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  #1  
Old 13-06-2012, 08:32 AM
DJ N
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How to Smooth Out Guiding Graph on My EQ6 Pro?

I recently did a complete strip-down, relube and rebuild of my EQ6 mount. I am extremely happy with the result and I am finding that it does run a lot smoother with a lot less backlash.

Last night I did a test imaging run to see how much improvement there is. Prior to the build, the DEC axis was deviating around 4 pixels either side of zero axis guiding with the ED80 piggybacked on the ED120 (sorry I didn’t take a capture of the graph). Attached is a capture of last night’s effort. I feel that it is running much better now; however, I believe that there may be a lot more room for improvement. I have been playing around with the parameters in both PHD Guiding and EQMOD, however just cannot get a smoother run. The polar alignment is pretty much spot on. In terms of drift alignment, the star remains “stationary” on the line for at least 8 minutes (ED120 900mm focal length with 12.5mm reticule). As a side note, I only drift align for azimuth as I set altitude with a Wixey digital inclinometer (to 0.1 degree accuracy).

Really would appreciate any additional suggestions, or am I asking too much from the EQ6.

In case it may help, the imaging setup on the EQ6 Pro is as follows:

ED120 = Moonlite Focuser = Hotech Flattener = T-thread Spacer = TS 9mm OAG (DMK21 guide camera) = QHY8L

I have also attached the test image from last night which is 5x 5minute subs (and I am very happy with the roundness of the stars).

Look forward to any suggestions,

Daniel
Attached Thumbnails
Click for full-size image (Guding Graph Post.jpg)
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Click for full-size image (Omega Centauri 11Jun12 ED120 QHY8L Hotech TAOAG 5x5min Post.jpg)
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  #2  
Old 13-06-2012, 09:44 AM
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whzzz28 (Nathan)
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Hi DJ N,

Do you run any dew control on your scope?
My graphs on my HEQ5 look similar when the guidescope starts to dew up. Like you my main image looks fine, but the graph doesn't look so great. If it dews up real bad, eventually PHD loses the star.

Does it guide like this from the start or takes a few mins before it gets to this stage?

Also have you setup a PEC profile?
Your DEC is up and down in a sort of pattern, so a PEC profile may help you (or not). There is a nice tool that will take a PHD log file and display some graphs for PEC training, which should help you determine if it is periodic error or something else.
Conveniantly, i can not remeber its name or where i got it from. I believe there is a link on Stark-labs website somewhere.

The only other thing i can think of is that maybe your mount is not levelled, but im guessing you have made sure it is as level as you can get it.

Finally, you can always try drift aligning altitude as well, won't hurt to check.

-edit-
I learn't to read, removed my stuff up.

-edit 2-
Found a month old image of PHD i took, this was with a QHY5 on an Orion ST80 guidescope. Possibly try the settings i used (RA hys/agr) and max DEC
http://core-au.net/astro/phd.png
(disregard terrible stars, thats not a tracking problem, main scope had a "problem")

Last edited by whzzz28; 13-06-2012 at 09:57 AM.
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  #3  
Old 13-06-2012, 11:58 AM
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troypiggo (Troy)
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I recently wondered something similar. First, quick question. How come you're using PHD for guiding when you have Maxim already?

In my case, turned out to be poor seeing combined with too short exposures on guide cam. I lengthened the guide cam exposures to 5 secs to average out the seeing a bit more and that made big improvement. Also set a delay after exposure of 1 sec to ave out seeing effects, and tweaked "min move" to better suit my imaging and guiding gear.

Good link on tweaking guiding settings: http://www.ccdware.com/resources/autoguidercalcv4.cfm
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  #4  
Old 13-06-2012, 01:22 PM
DJ N
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Quote:
Originally Posted by whzzz28 View Post
Hi DJ N,

Do you run any dew control on your scope?
My graphs on my HEQ5 look similar when the guidescope starts to dew up. Like you my main image looks fine, but the graph doesn't look so great. If it dews up real bad, eventually PHD loses the star.

Does it guide like this from the start or takes a few mins before it gets to this stage?

Also have you setup a PEC profile?
Your DEC is up and down in a sort of pattern, so a PEC profile may help you (or not). There is a nice tool that will take a PHD log file and display some graphs for PEC training, which should help you determine if it is periodic error or something else.
Conveniantly, i can not remeber its name or where i got it from. I believe there is a link on Stark-labs website somewhere.

The only other thing i can think of is that maybe your mount is not levelled, but im guessing you have made sure it is as level as you can get it.

Finally, you can always try drift aligning altitude as well, won't hurt to check.

-edit-
I learn't to read, removed my stuff up.

-edit 2-
Found a month old image of PHD i took, this was with a QHY5 on an Orion ST80 guidescope. Possibly try the settings i used (RA hys/agr) and max DEC
http://core-au.net/astro/phd.png
(disregard terrible stars, thats not a tracking problem, main scope had a "problem")
Hi,

Appreciate the feedback. Basically guiding is like this from the start. I do run dewheating, so this is not an issue. I will however investigate PEC training, as up until now, never used it.

Quote:
Originally Posted by troypiggo View Post
I recently wondered something similar. First, quick question. How come you're using PHD for guiding when you have Maxim already?

In my case, turned out to be poor seeing combined with too short exposures on guide cam. I lengthened the guide cam exposures to 5 secs to average out the seeing a bit more and that made big improvement. Also set a delay after exposure of 1 sec to ave out seeing effects, and tweaked "min move" to better suit my imaging and guiding gear.

Good link on tweaking guiding settings: http://www.ccdware.com/resources/autoguidercalcv4.cfm
Thanks for the link, I will have a read through. I have started playing around with the guiding function on Maxim last week, and it does work, so no excuses . I suppose just to see where I was with regards to the mount rebuild, I decided to use PHD simply as I am more familiar with it.
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  #5  
Old 13-06-2012, 06:41 PM
swannies1983 (Dan)
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Quote:
Originally Posted by DJ N View Post

I am very happy with the roundness of the stars.
At the end of the day, this is all that matters. Maybe try 10minute subs and see what the result is?

I can't answer why your DEC graph is like it is. I was in a very similar boat to you. My DEC line would go all over the place, mainly over correcting i.e. used to swing in the opposite direction by 1-2 pixels. I also re-greased the DEC axis, tried different settings, balanced slightly camera heavy, slight offset in polar alignment. Nothing worked.

An interesting section is in the 3rd quarter of your graph. The trace goes down before going up (by too much as well). Was there a command sent just before the trace went down? I used to get this as well.

At the end of the day, I have given up using PhD to guide in DEC. I just get a good polar alignment and manually correct in DEC every now and then.
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  #6  
Old 13-06-2012, 08:18 PM
DJ N
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Quote:
Originally Posted by swannies1983 View Post
At the end of the day, this is all that matters. Maybe try 10minute subs and see what the result is?

I can't answer why your DEC graph is like it is. I was in a very similar boat to you. My DEC line would go all over the place, mainly over correcting i.e. used to swing in the opposite direction by 1-2 pixels. I also re-greased the DEC axis, tried different settings, balanced slightly camera heavy, slight offset in polar alignment. Nothing worked.

An interesting section is in the 3rd quarter of your graph. The trace goes down before going up (by too much as well). Was there a command sent just before the trace went down? I used to get this as well.

At the end of the day, I have given up using PhD to guide in DEC. I just get a good polar alignment and manually correct in DEC every now and then.

Hi Dan,

Normally I run 12 minute subs and they are still OK. As I was imaging Omega, I though 5 minute subs would suffice. I was thinking of guiding with DEC guiding turned off, however will leave that for when we get some better weather.

I suppose as long as I am getting round stars, that is the main thing!

Thanks,

Daniel
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  #7  
Old 13-06-2012, 08:24 PM
swannies1983 (Dan)
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Quote:
Originally Posted by DJ N View Post
Hi Dan,

Normally I run 12 minute subs and they are still OK. As I was imaging Omega, I though 5 minute subs would suffice. I was thinking of guiding with DEC guiding turned off, however will leave that for when we get some better weather.

I suppose as long as I am getting round stars, that is the main thing!

Thanks,

Daniel
Yeah, unless you want lightning shots, then tonight isn't the night for astro imaging

I initially wanted the perfect PhD graph. As soon as the trace went +/-1 pixel, I would stop the exposure and start again. I soon came to realise the odd movement like that still produced round stars.

Also, what's your arcsec/pixel for your guiding and imaging setup?
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  #8  
Old 13-06-2012, 09:35 PM
DJ N
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Quote:
Originally Posted by swannies1983 View Post
Yeah, unless you want lightning shots, then tonight isn't the night for astro imaging

I initially wanted the perfect PhD graph. As soon as the trace went +/-1 pixel, I would stop the exposure and start again. I soon came to realise the odd movement like that still produced round stars.

Also, what's your arcsec/pixel for your guiding and imaging setup?
Some lovely lightning out there at the moment!

With regards to arcsec/pixel,

Imaging at 1.79 arcsec/pixel and guiding at 1.28 arcsec/pixel. When I previously had the ED80 piggybacked then guiding was at 1.93.

Cheers,

Daniel
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