Giordano Observatory · free tools

Astronomy calculators

Calcolatori per astrofili: ingrandimento e pupilla, magnitudine limite, focale ideale, riprese planetarie, regola NPF, backfocus, cannocchiale polare e rugiada.

Coming soon

Tools for amateur astronomers are on their way

Free tools for anyone who observes and photographs the sky, designed by our observatory: we're testing them with a small group of amateur astronomers before opening them to everyone.

  • Which telescope is right for you5 questions and the 3 right telescopes, with the reasons why
  • Field of viewYour telescope with any camera, on a real photo of the sky
  • What to image tonightThe best objects from your location, with the Moon, comets and meteor showers
  • Astronomy weatherClouds, humidity, dew and wind, hour by hour, with satellite and radar
  • Sky chart and MoonTonight's sky, the Moon's phases and sky events for your calendar
  • Camera databaseAstronomy cameras, DSLRs and mirrorless cameras compared
  • 21 calculatorsMagnification, exposure times, backfocus, mounts and more
  • Your observing logThe objects you've seen and imaged, with the 110-object Messier challenge

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The calculations you really need

Magnification, true field of view and exit pupil of an eyepiece; resolution and limiting magnitude of your telescope; ideal focal length for your camera and your seeing; focal ratio for planetary imaging; exposure time without star trailing using the NPF rule; backfocus with filters; position of Polaris in the polar scope; dew point; integration time and disk space.

In every calculator you can choose your telescope, eyepiece and camera from the database: the fields fill in automatically.

Data: object catalogue from Stellarium (SIMBAD/VizieR, CDS Strasbourg); Digitized Sky Survey sky photos (STScI/NASA) via hips2fits (CDS); sky map by Giordano Astronomia with ESA's Hipparcos and Tycho-2 star catalogues; places: GeoNames (CC BY 4.0); sky darkness from the NASA Black Marble 2016 night lights (VIIRS, NASA Earth Observatory / GIBS); ephemerides computed with J. Meeus's algorithms and JPL orbital elements. Camera data from the manufacturers' official spec sheets.

✦ Tools designed and developed by Mattia Toto for Giordano Astronomia · @toto.astrophoto