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New PHD2 static polar alignment tool

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61 replies to this topic

#51 pwarborg

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Posted 20 December 2017 - 01:29 PM

I was just wondering: I downloaded and installed version 2.6.4 of PHD2 yesterday. While the user guide does nicely walk one through 3 different PA routes with PHD2, my version seems only to offer drift align in the tools menu. Did I miss something?

I tried to post this in the PHD2 forum but somehow Google does not seem to like me. Even as a member of the group, I was not able to post anything.

I hope you guys don't mind that I posted the question here and can help me anyway!

Thanks,

Pat



#52 George Simon

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Posted 20 December 2017 - 01:49 PM

The two new PA routines (Static PA and Polar Drift Align) may be found in the latest developmental version (2.6.4dev5).



#53 pwarborg

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Posted 20 December 2017 - 02:34 PM

The two new PA routines (Static PA and Polar Drift Align) may be found in the latest developmental version (2.6.4dev5).

Ah... Okay. Thanks. Will check.


Edited by pwarborg, 20 December 2017 - 07:21 PM.


#54 AndyBooth

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Posted 20 May 2018 - 03:44 PM

This looks like a really good new feature, thanks for making it available.

One question, the notes say that PHD2 has to have been calibrated before selecting the reference star, it will be Polaris in my case.

Are there are rules as to which star to calibrate on before moving to Polaris?

same dec, within a certian hour angle range or anything?

Thanks


Edited by AndyBooth, 20 May 2018 - 04:01 PM.


#55 KenS

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Posted 20 May 2018 - 03:57 PM

You should calibrate your mount in the usual way. For many/most that means with a star near the celestial equator. If you guide with ST4 (On Camera) then calibrate on a star less than 60 degrees declination.



#56 AndyBooth

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Posted 20 May 2018 - 04:09 PM

Thanks Ken,

Actually I didn’t know that. 

I’ve been just picking a noticeable star in the same region as my target and calibrating on that.

I will try that next time.


Edited by AndyBooth, 20 May 2018 - 04:15 PM.


#57 KenS

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Posted 20 May 2018 - 05:26 PM

If you re using pulse guiding, PHD2 lets you calibrate once (preferably near the celestial equator) and reuse that calibration at other declinations. This is done with the Auto Restore Calibration on the guiding tab.

Calibrating on Polaris or any star near the pole is problematic because the movement in RA is so small. That's why PHD2 issues a warning for calibrations at declinations above 60 degrees. You can override it but it can result in an inaccurate calibration. For SPA in particular, the camera orientation is important but it does not need to know the guide rates. 

I'll add some notes on that to the video tutorials



#58 AndyBooth

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Posted 21 May 2018 - 02:43 AM

Thank you for the insight Sir!



#59 ThatsMyCoffee

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Posted 25 May 2018 - 12:46 PM

One question, the notes say that PHD2 has to have been calibrated before selecting the reference star, it will be Polaris in my case.

 

I wonder why this is?  The mount does not move during the SPA, so what difference does it make if calibration has been done or not?  Makes no sense to me...

 

Won't the SPA adjustments throw off the calibration anyway?  So you'll end up doing it again?



#60 KenS

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Posted 27 May 2018 - 08:00 PM

The calibration tells SPA how the camera is oriented. It uses that to get a reasonably good orientation of the star map.

The adjustments will only affect calibration when they are big enough to affect the dec drift during a calibration.

 

My recommendation is to start with the PDA tool to get a reasonable polar alignment without calibration. Is quick and easy to get within about 10'. Then calibrate and fine tune with either SPA or classic Drift Alignment. That amount of adjustment should not affect calibration.


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#61 LuscombeFlyer

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Posted 15 June 2021 - 05:18 PM

This thread is a bit old, but the closest I could find to my topic.
 

The video says to point the telescope "near the pole". How near is near? Within 5 degrees? 10, 20? I found myself chasing alignment around but never getting it close to 10' and wonder if my chosen star, Pherkad in Ursa Minor (Dec approx. 72°), was too far away?



#62 michael8554

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Posted 16 June 2021 - 09:41 AM

Software PA is used to refine your best attempt to point to the NCP.

 

That varies from using a magnetic compass, to best effort with a polarscope.

 

The instructions say "slew the telescope to point to Dec = +90".

 

So Dec = +72 is not close enough.




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