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PHD2: Weird star cross test results

astrophotography beginner
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#1 kidogofoto

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Posted 16 October 2018 - 05:25 PM

Hi guys!

 

So, I've been trying to get some decent guiding off my NEQ5 mount and 200P-DS scope with ZWO 280mm guide scope and ASI 120MM guide camera. Since results were disappointing, I decided to go back to basics and start with the most basic tests. So, first test is the star cross test. I set it to do 40 steps in each direction and had my camera (Canon EOS 600D full spectrum) record the whole thing. You'll find the result attached.

 

While the star cross test was being performed, I noticed a few things.

 

- North-South seemed to behave correctly. While changing direction, I noticed non-movement in the stars during only one single step. After this step, stars started moving in the opposite direction. Which is good I guess.

- East-West was another story all together. 30 steps it took to see the stars moving in the opposite direction.

 

Observing the final image I see another thing that is worrying me. It's the loop on the right hand side of the cross, and the 'hook' on the left hand side. I'm imaging with a 1000mm focal distance, but I would not expect this North-South movement while only East-West is being commanded to the mount. And I cannot begin to understand what might cause this undesired behaviour.

 

Could you please have a look at the attached picture and get me going in the right direction? I personnally suspect horrible backlash and possibly balancing or too much weight for this mount?

 

Thanks for taking the time to get a beginner going!

 

ABORT_LIGHT_337s_400iso_+20c_20181016-22h55m18s852ms.jpg



#2 calypsob

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Posted 16 October 2018 - 05:35 PM

what is a cross test? Is this some new feature in phd?  To me it looks like polar alignment is good. Im not sure how this test works but it seems to me that you are identifying periodic error in Ra and Polar alignment/Dec periodic error in the north/south movements. Im just making an educated guess, do you mind sharing more info on this test? 



#3 kidogofoto

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Posted 16 October 2018 - 05:39 PM

what is a cross test? Is this some new feature in phd? To me it looks like polar alignment is good. Im not sure how this test works but it seems to me that you are identifying periodic error in Ra and Polar alignment/Dec periodic error in the north/south movements. Im just making an educated guess, do you mind sharing more info on this test?

The cross test is in the tools menu of PHD and serves to check basic mount workings.
In an ideal situation, the cross should have arms perpendicular to each other and all arms should be straight and off roughly the same lengths.

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#4 kidogofoto

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Posted 17 October 2018 - 02:42 AM

I've the debug log. It's too big to attach here, so please get it via the link: https://drive.google...iew?usp=sharing

This cross test is the one started at 22:55. Hope this helps and that someone is able to get me going on solving my issues confused1.gif



#5 einarin

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Posted 17 October 2018 - 05:25 AM

Don't know about this test. Seems to be backlash which is typical for these mounts (at least in DEC).

Have you done Guiding assistant and followed its recommendations ?



#6 kidogofoto

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Posted 17 October 2018 - 09:56 AM

Don't know about this test. Seems to be backlash which is typical for these mounts (at least in DEC).

Have you done Guiding assistant and followed its recommendations ?

I have not. I will check tonight and both check the gearing and worm for sloppiness or stiction.



#7 pgs/sdg

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Posted 17 October 2018 - 11:39 AM

The folks at OPEN PHD GUIDING should be able to help.

I am working with them right now trying to solve some guiding problems.

 

https://groups.googl...pen-phd-guiding

 

if the link above does not work for some reason...just do a search for "OPEN PHD GUIDING "



#8 kidogofoto

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Posted 17 October 2018 - 11:54 AM

The folks at OPEN PHD GUIDING should be able to help.
I am working with them right now trying to solve some guiding problems.

https://groups.googl...pen-phd-guiding

if the link above does not work for some reason...just do a search for "OPEN PHD GUIDING "

Thanks, I posted this same issue there this morning

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#9 kidogofoto

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Posted 17 October 2018 - 01:09 PM

On a side note: checking the mount I just noticed that the built-in bubble level is waaayyy off. So I am not trusting that one again. I'll do the full procedure for leveling the tripod with a regular level from now on. That's surely help with PA as well.


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