| Jerusalem Compass The Incredible | 
 enlarge | Brand: Jerusalem Compass
Category: Sports
Buy New: $29.99
Avg. Customer Rating:  2 reviews
Sales Rank: 28769
Format: Cd-rom
Media: CD-ROM
MPN: IJC
UPC: 689076956093
EAN: 0689076956093
ASIN: B000E5WAAE
Availability: Usually ships in 1-2 business days
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| Editorial Reviews:
Product Description
The Incredible Jerusalem Compass will show you the proper direction for your daily prayers, anywhere in the world. No computer chips, no circuitry - this non-electric device spins and stops in the direction of Jerusalem from any place you are in the world. It's an incredible device that defies nature as it shows you the direction of your prayers and dreams. Made from solid brass, with an exquisite engraving on the brass cover. Comes with an attractive chain for attaching keys or for attaching to a belt buckle. Ships in an elegant jewelry case. Recommended by leading Rabbis.
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| Customer Reviews:
 A Very Novel, Useful, and Beautiful Device December 27, 2006
I have found my Jerusalem Compass to be a very unique aid for praying. Many times I have found myself in the "middle of no where", and by just opening the cover, I could turn in the direction of Jerusalem.
I find it to be beautiful, well made, and a very novel and inspirational gift.
 Caution regarding Jerusalem Compass manufacturer's claims August 9, 2006
3 out of 4 found this review helpful
While I have not purchased this device, I wish to provide a word of caution regarding the manufacturer's claim of "always points in the direction of Jerusalem". Firstly, one must manually adjust the device for one's current location, based on the "MPR calibration" number provided by the manufacturer (there's an online database search for many, but not all, cities in which one might find oneself). In email correspondence with the company, I have discovered that this calibration is merely the angular azimuth offset relative to True North based on a concept known as rhumb lines, which are constant heading paths along a curved surface between two locations (in this case, the Kotel is the destination, and the city of interest is the starting point).
The compass itself is a standard magnetic compass with what appears to be a manually programmable bias (i.e., the calibration value in degrees). One must be aware that magnetic compasses point towards Magnetic North, not True North, the difference being defined as Magnetic Declination. Unfortunately, Magnetic Declination is dependent on your current location, and Magnetic North is not a constant. The mathematical models used to compute Magnetic Declination have errors that change depending on how long it has been since the model has been updated (which typically happens once every five years, and which has recently been done in January 2005), so even the MD calculation is not guaranteed always. Additionally, magnetic compasses are notoriously susceptible to man-made magnetic fields (power distribution lines, large building structures, etc).
Therefore, the Jerusalem compass can be counted on to point in the general direction of Jerusalem (the Kotel), not the exact direction as claimed by the manufacturer in marketing material.
This is not to say that the product is not useful. As one moves closer in distance to Jerusalem, where you are more susceptible to North/South translation errors causing large angular swings from the "face East" method, or as one moves further North or South in Latitude relative to Jerusalem, the "face East" method would lead to significant error, and this instrument will help to point you in the right general direction.
In my estimation, someone who finds his travels mainly between such cities as Boston, NY, LA, or Miami, using a standard compass (or consulting a map), and orienting oneself along the east mark would work just as well, so long as you don't stand perfectly rigid during Prayer (if you move your body/head during Prayer, you could almost guarantee that you would face exactly at the Kotel at some time during Prayer). If one finds oneself traveling to Europe frequently (or even around Israel itself, which is subject to the greatest degree of error susceptibility), then this specific instrument could be a very big help, as cities such as London experience a larger angular error relative to "due East".
Of course, one could augment the MPR calibration value provided by the company with the proper Magnetic Declination value for your current location and date to provide a more accurate, but still not exact orientation. If you're interested, here is a Magnetic Declination calculator website (there is also a very good FAQ section) ... [...]
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