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Polar aling


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#1 Rsanalb

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Posted 26 November 2015 - 12:34 PM

 I have a huge problem with the polar aligned,  my observatory do not  access at south or east, so I have just west and north and not all grades from 40 impossible to access the stars.
 
Align 3, 5 or 7 stars and I can not go a star south to align.
 
This makes it impossible to govern the mount. Could you give me some solution?
 
Thanks


#2 MarkS

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Posted 26 November 2015 - 01:05 PM

Your inability to go to a south star is a real problem!  I do not know how to overcome that. But you should be able to set up within a few arcminutes in azimuth by determining exact true north and aligning the mount to it. With my mobile set-up, having established north by observing the shadow cast by a plumb line at noon, I can usually get within about 5 arcmin in azimuth. For altitude I use a digital inclinometer which usually gets within about 10 arcmin.

 

If you do this, and then trim the settings using the drift method, you should be able to get close enough (< 5 arcmin) for MLPT to work well. This may be tedious but, as your set-up is fixed, you will only have to do this once!

 

Others may be able to give you a better procedure, but I think you will be able get a satisfactory alignment following the above outline.

 

Mark



#3 GeorgeCarey

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Posted 26 November 2015 - 02:17 PM

As Mark says, the drift method may be your best option. It takes a long time, but as you have a permanent setup in an observatory, will only have to do it once.

What altitude can you get to in the South direction? Even if you cannot go much past the zenith, drift alignment should work.


ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk


#4 Rsanalb

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Posted 26 November 2015 - 10:50 PM

This is my south. 1 peg its the star to do polar aling.

I havent anymore star.

#5 Rsanalb

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Posted 26 November 2015 - 10:51 PM

Thanks for you reply

#6 pauloastro

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Posted 30 December 2015 - 12:55 AM

Hello,

After autoslew calculates the azimut and altitude error of the mount/telescope I point to any star that suits me (but the best position is near de south meridian and with Dec=0º) and using my camera pixels as a scale I move the centered star the correct amount of minutes given by autoslew using the mount adjustment screws. After this I restart a new pointing file. The cons. in this method are that you have to know your pixel scale and use some spreadsheet for help you convert the autoslew errors in arc minutes into pixeis of you camera.

 

After using the automatic pointing star in autoslew I found that this method converged more quickly for me for finding the celestial pole than the one used by autoslew (in teory I think that they are the same method).

And this work with any star on the sky.

Of course I don't recommend to use Polaris for this, but any other star can be used. But the more close to the south meridian and the Declination near 0º the more precision you have in pointing in the right direction.

 

 

Paulo. 

,


Edited by pauloastro, 30 December 2015 - 12:58 AM.

Paulo Nunes.

 

AstroSite: https://sites.google...trobicesse/home

 


#7 pauloastro

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Posted 22 July 2016 - 05:56 AM

Hello every one,

After re-collimating my GSO 200F4 telescope I had to make a new pointing file. Using the same 4 star at same dec. to quickly polar align, and using my camera pixel scale method (described on last post), after 3 iterations  i get a precision on both axis less that 2 arc min. All this on the Est side of the pier. Doing a new pointing file with 18 star, and using a normal optimisation for PA I get the incredible result of ZERO arc min in both axis for the PA error. Is this possible?

 

But after adding some more stars on the west side of the pier the error get bigger, for around 3 arc min on both axis.

 

Best regards,

Paulo.


Paulo Nunes.

 

AstroSite: https://sites.google...trobicesse/home

 





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