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Auto guiding performance depending on the sky location

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#1 maxsid

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Posted 14 June 2021 - 03:04 AM

Hello,

I am not that new to this but I have been reading the internets and still don't quite understand...

 

What is the toughest and easiest situation for autoguiding?

 

Meridian? Equator? Zenith?

 

Close to Zenith is the toughest?

 

Please advise.

 

Thanks!



#2 zxx

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Posted 14 June 2021 - 06:55 AM

I get the best guiding in the north sky, a target like M81 I can have a great RMS of .35 to .50. Same night target in the south can be well over 1.00. The Zenith can be tough will a mount with DEC backlash.



#3 unimatrix0

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Posted 14 June 2021 - 07:21 AM

I actually get a good result around the Zenith.  It gets worse towards the horizon , East or West, South or North -doesn't matter. 


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#4 Midnight Dan

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Posted 14 June 2021 - 08:21 AM

I actually get a good result around the Zenith.  It gets worse towards the horizon , East or West, South or North -doesn't matter. 

Same for me.

 

-Dan



#5 Peregrinatum

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Posted 14 June 2021 - 11:38 AM

seeing affects PHD2 performance, seeing is always best at the zenith, or at the meridian if you are tracking an object



#6 astrohound24

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Posted 14 June 2021 - 07:38 PM

I do great in the North Sky and around the Zenith. When I turn south it all goes south. Lol.
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#7 KTAZ

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Posted 14 June 2021 - 07:44 PM

This is directly related to how you balance.

 

If you balance "east heavy", you may have better guiding to the east which might deteriorate nearing the zenith and get worse after the flip.

 

If you balance equally (as I do) you may get your best performance near the zenith, even on both sides of the flip.

 

Balance is a decision made based on your mount. If you have a lot or RA backlash. east heavy may be a good choice. If not, just stay well balanced.


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#8 maxsid

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Posted 15 June 2021 - 03:03 AM

Good info guys!

The key things, I guess, are the seeing and balancing.

Higher up in the sky is better and East-heavy or well balanced.

 

Thanks!



#9 Juno18

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Posted 15 June 2021 - 05:50 AM

I try my best to get an even balance.

 

My guiding performance is consistency better in the northern sky any consistently the most challenging near the celestial equator. 

Oddly enough, even with my mounts huge backlash (13s), my guiding always gets better near and through the meridian!



#10 james7ca

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Posted 15 June 2021 - 06:31 AM

Somewhat depends upon your polar alignment. Polar alignment is more critical the closer you get to one of the poles, so if you have some alignment error you may get more drift and thus a need for more corrections the closer you are to the pole (and those corrections would likely need to be in both R.A. and Dec, meaning double the trouble). Similarly, if you were targeted directly at the pole you really don't need any tracking, but if your mount's polar axis isn't aligned directly to the pole then your (mis)tracking will continually move you away from the target (i.e. the pole).

 

That said, being closer to the pole means there is actually less movement as the target circles the pole, so random noise (error) in your drive may result in less movement in the target (think of it as kind of a lever, the closer to the axis of the pivot the less the displacement). 

 

However, seeing is probably the greatest determinant in the quality of your guiding and since seeing is normally (always?) better toward the zenith that may be where you get your best guiding. Also, as you move down toward the horizon the effects of atmospheric refraction become worse, meaning that stars will no longer be moving at the sidereal rate (their rate of motion appears to slow down and your guiding has to correct for that change).



#11 astrohound24

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Posted 15 June 2021 - 08:54 AM

When I turn to the south like I mentioned earlier, I rebalance and then it improves. Balance is so very important and I can see PA would be also.

#12 Birddogoby

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Posted 17 June 2021 - 10:35 PM

For me, my best guiding seems to be around the zenith although with my EQ6R mount, I usually get .3-5" (arc seconds) across the sky ever since I started balancing my mount differently.

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