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  #21  
Old 09-06-2019, 12:46 PM
Wavytone (Nick)
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Better than solar noon:

1. Use a plumb-bob on a string for an accurate vertical, with the string casting a shadow. Push a toothpick through the string near the top, to provide a reference point (at step 3). Plumb-bob suspended over a point marked on the ground (nail will do fine).

2. Choose a few pairs of times say 1:30, 2, 2:30 and 3 hours before and after solar noon, so the string will cast a longer shadow.

3. At each of the times before and after solar noon, mark where the reference point in the string falls (ie the intersection of string and toothpick).

4. Pull out a tape measure and subdivide the pairs using a tape measure. The midpoints lie on the north-south axis, as does the tip of the plumb-bob.
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  #22  
Old 09-06-2019, 01:33 PM
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Tinderboxsky (Steve)
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Interesting solution. Using the idea could be challenging in a confined area or on uneven ground. Might just take a little planning to manage successfully.


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Better than solar noon:

1. Use a plumb-bob on a string for an accurate vertical, with the string casting a shadow. Push a toothpick through the string near the top, to provide a reference point (at step 3). Plumb-bob suspended over a point marked on the ground (nail will do fine).

2. Choose a few pairs of times say 1:30, 2, 2:30 and 3 hours before and after solar noon, so the string will cast a longer shadow.

3. At each of the times before and after solar noon, mark where the reference point in the string falls (ie the intersection of string and toothpick).

4. Pull out a tape measure and subdivide the pairs using a tape measure. The midpoints lie on the north-south axis, as does the tip of the plumb-bob.
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  #23  
Old 09-06-2019, 01:37 PM
Wavytone (Nick)
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Youíre welcome. Itís a method as old as the pyramids
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  #24  
Old 09-06-2019, 01:51 PM
Sunfish (Ray)
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With any of these methods a flat level surface is essential.
Or the cast shadow will not be at the correct angle I think.

I also like the plumb bob idea. I have one tied under an old dumpy level which would be perfect . Surprising how accurate a plumb bob , a level and a long length of string can be.

Most laser measures have a projected circle of 3mm and their length is too short although they can mount on levelled camera mount.


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Interesting solution. Using the idea could be challenging in a confined area or on uneven ground. Might just take a little planning to manage successfully.
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  #25  
Old 09-06-2019, 02:13 PM
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Tinderboxsky (Steve)
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The ancient Egyptians would have had plenty of space to perfect this method.


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Youíre welcome. Itís a method as old as the pyramids
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  #26  
Old 09-06-2019, 02:23 PM
Wavytone (Nick)
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What's more the egyptians established a planar surface by building a low embankment and filling it with water, then standing sticks in the mud. The water level provided precise reference on the sticks to show how much to cut/fill.

So simple.
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  #27  
Old 09-06-2019, 02:52 PM
morls (Stephen)
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I love how these basic techniques reflect fundamental governing principles of the universe.
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  #28  
Old 09-06-2019, 05:30 PM
Startrek (Martin)
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Nick
I started off trying that ďold bushmanísĒ solar noon method to find true south with multiple time marks on the ground etc..but I found the single rod or dowel set at 90 deg a more reliable method.As long as you take care and be as accurate as you can with your line marking and spot on with your time ( Stellarium) itís a great method.
After I plonk the tripod down, line up , level , fit the mount , set home position and balance , I can polar align in 15 minutes with the Synscan Hand controller after 2 or 3 iterations ( I have no view of SCP at both sites )
Cheers
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  #29  
Old 09-06-2019, 05:51 PM
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I use an easier (for me) method, for daylight as well, using bright objects like Venus, Jupiter, Sirius or Moon. Avoid the Sun for safety reasons!

Needed: tripod, eq mount with setting circles, telescope with low power eyepiece (TFOV at least 1-2 degrees), inclinometer and bubble level, smartphone with sky charting app such as Stellarium for the position of a bright object.
Smartphone can be used as a level, but not quite accurate.
The telescope / eyepiece should be pre-focued to infinity.

'Inclinometer' can also be a wedge with an angle equal to your latitude combined with a bubble level.

* Put the tripod on the ground and guess where South is, maybe max 15 degrees off, and set it roughly level, no bubble level needed (yet)
* Set the altitude of the polar axis equal to your latitude using the inclinometer
* Point the telecope exactly to the zenith using the level and adjust the setting circles to 0:00 hour angle and declination to your latitude.
* Read position of the Moon, Venus or Jupiter (whatever is positioned favorably) on your smartphone: declination and hour angle
* Point the telescope to that object using the setting circles
* Move slowly the horizontal axis of the mount until the object is in the eyepiece

Then you are done. This works both in day and nighttime.
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  #30  
Old 16-08-2019, 09:57 PM
Multiverse (Grant)
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Quote:
Originally Posted by Startrek View Post
Here’s a method I use to find true south or as I have new view of the SCP at my 2 locations ( it’s very accurate and a good starting point for polar alignment )
Finding true south is the first thing you need to do when setting up your HEQ5 Pro tripod

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
Thanks Martin, I found your Solar Noon Shadow Method very useful.
I modified it slightly to suit my backyard observation location, it being all paved. I assembled a rod on right-angled bracket base, fine-tuned with nuts on U-brackets to achieve straight (plumb). Spirit level just attached magnetically. Use Stellarium to detetmine solar noon at that particular day, casts a nice shadow at solar noon which I have marked with chalk on the paver surface.
(Just trying to reduce file size of the photo for posting).

Last edited by Multiverse; 16-08-2019 at 10:23 PM.
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  #31  
Old 17-08-2019, 07:07 AM
Hemi
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This is a wonderfully interesting thread and Iíve read it many times. Do you guys use this method to find S, when traveling to a dark site though?

Hemi
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  #32  
Old 17-08-2019, 08:32 AM
Startrek (Martin)
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I use it at both my sites in Sydney and dark site south coast NSW but both have flat paved areas so it works extremely well
As long as you have reasonable flat ground it will work anywhere in the world
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  #33  
Old 17-08-2019, 11:56 AM
Hemi
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Yes but for mobile setups travelling to dark skies? Is this the method you use ?? I suspect not, if not what do you use?
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  #34  
Old 17-08-2019, 01:31 PM
Startrek (Martin)
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If you travel to a dark site out in the Bush all you need is a reasonably flat area of ground a bit wider than the area of your tripod , bring a spade with you to level the ground and thatís it. It wonít be as accurate as a backyard paved area but it will get you close enough as a starting point for your PA
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  #35  
Old 17-08-2019, 04:53 PM
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Allan_L (Allan)
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When we go to dark sites, we usually get there after (solar) noon.
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  #36  
Old 17-08-2019, 05:24 PM
Hemi
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Me too.....if you just want to get roughly South to start your PA routine then a compass is sufficiently accurate.....smaller than a spade as well. 😀.

Hemi
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