Astro lab - permanent set up - best s/w to polar align

[g__day (Matthew)]

I have a choice of four primary methods to polar align my mount - and they are all dis-agreeing. Would love to hear folks suggestions. My options are:


1. Vixen Skysensor2000-PC - put it into polar unaligned mode - align on three stars, move to any other star, switch it back to polar aligned mode and goto the same star - and then use the mount bolts to re-centre the star.


2. PEMPro - drift alignment routine


3. PHD2 - drift alignment routine (normal drift alignment - not the 180 degree rotate around the SCP) as I have no visibility to SCP in my location.


4. The SkyX Tpoint 200+ star model and Accurate Polar alignment routine. I have now done this method twice - and on subsequent runs with a fresh calibration model the instructions are the exact opposite of the preceding time.


5. Oops - forgot Sharpcap Pro's polar alignment routine - have that too, but like PHD2's pole method I can't use that (sorry Rob) because my astro lab simply doesn't give visibility to the SCP at all - not even close when the scope is on its side.


So all a tad annoying. Especially as the Software Bisque boy's stress drift alignment only really optimises your mount for one point in the sky and emphatically states their method is the gold standard. Just wish attempting it gave consistent results!


So I am now likely a few arc minutes off the refracted South celestial pole and would like to get this nailed to under an arc minute.


What would folk suggest who have set up a permanent scope in an astro lab?


Best regards,


Matthew

[turbo_pascale (Rob)]

I've paid the £10 to use SharpCap Pro's Polar align routine for my permanently mounted dome setup.

However, you have to have visibility within 5 degrees of the pole.
You've said you can't see the SCP, but not sure how close you can get.

Have a look here for more info.
https://www.sharpcap.co.uk/sharpcap/...olar-alignment

[billdan (Bill)]

When I had an EQ6 I used the static polar alignment procedure built into the EQ6 firmware. This would get me close to be Polar Aligned and then I would fine tune it with PHD2 drift alignment at the meridian and DEC=0.

I think drift alignment is the most accurate, however it is also the slowest method.
Problem being you have to wait for maybe 5 mins to see if the star is drifting N or S. Make an adjustment and then wait another 5 mins' to see if you improved the alignment or made it worse and you have to reverse the adjustment made.
If you are permanently setup in an Obs, I would suggest spend the time (1 hour) to get an accurate drift alignment. Then check once per month to see if it is still OK.

If your mount has poor backlash in DEC (like my EQ6 had) then it can be worthwhile to deliberately mis-align your P.A so the stars always drift in one direction (N or S). This way DEC corrections are always in one direction and less chance of the DEC motor having to go into reverse.

[g__day (Matthew)]

I have used PEMPro for hours at a time drift aligning - it is great for one star and one position - so I fear the Bisque guys may be right - drift alignment optimises for just one point in the night sky - not the whole of the night sky!


Anyone else who has set up a permanent astro lab with a German Equatorial mount and solved this problem care to share their method?

[multiweb (Marc)]

Originally Posted by g__day

I have used PEMPro for hours at a time drift aligning - it is great for one star and one position - so I fear the Bisque guys may be right - drift alignment optimises for just one point in the night sky - not the whole of the night sky!


Anyone else who has set up a permanent astro lab with a German Equatorial mount and solved this problem care to share their method?

The polar alignment in PEMPro is done at the meridian close to the equator then at the east or west horizon so very different parts of the sky on multiple stars. When you have those two trending horizontally then you're good to go. If you rely on only one star you might have your elevation or azimuth still wrong.

[g__day (Matthew)]

Hi Marc,


Even with two hours of drift refinement this way I get perfect tracking in some parts of the sky and poor tracking elsewhere...

[multiweb (Marc)]

Originally Posted by g__day

Hi Marc,


Even with two hours of drift refinement this way I get perfect tracking in some parts of the sky and poor tracking elsewhere...

oh wow, so you reckon the polar alignment is still off somehow? Could be balance as well. I always seem to track better when looking south than north or closer to the celestial equator.

[g__day (Matthew)]

Balance wasn't a factor as far as I could discern. Back then however it could well have been an interplay between the Skysensor2000-PC view of the sky interacting with PEMPros drift alignment. If the SS2K thinks your are even a tad out after a three star alignment it compensates for polar misalignment by running both Dec and RA motors to nullify this.


This can be both a blessing and curse - at it means a complex interplay is in effect when your are drift aligning - is the star really moving or is the SS2K predicting and nullifying assumed drift?


I try and remember to clear any SS2K three star alignment parameters and only do a one star alignment on the SS2K if I am doing any advanced alignment routine.

[g__day (Matthew)]

So from Tuesday night (200 star sky model) to Thursday night with 400 star model I am seeing varying pointing advice (about 8 arc minutes off where it said the refracted SCP was the night before) and a different pointing model solution.


If it isn't consistent how do I believe it?


Secondly I see the majority of my error appears to be in the North South axis - might that be DEC backlash or something else?


Lastly with TSX Tpoint am I best to set Backlash compensation in my mounts hand controller to zero and let Tpoint correct for this - or used software like PEMPro's backlash wizard to best tune my Dec settings in the mount before I let TSX and Tpoint work out an optimal pointing model?


Many thanks, Matthew

[g__day (Matthew)]

So at the end of the night / morning (4am) when I finally closed my star model down and did the last super model - after swinging its polar alignment advice all night it finally went back to the original assessment which is rather re-assuring:


Azimuth (MA)
Recommendation: Azimuth alignment is excellent. No additional azimuth adjustment is necessary.
Supporting information
MA is zero.
For latitude -33° 47' 28", rotate the mount clockwise (as seen from above) 0.0 arcseconds (0.0 arcminutes).



Elevation (ME)
Recommendation: Elevation alignment is good enough. No additional elevation adjustment is necessary.
Supporting information
ME is zero.
'Recommended ME' = 83.1 arcseconds (the refracted pole).
ME adjustment to get to above 'Ideal ME': 83 arcseconds (1.4 arcminutes).
The polar axis should be raised 83 arcseconds (1.4 arcminutes).



I was too tired to do the accurate polar alignment - so I shut it all down and will raise the 1.4 arc minutes on ME tonight.

[chuckywiz (Ben)]

Try Algnmaster. Its old but good software. You only need 2 bright stars to polar align accurately

Ben