How to Keep an Astronomy Observing Log

From the time humans have observed the night sky, they have kept records of their observations in various forms: stone, clay tablets, papyrus, parchment, tapestries, and paper. These observation logs have led to scientific discoveries, such as Edmond Halley's discovery that comets are solar system objects with their own orbits; and cultural practices, such as the 12-year cycle of the Chinese zodiac, inspired in part by the orbital period of the planet Jupiter. Keeping a log of your astronomical observations can help you distinguish objects, much as Charles Messier's catalog helped him distinguish nebulae, star clusters, and galaxies from the comets that interested him, and provide a written record you can use to corroborate or refute weather forecasts and to recall memorable observations, such as meteor showers and auroras. Following our steps and suggestions on how to keep an astronomy observing log of your own.


  1. Image titled Keep an Astronomy Observing Log Step 1
    Choose a record keeping medium that works for you. You can keep an observing log either on paper or on computer. A paper log is easier to take into the field with you than is a laptop computer, although you may find it easier to keep records on a computer than in printed form. Computer-based astronomy record keeping programs offer the options of pre-printed log forms and the ability to generate reports, as well as an astronomical database that can help you identify objects and the ability to search your own records to track the positions of planets and comets over time.
    • You may want to use several methods, such as a small notebook you carry into the field on which you make notes, which you transcribe to either a larger notebook or binder or onto a computer.
    • Some amateur astronomers like to include sketches with their notes. If you're one of them, you'll need to have a hard surface under your note-taking paper, such as a small clipboard.
    • Several websites offer pre-printed astronomy log forms you can use to record your observations on. One such site is that run by the American Association of Amateur Astronomers (;
  2. Image titled Keep an Astronomy Observing Log Step 2
    Record your observations in your astronomy log as soon as you can. The sooner you can commit your observation to print or computer, the more accurate your records will be-�not to mention that you may forget to do so entirely if you wait too long. This is where taking a simple notepad into the field with you may help.
  3. Image titled Keep an Astronomy Observing Log Step 3
    Record all the information appropriate to your observation. This may include some or all of the following:
    • The day and date of your observation session. You can record the date in either American format (month, day, year) or European/military format (day, month, year), although you may want to write out or use the abbreviation for the month name to avoid confusion on the part of others who may read your observing log.
    • The times your observing session began and ended. If your observing log includes sketches, include the times those sketches were made. Time should be expressed in Universal (Greenwich Mean) Time, or your local time, with the mention of whether it was Standard or Daylight Time.
    • Your observation location, preferably including your latitude and longitude, but at least the specific area you were conducting your observations in (city, state, backyard, field, park, etc.).
    • What kind of telescope you were using (refractor/reflector � Newtonian, Dobsonian), its focal length, eyepiece, magnification, apparent field of view, and any notes on its performance. If you use a lens filter, note how images compare with and without the filter.
    • What you were observing, including a detailed physical description and/or a sketch. Include an estimate of the object's size based on the angular field of view of your telescope's eyepiece. If the object is a comet, name the constellation the comet appears in and the constellations you searched to find it. If the object is a star cluster, include a count of how many stars you can see. If the object is a nebula or galaxy, include a description of how concentrated the stars or glowing gases are.
    • The amount of moonlight, which can affect how well you can see dimmer stars. You can also include an estimate of the apparent magnitude of the dimmest stars you can see directly overhead (transparency) and the approximate arc-second diameter of star images (seeing).
    • The local weather conditions, including the percentage of cloud cover, and any mist, fog, or haze.
    • You can also include non-astronomical observations such as the presence of wildlife or sources of light or other pollution that hamper your ability to see the sky. If you're sharing your observing session with other amateur astronomers, you may want to include their names and notes on their equipment for posterity. You can also include personal thoughts.


  • You may want to develop a code for recording your observations, such as "CH" to indicate you were hunting for comets during an observing session. If you do, include a translation key for anyone else who might read your records.
  • Consider using a headband or neckband light when doing your astronomical observations so that you have both hands free to write notes or make a sketch in your observing log. You can place a red cellophane filter over the lens, and there are headband lights available with switch controls to display either a red or a white light.
  • In addition to providing a source of freeware astronomy observing log programs, the Internet also features sites where you can post your astronomical observations for other astronomers to share. Some, such as let you post your observations for free and, for a fee, will help you track your progress in whatever observing program you're taking part in.
  • Consider taking part in an observing program. Local astronomy clubs and national organizations such as the American Association of Amateur Astronomers have observing programs for amateur astronomers ranging from the novice to the advanced level, the best known being to observe all 104 objects in the Messier catalog. Taking part in such a program may motivate you to keep your observing log regularly, and when you complete the program, the sponsoring organization will present you with a certificate of achievement.

Things You'll Need

  • Pen
  • Pencil
  • Notebook

Article Info

Categories: Astronomy