Tools

Tools to help you better understand or observe our Sun

• ☀Carrington rotationsConvert a date to its Carrington rotation number and back, and browse rotation start and end times.
• ✶Solar ephemerisP, B₀, L₀, right ascension, declination and Julian day for any UTC instant.
• ∑Wolf number calculatorGroups and spots to Wolf number, with an optional personal k coefficient.
• 📅Julian day converterConvert a UTC date and time to a Julian day and back.
• 🔭My observing sessionSunrise, meridian transit and sunset for a date and an observing site.
• 🌍Day and night mapWhere the Sun is up right now: the terminator and the subsolar point on a world map.
• 📄Printable Stonyhurst discAn A4 heliographic grid for any date, to lay under your solar projection.
• 🔖Embeddable badgeA live “Wolf today” badge for your club site or blog — one line of HTML.
• 🗓On this dayWhat the community observed on this calendar day, year after year.