Capn_Enigma

Very well, then. Source and quote, please?

To end the silly discussion whether or not wooden astrolabes were used aboard ships once and for all, allow me to quote from Dennis Fisher's excellent book Latitude Hooks and Azimuth Rings (p. 25 f): "But taking accurate sights with an astrolabe, a relatively simple proposition in a flat, stable desert, was next to impossible aboard a ship at sea. Usually three men were required. One braced his back against the mainmast while holding the instrument aloft. Another sighted the star. The third would read the angular height from the degree scale. Lining up the dimly shining Polaris through pinhole sights on a pitching, rolling deck demanded more skill than most seamen had, and if a breeze caught the instrument, sight taking was nearly impossible. To overcome the effects of wind and the ship's motion, marine astrolabes were often as small as 6 or 7 inches in diameter, and as heavy as 4 pounds. An astrolabe, however, is accurate in direct proportion to its size; a large instrument shows minute and second gradations more clearly than does a small one. As a result, errors of up to 5 degrees were common on smaller marine instruments. The Portuguese explorer Vasco da Gama circumvented these problems by going ashore to take sights with a large, wooden astrolabe hung from a tree branch. But for mariners far out at sea, the astrolabe was of limited use. Columbus had an astrolabe on his first voyage, but apparently never got accurate readings from it." Thus, if anyone tries to tell you that it is possible to sight stars with a wooden astrolabe aboard a ship, he's spinning a mighty gross yarn. I rest my case.

Excellent find, but this may also be an astronomical astrolabe to calculate sunrise /sunset, the transit of sundry stars in different latitudes or the position of planets. It does not necessarily indicate a Mariner's astrolabes. And as the quadrants are concerned, they don't need to be heavy. A lightweight wooden quadrant gives the exact same readings as a metal one.

Wooden astronomical / -logical astrolabe. Again, not the type used on board a ship.

Astrolabe accuracy is already small due to the small length of the alidade (usually about 8"), but the fact that wood expands / shrinks does not affect accuracy at all. What really affects accuracy is the weight (or lack thereof) of a wooden astrolabe. Imagine the following scenario: It is in the middle of the night, you are standing on the quarterdeck of a heavy galleon. A stiff breeze is blowing, but stars can be seen through the clouds, for the first time since two weeks. Since then, you have been navigating by dead reckoning. The ship is due to make landfall soon and you decide to shoot Polaris to get the latitude. Now there are two possible ways to proceed: 1) You take your trusty brass astrolabe. It is about 7 1/2" in diameter, 1/2 " thick and weighs about 4 pounds. You lift it to your eye and sight for Polaris. Although the wind is a coming in gusts now, the astrolabe hangs as steady as a rock. You have no problems taking Polaris' angle and thus are able to determine your latitude. And now for the alternative: 2) You take the wooden astrolabe that was sold to you by that slippery long- tongued merchant in the last harbor. It is about 10 " in diameter, 1/2" thick and weighs about 3 pounds. You lift it to your eye and sight for Polaris. The wind is coming in gusts now, and due to the large surface and the smaller weight, the astrolabe starts to sway to and fro. You try to steady it, but to no avail. Finally, after a struggle of several minutes, you manage to take an approximate altitude and thus latitude. What you don't know is that due to the swaying you had a deviation of 1.5 degrees in altitude and thus about 100 nautical miles error. Unaware of that, you plot the presumed course and have the helmsman steer it. This course leads you directly into the maw of the most treacherous shoals around. Well, which one of the two scenarios would you prefer?

'fraid the twit goes entirely on you, matey. First, learn the diff'rence 'twixt a Mariner's Astrolabe and an astronomical astrolabe, then start searching for that brain in that dead - eye o' yars and then - perchance - ask 'gain.

The following page allows you to download a template of a Mariner's Astrolabe, which is the only type of astrolabe used aboard a ship.

kanji - kahn'jee : From Japanese "Kan" (the Chinese Han dynasty) and "ji": glyph or letter of the alphabet. The Japanese word for a Han letter used in Japanese. Kanji signs are very popular for tattoos.

The following shops carry metal astrolabes: Renaissance Faire: Mariner's Astrolabe 170 $ Puzzlering: Mariner's Astrolabe 195 $ Saunders & Cooke: Various astrolabes, quadrants etc., rather expensive, starting from 475 $ upward. I cannot say anything about the quality of either astrolabe.

Ah! Now I see! Nice!

Almost no 16th century astronomical astrolabe would work today, neither would most 17th and even some 18th century astrolabes. This is due to the calendar reform carried out by Pope Gregor XIII beginning in 1582. He decreed that on October 4 of that year, the following day not be October 5 but October 15. This was due to inaccuracies of the Julian Calender used until that date. While Spain carried out the reform on October, 4/15 1582, most other catholic countries followed suit only in the next years. Protestant countries took even more time to implement the calendar, Switzerland, for instance, took until 1655, Germany until 1700, while England waited until 1752. Thus, the entire calendar scale of astronomical astrolabes manufactured before the reform in the respective countries is off by eleven days, thus rendering the astrolabe unusable.

First off, I am talking mariner's astrolabes here. Two feet astrolabes were never (Oops! I did it again ) used aboard a ship. If you think differently, please kindly quote a mariner's astrolabe in Stimson, Gunther or another source. Two- feet astrolabes were astronomical instruments with rete, changeable tablets etc., intended for static use on solid land. What's more, most of them were display pieces only, gifts to a sovereign for representation, never intended for real everyday use. With all due respect, Sir, if you continue to insist that wooden astrolabes were used aboard a ship, you are not very familiar with nautical realities. I assure you, trying to aim at a 2nd magnitude star (Polaris) standing on a swaying deck is difficult enough without the astrolabe fluttering in the breeze. If you have a deviation of only 1 degree in measuring Polaris, you are 60 nautical miles off in latitude and wham! there goes your navigation!

On the forearm it will hardly do the beauty of such a ship justice. One of our sailors had a three mast full rigged ship across his chest. Now that was something!

Though a wooden astrolabe is nice for learning how to use it, they were never used aboard a vessel. A wooden astrolabe, as you so rightfully pointed out, is lightweight and that defies the entire purpose of an astrolabe. They were meant to be heavy, having a thickness of up to an inch of brass, so that gusts would not disturb the already extremely complicated process of sighting the sun or the north star. Having built several astrolabes and other period instruments and used them aboard oceangoing ships myself, I can assure you that no pilot worth his salt would ever want to use a wooden one. Trying to sight Polaris with a lightweight astrolabe in everything but a light breeze borders on masochism.

See also this thread. Bodices are a main topic there, also aspects of gravity and biological considerations.

blackjohn, funny that you should mention that site. On the bottom of this page, pictures of some astrolabes that I have built are shown. Here's one of them:

I found the very same Ring Sundial on ebay last year and I sniped it at US$ 12.50, which I thought was a real steal. Congrats to your 1 $ buy! BTW The Ring Dial is from Franklin Mint and was in a series with other scientific instruments, among these an astrolabe, a gunner's level etc. I am still looking for those on ebay at a reasonable price, but so far, no luck.

Hey Patrick, ye ne'er heard of the Crimson Permanent Assurance? They got a decent flag, though:

LOL! No disrespect intended, but considered the massive Gibraltar force and the really huge Jolly Roger, they shoulda called us at least via radio and asked us if everything was shipshape!

Aye! My profile pic:

Boarding School?!? Be that a school for young pirates to learn their trade?!? LOL! That pun was completely unintended, but ye arrr right, of course! Young pirates, we were, and boarding, we did!

Too bad I'm not having any chopped off hands lying around for firing!

The already mentioned Ashley Book Of Knots [in knot # 3820] gives the dimensions as being six feet by three feet. Hope this helps.

This be the thread, you'll be lookin fer, mate? Like I wrote there, it's best to break out the old thimble and needle and sew it fer yer onesies.

Arrr, sharp eyes, ye got! Aye, that flag be based on Captain Vallo's flag from said movie. Difference is that the dagger's handle be pointing away from the flagstaff. T'was this movie that be my gateway drug to piracy and it made a big impression on me... quite literally: I also have this Jolly Roger as a tattoo on my left upper arm.