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EQ6 problem

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#1 HrAstro

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Posted 10 May 2009 - 05:08 AM

Ok, I'm really desperate and I need some help/theroy

I had the basic EQ6 mount and then I upgraded it on EQ6 SkyScan (new controller + motors). I had some good photos on 1200mm of focus like, http://www.hrastro.c...iangulumGalaxy/ , http://www.hrastro.c...5_BubbleNebula/ , http://www.hrastro.c...CrescentNebula/ .. after that I haven't gotten any good photos for a very long time 
When I'm auto-guiding the mount has very large oscilations... And now I'm going to stop yapping and show you the results. Here is the PHD log, http://www.hrastro.com/PHD.txt
Then screen-shot of PHD, http://www.hrastro.com/PHD.JPG
And analysis in the PEAS, http://www.hrastro.com/PEAS.jpg (autoguided on region of Lyra
More info,
Setup: EQ6 SkyScan controller ver. 3.24, C10-N (250/1200), Guide scopeMaksutov 90/1200 x 0.5 reducer + QHY5 camera.

I tried to take out the RA motor, but there is no change! There was no wind. Ihava a feeling that the mount is a little slower than it should be in tracking RA (when I turn on the Trend command in PEAS, that line is a little in the minus sign [-arcsec].

I have tried Guidemaster! The results where somewhat the same. After calibration I have got a message saying „Backslash is big, more than 1arcsec“

#2 HrAstro

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Posted 10 May 2009 - 07:18 AM

Here is one light frame taken with this setup
2min 400D http://www.hrastro.com/tracking.jpg ...

#3 Charlie Hein

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Posted 10 May 2009 - 07:31 AM

Please forgive the hasty edit on your image... Looking at your PEAS graph it seems your most severe bumps are coming very early in the worm cycle (see large "circle"). The two events shown there are many times greater than the next largest events, but it is almost impossible to tell exactly when they are occurring because the time scale is so long. Can you reload this chart and shorten the time scale (see small "circle") to the point where we can better see when those events happen? It could point to the source of the problem.

Charlie

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#4 HrAstro

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Posted 10 May 2009 - 08:01 AM

Ok,

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#5 Kaizu

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Posted 10 May 2009 - 10:13 AM

Have you checked the polar alignment. Yesterday, I got just similar images and I wondered the possible reason. After a little while I looked the levels and noticed that the bubbles were at the ends of the windows. The ground has defrosted and the mount has tilted a little. The autoguider can handle RA errors but not so well the DEC errors.

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#6 HrAstro

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Posted 10 May 2009 - 10:28 AM

Here is one light frame taken with this setup
2min 400D http://www.hrastro.com/tracking.jpg ...


These errors are in RA direction
I get this error for very long time now. Before that, everything was fine

#7 Charlie Hein

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Posted 10 May 2009 - 01:09 PM

Is this taken during an autoguiding session? If so (and I believe this to be the case) it may be very helpful to look at the unguided PE.

It is curious that the graph starts at the 2 second mark - and even more curious to find this major event happening at about 1.5 second intervals, as this doesn't map to any of the mechanical "noise generators" that I'm aware of in the EQ6. It may be time to look beyond the mechanicals.

Just supposing here... If this is taken during a guiding run could your guide rate and/or aggressiveness be too high - this might easily be why you see the graph in PHD running crazily back and forth like it does - try reducing the guide rate and/or aggressiveness a bit to see what effect this has on the graph in PHD.

Maybe you do have a large backlash in RA - if so, unbalance the rig towards the east a bit and see if this settles down the RA graph. Either way once the RA graph smooths out you have found the trouble. If neither adjustment does the trick then we may be back to looking for something internal to the mount.

EDIT: just had another thought - if backlash compensation has a high-ish value in it right now you might want to set it to a very small (but non-zero) amount so that it plays as little a role as possible while you're working this out.

#8 Mert

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Posted 10 May 2009 - 01:43 PM

By looking at the PEAS screen, IMHO it looks like
we can almost see 3 error events per worm cycle.
This more or less could point to the transfer gear.
If so, this gear could be loose, wobbling.

Q: Is it mounted between washers or O-rings?

Q: Do you have a webcam you could mount to do a
PERecording and post the data-file, maybe here
or on the EQMOD group?

With data we might be able to say something
a bit more precise. :shrug:

#9 HrAstro

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Posted 11 May 2009 - 03:34 AM

Update!

I have made 3 things yesterday:
1)I've played with the mechanics of EQ6. I have noticed this,

Backlash is "play" in the gears which you can feel by trying to rotate the axis with your hands while it is locked. If it wiggles back and forth - that's backlash. There's only a tiny spot between no backlash and motor stall, and it takes time to find.

I've found that text here, http://timsastroblog...up-for-eq6.html

2) I have reduced the guide speed to 0.125x

3) I've set the exposure time of the guide camera to 1sec, and the time between the pulses 1.5sec

Result: http://www.hrastro.com/PEAS_NEW.gif vs. old one http://www.hrastro.com/PEAS.jpg
or the same in PHD PHD, http://www.hrastro.com/vega.JPG vs. http://www.hrastro.com/PHD.JPG


Setup: Only ED80 on EQ6


Can someone please give me the results of their EQ? Can I be satisfied with this results? Some suggestions how to improve guiding within PHD program by looking yesterdays results?

#10 groz

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Posted 11 May 2009 - 11:38 AM

It is curious that the graph starts at the 2 second mark - and even more curious to find this major event happening at about 1.5 second intervals, as this doesn't map to any of the mechanical "noise generators" that I'm aware of in the EQ6. It may be time to look beyond the mechanicals.


Maybe dont look beyond the mechanicals _just yet_. If this is from a guided session, and 1.5 seconds is either the primary exposure duration, or some multiple of it (ie, 0.5 second exposures), then it's coming from slop in the gears (backlash) that's being aggrivated by guide commands, probably setting up a bit of an oscillation on a 1.5 second period, which correlates to every third guide adjustment.

#11 Dennis Sakva

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Posted 11 May 2009 - 11:53 AM

I would check the balance first. The mount should be east heavy which means that you need to find right (perfect?) balance slew your scope to the target you want to image and shift your counterweights a bit so that the eastern part is slightly heavier than your western one.

#12 Charlie Hein

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Posted 12 May 2009 - 06:19 AM

The new links are not working for me - I get a 404 error.

I don't have an EQ6 any more (moved up to a G-11), but there are many members in the club I belong to that do and many of those guys use PHD and rigs very similar to yours. I'll see if I can't get an example or two of their guiding graphs for comparison.

#13 Charlie Hein

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Posted 12 May 2009 - 06:40 AM

If this is from a guided session, and 1.5 seconds is either the primary exposure duration, or some multiple of it (ie, 0.5 second exposures), then it's coming from slop in the gears (backlash) that's being aggrivated by guide commands, probably setting up a bit of an oscillation on a 1.5 second period, which correlates to every third guide adjustment.


There certainly could be some significant backlash still left in the system, which is why Denis' idea is a great one to try as a quick check... and it may end up being better to leave some amount of slop in the gears anyway when all is said and done.

I would check the balance first. The mount should be east heavy which means that you need to find right (perfect?) balance slew your scope to the target you want to image and shift your counterweights a bit so that the eastern part is slightly heavier than your western one.


If the mount does have a significant amount of slop in the gears this will definitely help to settle things down.

#14 HrAstro

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Posted 12 May 2009 - 10:46 AM

OK, thanks... I'm now waiting the first opportunity to try some advices

And yes, in the attachment is one PHD graph screenshot. Setup was EQ6 SkyScan, 200/800 Newt, QHY5 and 300mm guidescope.
His guiding focal length is 50% shorter then my, but it is far more better. I'm now in contact with that person trying to resolve my problems

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#15 HrAstro

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Posted 12 May 2009 - 10:51 AM

The new links are not working for me - I get a 404 error.


Try now

#16 Charlie Hein

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Posted 12 May 2009 - 11:32 AM

The new links are not working for me - I get a 404 error.


Try now


links are working fine now - you have definitely improved things with your next try.

#17 Nebhunter

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Posted 13 May 2009 - 12:23 PM

Please keep posting your results, and any findings. I have a friend with a similar set up, and he is going through the exact same problems.

You might help others solve this problem.

#18 HrAstro

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Posted 15 May 2009 - 05:30 AM

Update!

Yesterday I was out again.
The only thing that helps is to set the hysteresis to 50. With the hysteresis of less then that, lets say 20, I have big oscillations like on the beginning of this story. Decreasing of aggressiveness does not help.

OK, how to check out that my backlash settings are correct? I have Backlash set to 0, and visually, I don't see that I have some delay in movement. maybe some software?

#19 HrAstro

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Posted 15 May 2009 - 05:49 AM

Ok, i figured out that Backlash by RA does not have the influence if the guide speed is set to 1x or less (because the motors are always spinning in the same direction)

#20 Charlie Hein

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Posted 15 May 2009 - 06:41 AM

Ok, i figured out that Backlash by RA does not have the influence if the guide speed is set to 1x or less (because the motors are always spinning in the same direction)


This is the main reason for the suggestion to make your load just slightly heavier on the east side of the mount. This "pre-loads" the RA gear set and just about completely eliminates RA backlash as an issue.

#21 Charlie Hein

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Posted 15 May 2009 - 06:48 AM

If you think of it try turning off the guide corrections in PHD and recording about 20 minutes of unguided tracking. That would give you over two worm cycles of raw PE to examine. The uncorrected PE would show any major mechanical bumps much better than the guiding runs do.

#22 HrAstro

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Posted 15 May 2009 - 07:15 AM

Will try

#23 HrAstro

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Posted 16 May 2009 - 04:45 AM

If you think of it try turning off the guide corrections in PHD and recording about 20 minutes of unguided tracking. That would give you over two worm cycles of raw PE to examine. The uncorrected PE would show any major mechanical bumps much better than the guiding runs do.


Hmmm, how to turn off guide corrections?

#24 Charlie Hein

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Posted 16 May 2009 - 12:46 PM

Here you go - click the brain icon to get to this - also, you might want to increase the search region in pixels to a large number so the star doesn't drift out while you record...

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#25 HrAstro

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Posted 17 May 2009 - 05:47 AM

Thanks






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