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Old 05-01-2020, 12:40 AM
OzMaz (John)
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Finding the South Celestial Pole.

Hi Folks,

After struggling for years I just can't work out how to locate the SCP.

I've given up using a polar scope, my eyes are too feeble and the ambient light hides the stars a little.

I used SharpCap and did a Polar Alignment and I can get the RA and declination to very small values which it regards a excellent.

I then use SynScan to do a three star alignment. None of the stars are within a degree and after a lot of searching I locate the stars. At the end I am told the alignment is successful.

If that is the case, why does the Maz value display three degrees? I thought it would have been a lot closer.

Any help gratefully accepted.
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Old 05-01-2020, 06:53 AM
Wavytone
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OK...

1. Use a clinometer app on a smartphone to carefully level the tripod head to 0.1 degree before putting the mount on top; this simplifies the setup by ensuring the elevation of the polar axis is the same each time. Note that the bubble level supplied is hopelessly inaccurate.

2. Use same clinometer to check the elevation of the polar axis equals your latitude, it is not hard to get this right to 0.1 degree.

3. I then use the dec circle (I have calibrated it) to adjust the azimuth of the mount by aligning on two stars, this routinely gets me to better than 1 degree in azimuth.

4. Often this is good enough, but if you want better, use SynScan itself to adjust the azimuth and elevation of the mount to better than 5 arc minutes - and I bet most users don't know it can do this, or that its quicker than drift aligning.

Section 11.3 Polar Alignment without Polar Scope
The polar alignment function can help users to polar align an equatorial mount accurately.
Here are the operating instructions:
1. Complete a 2-star alignment or a 3-star alignment. At the end of the alignment, the SynScan hand control will display the polar alignment error (refer to Section 3.3). Users can use the data to determine whether it is necessary to adjust the polar alignment.
2. Press the “MENU” shortcut key, and then access to sub-menu “Alignment\Polar Alignment ”, press the ENTER key to proceed to the next step.
3. The screen will display “Select a Star”.
• Use the scroll keys to browse through a list of star names and press the ENTER key to pick one as the reference star for polar alignment.
• The mount will start slewing to point the telescope to the reference star.
4. Use the direction keys to center the reference star in the eyepiece of the telescope after the mount stops slewing. Remember to end the centering operation with Up and Right direction keys. Press the ENTER key to proceed to the next step.
5. The screen will now display the polar alignment error in altitude (Mel=dd°mm’ss”). Users can then use the data to determine whether or not to adjust the altitude of the R.A. axis in the next step. Press the ENTER key to proceed.
6. The mount will slew to a new position. When it stops, the screen will display “Adjust Altitude:”. By using ONLY the altitude control of the mount (do not touch the azimuth control), bring the reference star back to the closest point to the center of the FOV of the telescope’s eyepiece. Remember the reference star’s current position in the eyepiece for later adjust- ment. Press the ENTER key to confirm the centering operation.
7. The screen will now display the polar alignment error. Users can then use the data to deter- mine whether or not to adjust the azimuth of the mount in the next step. Press the ENTER key again to proceed to the next step.
8. The mount will slew to a new position. When it stops, the screen will display “Adjust Azimuth:” By using ONLY the azimuth control of the mount (do not touch the altitude control), bring the reference star back to the closest point to the previous position (at the end of Step 6). Press the ENTER key to confirm the centering operation.
9. The screen will display the polar alignment error again, press the ENTER button to end the polar alignment process.
10. Go back to the “Alignment” menu on the SynScan hand control and execute another 2-Star or 3-Star alignment, and then check the polar alignment error data reported at the end of the 2-star alignment or 3-star alignment. Repeat Step 2 to Step 9 until the error is small enough and acceptable. Generally, users can get up to 1 arc-minute polar alignment accuracy after repeating this polar alignment process 2 or 3 times.

Last edited by Wavytone; 05-01-2020 at 07:05 AM.
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  #3  
Old 05-01-2020, 07:24 AM
Startrek (Martin)
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John
I’ve used the Synscan polar alignment routine for over 3 years with great success as I have no view of the SCP at my 2 locations , Sydney and South Coast. Usually takes around 15 minutes once mount is level , altitude is set using a digital inclinometer and pointing very close to south meridian line
Here it is in detail ....

Synscan Polar Alignment Routine V4 Skywatcher EQ Mounts ( used when no view of SCP )
1/ You will be using a 2 Star Alignment to start the process so nominate your 2 Alignment Stars on the same side of the meridian, one of which will be your Polar Alignment Star ( Alignment Stars should be fairly bright stars where possible to ensure they appear in the Synscan hand controllers data base, usually greater than magnitude 2.5 )
(Alignment stars for polar alignment ideally should be located between 35 degrees and 70 degrees in Altitude and no more than 50 degrees in Azimuth from the meridian) Important - Your Polar Alignment Star or 1st Star Alignment Star will be the one closest to the south meridian. To assist with locating and nominating your Alignment Stars use a Star Chart, a Planetarium like Stellarium or Cartes Du Ciel.
2/ Complete a 2 Star Alignment generally in accordance with Syncan 2 Star Alignment procedure. Start with your 1st Alignment Star close to the south meridian ( this will be your Polar Alignment Star as well ) and then 2nd Alignment Star away from south meridian no further than 50 degrees in Azimuth
3/ After completing a 2 Star Alignment press “Menu” then “Alignment” then “Polar Alignment” and then “Enter”
4/ The screen will display “ Select Star”. Scroll through list of stars until you find your previous nominated Polar Alignment Star and press “Enter”
5/ Mount will slew to the selected Polar Alignment Star
6/ Use direction keys on the hand controller to centre the Polar Alignment Star in the telescope eye piece reticle or Computer screen reticle. Once centred press “Enter”
7/ The hand controller screen will now display the polar alignment error ( degrees: minutes: seconds) then press “Enter” to proceed
8/ The mount will now slew to the new Altitude position. Now use the Altitude adjustment bolts only to move the Star to the closest point to the centre of FOV on the reticle eye piece or computer screen reticle. Remember this position and then press “Enter” to show the new polar alignment error ( degrees: minutes: seconds )
9/ Press “Enter” again and mount will slew to the new Azimuth position. Now use the Azimuth bolts only to move the Star to the closest point where the Star was centred in step 8. Press “Enter” to show the new polar alignment error
10/ Press “Enter” again to end the Polar Alignment procedure
11/ Go back to the “Alignment” menu in the hand controller and execute another “2 Star Alignment”. 1st Alignment Star will be your Polar Alignment Star which you should be already centred on from the previous Polar Alignment routine and 2nd Alignment Star is further away from the south meridian.Once the 2 Star Alignment is completed , the polar alignment error will be displayed on the hand controller ( degrees: minutes : seconds )
12/ Repeat the above procedures ( iterations) 2 or more times as required to reduce your polar alignment error below 1 arc second in both Altitude and Azimuth.
Polar Alignment Error displayed on hand controller should show as many zeros as possible
Eg: 1 arc minute error 000 01’ 00” Eg: 20 arc sec error 000 00’ 20”
Try and get below 1 arc minute error in both Altitude and Azimuth if conditions and time permit.
13/ Note: you must perform a 2 Star Alignment before you start with a Polar Alignment routine each time
14/ To improve accuracy of your Star centering and alignments , de focus the star slightly into a small donut shape, this way you can perform more accurate centering operations looking into your reticle eye piece or at your computer screen reticle
15/ The 2 Star Alignment stars you use for Polar Alignment maybe different from 2 Star Alignment stars you use for locating objects ( Goto) as the accuracy of Goto may improve with a wider distance between alignment stars in Azimuth.The 2 Star Alignment stars for Polar Alignment are fairly close to each other near the meridian and only span a small part of the night sky. The Polar Alignment routine obtains better results ( lower error ) when Alignment stars are within 50 degrees apart in Azimuth and closer to the south meridian at between 35 degrees and 70 degrees in Altitude.
16/ With some experience the Synscan Polar Alignment routine can usually be completed with sub arc minute PA error in around 15 to 20 minutes depending on seeing conditions
17/ Note: Star Alignment and Polar Alignment are two different processes
Star Alignment is used to tell the mount exactly its location in the night sky on an object using singular or multiple pointing model algorithms.
Polar Alignment is aligning the central axis of the mount and telescope to the South Celestial Pole using the Altitude and Azimuth adjustments. Depending on the accuracy of Polar Alignment,the celestial object will remain stationary in the FOV for at least a minute or so before any noticeable drift.
However Polar Alignment and Star Alignment do affect each other when adjustments are made. An adjustment of Altitude or Azimuth affects your star alignment accuracy, that’s why you perform a 2 Star Alignment after PA is adjusted.

Hope this helps
Good luck
Martin
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  #4  
Old 05-01-2020, 07:53 AM
Startrek (Martin)
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John
One item I forgot to note , in the Syncan manual it advises to complete centering your alignment Star using the Up and Right buttons on the hand controller to reduce backlash
I’ve tried with or without doing this and it made no difference to the Star Alignment or Polar Alignment accuracy
Now I just use any button to centre the Star as long as it is centred , then press enter
Also I use the Synscan Polar Alignment routine on both my HEQ5 mount and EQ6-R mount
Obviously the EQ6-R mount completes the process easier and in less time
When PA error is as low as I can get ( less than 1 arc minute ) I usually pick a star out to the east and up at 50 degrees and track it for a few minutes to see if there is any noticeable drift. Usually I can track the Star for 5 minutes or so without it moving off the reticle
Then I get on with imaging , select , target , Goto , frame, focus , guiding , capture plan etc....
For SA and PA I started using an Orion 20mm 70deg illuminated reticle eye piece but that method went over 2 years ago ( it was straining my neck and back ) when I connected my laptop to the mount 2metres away and use my DSLR and BYEOS which has a PA reticle crosshairs screen. I just sit at my little outdoor workstation on a drum stool , bought a 3m long curly cord for the Synscan Hand controller and perform my Star Alignment and Polar Alignment in relative ease and comfort , no more bending over the scope and mount
Cheers
Martin
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Old 05-01-2020, 08:17 AM
Startrek (Martin)
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John
This how I find my “True South Line” ( south meridian line ) or SCP line to set my tripod pointing true south ( not magnetic south )
Procedure looks complicated but it’s relatively easy and very accurate. I have permanent true south lines scored across my pavers at both sites so it’s easy now to just place the tripod down now
Here it is ......

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 ( approximately 1.5 sqm ) or where you will set up your telescope mount should be a reasonably flat and level area with a good view of the sun at around midday ( a paved , tiled or concrete area is preferable) At a remote site you will need to clear the ground and make it reasonably flat or level

Procedure

(Setting up for your Shadow)
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 the dowel NSEW

Finding Solar Noon Time

(Using your Planetarium like Stellarium )
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 )

(Finding Solar Noon on a Website)
Most meteorological websites show Solar Noon times at or near your observing location

Marking your Celestial True South Line

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 towards the south
At exactly Solar Noon time mark a thin line on the surface or 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 marks the Celestial Meridian (True North / South )

Use this line to align your tripod front leg “N”to True South and then set up your mount
I found this method far more accurate than any app or compass with magnetic declination

Hope this helps
Martin

I have written other procedures saved for “placing mount head on tripod” , “finding home position on mount” and “balancing mount”
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  #6  
Old 05-01-2020, 11:05 PM
Xeteth (David)
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John - one thing to consider if this is for astrophotography is to do plate solving. Personally, I use Sharpcap for polar alignment then let the plate solving function in Astrophotography Tool to do all the work for me.

Once I'm polar aligned I am able to slew to any target I want very quick and have it dead center of the frame without any worries.
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Old 06-01-2020, 12:16 AM
OzMaz (John)
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Thanks folks,

I appreciate your guidance. (pun intended.)

When the weather clears I'll try the recommendations out.

My difficulty is that SynScan and SharpCap seem to give different results. I was expecting the same result from both.

As well as your recommendations I am going to try and set up the polar scope again. After either of these methods I should be able to find the elusive Octans and get a third opinion.

I do plan to use the mount for astrophotography.
I've gone as far as I can with camera/tripod until I reach the star line behaviour. My camera/lens combination is just too slow, so I need a mount that follows the stars.

I don't have an observatory, so it's setup/teardown each viewing session. I have created a three metre flat area at the back of my yard that has pavers as it's surface. As my house block rises from the street I can nearly see over the house to the West from the flat area.

The alignment of the long axis of my block is very nearly East-West, so that's been a good starting point.

Thanks for all your advice.
I will try them all out.
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Old 06-01-2020, 01:29 AM
Hemi
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Hi Oz Maz,

This is what I do, and posted on a previous thread, (could not work out how to put the link)



It’s quite easy to get roughly polar aligned.
1. Firstly: get your mount setup to home position: the following link is brilliant.

https://www.youtube.com/watch?v=4fO6hyYtPwM


Next

You need a compass, inclinometer and a roughly leveled mount.

2. Point your telescope and mount to face true south. (Magnetic south plus offset for your location, can be found online). Can be approximate.

3. Raise the altitude adjustment of the eq mount to your latitude. (Found online), then fine tune using an inclinometer (iPhone worked for me). Again it is approximate.

4. Fire up the mount and add you location details. And align the GoTo.

5. Use the polar align routine (I’ve done this with celestron and SW) flavors. Follow the instructions. (You don’t use the controller, just the mechanical azimuth and altitude bolts)

6. Switch off. Loosen the clutches. Get the scope back to home. Redo GoTo, redo polar alignment.

7. You can re iterate as many times as you like. 3 worked for me, more yielded no improvement.

8. If you have ascom and a camera all working , then you can Switch over to that and use a windows program called PEM PRO. This has a polar alignment wizard. That will fine tune further if required.

I struggled for quite a while, but this worked very well for me. I have been getting 5m unguided at 700mm focal length.

The thing to remember is the initial polar alignment, where you plonk down your scope, doesn’t have to be super accurate. I only used a iPhone compass and inclinometer despite the caveats of magnetic interference etc so YMMV.

Good luck, and don’t forget to enjoy the process of getting there....all to easily done.

Cheers
Hemi
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