Quote:
Originally Posted by Startrek
You find the SCP using the Solar Noon Meridian Shadow method. Never fails I’ve used it at my 2 locations Sydney and South Coast and gets me really close to SCP to set up my tripod level and install mount ready to set home position, balancing, 2 star alignment and polar alignment using the “Synscan Polar Alignment Routine” with hand controller.About 2 or 3 iterations and I can get down to under 15 arc sec error in 15 minutes.
Finding Celestial True South using Solar noon meridian method
Items needed
1 metre length of 12mm timber dowel with a 2mm deep 90 deg cross cut into one end using a hacksaw
2 x 3 metre pieces of 1mm string cotton type
4 x weights like a brick or paver etc...
1 x straight edge, alum angle or ruler 500mm long would be good
1 x fine point black permanent marker
1 x 300mm long Stanley or quality boat type builders bubble level
1 x PC with a planetarium software program. Stellarium is a good choice as it’s free and easy to use
1 x Smartphone like an iPhone
Location
Your observing location ( solar noon meridian location too ) should be a reasonably flat and level concrete , paved or tiled ( hard surface ) area with a good view of the sun at around midday
Procedure
Erect timber dowel vertically below your preferred observing tripod position and use the 2 strings to anchors the dowel like tent guy ropes at NSEW using weights to hold it in position. Use your bubble level to ensure dowel is exactly vertical at 90 deg in all directions ( very important ) The hacksaw cuts at the top of the dowel make it easy to adjust NSEW
Pick a sunny day
Start your PC mid morning and open Stellarium. Rotate your cardinal point to the North position and raise view up until you see the Sun
Click on the Sun and then click on the clock , move the time forward or backward to the point where the Suns Alt/Az degrees goes from 359 deg to 0 deg or exactly bisecting the North South meridian line ( refer to top left hand data on screen for Az/ Alt deg )
Record this exact time which is Solar Noon ( eg 12.35pm )
Go to your observing location 10 minutes before Solar noon with your smartphone , ruler and permanent marker. The dowel should be casting a 12mm wide +500mm long shadow on the surface
At exactly Solar Noon time mark a thin line on the ground from the base of the dowel outwards along the exact centre of the shadow for at least 500mm ( be as precise as you can )
This line is the Celestial Meridian (True North South )
Use this line to align your tripod to True South
I found this method far more accurate than any app or compass with magnetic declination
Hope the above helps, there are numerous other ways to find true celestial south but this one works for me and has never failed at 2 different locations ( the sun never fails )
Cheers
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High Martin
How do you work out solar noon?
I used what is essentially your method only a couple of days ago starting the process to establish a true North South line...I worked out that at 152.5 longitude I should mark the line at 6 minutes before noon on the clock..I cant recall the way I arrived at this time however☺.
Alex