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  #1  
Old 14-08-2018, 04:32 PM
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xelasnave
Gravity does not Suck

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PHD guiding graphs.

I love the PHD graphs and the little target box but it would be nice to know what they indicate.
Can you help?


First the trend lines what do they indicate if they are going up or down?


In the little target what does this indicate.

If the dots go up or down or to the left or right.


I presume if the RA is trending up or down the solution in the first instance would be to adjust counter weights?


I run 1.5 seconds with RA aggression at around 100 and the dec sometimes nil and other times between 30 and 50.


Last night things were all over the place but after a few attempts at balance and taking off my new 70 mm guide viewing scope it seemed to be happier.

At about 12 oclock it seemed to work well at 2 minute exposure and the last 2 captures I risked 5 minutes which went very well as the stars were round.


The graph lines wander out of the graph box but it keeps guiding so I am not too worried but I would like them to stay where I can watch them


The ra was staying within a second range (I think that is the correct interpretation) but slowly drifted up and off the graph screen.


Its working but I would like to know what the trend lines and the target dots are telling me.


The screen print below was at the start of the night and I forgot to get one later but I just need to know what the various graphs and dots mean...


According to Polemaster my pole alignment was near perfect so I cant understand why dec should trend usually up and if the trend lines in RA are telling me the motors are fighting the counter weight or the scope side.

Alex
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  #2  
Old 14-08-2018, 04:54 PM
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Lognic04 (Logan)
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About 1" - I'd be happy with that! Don't worry about it, as it isn't spiking or anything.
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  #3  
Old 14-08-2018, 09:20 PM
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I think it needs about half an hour to settle in.
Although it is not staying level there is not must variation.
Alex
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  #4  
Old 14-08-2018, 10:41 PM
kens (Ken)
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Quote:
Originally Posted by xelasnave View Post
I love the PHD graphs and the little target box but it would be nice to know what they indicate.
Can you help?


First the trend lines what do they indicate if they are going up or down?
They show any drift - this is useful in declination with guiding off. When the drift settles down so the trend line is fairly static you can see the PA error displayed on the graph with the trend line. With guiding on the trend lines should be level.

In the little target what does this indicate.
Thats a scatter plot of where the guide star has been recorded. You want it tight and round. Useful for showing any eccentricity in guiding which can lead to oblong stars

If the dots go up or down or to the left or right.
Up/down is declination, left/right is RA. Any single dot is meaningless. The idea is to get a long period view of your guiding

I presume if the RA is trending up or down the solution in the first instance would be to adjust counter weights?
Not necessarily. Make sure guide output is enabled first. Or you might not have enough aggression.


I run 1.5 seconds with RA aggression at around 100 and the dec sometimes nil and other times between 30 and 50.
Not recommended. Reset to the default values and run the Guiding Assistant

Last night things were all over the place but after a few attempts at balance and taking off my new 70 mm guide viewing scope it seemed to be happier.
Sometimes its just good or bad luck.

At about 12 oclock it seemed to work well at 2 minute exposure and the last 2 captures I risked 5 minutes which went very well as the stars were round.


The graph lines wander out of the graph box but it keeps guiding so I am not too worried but I would like them to stay where I can watch them
Change the scale using the graph menu

The ra was staying within a second range (I think that is the correct interpretation) but slowly drifted up and off the graph screen.
That doesn't sound good. PHD2 should keep the guide star centred.

Its working but I would like to know what the trend lines and the target dots are telling me.
It looks like your mount is not responding to guide pulses. Could be backlash. The dots say much the same but in less detail

The screen print below was at the start of the night and I forgot to get one later but I just need to know what the various graphs and dots mean...
Learn to use the Help menu to go to your logs folder and attach the guide log. Screen shots are not useful for analysis

According to Polemaster my pole alignment was near perfect so I cant understand why dec should trend usually up and if the trend lines in RA are telling me the motors are fighting the counter weight or the scope side.
So many possible causes. This is where you use PHD2 as a diagnostic tool.
Alex
My responses in red above
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  #5  
Old 15-08-2018, 07:25 AM
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that_guy (Tony)
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Check your balance, if theres too much weight on one side the guiding pulses aren't strong enough to move the mount the correct amount. Also double check your polar alignment!
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  #6  
Old 15-08-2018, 07:32 AM
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vlazg (George)
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You are also guiding North, set to South or Auto
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  #7  
Old 17-08-2018, 07:02 AM
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Quote:
Originally Posted by kens View Post
My responses in red above
Thanks heaps.
Alex
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  #8  
Old 17-08-2018, 08:51 AM
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vlazg (George)
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Hi Alex,
I don't know if you have sorted your guiding as yet but here are a few more suggestions.

You don't need the AO graph so you can get rid of it unless you are using Adaptive optics which I assume you aren't.

You are using too bright a star for guiding, it is saturated so it can't establish a centroid, use a fainter star.

Increase your dec aggression to about 90.

Decrease your min motion, not sure what guide camera and guide scope you are using but I use about 0.15. These parameters should be established using the brain to set up.

When you have done this and it is calibrated use the guiding assistant and let it run for about 2min and let the backlash assistant run as well. The recommendations are usually pretty good and they can be set.

Again make sure you are guiding South but I use Auto.

George
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  #9  
Old 17-08-2018, 09:41 AM
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Thanks George.
The good thing is I have now got the mount running so well it produces reasonably round stars at 2 minutes.
I have pulled it all down and now on my way to the Gold Coast but when I return I will apply all the great advice I have received.
Also I just remembered that I have not done a PEC mount intruction...I used to do it on my EQ6 a decade ago and that helped a great deal.
AND..when taking the scope off last night I could feel it was not perfect balance...but what surprised me last night was how forgiving the star loss was...it would loose ot but when I would go over to check it had found it again.
Your comment re stars os most helpful as I think in addition the guide scope could have a better focus...I may use the new 70 mm finder as a guide scope...
I am just so happy to have got this far as I have only started guiding recently and to get polar aligned in minutes is a huge step forward.

Alex
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  #10  
Old 21-08-2018, 09:36 AM
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Last night the guiding was terrible.
The irony is I took ages to balance everything...I did not get around to addressing the problem as it took me an hour and a half to set up as I had to pull it all down and put it away for the Pink weekend.
But just setting up again I learnt a few things...make a work flow check list☺
I turned the filter wheel around to gain mount clearance and as a result the camera had to be rotated 180 degrees so when I went to get more data for the Prawn Nebula it was upside down.
And so I tried stacking the first images with the upside down images in Deep Sky Stacker and surprise it stacked them.
Nice to know...but I felt the cold and had to give it in at 11 pm and only managed 15 HA subs...I think tonight I will just work on getting things working better as I have enough data to play with.
Yesterday I purchased a little drawing pad which should help with processing...it makes it easy to draw with the lasso tool for example.
Baby steps baby steps.
Alex
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