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How often do you have do a new PA/model?


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#1 Corpze

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Posted 22 March 2016 - 01:38 PM

Hi, i was just curious of how often you really have to do a new Polar Align due to the precession.

Another question i have been wondering over is if you have to do a new model for the autumn/spring or if you are good to go with a good model throughout the whole year?

 

/Daniel



#2 Jay

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Posted 22 March 2016 - 07:43 PM

Hi Daniel,

 

I do Polar alignment and pointing model only once when the season starts in September (ends in April)....if using the same scope all the time. If switching scopes then I'll do the alignment and model again.

 

Jay

 

P.S. I have a permanent observatory



#3 Corpze

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Posted 23 March 2016 - 02:28 PM

Thanks for your input Jay :)

/Daniel



#4 ChristerS

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Posted 25 March 2016 - 06:03 PM

Hi Daniel,
 
Here is a comment from Dr Keller what he suggests.
 
" So make the big pointing file only every month or so and inbetween, use few stars like 3 or 5 to make a pointing file and select the Polar Alignment only.
The idea behind this is that most of your system is changed but PA may be off.
Another option is to optimize PA and collimation only (makes sense if you have >=5 stars).
You will save a lot of time but get about the same result.
This is especially the case when you do MLPT anyway.
When you enter the advanced pointing window you can manually select which parameters you want to be fitted against your new pointing file."
 
from the link below...
 
/Christer

Cheers,
//Christer

www.astropix.se


#5 Corpze

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Posted 10 April 2016 - 07:45 AM

Well, it is a while ago i made my model (end of January) and it worked well quite a few weeks, but as of last night, the tracking was not good. (No error in tracking, just not good)

 

I guess I have to do a model every other month or so. - But why?

 

I should mension that the ice in the ground "might" have altered the concrete/pier... even though it is almost a ton of concrete in the ground it might have moved due to what we here in Sweden call tjällossning :)

 

So, is this beaviour the same with other mounts? or is it just ASA that looses tracking performance over time?

 

/Daniel



#6 robertp

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Posted 10 April 2016 - 01:01 PM

Hi Daniel,

 

I would recommend to check your polar alignment using Sequence and the predefined standard grids "3 star polar east" or "3 star polar west".

I do not have a massive pier like you but the ground in my garden settles/moves significantly over time. When I recently did a new polar alignment after about 6 months of not checking it, PA was off by more than 14 arcminutes.

Checking PA only takes about 10 minutes and then you should have a good idea whether your pier really moves or something else is going on.

 

Best regards and clear skies,

 

Robert



#7 john32712

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Posted 26 April 2016 - 01:26 AM

Hi Robert,

 

Is it possible for you to detail this procedure? That is, using Sequence to check PA?

 

Thanks,
 

John



#8 robertp

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Posted 26 April 2016 - 06:41 PM

Hello John,

 

here's how I check my PA from time to time:

 

* start Autoslew and Sequence

* within Sequence, go to the "Autopoint" Screen and click "AutoGrid"

* in the upper right area of the screen underneath "standard Grids" select either "3 Star Polar East Side" or "3 Star Polar West Side", depending on whether you want to do the check east or west of the meridian.

* click "Load" and you should now see the three positions that have the same declination

* click on "start" to start generating the pointing file with the three positions

* Solve the pointing file and make sure that all three positions are solved successfully

* go to Autoslew and load the autopointing file you just generated

* Calculate the pointing file by selecting the option that says something like "polar alignment only same declination" or something similar (I have no access to my system at the moment, so that's from my not so reliable memory)

Now you can see the calculated PA deviation and you can do a polar adjust.

 

Hope this is clear enough, if not, let me know and I will describe it in more detail.

 

Best regards,

 

Robert



#9 john32712

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Posted 04 October 2016 - 04:42 AM

Robert,

Apologies, I never told you thanks for posting the PA check procedure!

John




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