phd2 drift alignment

[Atreta]

Hi,

i need some help again, this month nights are looking great but i can't seem to get to image anything at all anymore, not even 30 seconds pictures.

tried to use phd2 to do a drift alignment, i took some screenshots to show how it went, then after i did the drift alignment i slewed to give eta carine nebula a try, but 30 seconds pictures  gave terrible trailing. one other thing that happens when i try to calibrate with phd2 is the non orthogonal error, what does it mean? i can't make it go inside de 10 degrees  tolerance that phd2 tells it should be.

please please help, instead making improvements, it looks like i'm moving backwards.

here are the screenshots:

east, the nearer to the horizon as i could get.

 

meridian.

 

thank you.

 

[PhotoGav]

I feel your pain Frank, it's the most frustrating thing when the sky is clear but equipment problems stop you from using it. I have tried and failed with the PHD2 drift align tool in the past too. No idea what I was doing wrong and I have no idea what you are doing wrong. All I can suggest is that you try Alignmaster instead. If you do, just be careful with the pointing model in EQMod as that can screw things up, especially if you plate solve to get to stars. I can tell you how I use it if you decide to go down that route and would like me to... Good luck.

[Petergoodhew]

Frank,

Your drift alignment looks perfect to me - better than I have achieved.

I have experienced similar problems to those that you describe. I couldn't achieve decent PHD2 calibration, with non-orthogonal errors. It was caused by significant backlash problems with my mount, and now that I've fixed the backlash I have no problems with PHD2 alignment.  So I would suggest checking your backlash. 

Peter

[gnomus]

Guiding is a dark art indeed.  It has been guiding issues that have brought me closest to throwing all of the equipment over the garden fence in frustration (and I mean that literally)!!!

For a different perspective, I couldn't get Alignmaster to work for me at all and I generally use PHD2's drift align feature.  (I found that I couldn't get the star re-centred very easily in Alignmaster, then when I re-ran it, it was often further out that it was before my adjustment!)  At first, I couldn't get very far with PHD2 drift align either - this was because I kept making corrections too soon - that is, I was trying to correct PE rather than the actual PA error.  You need to give it a good couple of minutes (or more) in PHD2 to get a reliable indication of the trend.  I don't know if this is an issue for you or not, but the screenshot seems to show a relatively short period of guiding (or perhaps you use a different scale to me).

Having said all that, if your PA error is as stated (do I see 0.2 arcminutes?) then that is excellent and probably cannot be improved upon).

Having said that I have found in the past that I can have quite a bad PA error but still get OK(-ish) subs.  If you are getting terrible trailing then I wonder if there is another problem.  Flexure springs to mind.  Are you certain everything is tightened down and that no cables are dragging?  I assume the mount has been working normally?    

[Davey-T]

Looks OK but change the y to 4 rather than 16.

You can double check drift visually with an illuminated reticle eyepiece.

Dave

[kens]

Post the guide log from when you did the calibration. It contains much more information than the screen shot. Next time switch on the star profile with menu View > Display Star Profile.

A screen shot of that can be useful. Your RMS errors are so low I would suspect you were drift aligning on a hot pixel

[Owmuchonomy]

As Dave says plus change your X to 100.  It doesn't look as though you are drift aligning though because your mount is making corrections.  During the PHD2 drift alignment, corrections are not made I imagine.

[alacant]

Hi

Are you looking for the pink circle? Just thinking out loud as I've never had alignment as good as that. I wonder whether the pink circle disappears altogether when you're right on the spot? What I found in my short guiding history is that it has never been PHD2 at fault. Always a cable, a clutch or overlooking something really basic. Oh, and I also found that my power supply wasn't good enough to drive the mount. I had to change my old computer supply (which had the wrong voltage anyway) to a 6A [edit]12[/edit]V supply. Not much I'm afraid but I know how it feels to image nothing under a clear sky. When you think you've tried everything, someone will come up with something that leads you to crack it... HTH

[steviemac500]

I have never drift aligned with PHD2, just click and go and it's worked every time. I've had subs up to 10 minutes, I would see what your results are like without it.

[MY Yau]

18 hours ago, Davey-T said:

Looks OK but change the y to 4 rather than 16.

You can double check drift visually with an illuminated reticle eyepiece.

Dave

what focal length eyepiece should i use for a Skywatcher 80ed?

[Atreta]

21 hours ago, PhotoGav said:

I feel your pain Frank, it's the most frustrating thing when the sky is clear but equipment problems stop you from using it. I have tried and failed with the PHD2 drift align tool in the past too. No idea what I was doing wrong and I have no idea what you are doing wrong. All I can suggest is that you try Alignmaster instead. If you do, just be careful with the pointing model in EQMod as that can screw things up, especially if you plate solve to get to stars. I can tell you how I use it if you decide to go down that route and would like me to... Good luck.

Gav, i'll try again to align it in the weekend to see if was doing something wrong, i have a friend in here that has some more experience with imaging and i'll lend him my mount so he can check if there is something wrong with it.

20 hours ago, Petergoodhew said:

Frank,

Your drift alignment looks perfect to me - better than I have achieved.

I have experienced similar problems to those that you describe. I couldn't achieve decent PHD2 calibration, with non-orthogonal errors. It was caused by significant backlash problems with my mount, and now that I've fixed the backlash I have no problems with PHD2 alignment.  So I would suggest checking your backlash. 

Peter

thanks peter, looks like my mount has ldomr of backlash in the RA, if i press the right button in the synscan it keeps moving for a period of time. I just read astrobaby's guide to worm adjustment and maybe get the courage to mess with it

19 hours ago, kens said:

Post the guide log from when you did the calibration. It contains much more information than the screen shot. Next time switch on the star profile with menu View > Display Star Profile.

A screen shot of that can be useful. Your RMS errors are so low I would suspect you were drift aligning on a hot pixel

kens, thanks, at first i thought about that too, if it was a dead pixel or a hot pixel. i'll give it another go and post the logs.

 

[Atreta]

20 hours ago, gnomus said:

Guiding is a dark art indeed.  It has been guiding issues that have brought me closest to throwing all of the equipment over the garden fence in frustration (and I mean that literally)!!!

For a different perspective, I couldn't get Alignmaster to work for me at all and I generally use PHD2's drift align feature.  (I found that I couldn't get the star re-centred very easily in Alignmaster, then when I re-ran it, it was often further out that it was before my adjustment!)  At first, I couldn't get very far with PHD2 drift align either - this was because I kept making corrections too soon - that is, I was trying to correct PE rather than the actual PA error.  You need to give it a good couple of minutes (or more) in PHD2 to get a reliable indication of the trend.  I don't know if this is an issue for you or not, but the screenshot seems to show a relatively short period of guiding (or perhaps you use a different scale to me).

Having said all that, if your PA error is as stated (do I see 0.2 arcminutes?) then that is excellent and probably cannot be improved upon).

Having said that I have found in the past that I can have quite a bad PA error but still get OK(-ish) subs.  If you are getting terrible trailing then I wonder if there is another problem.  Flexure springs to mind.  Are you certain everything is tightened down and that no cables are dragging?  I assume the mount has been working normally?    

i guess it's something mechanical or maybe the power source of the mount(the original one burned out), one certain day if went away a bit and the scope was struggling agains the tripod, don't know if that messed with it

 

[Atreta]

20 hours ago, Davey-T said:

Looks OK but change the y to 4 rather than 16.

You can double check drift visually with an illuminated reticle eyepiece.

Dave

thanks, i'll change the next time i use it

19 hours ago, Owmuchonomy said:

As Dave says plus change your X to 100.  It doesn't look as though you are drift aligning though because your mount is making corrections.  During the PHD2 drift alignment, corrections are not made I imagine.

now you got me, i don't know that either, i just presssed the adsjut, adjusted the azimuth and altitude when need and hit drift again, the program selected the star and so on.

1 hour ago, steviemac500 said:

I have never drift aligned with PHD2, just click and go and it's worked every time. I've had subs up to 10 minutes, I would see what your results are like without it.

i'd love if it worked that way for me

 

[Petergoodhew]

2 hours ago, Atreta said:

Gav, i'll try again to align it in the weekend to see if was doing something wrong, i have a friend in here that has some more experience with imaging and i'll lend him my mount so he can check if there is something wrong with it.

thanks peter, looks like my mount has ldomr of backlash in the RA, if i press the right button in the synscan it keeps moving for a period of time. I just read astrobaby's guide to worm adjustment and maybe get the courage to mess with it

kens, thanks, at first i thought about that too, if it was a dead pixel or a hot pixel. i'll give it another go and post the logs.

 

If you have a lot of backlash them I'm pretty sure that's the problem.  It took me a while to raise the courage to fix it using Astrobaby's guide - but it wasn't as difficult as I thought. Since fixing it about a year agio I have had no more problems.

Good luck, Peter

[Davey-T]

6 hours ago, MY Yau said:

what focal length eyepiece should i use for a Skywatcher 80ed?

9mm or 12mm should do, if you can afford it get a graduated one.

https://www.firstlightoptics.com/baader-planetarium/baader-microguide-illuminated-reticle-eyepiece.html

Dave

[Atreta]

just dropped the mount to my friends house,  he'll check it out for me and see if he can get it to better use. 

I'll post when i have more news,  thanks again to everyone that helped. 

[MY Yau]

On 5/12/2016 at 17:45, Davey-T said:

9mm or 12mm should do, if you can afford it get a graduated one.

https://www.firstlightoptics.com/baader-planetarium/baader-microguide-illuminated-reticle-eyepiece.html

Dave

what's the purpose of the other guides other than the cross hair?

[Davey-T]

You can align the gradations with celestial north / south and measure your drift in arc seconds

(I've got a formula somewhere to input your scope spec's to work out the size of the spaces in relation to the scope)

You can use it to measure size / separation of celestial objects etc.

Dave

 

[tomato]

Sorry I am a bit late into this thread. 

My experience is very similar to Gnomus, I too started out on AlignMaster but struggled to recentre  the star with Az and Alt adjusters.

PHD2  drift align works much better for me, but you must calibrate first and connect via ASCOM if you can then the Magenta error circle gives you a good guide on how much adjustment to make each time.

Also a very good tip to let the drift align run for at least 3 minutes, the initial trend line can jump about quite a bit before it settles down to give you an accurate indication of the error.

[gnomus]

3 minutes ago, tomato said:

Sorry I am a bit late into this thread. 

My experience is very similar to Gnomus, I too started out on AlignMaster but struggled to recentre  the star with Az and Alt adjusters.

PHD2  drift align works much better for me, but you must calibrate first and connect via ASCOM if you can then the Magenta error circle gives you a good guide on how much adjustment to make each time.

Also a very good tip to let the drift align run for at least 3 minutes, the initial trend line can jump about quite a bit before it settles down to give you an accurate indication of the error.

I don't actually bother with the magenta circles - I just keep an eye on the trend lines.  I am not sure that I see a great deal of difference between doing this and visual drift alignment EXCEPT for one thing - with visual drift alignment you are using what will be the imaging scope rather than the guide scope.  I don't know how important this is.  

[tomato]

Yes, I worried that drift aligning via the guide scope would not be as good as drift aligning through the imaging scope but concluded that all the other dual scope drawbacks aside, flexture etc. then it should be Ok. 

I suppose the proof is how small and regular the star shapes are in the subs, for me currently this isn't my major problem, (not compared to eliminating gradients and dust bunnies....)

[View2]

My mount has a resolution of 0.09 arc sec and i am wondering about the 0.2 arc sec statement above being  achieved via drift aligning?  Obviously I'm new to the topic of AP guiding and haven't jumped in yet. 

This looks easy enough, but if you get 0.2 arcsec errors what is the advantage to a guide scope and phd2?

[Astrofriend]

Hi,

I can't see what's wrong with your setup. For me phd2 driftalign work perfect. I have a eq6 mount and off axis guiding on a 682mm telescope. Polar align precision I get as best is one arc minute.

I have a tutorial on my homepage. Maybe it could help:

http://astrofriend.eu/astronomy/tutorials/tutorial-drift-align/tutorial-drift-align.html

Lars

[View2]

Perhaps I need to read ieq45p manual again. Maybe it is 0.09 arc min lol

[View2]

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On 5/12/2016 at 21:35, Atreta said:

i guess it's something mechanical or maybe the power source of the mount(the original one burned out), one certain day if went away a bit and the scope was struggling agains the tripod, don't know if that messed with it

 

It says 0.09 arcsec resolution . To what does that refer?
(1.7) in the category 
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 Ultra-accurate tracking with temperature-compensated crystal oscillator (TCXO) 
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 Resolution: 0.09 arc second 
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