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Precise polar alignment with Star Adventurer Mini in the southern hemisphere

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#1 nikolav

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Posted 18 June 2019 - 06:32 PM

I live in New Zealand, hence no bright Polaris here to help. I can make a rough polar alignment based on my altitude and azimuth location, but that’s not good enough. I have a place in my garden where the South pole is directly visible. But I have trouble seeing the octanis starts trough the polarscope. I tried multiple times and probably only one of them I’m almost sure I saw them and aligned the mount correctly.
In theory I’m aware at least with the drift alignment method, but I don’t think it’s applicable here.
Are there any other tricks I can use to do perfect alignment when using lens in the 100mm – 300mm range?



#2 Cajundaddy

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Posted 18 June 2019 - 06:37 PM

Learn to identify the SCP with binoculars and get as close as you can with the polar scope.  Drift alignment will allow you to get very precise so that is a skill worth knowing.



#3 nikolav

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Posted 18 June 2019 - 07:16 PM

Learn to identify the SCP with binoculars and get as close as you can with the polar scope.  Drift alignment will allow you to get very precise so that is a skill worth knowing.

Can I use the drift alignment method with say 300 mm. lens. I would think the field of view would be too wide and the lack of a cross-hair to assist will make this too difficult and not precise enough?



#4 DuncanM

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Posted 18 June 2019 - 07:18 PM

Is there light pollution nearby that is effecting your night vision?  You might try covering your head with a towel or jacket to block the light. IIRC (it's been a while...) the four stars in Sigma Octantis should be fairly easily visible

 

Level the tripod carefully and then use a builder's angle finder to set the latitude as exactly as possible, then you can pan the PAS along the suspected location of the SCP until you locate the 4 stars. 

 

 

It is really important to ensure that the PAS is aligned with the polarshaft. You can test this by observing that the crosshair doesn't move when the PAS is centred on a distant object and the mount is rotated in RA.



#5 Marcelofig

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Posted 18 June 2019 - 07:59 PM

I use a Polemaster and it helps a lot, because Sigma Octantis is practically invisible to the naked eye. And even less from areas of high light pollution.

 

PHD2 also works very well. Here are some video tutoriales, precisely in the southern hemisphere (I think so, it needs a guide camera and a guide scope, because as far as I know PHD2 doesn't work with a DSLR).:

 

https://www.youtube....IGwbutr2z_yabD8



#6 nikolav

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Posted 18 June 2019 - 08:06 PM

Yep, there is star pollution mainly in the southern direction. I'll try covering my head - I never thought of this.

All the rest you advise is precisely what I do. I suspect my rough polar alignment is not good enough. My seeing is not as good as it used to be as well frown.gif

To make things even worse the only way the polarscope can see the south pole is when I fully extend the mount - about my own height which is about 1.80 m. This doesn't help with stability. Yes, I could travel to another location, but this wasn't the idea of taking astro pictures in my back yard...

 

So, probably the correct question should be: is there any way to achieve very precise polar alignment with a small tracker without using the polar scope?


Edited by nikolav, 18 June 2019 - 08:46 PM.


#7 OldManSky

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Posted 18 June 2019 - 08:47 PM

You can do DARV polar alignment with your lens. No crosshairs needed

 

https://www.cloudyni...bert-vice-r2760


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#8 nikolav

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Posted 18 June 2019 - 08:53 PM

I use a Polemaster and it helps a lot, because Sigma Octantis is practically invisible to the naked eye. And even less from areas of high light pollution.

 

PHD2 also works very well. Here are some video tutoriales, precisely in the southern hemisphere (I think so, it needs a guide camera and a guide scope, because as far as I know PHD2 doesn't work with a DSLR).:

 

https://www.youtube....IGwbutr2z_yabD8

I'm probably buying a Polarmaster at a later stage for my telescope mount. But with the Star Adventurer I can't use neither of these I reckon. All in all the setup consists of the mount, the DSLR with some lens attached and possibly a computer connected to the DSLR if that's will be of any help. Nothing else.



#9 SteveInNZ

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Posted 19 June 2019 - 01:05 AM

Use your camera.

 

Use the Alt-Az adjustments of the SA to point the polar scope at something easily identifiable (like Jupiter at the moment). Center it in the polar scope.

Leaving the alt-az as they are, position the camera to point at the same object using the ballhead or RA/Dec adjustment. Center it in the frame so that it is zoomed in looking at an image.

The camera and the RA axis are now aligned. From now, don't touch the ballhead or RA/Dec adjustments. Just move the alt-az to point your camera at the south pole.

You'll have to experiment to find an exposure that works for lens, light pollution, etc.

I'm in the Auckland burbs and can't see much naked eye but the camera can easily distinguish the Trapezium.

I posted my guide to getting to the Trapezium here.

If you can, try and get out to a fairly dark sky so that you can get a feel for the sizes/brightness/spacing of the stars. Once you know how to recognise the little triple star asterism, you can get the Trapezium into the polar scope with just a few shots in the city.

 

Steve.


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#10 nikolav

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Posted 19 June 2019 - 04:12 PM

Thanks guys!

I'll try both methods described once it clears up.



#11 DuncanM

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Posted 19 June 2019 - 05:43 PM

Thanks guys!

I'll try both methods described once it clears up.

Almost forgot...You can use Google Earth to determine where south is, very accurately.

 

Find your property and then zoom out and locate an object that is due south from your observing location. line up the mount so that it is aligned on that object and you'll be aimed south within a degree or so of the SCP. This should help find the 4 stars in Octantis and align your reticule on them.


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