The solar noon shadow Method of finding True South

[Jethro777]

I would love some help setting up my new HEQ5 Pro mount correctly.
Having just come from a Dob background and not seeing the southern pole due to the trees blocking the way means I am struggling with many new things. :shrug:
If your in Brisbane, Logan and have one yourself, it could help by my dropping by and seeing how it's done, or I would be grateful for a visit.
PM me if you can help. :thanx:

[Startrek]

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

[Jethro777]

That is absolutely fascinating.
I am going to study that carefully, but still need some help. :)

[Startrek]

Next step after setting up your tripod and facing True South is to set the Home Position of your Mount head as follows -

How to set “Home Position” on the HEQ5 Pro Mount

1/ Level tripod base on NSEW axis with a good bubble float level ( be as accurate as you can )
2/ Install mount head and ensure counterweight shaft is pointing down along the south leg
3/ Set your Altitude on the mount head to your current location and lock in
4/ Try as best as you can to centre the Azimuth position along the centre axis of the mount ( I use a ruler in mm to make sure there are equal gaps both sides of the Azimuth bolts to the mount )
5/ Do not install counter weight’s , telescope or accessories on the mount
6/ Release the RA clutch and rotate the head anticlockwise until the counterweight shaft is level at exactly 90 deg then lock the RA clutch
7/ Release the RA clock scale and rotate it anticlockwise unit the pointer reaches 6.00 ( 18.00 ) Leave the RA clock released
8/ Unlock the RA clutch and then return the RA axis to the original “Home” position and lock it when the pointer reaches the “12” o’clock mark. Lock the RA clutch
9/ Unlock the DEC clutch and rotate the DEC axis until the saddle is exactly level to 90 deg then engage the DEC clutch again
10/ Release the DEC degrees scale and rotate it until it is set on the marker at 90 deg. Leave the DEC scale released
11/ Unock the DEC axis and rotate it until the DEC scale reads zero “0” then lock the DEC clutch
12/ The mount should now be in the Home Position
13/ Both RA clock scale and DEC degrees scale can now be rotated so the pointer arrows reach the zero “0” mark and then screw down and lock
14/ You are now ready to Balance your telescope mount in both RA and DEC

[Jethro777]

For the first part, you say the dowel will cast a shadow at noon - I always thought at noon the only shadow would be the diameter of the dowel -.no shadow. Am I wrong?

Please check picture if I have the concept right.

Assuming I can draw the shadow cast by the dowel, how do I make sure the Mount is aligned exactly in that direction?

Really appreciate the info on home position.
I worked out the zero point is 3" mark on the west side of the scale (150 (+10 time offset x 15) degrees east - 153 degrees longitude at the viewing location), but don't quite understand what to do with that information yet. :)

[Startrek]

Important: this method will only work accurately on hard flat reasonably flat surfaces like concrete , paved or tiled areas etc. it won’t be accurate on dirt or grass etc...
The dowel will cast a shadow line about 12mm wide and 500mm long along the ground towards the south. Mark a thin texta line or score the ground with a tile cutter from the central base of the dowel along the centre of the 12mm wide shadow toward the end of the shadow or south. I actually extended the line on the ground longer to about 1 metre so setting up the tripod is easier to align on this “ South Celestial Pole” line

This line you just marked on the ground is now pointing True South and will be used all the time to set up your tripod
Make sure the area you choose is reasonably flat and has a good view of the sky in all directions as best as possible
Does the above now make sense ?

[Startrek]

Your concept is correct !
Once the line is marked I then set up my tripod with the leg marked “N” on the top base pointing roughly towards south in this line
Your tripod then must be levelled as best as you can in all directions
Then I use 2 x 1 metre lengths of 30 x 30mm aluminium angle , first one sits on the ground along the new true south line with the end just touching the inside centre of the tripod leg, move the tripod leg to line up with the aluminium angle and second runs across the 2 other ( east and west legs ) tripod legs or feet at the bottom
I then use a builders right angle square to align the right angle formed by the 2 lengths of aluminium until it’s exactly at right angles with no gap along the south facing aluminium
Once again do this as accurately as possible
The tripod is now set up facing True South

Sorry it’s a bit confusing
I’ll try to send a diagram

Hopefully you get the idea

[Startrek]

Drawing attached to hopefully explain the concept
It’s seems long winded and daunting but once you do it a few times it takes only a few minutes to set your tripod and get on with setting home position, balancing and then polar alignment
I gave up a few times at first but I was determined to achieve it and now I’m really enjoying the hobby both observing and imaging the universe
There are many other ways to set up an equatorial Mount but mine works for me every time

[Startrek]

Sorry I just went over your reply
During setting the home position on the mount just worry about setting your elevation on the mount using the Alt bolts , the long chrome ones , it’s the latitude of your location site you set ( forget about the longitude for the moment )
I use a builders electronic angle device Accumaster to set the Altitude or Latitude. It’s only accurate to one decimal point but good enough
The Dec bolts ( black knob small ones ) are for your Azimuth adjustments which comes later when you polar align, just screw then in evenly both sides until just touching the centre post on your tripod base circle. I use a ruler to ensure they are equal both sides to the mount
Hope the above makes sense

[DJScotty]

Pm sent

[Sunfish]

Very clever idea to use the sun to find true North.
And to keep a mark once you find it.

I have been thinking of building a slab on the alignment.

I also use a Lieca Disto measure inclinometer to find the lattitude angle as I can not see the pole. And a DSLR astrotracer GPS to get a rough North in the field.

After that it is drift alignment to fine tune. That is simple and always reliable.

[Jethro777]

>I also use a Lieca Disto measure inclinometer to find the lattitude angle as I can not see the pole.

That's interesting, how do you do that?

P.s. DJScottyis going to help me set it up next week, but this is a really interesting discussion on how to align without the southern celestial pole being visible.

[Sunfish]

If you own a laser measure they often have an inclinometer built in which is accurate to within 0.2 of a degree. Just placing on the mount at right angles to the polar scope axis will tell you if your lattitude angle setting is close to correct.

Also helps to get the scope pointing more or less toward the pole in the field and less troublesome than a level in the dark..

Then drift align to fine tune if you can not see the pole . Cheaper and more fun than cameras and software using the stars with a little benefit of learning something. This explains drift alignment:


http://canburytech.net/DriftAlign/DriftAlign_1.html

[Allan_L]

Re: establishing solar noon
I found this site useful

http://www.solar-noon.com/

[Allan_L]

Assuming you are south of the tropic of Capricorn (23.43677° south of the Equator - eg south of Rockhampton )
you will always have a southerly inclined shadow (in daylight).
At Solar Noon it is pointing directly true South, AFAIK.

[Startrek]

The solar noon shadow method of finding true south has worked extremely well for me at my 2 sites
After the first 2 star alignment I’m usually down to around 15 to 20 arc minutes straight off the bat from plonking the tripod down, levelling, setting home position and balancing.
After 2 or 3 iterations I’m down to less than 15 arc sec , my best has been 2 arc sec error
Initially I tried the compass magnetic declination method when I first bought the mount and I was way out all the time so I ditched the compass ( good quality Silver compass for mountaineering )
Can’t beat the good ol sun , never lets me down
Cheers

[Astronovice]

Are you saying that if you are North of the Tropic of Capricorn (as I am being just North of Cairns) that this method won’t work? I was hoping to use this method as I have no clear view of the SCP and so much steel around where I set up that a magnetic compass is unreliable😒.

[Startrek]

Just a reminder , if anyone decides to use the solar noon shadow method to find true south then make sure you are as accurate as you can with your solar noon timing, levelling and measuring
Check wooden dowel is standing 90 deg on all directions NSEW
Mark line on ground in centre of shadow at exactly solar noon
Mark line on ground in centre of shadow as accurately as possible

The more care you take with these steps , the closer you will be to True South and therefore ensure a good starting point for polar aligning your mount.
Cheers

[Allan_L]

Not exactly.
But I would expect there will be times when you get no noon shadow (sun directly over head) and times when your noon shadow points North (ie the sun is South of your position - around December summer solstice).
But for all other times the procedure should work OK - just that your shadow will be shorter than those further south. :shrug:

[Tinderboxsky]

Agreed.
It also pays to have everything set up and ready well before the expected solar noon time. If one is using a long shadow line, it is surprising how quickly the shadow moves. One needs to be ready to seize the moment and note the exact point. If not, in an instant, the shadow has moved on.
Experience speaking here! In my rush at the time, I missed the moment. At least the Sun came up again the next day and all was good.

[Wavytone]

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.

[Tinderboxsky]

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.

[Wavytone]

You’re welcome. It’s a method as old as the pyramids ;)

[Sunfish]

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.

[Tinderboxsky]

The ancient Egyptians would have had plenty of space to perfect this method.

[Wavytone]

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.

[morls]

I love how these basic techniques reflect fundamental governing principles of the universe.

[Startrek]

Nick
I started off trying that “old bushman’s” 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) it’s 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

[skysurfer]

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.

[Multiverse]

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).

[Hemi]

This is a wonderfully interesting thread and I’ve read it many times. Do you guys use this method to find S, when traveling to a dark site though?

Hemi

[Startrek]

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

[Hemi]

Yes but for mobile setups travelling to dark skies? Is this the method you use ?? I suspect not, if not what do you use?

[Startrek]

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 that’s it. It won’t be as accurate as a backyard paved area but it will get you close enough as a starting point for your PA

[Allan_L]

When we go to dark sites, we usually get there after (solar) noon.

[Hemi]

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