Hi Mac: (hope you don't mind me cc'ing this to the List. I think it's interesting and might be of use to somebody else who wants to use the Time Method for laying out a bid dial).
I'm so glad you asked all those important questions about the marking techniques we'll be using. This was what I was going to ask you next after you had a chance to review the list of materials and Zonal/MST timetable. I given a lot of thought to how we will mark the time points. I've practiced my technique using the house roof's shadow. Here's how I'm thinking we will do it: First of all, I realized that this is at least a two man job. Three people would be even better. We will have to work in shifts (the bathroom is 1/2 block away!). June 20th is our setup and practice day when we'll prepare the area for marking and do some time point markings. We will be there before sunrise. We will do a practice sighting and marking of the sunrise direction and time, using just our eyes and no shadow sharpener. This will give us a good idea of where the sun will rise on the following day and where to tie our perimeter guide string. Then, we will begin to prepare the area. First, we determine the position of the perimeter time markings. This rectangular dial face has markings on the west, north and east sides and we will refer to them that way. We'll put metal stakes at the corners and at the sunrise and sunset points on the perimeter timelines. We tie surveyor's string between the stakes and sweep the excess pea gravel away underneath the string to expose the black asphalt below. A smooth surface will allow the flat head nails to be driven in completely and it will be easier to see the pinhole image. After the guide string is in place we'll attempt some practice time markings. We'll use the precalculated Zonal/MST timetable for June 20. We'll set the radio clock on the ground so we both can see it. One person will hold the shadow sharpener so that the 1/2 disk solar image is centered on the string. I've practiced this and it's fairly easy, but I used a white paper for a screen. We may have some problems seeing a good image on rough black asphalt, so if that's a problem, we can place a piece of paper on top of the asphalt but underneath the string. We'd focus the sharpener on the paper. Then at the correct watch time indicated on the Zonal/MST timetable, the other person drives a nail through the center of the pinhole image into the asphalt. I'm pretty sure this technique will work well for most of the day, however there is a problem when the sun is low in the sky. The sharpener's image becomes a very elongated obnoxious ellipse making it difficult, if not impossible to see the 1/2 disk solar image. we'll have to do some guesstimating of the correct position at these times. This is one of the good reasons we should go a day early for a dry practice run. Also, since the distance between the style and the penumbra is constantly changing during the day, we will experiment with different sized pinholes throughout the day. We'll stay up there until sunset in order to mark the sunset points. Then we have to drive all the way back to Tucson unless I can talk Kitt Peak into letting us use one of the log cabins they have for visiting astronomers. On June 21 we must leave Tucson at 3:00 am in order to be at the observatory before sunrise at 5:21 am. Then we'll begin marking the 182 time points every five minutes from sunrise to sunset at 7:31 pm. We'll also mark the two points where the styles shift and the six sunrise and sunset points of the equinoxes and solstices. We'll also mark Zonal Time High Noon. Have I forgotten anything? Here is a list of materials we might need. (As Mac said it is "exhaustively complete" but I just don't want to forget anything since we'll be in the middle of nowhere we can't just run to a hardware store.) McMath-Pierce Sundial Marking Equipment 100 ft. Surveyors tape (cm would be better) Book (Waugh) Broom (for sweeping gravel from underneath time lines) Business Cards Calculator Camera Carpenter's Square Chair w/ cushion (2) Chalk string Compass Cooler (Breakfast, lunch, water, etc.) EOT Corrections List Flat-head Nails Folding Table Hammer Hat Inclinometer Knee pads Masking Tape Model of Sundial Nail Stakes for String (about six) Newspaper Numerals (aluminum. 6am to 7pm and 14, 30 min.) Paper Pencils & Eraser Proposal (printed) Radio Radio Clock Ruler Shadow Sharpeners (various sizes) Sharpee Pen Spray paint (Orange) Sunblock Sunglasses Surveyor's string Washers (1" flat galv. steel) Watch If anybody has any suggestions let me know. Thanks John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "Mac Oglesby" <[EMAIL PROTECTED]> To: "John Carmichael" <[EMAIL PROTECTED]> Sent: Wednesday, June 12, 2002 3:55 AM Subject: Re: Accuracy > > Hello John, > > I didn't think to try DeltaCad, for the filename was so long the > suffix didn't show. But, you're right, it wouldn't have opened with > my DeltaCad 4. > > This chart should be a lot of help as you travel through your > marathon marking day. Better have some paper weights or a large > clipboard to keep your sheet(s) from blowing away. You may not be as > compulsive as I tend to be, but I'd have a spare printout secure in > an attache case (or locked safely in the car). I'd likely have a > spare watch, too! > > It'll be a stressful day, marking close to 200 points very precisely. > Happily, these are independent events, and errors won't > accumulate---if you miss the proper location for a mark (or miss > making a mark altogether) subsequent marks won't suffer. > > I see you have the EoT at "High Noon" on 6-21-2002 at Kitt Peak > listed as 107.46 seconds. The Dialist's Companion shows that value > for 12:00:00 MST. At local apparent noon, when "dial time" is > 12:00:00, TDC gives 107.715 seconds. Not that a quarter of a second > matters. In John Davis' glossary, "Noon" is the moment of the sun's > transit. It's a local event, not by the clock. I didn't spot a > definition for "High Noon". (That's a Grace Kelly/Gary Cooper movie, > right?) <G> > > John, I'm having trouble visualizing exactly what will be happening, > especially with respect to the shadow sharpener(s), at the moment any > particular time point is being marked. Have you rehearsed this > process? I mean, have you run through a simulation, using a chalk > line on the ground and the shadow from a roof line? I'm trying to > imagine how one juggles a hammer and nail and a shadow sharpener and > a watch, etc. The mark must be made at a particular time, which the > watch supplies, but exactly where along the line? Where will the > shadow sharpener be held, and how kept steady? Can you describe what > the watcher of the shadow sharpener is looking for to decide where to > make the time mark? > > I continue to wish you best of good fortune in this project. > > Mac > > > > > > > >Hi Mac > > > >I laughed at your term "exhaustively complete" because there are some things > >that we probably won't need. I just didn't want to forget anything because > >we'll be miles away from any store. > > > >I bet I know why you couldn't open my Delta Cad file. I use DC version 5.0. > >If you have version 4.0 you won't be able to open it. Somebody else I wrote > >to had that problem. So is a good old reliable PDF file of the time table. > > > >John > > > >John L. Carmichael Jr. > >Sundial Sculptures > >925 E. Foothills Dr. > >Tucson Arizona 85718 > >USA > > > >Tel: 520-696-1709 > >Email: [EMAIL PROTECTED] > >Website: <http://www.sundialsculptures.com> > >----- Original Message ----- > >From: "Mac Oglesby" <[EMAIL PROTECTED]> > >To: "John Carmichael" <[EMAIL PROTECTED]> > >Sent: Tuesday, June 11, 2002 6:24 PM > >Subject: Re: Accuracy > > > > > > > > > > John, > > > > > > The list of materials seems exhaustively complete. For some reason, I > > > cannot open the list of time marks. > > > > > > Mac > > > > > > > > > > > > > > > > > > > > > > > > >Hi Mac > > > > > > > >I'm sending you two attachments. One is a list of the materials we will > >be > > > >needing to mark the time points. The other is a list of all the five > >minute > > > >time marks in both Zonal Time (sundial time) and Clock Time (Zonal Time > > > >corrected for EOT) for June 21. I made this list in a large paper > >printout > > > >so that we won't have to do any EOT math conversions in our heads. > > > > > > > >Any thoughts, suggestions? > > > > > > > >John > > > > > > > >John L. Carmichael Jr. > > > >Sundial Sculptures > > > >925 E. Foothills Dr. > > > >Tucson Arizona 85718 > > > >USA > > > > > > > >Tel: 520-696-1709 > > > >Email: [EMAIL PROTECTED] > > > >Website: <http://www.sundialsculptures.com> > > > >----- Original Message ----- > > > >From: "Mac Oglesby" <[EMAIL PROTECTED]> > > > >To: "John Carmichael" <[EMAIL PROTECTED]> > > > >Sent: Monday, June 10, 2002 6:58 PM > > > >Subject: Accuracy > > > > > > > > > > > > > > > > > > Hello John, > > > > > > > > > > One thing that keeps rattling around in my mind about the accuracy of > > > > > the Kitt Peak dial is that I'm finding it hard to believe that the > > > > > edges of the wind screen tube are absolutely straight. It's almost a > > > > > certainty that the shadow casting edges are not precisely straight > > > > > lines. This means, of course, that no matter how carefully you mark, > > > > > empirically, an hour point at the summer solstice, at some later date > > > > > when the declination of the sun causes another portion of the style > > > > > to be casting the shadow which intersects the same hour point, the > > > > > dial may show a different time from what is expected. > > > > > > > > > > Certainly I'm not suggesting your project is unworthy, or doomed to > > > > > failure. Rather, don't be surprised if the accuracy of the dial is > > > > > not constant over an entire year. The dial may be accurate to within > > > > > 10 or 15 seconds on the day it's created, but that may not be true 2 > > > > > months, or 2 weeks, or even 2 days later. > > > > > > > > > > Best wishes, > > > > > > > > > > Mac > > > > > > > > > > > > >Attachment converted: Macintosh HD:McMath-Pierce Sundial Marking E > > > >(WDBN/MSWD) (00046972) > > > >Content-Type: application/octet-stream; > > > > name="McMath-Pierce Sundial Face (laylout EOT corrected).dc" > > > >Content-Disposition: attachment; > > > > filename="McMath-Pierce Sundial Face (laylout EOT corrected).dc" > > > > > > > >Attachment converted: Macintosh HD:McMath-Pierce Sundial Face (lay > > > >(????/----) (00046973) > > > > > > > > > >Attachment converted: Macintosh HD:McMath-Pierce Sundial Face (lay > >(PDF /CARO) (000469B0) > > -
