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Help interpreting PHD2 Logs (poor autoguiding)

astrophotography imaging
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#1 francomeconi

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Posted 28 May 2020 - 02:46 PM

Hi Everyone, I'm trying to give autoguiding a chance with the hope of improving my astrophotos, however I've been having several issues and haven't been able to get a decent photo yet. I'm realizing that poor/defective guiding is worse than no guiding at all! Anyways, my setup is a Skywatcher reflector 150/750 on EQ3 dual axis motors using PicGoto, and using a meade 6x50 (200 mm focal lenght) finderscope paired with a xbox live vision webcam for autoguiding with PHD2. I know this isn't the best setup but it's the one I can afford at this time... Anyways, after reading several helpful threads in this forum and the PHD2 guides and help files, I still haven't been able to narrow down what my particular problems are. Basically one of the main problems I have is that the guiding in DEC will periodically go crazy and lose the star and take forever to "bring it back". I suspect large DEC backlash could be a problem. I nearly always calibrate before imaging a particular object, and most of the times I'll get a large DEC backlash warning when calibration completes. Other times the warning will be about RA rates being lower than DEC rates. Sometimes, just sometimes, I won't get a warning message but still my guiding will be quite bad. At the best times the guiding error will be about 1.7" but soon enough I'll get a large jump either on DEC or sometimes even in RA. At other times, guiding will be quite good in DEC but the error on RA will be twice as large as in DEC, resulting in elongated stars. Anyways, like I said, every night (or even on different objects on the same night) it'll be a different thing. I'm attaching my logs from last night with the hope that someone might give me a clue as to what my problems might be? I also tried setting off my polar alignment a little bit so stars drift north and enable south guiding only, that seemed to work at first but then not really... All these problems result on my light frames being either elongated, or jagged, or with L shaped stars, even in 30 or 60" subs.

 

Anyways, if anyone can lend a hand I'll be really grateful.

 

Thanks!!

Attached Files



#2 psuaero

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Posted 28 May 2020 - 02:51 PM

I've found that the guys over at OpenPHD2 to be super helpful (I'm not saying that the CN members won't be). They'll analyze your guiding logs and make suggestions for improving your guiding. From the feedback I've gotten to my own guiding I feel like they are or might be developers of the software.

 

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

 

Post there. Give them a list of your equipment and software and any PHD2 guiding/debug logs you have and see what they can do.


Edited by psuaero, 28 May 2020 - 02:52 PM.

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#3 StephenW

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Posted 28 May 2020 - 03:20 PM

I think your core problem is your DEC guiding settings:

 

>Y guide algorithm = Resist Switch, Minimum move = 0.100 Aggression = 80% FastSwitch = enabled

 

I would greatly "relax" these settings by increasing the minmove (maybe to 0.3 for starters), reducing aggression to 70% and disabling FastSwitch.  The current settings are causing DEC to wildly oscillate back and forward 

 

Did you do a GA run and use the settings it suggested?

Also, do you have a lot of mechanical "play" in your DEC setup?

 

edit: After looking at your final guiding session some more, it appears you some more severe DEC issue - maybe a cable dragging?   Can you post a pic of your setup?


Edited by StephenW, 28 May 2020 - 03:25 PM.


#4 francomeconi

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Posted 28 May 2020 - 03:31 PM

I think your core problem is your DEC guiding settings:

 

>Y guide algorithm = Resist Switch, Minimum move = 0.100 Aggression = 80% FastSwitch = enabled

 

I would greatly "relax" these settings by increasing the minmove (maybe to 0.3 for starters), reducing aggression to 70% and disabling FastSwitch.  The current settings are causing DEC to wildly oscillate back and forward 

 

Did you do a GA run and use the settings it suggested?

Also, do you have a lot of mechanical "play" in your DEC setup?

Thanks, I actually changed the min move to 0.100 (from the default 0.200) just last night, but the problem didn't seem to improve or worsen compared to other nights. However it seems that I changed it "the wrong way" and I'll definetly try to set it at 0.3. I Do have mechanical play on the DEC axis... It used to be much worse but I managed to tighten the mount and reduce it. Still, there's a fair amount of backlash. Just to be sure, backlash is when the motor turns for a while until the cogs actually engage, right?

 

I've done several GAs since I started autoguiding during the past 10 or so nights, each time I'll get a slightly different suggestion though not wildly varying and not really helping all that much. 

 

Oh! One more thing, I can't seem to be able to get PHD to recognize when I've done a meridian flip. There's an option on the picgoto server to select which side of the pier the scope's on, and that works fine when doing go-to with stellarium, but as far as PHD2 is concerned, it's like it ignores that option and always goes crazy when I start guiding after a flip, forcing me to recalibrate. The flip is being done "manually", that is, disengaging the motors and moving the scope by hand, not with the mount controls.



#5 francomeconi

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Posted 28 May 2020 - 03:32 PM

I've found that the guys over at OpenPHD2 to be super helpful (I'm not saying that the CN members won't be). They'll analyze your guiding logs and make suggestions for improving your guiding. From the feedback I've gotten to my own guiding I feel like they are or might be developers of the software.

 

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

 

Post there. Give them a list of your equipment and software and any PHD2 guiding/debug logs you have and see what they can do.

Thanks, I've just joined and posted there as well.



#6 bobzeq25

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Posted 28 May 2020 - 03:33 PM

Hi Everyone, I'm trying to give autoguiding a chance with the hope of improving my astrophotos, however I've been having several issues and haven't been able to get a decent photo yet. I'm realizing that poor/defective guiding is worse than no guiding at all! Anyways, my setup is a Skywatcher reflector 150/750 on EQ3 dual axis motors using PicGoto, and using a meade 6x50 (200 mm focal lenght) finderscope paired with a xbox live vision webcam for autoguiding with PHD2. I know this isn't the best setup but it's the one I can afford at this time... Anyways, after reading several helpful threads in this forum and the PHD2 guides and help files, I still haven't been able to narrow down what my particular problems are. Basically one of the main problems I have is that the guiding in DEC will periodically go crazy and lose the star and take forever to "bring it back". I suspect large DEC backlash could be a problem. I nearly always calibrate before imaging a particular object, and most of the times I'll get a large DEC backlash warning when calibration completes. Other times the warning will be about RA rates being lower than DEC rates. Sometimes, just sometimes, I won't get a warning message but still my guiding will be quite bad. At the best times the guiding error will be about 1.7" but soon enough I'll get a large jump either on DEC or sometimes even in RA. At other times, guiding will be quite good in DEC but the error on RA will be twice as large as in DEC, resulting in elongated stars. Anyways, like I said, every night (or even on different objects on the same night) it'll be a different thing. I'm attaching my logs from last night with the hope that someone might give me a clue as to what my problems might be? I also tried setting off my polar alignment a little bit so stars drift north and enable south guiding only, that seemed to work at first but then not really... All these problems result on my light frames being either elongated, or jagged, or with L shaped stars, even in 30 or 60" subs.

 

Anyways, if anyone can lend a hand I'll be really grateful.

 

Thanks!!

The fundamental problem is that mount with a large telescope on top.  Autoguiding is necessary to get the best from any mount, but it won't make an inadequate mount work like a good one.

 

Cost is a reliable measure of mount quality.  The CG3 cost a couple of hundred dollars.  My recommended absolute minimum mount for that scope would be an HEQ5/Sirius, or an iOptron 30Pro.  All about $1200.

 

Beginners usually underestimate how good a mount is needed for imaging, and what one costs.  The CG3 could handle a DSLR with a fairly short focal length lens.

 

By all means try to do better by tweaking PhD2.  Just don't spend too much time on it, I think it unlikely you can fix this in PhD2.  If you could people wouldn't spend money on good mounts.

 

My advice, since you can't afford much money?  Try the camera/lens approach.   That could let you see if this is something you want to pursue.  You put the camera/lens on the mount with something like this.

 

https://www.amazon.c...e/dp/B0000XMYFQ


Edited by bobzeq25, 28 May 2020 - 03:40 PM.


#7 francomeconi

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Posted 28 May 2020 - 03:42 PM

The fundamental problem is that mount with a large telescope on top.  Autoguiding is necessary to get the best from any mount, but it won't make an inadequate mount work like a good one.

 

Cost is a reliable measure of mount quality.  The CG3 cost a couple of hundred dollars.  My recommended absolute minimum mount for that scope would be an HEQ5/Sirius, or an iOptron 30Pro.  All about $1200.

 

Beginners usually underestimate how good a mount is needed for imaging, and what one costs.  The CG3 could handle a DSLR with a fairly short focal length lens.

 

By all means try to do better by tweaking PhD2.  Just don't spend too much time on it, I think it unlikely you can fix this in PhD2.  If you could people wouldn't spend money on good mounts.

 

My advice, since you can't afford much money?  Try the camera/lens approach.   That could let you see if this is something you want to pursue.  You put the camera/lens on the mount with something like this.

 

https://www.amazon.c...e/dp/B0000XMYFQ

Absolutely makes total sense! However, having said that, your post just made me realize last night I changed my setup thinking exactly that same thought, I should give the mount a break, so I just mounted my sony a6300 with a 170-500mm sigma zoom less. I had to remove the large counterweight to balance it, it's a really light setup. So yeah, absolutely agree, but still, I should at least get decent guiding for 60-120" right?



#8 Jvtucke

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Posted 28 May 2020 - 03:44 PM

Go to the websites below and you'll find a PHD guiding log viewer as well as a tutorial for analyzing your logs and improving guide performance.

 

https://openphdguidi...hd2-log-viewer/

 

https://openphdguidi...uiding-results/



#9 StephenW

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Posted 28 May 2020 - 03:54 PM

>backlash is when the motor turns for a while until the cogs actually engage, right?

Yes.

 

>so I just mounted my sony a6300 with a 170-500mm sigma zoom less

 

Was the log you posted with the scope or the lens attached?



#10 francomeconi

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Posted 28 May 2020 - 04:09 PM

The log attached is for the lens on the mount, not the scope, sorry for that. Though, honestly, reviewing the log from last night and comparing it with logs from other nights when the scope was mounted, it all looks kind of the same... But yes, this attached log is indeed for the sony a6300 camera with 170/500 mm sigma apo zoom lens + meade 5x60 scope with xboxlive vision webcam for guiding. So a really light setup. Altough, coming to think of it, this setup is quite unbalanced on the dec axis.

 

One more thing that completely baffles me is that at one point I did a test guiding with a really bright star (arcturus) and I got really good guiding results for about 15 minutes (log section 6). I guided on that because I used the drift align function just to check and tweak my polar alignment (I'm on the southern hemisphere so no polaris here).

 

 

>backlash is when the motor turns for a while until the cogs actually engage, right?

Yes.

 

>so I just mounted my sony a6300 with a 170-500mm sigma zoom less

 

Was the log you posted with the scope or the lens attached?



#11 StephenW

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Posted 28 May 2020 - 05:45 PM

>Altough, coming to think of it, this setup is quite unbalanced on the dec axis

 

Yeah, you really want to be balanced, or maybe just a slight imbalance.

 

>I did a test guiding with a really bright star (arcturus) and I got really good guiding results

 

That is surprising - bright stars will cause PHD2 to saturate which makes it very difficult to determine and track the centroid - one possibility is that it was so saturated (spanning multiple pixels) that PHD2 couldn't detect any movement, and so guiding appeared to be "good" when in fact it may have been unable to guide at all...


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#12 francomeconi

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Posted 28 May 2020 - 07:31 PM

>Altough, coming to think of it, this setup is quite unbalanced on the dec axis

 

Yeah, you really want to be balanced, or maybe just a slight imbalance.

 

>I did a test guiding with a really bright star (arcturus) and I got really good guiding results

 

That is surprising - bright stars will cause PHD2 to saturate which makes it very difficult to determine and track the centroid - one possibility is that it was so saturated (spanning multiple pixels) that PHD2 couldn't detect any movement, and so guiding appeared to be "good" when in fact it may have been unable to guide at all...

Thanks, I'll try and see what I can do for balance, I'm sure there's a way. Any thoughts on those guidelogs?



#13 StephenW

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Posted 28 May 2020 - 09:44 PM

>Any thoughts on those guidelogs?

 

They are very impressive, in a scary kind of way wink.gif.   

 

There appears to be "something" preventing DEC responding to guide corrections, slowly (over a couple of minutes) building up until DEC finally moves and over corrects, and then the cycle starts over again.

 

Could be a really severe imbalance, or cable drag - not really sure.   I would definitely try getting your RA and DEC well balanced, and making sure there is nothing preventing DEC from moving (yo can test this by sewing manually - does it move smoothly?).  Then get a good calibration and try again.  Oh, and make sure your guide scope/cam are also well secured and not being dragged.

 

 

scary_impressive.jpg



#14 bobzeq25

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Posted 28 May 2020 - 10:23 PM

Absolutely makes total sense! However, having said that, your post just made me realize last night I changed my setup thinking exactly that same thought, I should give the mount a break, so I just mounted my sony a6300 with a 170-500mm sigma zoom less. I had to remove the large counterweight to balance it, it's a really light setup. So yeah, absolutely agree, but still, I should at least get decent guiding for 60-120" right?

If you have a 50mm lens, I'd start with that.  Once you have that working is the time to go longer.

 

With my $500 iOptron Skyguider my limit at 200mm was 60 seconds.

 

I'm not trying for perfect images here.  I'm trying to get you going.


Edited by bobzeq25, 28 May 2020 - 10:54 PM.



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