RE: signal mirrors with attachment
Tony Moss wrote: > >I found a couple of web sites on signal mirrors. > >http://www.equipped.com/signal.htm#ReflectionsOfLight > >describes how they work and how to use them. I also made a sketch of how > >I think it works. The attached bit map file shows this. > > I understood the principle immediately from your diagram. 'One picture > is worth 1 words' Well, I'm sorry, but I haven't caught on yet. Bob refers twice to an image of the sun, but I don't see from his diagram how or where any image of the sun should be visible. The web site explains, "The fireball is produced by retrodirective reflection from small metalized glass spheres adhered to a mesh grid or cloth disk with a center hole." I could understand it if the reflective material consisted of needles or flakes perpendicular to the plane of the mirror, but spheres don't seem to be direction specific enough. Wouldn't they look bright regardless of the orientation of the mirror? Please try to share your insight! --Art Carlson
Sorry about the huge attachment
Hello All, Sorry about the huge attachment that I submitted yesterday on the signal mirror. I managed to choose the worst format(.bmp) 402838 bytes. This for a drawing of about 20 lines and 50 characters.One of the dangers of working on a system without modem limitations and basically unlimited file space. If I had choosen a gif format the same image came down in 6796 bytes. If anyone is interested but didn't have the time or equipment to download the .bmp file let me know and I can email the .gif file. I now have figured out how to generate my sketches in Visio on a pc and convert it to a gif file on my unix workstation for attachment. Bob 33 North 117 W
Re: heliograph
John Schilke wrote: > To pursue this thread just a bit further, does anyone know of a source to > buy any of these devices we've been discussing. It was so long ago that > I saw one that I'd have no idea where to start looking. > Thanks, > John John, One of the links earlier http://www.equipped.com/signal.htm#ReflectionsOfLight in this dialog leads to the following. http://www.malcolmmurray.com/rescue/index.html (they claim 20 mile range) I also wouldn't be supprized if REI or other outdoor outfitters carry them. Bob
Re: signal mirrors
Arthur Carlson wrote: > Tony Moss wrote: > > > >I found a couple of web sites on signal mirrors. > > >http://www.equipped.com/signal.htm#ReflectionsOfLight > > >describes how they work and how to use them. I also made a sketch of how > > >I think it works. The attached bit map file shows this. > > > > I understood the principle immediately from your diagram. 'One picture > > is worth 1 words' > > Well, I'm sorry, but I haven't caught on yet. Bob refers twice to an image > of the sun, but I don't see from his diagram how or where any image of the > sun should be visible. The web site explains, "The fireball is produced by > retrodirective reflection from small metalized glass spheres adhered to a > mesh grid or cloth disk with a center hole." I could understand it if the > reflective material consisted of needles or flakes perpendicular to the > plane of the mirror, but spheres don't seem to be direction specific enough. > Wouldn't they look bright regardless of the orientation of the mirror? > Please try to share your insight! > > --Art Carlson Art, The old mirror I have seems to have a steel mesh (about like window screen) with what looks like aluminum oxide abrasive grit on the wire. I don't think that it has to be a pure retro reflector. If it was too good it would blind the operator. I think the partial reflection on the glass surface closest to the eye attenuates the image of the sun. However the"fire ball" they talk about is kind of a fuzzy thing and is brightest in the direction of the reflected sun. "As I said before it also works away from the screen but not nearly so bright. I have always assumed that this scattering is due to surface defects of the glass but heck it is only my theory. I guess maybe I will consult an optical engineer we have tomorrow. I suppose if we really want to know maybe we should contact one of the manufacturers. This discussion reminds me of the CAR TALK letter that Tom and Ray received where the writer wondered if two people who don't know what they are talking about when combined know less than either by themselves. Bob
Re: heliograph
I'm interested. Charlie Mead 136 Emerald Cove Lane Rockwood, TN 37854 (423) 354-1993 Received: from mailsorter-101-2.bryant.webtv.net (209.240.198.96) by postoffice-132.iap.bryant.webtv.net; Thu, 24 Jun 1999 17:46:40 -0700 (PDT) Return-Path: <[EMAIL PROTECTED]> Received: from mail1.rrz.Uni-Koeln.DE (mail1.rrz.Uni-Koeln.DE [134.95.100.208]) by mailsorter-101-2.bryant.webtv.net (8.8.8/ms.graham.14Aug97) with ESMTP id RAA14585 for <[EMAIL PROTECTED]>; Thu, 24 Jun 1999 17:46:39 -0700 (PDT) Received: (from [EMAIL PROTECTED]) by mail1.rrz.Uni-Koeln.DE (8.9.1a/8.9.1) id BAA00330 for sundial-out; Fri, 25 Jun 1999 01:59:43 +0200 (MET DST) Received: from pike.sover.net (pike.sover.net [209.198.87.34]) by mail1.rrz.Uni-Koeln.DE (8.9.1a/8.9.1) with ESMTP id BAA00321 for ; Fri, 25 Jun 1999 01:59:41 +0200 (MET DST) Received: from [207.136.202.56] (tempa56.bf.sover.net [207.136.202.56]) by pike.sover.net (8.9.3/8.9.3) with ESMTP id TAA20329; Thu, 24 Jun 1999 19:59:19 -0400 (EDT) Comments: SoVerNet Verification (on pike.sover.net) [207.136.202.56] from tempa56.bf.sover.net [207.136.202.56] 207.136.202.56 Thu, 24 Jun 1999 19:59:19 -0400 (EDT) X-Sender: [EMAIL PROTECTED] Message-Id: <[EMAIL PROTECTED]> In-Reply-To: <[EMAIL PROTECTED]> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Thu, 24 Jun 1999 19:59:01 -0400 To: John Schilke <[EMAIL PROTECTED]> From: Mac Oglesby <[EMAIL PROTECTED]> Subject: Re: heliograph Cc: Sundial List Sender: [EMAIL PROTECTED] Precedence: bulk >To pursue this thread just a bit further, does anyone know of a source to >buy any of these devices we've been discussing. It was so long ago that >I saw one that I'd have no idea where to start looking. >Thanks, >John For whatever it's worth, Sigma Scientific, Inc. of Ontario, CA 91761 made a Signal Mirror (model MS-23) which at one time was included in survival kits sold to (civilian) pilots. I bought a signalling mirror as a part of such a kit about 20 years ago. The mirror has a center hole for sighting and has a 'glowing grid'. More recently, I notice that a 2" by 3" emergency signal mirror featuring a trademarked targeting star for precise signal aiming is available from Sporty's Pilot Shop, Clermont County Airport, Batavia, OH 45103 USA. (Item 9465A; $9.95). 1-800-543-8633. If anyone wishes, I could try to scan the catalog illustration and send it upon request. Cheers, Mac
RE: Outdoor finish for wooden sundials
Hi all: Several days ago someone wrote to the list who had been using automotive clear coat to protect wood placed outdoors. I emailed them for further information and product sources but I never received a reply. I have lost their email address but was hoping that someone on the list received that information or has some of their own which they could send me (or publish on the list). Stone and steel dials are wonderful but I am anxious to try one in wood so I can introduce lots of color. I own a wooden boat (Mahogany,built in Holland in 1948) and have never found any varnish or epoxy finish to last for very long and I'm wondering if the clear coat is the answer.
RE: signal mirrors with attachment
On Thu, 24 Jun 1999, Arthur Carlson wrote: > Tony Moss wrote: > > > >I found a couple of web sites on signal mirrors. > > >http://www.equipped.com/signal.htm#ReflectionsOfLight > > >describes how they work and how to use them. I also made a sketch of how > > >I think it works. The attached bit map file shows this. > > > > I understood the principle immediately from your diagram. 'One picture > > is worth 1 words' > > Well, I'm sorry, but I haven't caught on yet. Bob refers twice to an image > of the sun, but I don't see from his diagram how or where any image of the > sun should be visible. The web site explains, "The fireball is produced by > retrodirective reflection from small metalized glass spheres adhered to a > mesh grid or cloth disk with a center hole." I could understand it if the > reflective material consisted of needles or flakes perpendicular to the > plane of the mirror, but spheres don't seem to be direction specific enough. > Wouldn't they look bright regardless of the orientation of the mirror? > Please try to share your insight! > > --Art Carlson > Well, as best I can make it out, the spheres act as lenses with focal length equal to their diameter. If they are embedded in a reflective background, an incoming bundle of parallel rays is focussed to a point (disregarding spherical aberration) on the rear surface, reflected back (must be along complementary paths!), and recollimated into a parallel bundle again - directly back along the entry path. From the diagram, a small part of the light from the sun passes through the hole in the silvered layer, reflects off the rear glass surface onto the beads, and returns to the same point on the rear surface. Some of the return light is reflected back towards the sun, and some penetrates the rear surface, to the user's eye. He sees a diffuse, much dimmed virtual solar image, aligned with the direction the major part of the reflected light takes, towards the target. Dave
Re: Old idea?
[EMAIL PROTECTED] wrote: > > I just had an idea, and as a newbie, I thought I'd bother you with it. > There is a sundial which is a disk with a rod for a gnomon running > perpendicularly through its center. I understand the problem is that > it can only be read from the top in the summer and the bottom in the > winter. Has anyone tried making the dial of acrylic/perspex/glass? > Seems like if it were, say, 300 mm in diameter and the outer 30 mm > were frosted, you could read it from the top in any season. Comments? > > I wonder if this type of dial is strong enough if supported only by its > gnomon. If not, then I suppose you would have to support the dial plate > separately, taking away much of its simplicity of construction. > > Thanks, > John B Hi John, There are optical equatorial sundials, made of plexiglass by Erich Pollähne, that can be read from the top, also in winter. The dial operates with a spot of light, not with a shadow. Erich Pollähne MEKU GmbH Am Weingarten 14 30974 Wennigsen Germany Happy dialling, Fer. -- Fer J. de Vries [EMAIL PROTECTED] http://www.iaehv.nl/users/ferdv/ lat. 51:30 Nlong. 5:30 E
sunrise/sunset calculator
Hello dialists: The Arizona Daily Star did a little story today on a great website which will give you the exact time of sunrise and sunset for 130,406 U.S. locations for any date! David Shaw's easy-to-use site also indicates the exact latitude and longitude of these locations. It is fun to see by how much the moment of sunrise and sunset changes even at different locations within the same city. check it out: http://www.jabberwocky.com/photo/suntimes.html John Carmichael http://www.azstarnet.com/~pappas
Re: Heliograph
I am lucky enough to own a heliograph, having recently bought it from
another BSS member. It dates from WW1, and looks just like the one in Peter
Mayer's jpeg with the exception that the sighting vane is more complex, with
a set of cross wires and a fold-down vane on which the dark spot from an
unsilvered spot in the centre of the mirror is aligned.
It's described as a Mk5, and comes with its own mahogony tripod and set of
spares etc. There is a range of attachments (most in very solid brass)
included in the leather carrying bag. One of these is a duplex mirror, used
when the sun and the receiving station are in opposite directions. This
mirror, which fits on the arm were the sighting vane is in the jpeg, is
always used to direct the sun onto the main signalling mirror when the sum
of the angles of incidence and reflection is 90 degrees or more. The main
mirror has a slow motion screw so that the operator can track the sun during
long messages.
I have full instructions on how to set up and use, but they run to several
pages so I won't reproduce them unless anyone contacts me directly.
The accompanying book ("The Heliograph - A short history" by Alan Harfield,
pub Royal Signals Museum, 1981, ISBN 0950121835) describe achieving signal
ranges of up to 53 miles with a 5 inch mirror (like mine), and up to 83
miles to 9" and 12" mirrors. This was done in the mountains in northern
India. Heliographs were also much used in the States, for example by
General Miles in 1878/9, and there are various quotes from Geronimo, who
believed the flashes were spirits!
All I need to do now is find someone else with a heliograph, and then we can
have aconversation (after I've learned Morse!)
Regards,
John Davis
heliograph
To pursue this thread just a bit further, does anyone know of a source to buy any of these devices we've been discussing. It was so long ago that I saw one that I'd have no idea where to start looking. Thanks, John
Re: sunrise/sunset calculator
Hi John, If you are interested in site specific solar data try using my Solar Calculator, URL below. As well as accurate sunrise, sunset and transit time(s) it will produce a variety of other solar data values. Also, mention of a world map with the solar terminator came up recently, I have another cgi application that I wrote that produces such a map as well as a number of instantaneous solar data values, see second URL below. Incidentally, I am in the midst of updating the program to overly the region of the Earth under shadow with the corresponding portion of a world map showing the "city lights" at night. Montana sure looks like a good spot to set up a telescope... http://www.gcstudio.com/suncalc.html http://www.gcstudio.com/cgi-bin/sunmap Enjoy, Luke John Carmichael wrote: > > Hello dialists: > > The Arizona Daily Star did a little story today on a great website which > will give you the exact time of sunrise and sunset for 130,406 U.S. > locations for any date! David Shaw's easy-to-use site also indicates the > exact latitude and longitude of these locations. It is fun to see by how > much the moment of sunrise and sunset changes even at different locations > within the same city. > > check it out: http://www.jabberwocky.com/photo/suntimes.html > > John Carmichael > http://www.azstarnet.com/~pappas
Re: heliograph
>To pursue this thread just a bit further, does anyone know of a source to >buy any of these devices we've been discussing. It was so long ago that >I saw one that I'd have no idea where to start looking. >Thanks, >John For whatever it's worth, Sigma Scientific, Inc. of Ontario, CA 91761 made a Signal Mirror (model MS-23) which at one time was included in survival kits sold to (civilian) pilots. I bought a signalling mirror as a part of such a kit about 20 years ago. The mirror has a center hole for sighting and has a 'glowing grid'. More recently, I notice that a 2" by 3" emergency signal mirror featuring a trademarked targeting star for precise signal aiming is available from Sporty's Pilot Shop, Clermont County Airport, Batavia, OH 45103 USA. (Item 9465A; $9.95). 1-800-543-8633. If anyone wishes, I could try to scan the catalog illustration and send it upon request. Cheers, Mac
Re: Another Kipling Heliograph Poem
Bravo, Richard! It's the very one I had in mind. Thank you. >(This one's not so vernacular.) > >A Code of Morals >by Rudyard Kipling > [snip] Peter -- Peter Mayer | [EMAIL PROTECTED] Politics Department | University of Adelaide | 'phone:+61.8 8303 5606/5610 Adelaide, SA 5005 | FAX: (+61.8) 8303 3446 AUSTRALIA | --
Re: heliograph
Thank you Richard. What an excellent ode on retirement. Your second posting is an excellent warning on the security and privacy of e-mail. Score another point for the eclectic nature of this list. Roger Bailey > >Here it is. It's a bit more dialectal than you remember! ;-) > > >Chant-Pagan >by Rudyard Kipling > >ENGLISH IRREGULAR, DISCHARGED > >Me that 'ave watched 'arf a world >'Eave up all shiny with dew, >Kopje on kop to the sun, >An' as soon as the mist let 'em through >Our 'elios winkin' like fun -- >Three sides of a ninety-mile square, >Over valleys as big as a shire -- >"Are ye there? Are ye there? Are ye there?" >An' then the blind drum of our fire . . . >An' I'm rollin' 'is lawns for the Squire, >Me! >
Re: heliograph
I wonder if this thread relates to the previous discussion on the use of reflections from compact discs. A circular mirror with a hole in the middle... sounds familiar. What we need is a technique to modify the clear ring in the middle of a CD to capture "retrodirective reflection" showing the orientation of the sun. The coloured diffraction patterns may be quite useful for communicating with alternate universes. I have found obsolete software CDs from Sun Microsystems to be particularily effective for these purposes. Roger Bailey At 03:57 PM 6/24/99 -0700, John Schilke wrote: >To pursue this thread just a bit further, does anyone know of a source to >buy any of these devices we've been discussing. It was so long ago that >I saw one that I'd have no idea where to start looking. >Thanks, >John >
Re: Signalling mirrors
"At least you weren't sending advice a la Kipling's Jones on 'the Hurrum Hills above the Afghan border'," reflected Tom Semadeni.
Re: signal mirrors with attachment
Bob. >I found a couple of web sites on signal mirrors. >http://www.equipped.com/signal.htm#ReflectionsOfLight >describes how they work and how to use them. I also made a sketch of how >I >think it works. The attached bit >map file shows this. I understood the principle immediately from your diagram. 'One picture is worth 1 words' Many Thanks Tony
