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                                       Click on Images to Enlarge

Determining True North
Before, After and During Transit

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As can be seen, the shadow of the sun on the opposite side of the sonotube(cast by a vertical line, ie, the rod; and directed through the center of the sonotube) was taken at several intervals before, during and after the sun's transit.  The spacing between these points (taken at 11:30, 11:40, 11:52((transit)), 12:00 and 12:10) is essentially as would be expected (noting that the transit point is 12 minites after the 12:40 mark).  These extra points are advisible, in case some error is made at the transit point. 
 
 
 
 
 
 
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Star Party Rescheduled and Project Delayed
 
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Well, we were ready to pour the cement and, by coincidence, we had a Star Party scheduled.  Both were temporarily postponed.  For some reason, Paul and Dave thought that -27 degrees F might be a bit to cold for pouring.  As for the Star Party, with the usual gang of kids, I thought it best to hold off for a while.  I shot this image of my "Davis" weather station, which is about 20 feet from the observatory site.  Note the wind chill reading.  Amazingly there were a few, including Dr. George Glass (a real amateur astronomer who can find just about any object with his binoculars...his computerized telescope is hard wired in his brain), and his son, who still wanted to meet !! 
 
 
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Ready for the Deck and Wiring

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Both sonotubes complete.  As can be seen, 18 inch deep trenches run in the background from the future north end of the building to my garage.  In Maine, 18" is required for the outside electrical lines.  Note the electrical and computer lines will be in separate trenches and are over 2 feet apart.  Since the elecrical is shielded in metal conduit, this is overkill, but I don't want to risk any problems wih the power lines interfering with the network (ccd images, autoguiding data, etc).  I saw this happen first hand in my houseside observatory, and it took me several hours to track the problem down.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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True North Marked

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The direction of true north follows a line from the point at which the rod contacted the sonotube, extending through the center of the sonotube (marked here with an asterix), and ending where the shadow contacted the opposite side of the sonotube. These points will be securely marked with two nails in the sonotube with a string running between them. The mounting plate has also been scribed (using a T-square) through its center and these two lines will be alligned. Please note that in determining north its best to have the surface of the sonotube level, so that the center of the sonotube can be easily measured, and to ensure multiple points (before and after transit) will be be evenly separated when comparing points before and after transit. 
 
 
 
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The moment of truth...

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For some reason, the actual moment of pouring the cement was one of the more nerve racking from my perspective.  The forms were filled with rebar.  As per the concrete company's recommendation, all was at least three inches of the edge of the sonotube. The concrete was mixed with fiberglass and mixed for setting at cold temperatures.  The actual pouring happens rather quickly and care needs to be taken that the sonotube is not disturbed and that the concrete is well dispersed.  We were able to pour it all at once, as, despite my concern, the concrete in the sonotube was not heavy enough to push out the cement in the base of the foundation.
 
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An Unusual Project...

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There's Paul (right) and Dave Murphy, of Murphy's Construction (in Lewiston, Maine).  Paul specializes in renovations and unusual projects.  He has assured me that this more than qualifies as an unusual project (I can't image why...).  He's been in touch with Brad and Wayne from SkyShed (www.skyshed.com), and we've decided to put our custom SkyShed on a deck (though they generally build a very solid structure at ground level, floor and all).  Hopefully next week there will be photos of the electrical and computer lines, and a deck.  Once this is done Brad will be coming down from Canada (yes, in the dead of winter) to build the SkyShed. Next the Pier Tech adjustible mounts (www.pier-tech.com)  will be placed. Once placed the Meade GPS LX-200 (with piggy back Tel-Vue NP 101) will be added.  Then we wait for the Ritchey-Chreiten 16" Truss Telescope being built by RC Optical Systems (www.rcopticalsystems.com), and its Paramount ME mount (www.bisque.com), both of which are expected in April.  To this scope a piggyback Takahashi 106 will be mounted.  There should be plenty to do while we wait.  Lastly John Smith ( www.hiddenloft.com ) will be coming out to fine tune  the setup and correct all our mistakes !!
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Never Trust a Compass !!

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John Smith warned me about using a compass (he's known of a few disasters trying to set north with a compass).  The transit method is combersome and it is very tempting to use a compass (manual or electronic).  This diagram shows how inaccurate this can be.  This compass it the standard Meade LX200 compass which has been adjusted for magnetic north (and confirmed with a LX-200 which is exactly polar alligned).  As can be seen the N/S line given by this compass is about 8 degrees off when compared to the transit N/S line.  By moving the rebar below it this can vary from 5 to 15 degrees (even with the leveling bubble in the compass exactly centered).  Never trust a compass !!
 
 
 
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Mounting Plate

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Once the cement was leveled at the top of the sonotube the mounting plates, J hooks down, were placed.  A string was run along the previously marked N/S lines on the sonotube (small nails placed).  The outside of the sonotube was also marked (as the inside was filled with cement !!).  The plate was centered and the previously scribed line on the plate was exactly aligned with the string.  The process of keeping the plate level continued for about three hours.  The Software Bisque level was very handy and is clearly much more accurate and sensitive than the standard carpentry levels.  At the moment of the suns' transit, at 11:53 AM on 12/30/04, the mounting plates were again checked and the shadow ran exactly along the scribbed line of the plates (I was almost afraid to check).   
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Next: Run Out the Lines...

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For the computer/low voltage lines we ran 3" PVC conduit. Although large, it was easier to run the lines through them, especially since all the lines are run in duplicate (just in case).  The electrical was run in by PVC to code (and therefore inside run through metal conduit).  The trenches are 18" deep (electrical code).  Note that the power lines remain at least 2 feet from the computer lines.  Low voltage lines, such as those which will turn on the servo which will open the roof, are run with the computer networking lines. In the near future a modified diagram of the circuits will be added to the site, which will hopefully make sense out of the lines.
  The blankets in the background are covering the two piers which were poured two days ago.  There are high voltage lights inside to keep the piers from freezing while the cement dries. 
 
 
 
 
 
 
 
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