RE: Measurements on the Equinox
Fernando The rope is longer than the distance between the pegs x and y. (I hope the characters / and \ work as forward and backward oblique on your screen and you will need to look at this in a fixed width font I expect.) Pick a point * which I shall draw nearer the end x and move so that the rope is taut from * to x and also from * to y *_ / -_ / -_ x y Here * is shown above the line x - y Move to the other side of the line keeping hold of * with it taut again Now you have x y \ _- \ _- *- and connect the two points where you held * taut *_ /I -_ / I -_ x I y \ I _- \I _- *- like a kite shape You see that the line I I I I between the * and * is at right angles to the line x--y Regards Andrew James
Re: Measurements on the Equinox
Sorry, but I have not been able to visualize this. No matter how I look into it, I can't seen how it will generate a perpendicular line. I see the pegs and cable as follows: + W o=o E + Where do I pull the rope taut? I'd imagine where the crosses are (+) but I can't see how it will work. Can someone help this guy who can't use the right side of his brain? - fernando John Carmichael wrote: Rudolph: What a great idea! No math or plotting! This method also seems like it would be very precise (If there is no stretch in the rope. A chain or cable metal cable might be better than a rope for super precision). John Yes, yes yes! Laying out lines is really fun and healthy. To derive the meridian from the east-west line, you don't even have to use a Pythagorean triangle. If you peg two points on the E-W line (not too close together) and connect them with a long rope, you can pull the rope taut first on one side of the E-W line, then on the other, each time grasping the rope in the same point. That point can be anywhere on the rope, although not too far from the middle (of the rope) is best. If you mark the two places you can reach that way, you have two points of the meridian. Have fun! Rudolf - Original Message - From: Wm. S. Maddux [EMAIL PROTECTED] (...) Although it might seem a bit like watching the grass grow, a dialist can find peculiar, but real, pleasure while doing this, just to see the the straight W to E line reveal itself again, as it always has. Later you can draw the local meridian at a right angle, anywhere along this established line, which is a most essential thing to know for any dialing project. (The good old Pythagorean ratio of 3:4:5 for the sides of a measured right-triangle is a good way to lay off the right angle.) (,,,) -- Fernando Cabral Padrao iX Sistemas Abertos mailto:[EMAIL PROTECTED] http://www.pix.com.br Fone Direto: +55 61 329-0206mailto:[EMAIL PROTECTED] PABX: +55 61 329-0202 Fax: +55 61 326-3082 15º 45' 04.9 S 47º 49' 58.6 W 19º 37' 57.0 S 45º 17' 13.6 W
Re: Measurements on the Equinox
Fritz Stumpges wrote: Hi Don't pull the rope too tight, leave a little slack. Now grab the rope anywhere near the middle and pull it snuggly to one side and mark the spot. Then holding the rope at the same spot move to the other side and repeat. I love the simple ideas people on this list come up with!!! Explanations are pouring in so quickly I am almost flooded. Thank you all guys. I am reproducing Fritz' explanations because it sounded crystal clear to me. My mistake was to think in two cables instead of one. + (A) /--\ W (o o) E \--/ + (B) That's how I had tried it. The cable has two legs. I tried to pinch A and B and the same time and pull them apart. Not good. Now I got it. And I also understand why John Carmichael suggests using a metal cable or chain. Thank you all guys. So simple and still there are some dumb people who can not understand it. These guys should not be in this list of bright people :-) - fernando -- Fernando Cabral Padrao iX Sistemas Abertos mailto:[EMAIL PROTECTED] http://www.pix.com.br Fone Direto: +55 61 329-0206 mailto:[EMAIL PROTECTED] PABX: +55 61 329-0202 Fax: +55 61 326-3082 15 45' 04.9" S 47 49' 58.6" W 19 37' 57.0" S 45 17' 13.6" W
Re: Measurements on the Equinox
Rudolph: What a great idea! No math or plotting! This method also seems like it would be very precise (If there is no stretch in the rope. A chain or cable metal cable might be better than a rope for super precision). John Yes, yes yes! Laying out lines is really fun and healthy. To derive the meridian from the east-west line, you don't even have to use a Pythagorean triangle. If you peg two points on the E-W line (not too close together) and connect them with a long rope, you can pull the rope taut first on one side of the E-W line, then on the other, each time grasping the rope in the same point. That point can be anywhere on the rope, although not too far from the middle (of the rope) is best. If you mark the two places you can reach that way, you have two points of the meridian. Have fun! Rudolf - Original Message - From: Wm. S. Maddux [EMAIL PROTECTED] (...) Although it might seem a bit like watching the grass grow, a dialist can find peculiar, but real, pleasure while doing this, just to see the the straight W to E line reveal itself again, as it always has. Later you can draw the local meridian at a right angle, anywhere along this established line, which is a most essential thing to know for any dialing project. (The good old Pythagorean ratio of 3:4:5 for the sides of a measured right-triangle is a good way to lay off the right angle.) (,,,)
R: The equinox
This year the Equinox will be on Sep 22 at 17:27 UT. There is a useful link for this kind of data : http://aa.usno.navy.mil/aa/data/docs/EarthSeasons.html Best regards Alberto Nicelli Italy (45°28' N ; 7°52' E) -Messaggio originale- Da: Dave Bell [mailto:[EMAIL PROTECTED] Inviato: martedì 19 settembre 2000 21.53 A: SUNDIAL@rrz.uni-koeln.de Oggetto: Re: The equinox Exactly when IS the Equinox htis month? Maria mentioned Sep 22, and I thought I had heard Sep 21. Easily explained, if the precise time is early enouhg (GMT) on the 22nd, but I haven't located an ephemeris... Dave
Re: Measurements on the Equinox
Sarah contributed: somebody once said to me that if someone does not undestand you, you have not explained well enough! Or to take it a little further The pupil should exceed the master or the master has failed Now who said that? Tony M.
Re: Measurements on the Equinox
Fernando, Here is a small GIF to illustrate the concept. It is a nice example of symmetry. The thick lines represents the rope, and the little squares show where it is gripped and marked. Bill Attachment converted: Macintosh HD:R-ANG.GIF (GIFf/JVWR) (0001BF30)
