The Astrolabe: the original astronomical computer

//The Astrolabe: the original astronomical computer
The Personal Astrolabe from Janus is an inexpensive astrolabe recreation that makes the joys and mysteries of the astrolabe available to everyone. Most astrolabe reproductions are intended to teach you a little about astrolabes but are not intended to be used. The Personal Astrolabe teaches you about astrolabes, and is also a useful instrument. The Personal Astrolabe is the most accurate astrolabe ever made.  Period.It is called The Personal Astrolabe because each instrument is custom made for you, imprinted with your name and city, and includes a set of problems worked specifically for your instrument. The Personal Astrolabe comes with a 50 page wire bound book that explains astrolabe use, theory, history and includes the necessary astronomical background.The Personal Astrolabe is 7 inches by 8.3 inches (slightly larger than most classic instruments). The Personal Astrolabe is not a kit. It is a fully functional astrolabe, assembled and ready to use. It is produced by printing the components on a high resolution printer on heavy card stock. The front and back are accurately aligned using special tooling, drilled, cut out, laminated in plastic, recut and assembled. The rete of The Personal Astrolabe is printed on transparent material and includes 150 stars arranged in familiar constellations.

All astronomical values are calculated for each instrument including the obliquity of the ecliptic, the time of the vernal equinox for your longitude, aphelion and perihelion, and stars are rigorously precessed to the date of the instrument.

Each Personal Astrolabe is calculated for your latitude and longitude to the nearest minute of arc, and for any date you choose (we have made instruments for as far back as 2800 BC). We recommend 2010 or 2014 as the year for current instruments. These years are halfway between leap years and somewhat of an average for the date and time of the vernal equinox on the back calendar scale. Additional plates for each 5° from 25°, a plate for all horizons, a plate for 0° and 90° latitude and a plate of celestial latitudes are included. Your Personal Astrolabe can be used anywhere within several hundred miles of your home with good accuracy.   The Personal Astrolabe is surprisingly rugged.  Instruments made 15 years ago are still in use, with little sign of age.

The purpose of The Personal Astrolabe is to draw people into the history of astronomy by offering a fully functional astrolabe at an affordable price.  We feel strongly that cost should never be a barrier to education.  We have shipped over 6,200 astrolabes to 60 countries since its introduction.  We are proud that many, if not most, of the astrolabes we have made are the first ones ever made for their location.  It is possible that more people have become familiar with astrolabes through The Personal Astrolabe and The Electric Astrolabe than all previous publications combined.

Information on prices and ordering is at the bottom of this page.

The Personal Astrolabe is also available for southern latitudes.

Two models are offered:

  • The Classic Edition of The Personal Astrolabe recreates a 16th century European astrolabe, and will be valued by anyone with an interest in the history of astronomy and timekeeping.


  • The Modern Edition of The Personal Astrolabe  applies astrolabe principles to an instrument that uses modern terminology and time keeping. The rete of the Modern Edition of The Personal Astrolabe is divided directly by the calendar and can be set in a single step. The kidney shaped scale on the back is the equation of time which is used to convert from apparent solar time to the time in your time zone. The Modern Edition of The Personal Astrolabe is attractive to amateur astronomers, astronomy students and anyone with an interest in astronomy. It is also in use at innovative colleges and universities, secondary and elementary schools around the world for teaching the principles of positional astronomy.


[Modern Edition]


The price for a single instrument is $29.00, US shipping included. Both instruments can be ordered as a “Combination Package” for $40.00, US shipping included. The “Combination Package” includes a single book that describes both models.  Payment can be made with PayPal, personal check or whatever is most convenient for you.

For ordering details and information on international shipping, you can download the order form and ordering instructions as a PDF (44 KB). This order form is a PDF form that you can fill out and print on your computer with Adobe Acrobat.

Contact Janus for information on academic discounts and orders for resale.

You can download The Personal Astrolabe  information as a PDF (1.25 Mb) or send your mailing address to:

18 Kingsbridge Road
Rehoboth Beach, DE   19971

National Language Support

There are only a few elements on The Personal Astrolabe that benefit from national language translation.  The back of the Classic Edition includes the month names and the zodiac sections are on the back and rete.  The Modern Edition back has the calendar, as does the Modern Edition rete.  There is some additional annotation to show the owner’s longitude and longitude correction.

So far, we are able to offer The Personal Astrolabe using the following languages:

  • English
  • Latin (Classic Edition only)
  • French
  • Spanish
  • German
  • Italian
  • Swedish
  • Dutch
  • Portuguese
  • Czech
  • Polish (incomplete)
  • Norwegian (Bokml and Nynorsk)
  • Russian (with special handling)

We can provide language support in any Western language (ISO Latin 1 / ISO 8859-1) or Central European language included in the CE code page (MS Windows 1250).   There is no charge for implementing additional languages that meet these standards.  All you need to do is send the translations (including all accents!) for:

  • Month names
  • Zodiac names
  • North
  • South
  • East
  • West
  • Longitude
  • Longitude Correction
  • Minutes (min.)
  • Seconds (sec.)

It takes a few days to implement a new language and we will send you samples to proof before making your astrolabes.

The book that comes with The Personal Astrolabe is available from us only in English.  Write to us if you would like to translate it and we will work something out.

We are anxious to implement The Personal Astrolabe in an Arabic version, or any other right-to-left-language, but we do not have either the required PostScript Type 1 font or the language knowledge to do it alone.  Write to us if you would like to cooperate on a project to do this.


18 Kingsbridge Road
Rehoboth Beach, DE 19971
or send e-mail to James E. Morrison, Janus.

Janus (pronounced JAY-nus) is named for the Roman god of doorways and beginnings. Janus is usually depicted as having two faces: one looking forward and one looking back to remind you that the future is a product of the past. The spirit of Janus the god perfectly describes the objectives of Janus the company. Janus exists for one and only one reason; to make astronomy education more interesting and more fun. This objective is accomplished by making high quality, inexpensive recreations of historical astronomical instruments available for astronomy education.

2017-05-08T18:02:52+00:00May 1st, 2015|Categories: Uncategorized|

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