How to use an astrolabe I Curator's Corner S3 Ep1 #CuratorsCorner

Curator William Greenwood talks us through the different parts of an astrolabe and how to use it.

#CuratorsCorner #astronomy #astrology

[iaincaillte]

How many nights and days of observation, how many calculations, how much metallurgical skill went in to making that device? When one holds an astrolab, one holds centuries in one's hand. Humility is the word.

[marksminis]

The astrolabe was the first widely available hand held computer / calculator. There were expensive, but brass ones were affordable by many. The first book written in modern English, by Chaucer, is a guide to using the astrolabe. I have one and figured out how to use it. It is about 4" in diameter and can tell time to within 15 min depending on season. If you can identify a star in the sky that is on one of the spurs, you can tell time at night even more accurately. I love mine it's a sweet little personal treasure. Bought it at a Renaissance Faire.

[GhstClown]

"Astrology is seen as somewhat less scientific" - understatement of the century, right there.

[typograf]

My father once made an astrolabe for his class (he was a teacher). It came in two versions, one handheld of plywood, paper, copper and acetate film - used handheld. The other solely made from acetate film was used on an overhead projector. I still have the plywood version.

[Phlebas]

Sometimes I love this modern information era. I was reading an article about celestial navigation, astrolabes were briefly mentioned, and out of sheer curiosity, I asked Google how these instruments work. This video came up, which gave me a pretty good general idea.

Now I've found a really good YouTube channel that I was previously unaware of. Subscribed!

On another note, I'm a field archaeologist. I've done it for six years and I feel I have at least another six years in me, but curation interests me as a possible future career that's a little less physically demanding.

[ingeborg-anne]

At this point I've started imagining that every curator at the museum have a literal corner in which they spend their days :D

[johng.arkenberg]

I think it's wonderful to see how many videos there are now about the astrolabe and its use. My parents bought me a reconstruction when I was a teenager to better learn astronomy and I still use it. The diagram at 1:42 is misleading because the plate is not oriented properly so that it would give a correct reading. The close up of the astrolabe in the curator's hands at 3:04 has a correctly oriented plate. The dotted line they say is "directly above you" is the meridian and it should be pointing straight up towards the ring. The orientation of the plate is critical so that you can to read the correct time since the edge of the astrolabe reads out like a 24 hour clock face. When he says this "is directly above you" he was probably pointing at the zenith, which is the point in the middle of the concentric rings on the plate. As I said before, the dotted line is really the meridian which is the line from North to South that passes through the zenith. Also, the horizon is not a straight line on an astrolabe, but actually the curved line that bends under the pin in the center. If the plate was properly oriented the horizon would begin at around 6a.m. on the right side of the astrolabe's edge, curve under the central pin and end at 6p.m. on the left edge. In this illustration it goes from 8a.m. to 8p.m.

I can understand some of the confusion about how it works since that is sort of glossed over. A simple attempt to explain is that you use the alidade to measure the height, or altitude, of the sun (or a star at night) above the horizon. The rete allows you to then position the sun or star on the plate at the same altitude you measured. If you use a rule to trace from the location of the sun or star through the pin to the edge you can read the time out at the edge as a 24 hour clock. More importantly, you can use it to calculate where the sun and stars will be throughout the year. However, and here is the big limitation, so long as you have the plate made for the latitude you are currently at.

Still, a remarkable piece of technology!

[adel-a]

The first astrolabes were mainly used for triangulation giving latitude and simple distances. Al Fazari 8th century, added angular scales. Al Battani, in his book Az-zij was the first to write the mathematics behind the now sophisticated device. They represent the most important stars in the celestial sphere. Alkhawarizmi made good use of it finding the angle of the ecliptic, the Earth's tilt on it's revolution around the sun.
However, this astrolabe is quite small. A pocket version? It must have been useful and practical for travellers.
Whatever the case during the Islamic civilisation, a whole new craft was invented to keep up with the demand on astrolabes around the Islamic world.
Another interesting point is that women too were into this craft to make delicate and accurate astrolabes. These were delicate and beautiful pieces of art as well accurate and practical scientific tools.

[devakadesilva]

Thanks for a wonderfully genuine explaination. Love it when people put aside their egos and try to bring out unbiased and factual information as much as possible. That last reflection on whether its clear, showed your intent. Thank you!

Also, magnificent invention of our predecessors. Reminded me that we must never forget that we are all here today, in this supposed modern era, because of those who studied hard, progressed science, and invented things. Rather than receiving these things easily, for our conveniences, we must recognize the importance of our own development so that bring about advancement. But NOT at the cost to human values, ethics or biological development. Convenience is a silent killer of growth.

[kristenmoonrise]

This is so interesting. I'm learning both astrology and Arabic. Thanks for sharing!

[iremtalks]

A similar astrolabe is displayed at Pera Museum in Istanbul. It is fascinating to see how it actually works because it is not quite easy to guess how. Even though I watched it 4 years too late, thank you so much for this video.

[apcolleen]

This is by far the best explanation at how these are used. Thank you.

[chicken_kiev]

I came across astrolabes while studying for GCSE and was wondering how they actually worked. This video answered all of my questions, thank you.

[ashy]

I have never been so engrossed in a video on you tube.
Thank you.
Ashraf from Scotland 🏴󠁧󠁢󠁳󠁣󠁴󠁿

[SilverEye]

Interesting. I've seen these devices but never knew how they worked.

[JEEDUHCHRI]

I tend to take for granted that in the present we are surrounded by so many items that have been created with precision. Even down to the most mundane household items are still made with a machine level of quality and precision.

Imagine being a peasant 1200 years ago. Most of your interaction with man made objects would mainly be with items made with care and attention but still rather rough (comparatively speaking).

But it must’ve been so very rare to come in contact with something made with such attention to detail and top quality. An object which demanded the builder to be precise and unerring in many ways.

Absolutely fascinating.

Not to besmirch the craftsmanship of tools, clothing, homes, art, etc of those times way back. Just that a machine like object must’ve been very alien to most common folk.

[Otokichi]

Astrolabe: Holding the World, the Heavens, and the Underworld in your hand(s).

[sailbyzantium]

Well, cool! More of this kind of ancient and medieval astronomy, please!

[littlejuicebox]

That's such a beautiful device, thank you for the in depth explanation and telling us what each part was called

[clearcrystal]

This is amazing. Thank you so much for this video. Now I want more from any civilization! Thank you for sharing!