. Location data (latitude/longitude) is stored only in your browser's localStorage. No data is transmitted to FastTool servers or any third party.

Astro & Photo

天文観測・天体写真ツール

Your complete astronomy toolkit — from golden hour planning to deep-sky telescope alignment. Every tool runs 100% in your browser, offline-ready, zero data upload.

Astro & Photo ツールを探索

ソーラーインサイトプロ

Golden hour, sunrise/sunset, sun position tracker, UV index, and daylight planning — all computed locally.

薄明計算ツール

Civil, nautical, and astronomical twilight times for any date and location — find your true dark-sky window.

ムーンシンク

Moon phase calendar, lunar illumination percentage, moonrise/moonset times, and photography windows.

望遠鏡視野計算ツール

Eyepiece field of view, magnification, exit pupil, and CCD sensor coverage for your telescope setup.

恒星時計算ツール

Local and Greenwich sidereal time for precise telescope mount alignment and GoTo calibration.

行星時間計算ツール

Classical Chaldean planetary hours for any date and location — plan your observation by traditional timing.

天文学の基礎

ゴールデンアワーとは？

Golden hour occurs shortly after sunrise and before sunset when sunlight travels through more atmosphere, producing soft, warm light ideal for landscape and architectural photography.

月の満ち欠けと観測

A bright full moon washes out faint deep-sky objects like galaxies and nebulae. The best observation nights fall around the new moon when the sky is darkest.

恒星時が重要な理由

Earth rotates once every 23h 56min relative to the stars (sidereal day), not 24h. Telescope mounts use local sidereal time (LST) to track celestial objects.

天文薄明と市民薄明

Civil twilight is bright enough for outdoor photography without artificial light. Astronomical twilight is when the sky is truly dark — essential for deep-sky astrophotography.

よくある質問

Which tool should I start with for observation planning?: Start with Solar Insight Pro to find sunset and golden hour times. Then check MoonSync to see if the moon will interfere with your session. Finally, use the Twilight Calculator to find when the sky becomes truly dark.
Do I need an internet connection to use these tools?: No. All astronomy tools run entirely in your browser using client-side JavaScript. After the page loads, every calculation is performed locally.
How accurate are the calculations?: Solar and twilight calculations use the algorithm from Meeus' Astronomical Algorithms (1998) with precision to ±1 minute. Sidereal time follows the IAU 2006 precession model.
Is my location data shared with any server?: No. Location data (latitude/longitude) is stored only in your browser's localStorage. No data is transmitted to FastTool servers or any third party.

All tools on this page run 100% in your browser. No data is collected, stored, or transmitted. Works offline after initial page load.