Subject: Re: Astrolabe Makers?

From: [email-masked]
Date: 5 Dec 1996 12:12:21 GMT

There's a company that recreates medieval/renaissance astrolabes, if that
would be of help, though I can't find the catalog at the moment.  $150 for
the least expensive if I remember.

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From: [email-masked]
Date: 5 Dec 1996 19:24:53 GMT

Dear fellow friend:

For the uneducated, what are Astrolabes ?

Thank You.

Alberto
>from  London

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From: [email-masked] (John O. Kopf)
Date: 6 Dec 1996 05:51:06 GMT

> For the uneducated, what are Astrolabes ?

A medeval mechanical computer/"surveying instrument"...contained a star
chart so you could hold it up to the sky and twist some bits to find
directions (e.g., the arab caravans used it extensively to find Mecca;
also used for navigation).

JK

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From: [email-masked] (Steve Rayner)
Date: Sat, 7 Dec 1996 11:30:18 GMT

In a previous article, [email-masked] ("Alan K. Gideon") says:

>John O. Kopf wrote:
>Also used by Columbus (really!)
>
>-- 
>Alan K. Gideon, P.E. | Naval Architect & Marine Engineer
>                     | [email-masked]
>
>"If you're not still learning, you've already retired 
>     - your boss just hasn't noticed yet."
>	                         Peter Coffee, November 1996
>
>
>

Yep! The astralabe was used until Hadley invented the sextant in 1785.

-- 
Steve. 

******************Knowledge is wasted if it is not shared.*******************

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From: [email-masked] (darylb)
Date: 6 Dec 1996 22:56:50 GMT

> For the uneducated, what are Astrolabes ?

Round flat brass things ;^)

They are a an early mechanical computor for resolving problems in
spherical geometry quickly and easily.

In the "classic" form they contain a latitude specific plate which shows
the horizon and a gridwork of altitude/azimuths above the horizon. They
can also show elevations below the horizon for twilight calculations.
Above that is a rotating fretwork of metal (called a rete) representing
the celestial sphere. The fretwork usually has little points which
represent specific stars. The ecliptic (an offset circle) is also included
on the rete. Around all this is a 24hr timescale and on top of everything
a rule representing the sun. 

You set the edge of the solar rule (representing the sun) to it's position
on the ecliptic for that date. You then rotate both rete and the rule
(preserving it's position on the rete) so that the edge of the rule is on
the current time. Where the rule intersects the ecliptic over the gridwork
is the position of the sun at that time and date (ie 36deg high, 26deg
south of east, say). 

Similarly you can sight the position of the sun (using another rule on the
back that has sights) and work out the time or you can place the sun on
the horizon and find the time of sunrise or sunset on the date you
queried. Similarly you can do the same for stars. etc etc etc etc etc

The list of things this thing can do is nearly endless the only down side
is you need a plate for each latitude. To remedy that there are universal
versions but they have some down sides too. But that's another story 8^)

If your really interested check out this for a start;

http://myhouse.com/mc/planet/astrodir/astrolab.htm

Hope that helps

Cheers
Daryl

-- 
- Clouds are high flying fogs.
- ³...ethidium bromide is a potent mutagen and carcinogen, and
the Merck index lists it as having a somewhat bitter taste²
- All waste ultimately becomes food.

---

From: Rick Cook <[email-masked]>
Date: 7 Dec 1996 00:25:50 GMT

>For the uneducated, what are Astrolabes ?
An astrolabe is a primitive navigation instrument designed to measure the
height of a star above the horizon, thereby letting you determine how far
north or south you are. Mechanically they are quite simple, being a metal
circle with one or two sighting vanes that pivot at the center. However
they need to be marked off and ruled rather precisely.

Quite a handsome piece of work, especially since they were often decorated.
Chaucer wrote a treatise on how to use one.

--RC

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From: "Alan K. Gideon" <[email-masked]>
Date: Fri, 06 Dec 1996 07:52:17 -0500

---

From: [email-masked]
Date: 7 Dec 1996 14:17:28 GMT

Daryl:

Thanks for putting so much effort into a very descriptive
detailed reply.

In fact I was looking into my local lang. dic. and I was unable
to find it, its so intresting to enrich once horizon.

Alberto

---

From: Rick Cook <[email-masked]>
Date: 8 Dec 1996 20:46:57 GMT

Abrasha wrote:
>I have no problem with sharing my expertise on subjects I know >something
about, but it  rubs me the wrong way when people seem to be >plain lazy and
not willing to use the resources available to them.
I understand your annoyance, but in this case I think it is misdirected.

The questioner simply wanted to know what the thing is. A one or two
sentence response would have sufficed. It seems to me that's a perfectly
appropiate question in the NG.

--RC

---

From: Rick Cook <[email-masked]>
Date: 8 Dec 1996 20:47:00 GMT

Abrasha wrote:
>This is a treatise on the Astrolabe which Chaucer wrote to explain the use
>of the device 
>to his 10 year old son Lewis.  The entire text of this treatise is
>available online in 
>Middle English (without illustrations) at
>http://www4.torget.se/artbin/art/oastro.html 
>If you are not well versed in Middle English, you won't even get through
>the first 
>paragraph though.
>
I managed to struggle through it 20 years or so ago when my first wife was
in the M.phil program at University College Dublin. But I had to look up
some other references to make sense of what I was reading.

--RC

---

From: Abrasha <[email-masked]>
Date: Mon, 09 Dec 1996 00:54:51 -0800

> appropiate question in the NG.

I disagree.  A two WORD querie of the Web would have provided the person who asked the 
question with a wealth of information.  All the person would have needed to type, would 
have been "Infoseek" (or Alta Vista or Webcrawler or etc., etc.) and then "astrolabe" 
and he would have received more than 900, yes NINE HUNDRED, references relating to 
astrolabe.

Yet he chose to ignore the very existance of the medium he is participating in, by 
posing the question to the ng, which in my opinion is an extreme example of laziness.

Apropos, I did post a seperate and rather lenghty response to a poster (I think it was 
you) who called the astrolabe a PRIMITIVE instrument, which really set my remaining 
hairs on end.  Besides, I did supply a very valuable URL relating to astrolabes in both 
my posts.

And while I am on the subject and on my soap box in rant mode, I am equally annoyed at 
the seemingly endless string of people who ask questions as to where to find certain 
items, manufactured in the US.  Invariably, ALL of these questions can be answered by 
searching the Thomas register Online, which I believe is mentioned in the FAQ's of this 
ng.  

Nevertheless, I have many times responded politely to these posts and have given the URL 
of the Thomas Register as well as the results of the searchers I did for the posters of 
the questions.

Every once in a while, all those drips make the bucket get full and it needs to be 
emptied out.  The bucket is empty now, so I can take a bunch of drips again, but sooner 
or later it will fill up again.

Boy, I do feel a little better now.

Abrasha
http://www.abrasha.com

---

From: Abrasha <[email-masked]>
Date: Sun, 08 Dec 1996 01:11:18 -0800

Rick Cook wrote:
> height of a star above the horizon, 

Astrolabes are not primitive at all, but rather very sophisticated astronomical devices 
capable of solving many astronomical problems.  The typical astrolabe was not a 
navigational instrument although an instrument called the mariner's astrolabe was 
used widely.

Astrolabes were used to tell time during the day or night, to find the time of sunrise 
and sunset and, thus, the length of the day, to locate celestial objects in the sky, 
and as a handy reference of celestial positions.  To name just a few of it's many uses. 

Islamic prayer times are astronomically determined, and the astrolabe could be used
to determine the required times. Modern astrolabes, such as the Personal Astrolabe, can 
be used to solve astronomy problems involving sidereal time and can be used with modern 
civil time.

I own to books on the subject

"The Planispheric Astrolabe"

Published by The Department of Navigation and Astronomy
National Maritime Museum, Greenwich

"Chaucer on the Astrolabe" with original illustrations

Revised from the 1931 Oxford Edition by R.T. Gunther
Published by Norman Green in 1977

This is a treatise on the Astrolabe which Chaucer wrote to explain the use of the device 
to his 10 year old son Lewis.  The entire text of this treatise is available online in 
Middle English (without illustrations) at http://www4.torget.se/artbin/art/oastro.html 
If you are not well versed in Middle English, you won't even get through the first 
paragraph though.

The astrolabe described in the Chaucer book that I have, used to be made by a local Bay 
Area company.  Greene Designs, PO Box 8451, Emeryville, CA 94662.  I do not know if they 
are still in business.  It wasn't a particularly precise instrument and rather crudely 
made of cast pewter, but it was a good device to teach the uses of the instrument.

There are a great number of Web sites (972) devoted to astrolabes and I suggest that you 
use the Yahoo or Infoseek search engines, to name just a couple, to find them.  
Cyberspace is a great place to hang out and find stuff, but you have to be willing to 
use your head and keyboard a little.  INFORMATION SUPER HIGHWAY ... remember that 
terrible phrase?

Just one site to get you started though:  
http://myhouse.com/mc/planet/astrodir/astrolab.htm

I tried to make an astrolabe once.  I failed miserably.  I did not possess the proper 
tools to lay out, scribe and engrave certain arcs accurately.  The makers of Islamic 
astrolabes of the 8th and 9th centuries AD did.  Not only did they have the tools, they 
also had the neccessary skills.  And a quite remarkable knowledge of astronomy.

To call astrolabes PRIMITIVE is an insult to the inventors and makers of these fine and 
precise instruments (the original astronomical computer), and displays a rather pathetic 
lack of knowledge about the subject.

Abrasha
http://www.abrasha.com

---

From: [email-masked] ("Paul C. Dickie")
Date: Tue, 10 Dec 96 03:20:42 GMT

In article <[email-masked]> [email-masked] "Abrasha" writes:

>I disagree. 

But of course Abrasher disagrees!  He's so utterly convinced that he's 
absolutely right that he simply won't consider it possible that, in fact, he
might be utterly *wrong*...

> A two WORD querie of the Web would have provided the person who asked the 
>question with a wealth of information.  All the person would have needed to
> type, would have been "Infoseek"... <yak, yak, yak... snipped>

That assumes that the questioner *has* web access. Some folk don't.

>Yet he chose to ignore the very existance of the medium he is participating 
>in, by posing the question to the ng, which in my opinion is an extreme 
>example of laziness.

Yet that follow-up seemed to shew that its author had confused the WWW with
Usenet; one might suppose that to indicate not sloth but stupidity...

>Besides, I did supply a very valuable URL relating to astrolabes in both 
>my posts.

Which is of approximately zero help to someone without web access!

>And while I am on the subject and on my soap box in rant mode, I am equally
>annoyed at the seemingly endless string of people who ask questions as to 
>where to find certain items, manufactured in the US.  Invariably, ALL of 
>these questions can be answered by searching the Thomas register Online, 
>which I believe is mentioned in the FAQ's of this ng.  

Do they *all* have WWW access?  If not, such a response is useless...

>Nevertheless, I have many times responded politely to these posts and have
>given the URL of the Thomas Register as well as the results of the searchers 
>I did for the posters of the questions.

If they don't have web access, one might as well tell them the shelf number on 
which a book is to be found at one's own local public library!

>Every once in a while, all those drips make the bucket get full and it needs 
>to be emptied out.  The bucket is empty now,

Does that mean that Abrasha will make less, or more, noise?

-- 
< Paul >

---

From: [email-masked] (Steve Rayner)
Date: Tue, 10 Dec 1996 11:18:54 GMT

He is in a good spot to look at one or more.  I believe that the British 
Museum has some.  Another source would be the Clockmakers Museum in the 
Guildhall.  Possibly even the Science Museum.

In a previous article, [email-masked] (Rick Cook) says:

>net!uunet!in2.uu.net!192.80.63.252!delphi.com!usenet
>From: Rick Cook <[email-masked]>
>Newsgroups: rec.crafts.metalworking
>Subject: Re: Astrolabe Makers?
>Date: 8 Dec 1996 20:46:57 GMT
>Organization: Galahad
>Lines: 12
>Message-ID: <[email-masked]>
>References: <[email-masked]>
>NNTP-Posting-Host: bix.com
>X-Newsreader: Galahad 1.3
>
>Abrasha wrote:

-- 
Steve.

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From: "w.j.ward" <[email-masked]>
Date: 11 Dec 1996 04:00:54 GMT

I would like to also point out that, according to James Burke in his TV
series, "The Day the Universe Changed", the develpment of the tooling
necessary to mark off the astrolabe lead to machine tools as we know them
today.  The innovator (don't remember who it was now) basically created a
dividing head...a toothed wheel with a screw to advance the wheel.
-- 
God ==> Man ==> State

W.J.Ward, Redford Twp., Michigan

Rick Cook <[email-masked]> wrote in article <[email-masked]>...

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From: Abrasha <[email-masked]>
Date: Sat, 07 Dec 1996 23:42:18 -0800

> For the uneducated, what are Astrolabes ?

Dear Alberto (and others),

I don't get it.  This is the INTERNET remember.  The INFORMATION SUPER HIGHWAY as some 
people like to call it.  I hate that name, but is does describe the place to some 
extent.

Ever heard of Yahoo, Infoseek.  Well, EDUCATE YOURSELF, and take a look.

I will give you just one site of the 972 that I found (that's right nine hundred and 
seventy two) the URL is:  http://myhouse.com/mc/planet/astrodir/astrolab.htm

I have no problem with sharing my expertise on subjects I know something about, but it 
rubs me the wrong way when people seem to be plain lazy and not willing to use the 
resources available to them.

The Internet is an incredible research tool, if only you would use it!  So get off your 
butt and use your head, and your keyboard a little.

Abrasha
http://www.abrasha.com

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From: [email-masked] (Alan Frisbie)
Date: 10 Dec 96 10:26:30 PDT

In article <[email-masked]>, 
Abrasha <[email-masked]> writes:

> I don't get it.  This is the INTERNET remember.  The INFORMATION SUPER
> HIGHWAY as some  people like to call it.  I hate that name, but is does
> describe the place to some  extent.

> I have no problem with sharing my expertise on subjects I know something
> about, but it  rubs me the wrong way when people seem to be plain lazy and

> The Internet is an incredible research tool, if only you would use it! 
> So get off your  butt and use your head, and your keyboard a little.

That is all well and good if one has access to these resources.
Please remember that many of us read this newsgroup via UUCP
links.   UUCP does not offer the capability to read web pages,
etc.   On the other hand, it operates entirely in the background,
delivering e-mail direct to my desk and lets me read newsgroup
postings with a simple dumb terminal.   Sure, it doesn't have
color or graphics, but neither do any of the postings in
rec.crafts.metalworking.

Not everyone has (or needs) the latest and greatest technology.
What we do need is for everyone in this newsgroup to be polite
and considerate of everyone else.   This includes keeping your
postings to a width that are readable.   65 characters is a
width that is not only very readable, but also allows several
levels of quoting before the 80-character wrap limit of most
terminals is reached.

--  Alan E. Frisbie               [email-masked]
--  Flying Disk Systems, Inc.

---

From: [email-masked] (darylb)
Date: 10 Dec 1996 22:26:32 GMT

Hey guy's, calm down. This group is meant for freindly info exchange. It
appears some people may be on the information foot path 8^). Hey that's
OK. I asked the original question and was only delighted to answer the
query as to what an astrolabe was (and I'm a 2 finger typer too). I
suspect a few people who never thought to ask learned something new. I
only wish some of this traffic was directed at my original question as to
how they (the mater) are put together. Thick solid vs thin sheet rivited
to thick piece.

One who likes his "meat" rare ;^)
Daryl