AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?


dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@...
 

I am wondering if I may have an issue with my AP 1100 GTO mount.

I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.

Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.

I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.

I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.

It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?




Alan Pryor
 

If all else fails check the tightness of all of your screwed connections. Your bolting to your telescope; the bolting of the saddle to the mount; the bolting of the sections of your declination and RA axis.

Check the stability of your optics too. No mirror flop. No looseness of secondary. Tightness of all camera components.

I only mention this because I had a situation where the continual hot/cold (day/night) caused some of my bolting to loosen. I had guiding problems. Once I went through a check of all my bolting the problem was resolved.

That may not be your issue, but it does not hurt to check.

Alan

Sent from Mail for Windows 10

From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto]
Sent: Sunday, September 3, 2017 10:38 AM
To: ap-gto@...
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?




I am wondering if I may have an issue with my AP 1100 GTO mount.
I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.
I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.
It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?









[Non-text portions of this message have been removed]


Tony Benjamin <tonybenjamin@...>
 

Hi Alan,

 

Unfortunately I just did that as I recently put all my cables through the mount and made sure all was tightened as I put things back together.

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Sunday, September 03, 2017 8:48 AM
To: ap-gto@...
Subject: RE: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

 

If all else fails check the tightness of all of your screwed connections. Your bolting to your telescope; the bolting of the saddle to the mount; the bolting of the sections of your declination and RA axis.

Check the stability of your optics too. No mirror flop. No looseness of secondary. Tightness of all camera components.

I only mention this because I had a situation where the continual hot/cold (day/night) caused some of my bolting to loosen. I had guiding problems. Once I went through a check of all my bolting the problem was resolved.

That may not be your issue, but it does not hurt to check.

Alan

Sent from Mail for Windows 10

From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto]
Sent: Sunday, September 3, 2017 10:38 AM
To: ap-gto@...
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

I am wondering if I may have an issue with my AP 1100 GTO mount.
I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.
I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.
It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?


bw
 

Hi Tony.  If you'll post your guide log on our PHD2 support forum, we can probably help you figure out what's going on.

https://groups.google.com/forum/#!forum/open-phd-guiding

Cheers,
Bruce


Tony Benjamin <tonybenjamin@...>
 

Will do,

 

Thanks

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Sunday, September 03, 2017 7:22 PM
To: ap-gto@...
Subject: [ap-gto] Re: AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

 

Hi Tony.  If you'll post your guide log on our PHD2 support forum, we can probably help you figure out what's going on.

https://groups.google.com/forum/#!forum/open-phd-guiding

Cheers,
Bruce


Roland Christen
 


Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
Hello,

If you have one of our original gearboxes, then re-meshing is quite simple and wouldn't hurt. However, I don't think that this will do anything to your guiding. As you noted above, you are getting .7 in RA. That axis is not affected whatsoever by gear mesh since the action of guiding in RA does not involve reversal of the axis, it just speeds up or slows down in response to guide signals. It is generally the Dec axis that is most affected by gear mesh, in that it takes longer to reverse if the mesh is loose.

IMPORTANT:  You may be trying to calibrate and guide at a speed other than 1x sidereal. Please check and make sure that all your calibration is done at 1x, and guiding also! This is important, especially for the Dec axis. Reversal takes way too long at the slower guide rates. Calibrate at the celestial equator near the meridian in order to get the best cal numbers. You can use those setting anywhere in the sky.

Your other observation that stars are a bit out of round even in short exposures hints at something else besides guiding. Typically if stars are out of round in a very short exposure, you have astigmatism in the optical system. You can verify this by taking a 1 second exposure of a suitable bright star and checking the roundness. Sometimes an optical system will show tight round stars when you are at perfect focus, but show slightly oval stars when you are slightly out-of-focus. An out-of-focus guide star also affects guiding negatively.

With PHD you have all the resources to determine if the mount's gear mesh (Dec Axis) is good or not. You might want to run this test to see what you get. Doing a gear mesh on the original gearbox is as simple as loosening two screws, wiggling the gearbox to make sure that the springs are pushing the gears into mesh, and then tightening the screws back again (see you manual or our website on gear mesh). You can tell if the mesh is tight by pushing gently on the end of your tube assembly back and forth and noting if you can feel any looseness. One trick that i have discovered on the original gearbox is to tighten fully just the right side screw, then check the mesh by moving the scope back and forth. If it feels tight and you cannot feel any movement, your mesh is correct, and now simply turn the other screw until it touches the end, but do not tighten it fully. This will allow the springs to keep the gearbox in full mesh all the way around the gearwheel.

The same can be done with the RA axis, and you can check the mesh by pushing on the counterweight shaft gently back and forth to see if there is any looseness (be sure to have the counterweight shaft fully screwed in!).

One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.

I know this is a long post, but please read it and note the points above. Use the tools in your PHD program to help you troubleshoot any issue. They are quite powerful and can tell you a lot.

Roland Christen
Astro-Physics inc.


-----Original Message-----
From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto] To: ap-gto
Sent: Sun, Sep 3, 2017 9:38 am
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?



I am wondering if I may have an issue with my AP 1100 GTO mount.
I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.
I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.
It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?





Tony Benjamin <tonybenjamin@...>
 

Hi Chris,

 

Thank you for the info below, it is appreciated.

 

My mount (as far as I know) has the newest gearboxes, it is a GTOCP4 so I don’t think I need to re-mesh. I have checked/rechecked to make sure the boxes are tight and the backstops are tight. There is no play in either axis if I push on them externally. Everything looks good.

 

I confirmed that all items (AP V2 ASCOM driver/APCC/PHD2 are all at 1.0x sidereal rate.

 

I have done all PHD2 calibrations at the recommended position of +/- 20 degrees of the celestial equator and within an hour of the meridian.

 

I very recently did adjust my collimation as I did have a slight out of collimation issue. It has been reposted by Gold Focus as being very good now and my recent photos show it – prior to this issue.

 

“One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.”

 

How do you turn off the guiding? – just turn the aggressiveness down to “0” on both RA and Dec? PEC will be on for this?

 

Last night I got fed up with things (I lost a lot of subs - 50% of 1 min exposure due to these oval stars). I had never updated the AP factory set PEC curve – I bought the mount brand new and have had it for over a year now. So I went ahead and tried PEMPro for the first time. I muddled through the help file while trying to get a new curve (the help file is not the most intuitive with a lot of X and Y stuff I’m not sure on). Anyway in the end I did get a new PEC – I let PEMPro run for 6 cycles – and uploaded to the mount. I then took about 20 x 1min exposures with this new PEC curve and 18 of the 20 were perfect and the two that were tossed may have been me moving around in the observatory or a result of an AF run. Also the RMS numbers were now lower both at or slightly below .5 arcsec with the Total RMS error around .6 arcsec – so definite improvement.

 

I have the settle factors at 2.0px for 6 sec – is that enough or should I increase the time? I’m at 2800mm FL @ .28 image scale?

 

So I guess for now I will keep things as they are and see if the nice stars continue?

 

Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??

 

 

Thanks Chris

 

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, September 04, 2017 7:52 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

 

 

Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.

Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.

Hello,

 

If you have one of our original gearboxes, then re-meshing is quite simple and wouldn't hurt. However, I don't think that this will do anything to your guiding. As you noted above, you are getting .7 in RA. That axis is not affected whatsoever by gear mesh since the action of guiding in RA does not involve reversal of the axis, it just speeds up or slows down in response to guide signals. It is generally the Dec axis that is most affected by gear mesh, in that it takes longer to reverse if the mesh is loose.


IMPORTANT:  You may be trying to calibrate and guide at a speed other than 1x sidereal. Please check and make sure that all your calibration is done at 1x, and guiding also! This is important, especially for the Dec axis. Reversal takes way too long at the slower guide rates. Calibrate at the celestial equator near the meridian in order to get the best cal numbers. You can use those setting anywhere in the sky.

 

Your other observation that stars are a bit out of round even in short exposures hints at something else besides guiding. Typically if stars are out of round in a very short exposure, you have astigmatism in the optical system. You can verify this by taking a 1 second exposure of a suitable bright star and checking the roundness. Sometimes an optical system will show tight round stars when you are at perfect focus, but show slightly oval stars when you are slightly out-of-focus. An out-of-focus guide star also affects guiding negatively.

 

With PHD you have all the resources to determine if the mount's gear mesh (Dec Axis) is good or not. You might want to run this test to see what you get. Doing a gear mesh on the original gearbox is as simple as loosening two screws, wiggling the gearbox to make sure that the springs are pushing the gears into mesh, and then tightening the screws back again (see you manual or our website on gear mesh). You can tell if the mesh is tight by pushing gently on the end of your tube assembly back and forth and noting if you can feel any looseness. One trick that i have discovered on the original gearbox is to tighten fully just the right side screw, then check the mesh by moving the scope back and forth. If it feels tight and you cannot feel any movement, your mesh is correct, and now simply turn the other screw until it touches the end, but do not tighten it fully. This will allow the springs to keep the gearbox in full mesh all the way around the gearwheel.

 

The same can be done with the RA axis, and you can check the mesh by pushing on the counterweight shaft gently back and forth to see if there is any looseness (be sure to have the counterweight shaft fully screwed in!).

 

One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.

 

I know this is a long post, but please read it and note the points above. Use the tools in your PHD program to help you troubleshoot any issue. They are quite powerful and can tell you a lot.

 

Roland Christen

Astro-Physics inc.

 

 

-----Original Message-----
From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Sun, Sep 3, 2017 9:38 am
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

I am wondering if I may have an issue with my AP 1100 GTO mount.

I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.

Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.

I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.

I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.

It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?

 

 

 


Michael Fulbright <mike.fulbright@...>
 

You could set aggressiveness to 0 or you can disable guide corrections in the "Advanced Settings" dialog under the "Guiding" tab - the field is called "Enable mount guide output".

http://openphdguiding.org/man/Advanced_settings.htm

Michael Fulbright


Tony Benjamin <tonybenjamin@...>
 

Ah great, thank you Michael.

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, September 04, 2017 8:50 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

 

You could set aggressiveness to 0 or you can disable guide corrections
in the "Advanced Settings" dialog under the "Guiding" tab - the field is
called "Enable mount guide output".

http://openphdguiding.org/man/Advanced_settings.htm

Michael Fulbright


Roland Christen
 


Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??
 
A PE curve cannot be that bad to affect a guided image. I suggested that you do an unguided image but monitor your guider graph. Unguided means turning the aggressiveness to zero, but you still get to see what the guider is doing. You can turn PE on, and see what you get, then turn PE off and compare the results. Without knowing this data, you will never know anything about your system, and anything you do will be like shooting in the dark.

You say that your image scale is .28 arc seconds per pixel. That is rather severely oversampled, since the atmosphere rarely if ever lets you achieve 1.5 arc sec FWHM resolution. You also don't specify how you guide. Off-axis guider or separate guide scope? That makes a huge difference.

When you did the PE run in PEMPro, did the 6 cycles all lie on top of each other with the Adjust Drift boxes checked? Did you make sure that the run was made with PE turned OFF? Then did you do one last run with PE turned ON to check the improvement (Important: do not download this curve!).

Roland Christen
Astro-Physics Inc.


-----Original Message-----
From: 'Tony Benjamin' tonybenjamin@... [ap-gto]
To: ap-gto
Sent: Mon, Sep 4, 2017 10:37 am
Subject: RE: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?



Hi Chris,
 
Thank you for the info below, it is appreciated.
 
My mount (as far as I know) has the newest gearboxes, it is a GTOCP4 so I don’t think I need to re-mesh. I have checked/rechecked to make sure the boxes are tight and the backstops are tight. There is no play in either axis if I push on them externally. Everything looks good.
 
I confirmed that all items (AP V2 ASCOM driver/APCC/PHD2 are all at 1.0x sidereal rate.
 
I have done all PHD2 calibrations at the recommended position of +/- 20 degrees of the celestial equator and within an hour of the meridian.
 
I very recently did adjust my collimation as I did have a slight out of collimation issue. It has been reposted by Gold Focus as being very good now and my recent photos show it – prior to this issue.
 
“One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.”
 
How do you turn off the guiding? – just turn the aggressiveness down to “0” on both RA and Dec? PEC will be on for this?
 
Last night I got fed up with things (I lost a lot of subs - 50% of 1 min exposure due to these oval stars). I had never updated the AP factory set PEC curve – I bought the mount brand new and have had it for over a year now. So I went ahead and tried PEMPro for the first time. I muddled through the help file while trying to get a new curve (the help file is not the most intuitive with a lot of X and Y stuff I’m not sure on). Anyway in the end I did get a new PEC – I let PEMPro run for 6 cycles – and uploaded to the mount. I then took about 20 x 1min exposures with this new PEC curve and 18 of the 20 were perfect and the two that were tossed may have been me moving around in the observatory or a result of an AF run. Also the RMS numbers were now lower both at or slightly below .5 arcsec with the Total RMS error around .6 arcsec – so definite improvement.
 
I have the settle factors at 2.0px for 6 sec – is that enough or should I increase the time? I’m at 2800mm FL @ .28 image scale?
 
So I guess for now I will keep things as they are and see if the nice stars continue?
 
Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??
 
 
Thanks Chris
 
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, September 04, 2017 7:52 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?
 
 
 
Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
Hello,
 
If you have one of our original gearboxes, then re-meshing is quite simple and wouldn't hurt. However, I don't think that this will do anything to your guiding. As you noted above, you are getting .7 in RA. That axis is not affected whatsoever by gear mesh since the action of guiding in RA does not involve reversal of the axis, it just speeds up or slows down in response to guide signals. It is generally the Dec axis that is most affected by gear mesh, in that it takes longer to reverse if the mesh is loose.

IMPORTANT:  You may be trying to calibrate and guide at a speed other than 1x sidereal. Please check and make sure that all your calibration is done at 1x, and guiding also! This is important, especially for the Dec axis. Reversal takes way too long at the slower guide rates. Calibrate at the celestial equator near the meridian in order to get the best cal numbers. You can use those setting anywhere in the sky.
 
Your other observation that stars are a bit out of round even in short exposures hints at something else besides guiding. Typically if stars are out of round in a very short exposure, you have astigmatism in the optical system. You can verify this by taking a 1 second exposure of a suitable bright star and checking the roundness. Sometimes an optical system will show tight round stars when you are at perfect focus, but show slightly oval stars when you are slightly out-of-focus. An out-of-focus guide star also affects guiding negatively.
 
With PHD you have all the resources to determine if the mount's gear mesh (Dec Axis) is good or not. You might want to run this test to see what you get. Doing a gear mesh on the original gearbox is as simple as loosening two screws, wiggling the gearbox to make sure that the springs are pushing the gears into mesh, and then tightening the screws back again (see you manual or our website on gear mesh). You can tell if the mesh is tight by pushing gently on the end of your tube assembly back and forth and noting if you can feel any looseness. One trick that i have discovered on the original gearbox is to tighten fully just the right side screw, then check the mesh by moving the scope back and forth. If it feels tight and you cannot feel any movement, your mesh is correct, and now simply turn the other screw until it touches the end, but do not tighten it fully. This will allow the springs to keep the gearbox in full mesh all the way around the gearwheel.
 
The same can be done with the RA axis, and you can check the mesh by pushing on the counterweight shaft gently back and forth to see if there is any looseness (be sure to have the counterweight shaft fully screwed in!).
 
One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.
 
I know this is a long post, but please read it and note the points above. Use the tools in your PHD program to help you troubleshoot any issue. They are quite powerful and can tell you a lot.
 
Roland Christen
Astro-Physics inc.
 
 
-----Original Message-----
From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Sun, Sep 3, 2017 9:38 am
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?
 
I am wondering if I may have an issue with my AP 1100 GTO mount.
I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.
I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.
It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?
 
 
 



Tony Benjamin <tonybenjamin@...>
 

Hi Chris,

 

Thank you for the information.

 

I will do 2 x 5 min unguided subs (one with PEC on and one with PEC off) with the aggressiveness turned down to “0” on the RA and Dec in PHD2. I guess I could just uncheck the “Enable mount guide output” on the guiding tab of advanced setup as well – that would amount to the same thing?

 

Yes, my seeing isn’t usually bad around here – averaging 2.0 – 2.5. I am using an OAG. It’s a SX attached directly to the SX filter wheel, so quite solid/rigid. Guide camera is a SX Ultrastar.

 

I have zero experience with PEMPro, so unfortunately the six cycles did not lay on top of each other (guess I didn’t have the “Adjust Drift” boxes checked. I just looked for this box and cannot see it as an option under the “Acquire Data” Tab? I will keep looking for it. I did have PE turned “Off”.

 

No, I didn’t do a run in PEMPro with the new curve to see the difference – I just went and uploaded it to the mount.

 

I will get on this ASAP – but of course the wx has turned now and no clear nights in the forseeable future.

 

 

Thanks Again

 

Tony

 

 

 

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Tuesday, September 05, 2017 7:44 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

 

 

Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??

 

A PE curve cannot be that bad to affect a guided image. I suggested that you do an unguided image but monitor your guider graph. Unguided means turning the aggressiveness to zero, but you still get to see what the guider is doing. You can turn PE on, and see what you get, then turn PE off and compare the results. Without knowing this data, you will never know anything about your system, and anything you do will be like shooting in the dark.

 

You say that your image scale is .28 arc seconds per pixel. That is rather severely oversampled, since the atmosphere rarely if ever lets you achieve 1.5 arc sec FWHM resolution. You also don't specify how you guide. Off-axis guider or separate guide scope? That makes a huge difference.

 

When you did the PE run in PEMPro, did the 6 cycles all lie on top of each other with the Adjust Drift boxes checked? Did you make sure that the run was made with PE turned OFF? Then did you do one last run with PE turned ON to check the improvement (Important: do not download this curve!).

 

Roland Christen

Astro-Physics Inc.

 

 

-----Original Message-----
From: 'Tony Benjamin' tonybenjamin@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Mon, Sep 4, 2017 10:37 am
Subject: RE: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

Hi Chris,

 

Thank you for the info below, it is appreciated.

 

My mount (as far as I know) has the newest gearboxes, it is a GTOCP4 so I don’t think I need to re-mesh. I have checked/rechecked to make sure the boxes are tight and the backstops are tight. There is no play in either axis if I push on them externally. Everything looks good.

 

I confirmed that all items (AP V2 ASCOM driver/APCC/PHD2 are all at 1.0x sidereal rate.

 

I have done all PHD2 calibrations at the recommended position of +/- 20 degrees of the celestial equator and within an hour of the meridian.

 

I very recently did adjust my collimation as I did have a slight out of collimation issue. It has been reposted by Gold Focus as being very good now and my recent photos show it – prior to this issue.

 

“One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.”

 

How do you turn off the guiding? – just turn the aggressiveness down to “0” on both RA and Dec? PEC will be on for this?

 

Last night I got fed up with things (I lost a lot of subs - 50% of 1 min exposure due to these oval stars). I had never updated the AP factory set PEC curve – I bought the mount brand new and have had it for over a year now. So I went ahead and tried PEMPro for the first time. I muddled through the help file while trying to get a new curve (the help file is not the most intuitive with a lot of X and Y stuff I’m not sure on). Anyway in the end I did get a new PEC – I let PEMPro run for 6 cycles – and uploaded to the mount. I then took about 20 x 1min exposures with this new PEC curve and 18 of the 20 were perfect and the two that were tossed may have been me moving around in the observatory or a result of an AF run. Also the RMS numbers were now lower both at or slightly below .5 arcsec with the Total RMS error around .6 arcsec – so definite improvement.

 

I have the settle factors at 2.0px for 6 sec – is that enough or should I increase the time? I’m at 2800mm FL @ .28 image scale?

 

So I guess for now I will keep things as they are and see if the nice stars continue?

 

Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??

 

 

Thanks Chris

 

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, September 04, 2017 7:52 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

 

 

Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.

Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.

Hello,

 

If you have one of our original gearboxes, then re-meshing is quite simple and wouldn't hurt. However, I don't think that this will do anything to your guiding. As you noted above, you are getting .7 in RA. That axis is not affected whatsoever by gear mesh since the action of guiding in RA does not involve reversal of the axis, it just speeds up or slows down in response to guide signals. It is generally the Dec axis that is most affected by gear mesh, in that it takes longer to reverse if the mesh is loose.


IMPORTANT:  You may be trying to calibrate and guide at a speed other than 1x sidereal. Please check and make sure that all your calibration is done at 1x, and guiding also! This is important, especially for the Dec axis. Reversal takes way too long at the slower guide rates. Calibrate at the celestial equator near the meridian in order to get the best cal numbers. You can use those setting anywhere in the sky.

 

Your other observation that stars are a bit out of round even in short exposures hints at something else besides guiding. Typically if stars are out of round in a very short exposure, you have astigmatism in the optical system. You can verify this by taking a 1 second exposure of a suitable bright star and checking the roundness. Sometimes an optical system will show tight round stars when you are at perfect focus, but show slightly oval stars when you are slightly out-of-focus. An out-of-focus guide star also affects guiding negatively.

 

With PHD you have all the resources to determine if the mount's gear mesh (Dec Axis) is good or not. You might want to run this test to see what you get. Doing a gear mesh on the original gearbox is as simple as loosening two screws, wiggling the gearbox to make sure that the springs are pushing the gears into mesh, and then tightening the screws back again (see you manual or our website on gear mesh). You can tell if the mesh is tight by pushing gently on the end of your tube assembly back and forth and noting if you can feel any looseness. One trick that i have discovered on the original gearbox is to tighten fully just the right side screw, then check the mesh by moving the scope back and forth. If it feels tight and you cannot feel any movement, your mesh is correct, and now simply turn the other screw until it touches the end, but do not tighten it fully. This will allow the springs to keep the gearbox in full mesh all the way around the gearwheel.

 

The same can be done with the RA axis, and you can check the mesh by pushing on the counterweight shaft gently back and forth to see if there is any looseness (be sure to have the counterweight shaft fully screwed in!).

 

One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.

 

I know this is a long post, but please read it and note the points above. Use the tools in your PHD program to help you troubleshoot any issue. They are quite powerful and can tell you a lot.

 

Roland Christen

Astro-Physics inc.

 

 

-----Original Message-----
From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Sun, Sep 3, 2017 9:38 am
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?

 

I am wondering if I may have an issue with my AP 1100 GTO mount.

I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.

Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.

I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.

I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.

It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?

 

 

 

 


Roland Christen
 


I will do 2 x 5 min unguided subs (one with PEC on and one with PEC off) with the aggressiveness turned down to “0” on the RA and Dec in PHD2.
I think you misunderstand. There is no point in taking an unguided sub because for sure all the stars will be oval, and that will not reveal anything to you.

The reason for the unguided run is to look at the resultant guider graph so you can determine the baseline seeing component before you do an actual guided run. Then compare both guider graphs and the RMS values. And you don't need to do 5 minute runs to determine the seeing component, just a quick 60 second look at the guider graph is enough and you will see how stable the air is.

One thing you might want to do is to bin your guider 3x3 because at your focal length you do not want to have a wildly pulsating guide star. If you are trying to guide at 1x1 binning on the guider chip, your guide software will be trying to follow every wiggle and pulsation in a desperate attempt to keep the star on the center point. At this time of year the temperatures are dropping rapidly in the evening and this results in plumes of warm air escaping up the baffle tube of a Schmidt-Cass scope. The warm air comes from the retained heat of the primary mirror, and the baffle tube is a natural chimney. These plumes cause havoc in the guide star, and will also produce out-of-round star images. These plumes do not go away until way early in the morning.

The cycles in PEMPro will NEVER lay on top of each other because for 6 cycles you inevitably get some RA and Dec drift, even if you have done a very careful drift alignment. 6 cycles is more than 1/2 hour of exposure, and it would be a miracle if there was no drift in either axis for that amount of time. That's why Ray has included the option of removing the drift portion of the data so that you can see if there are any anomalies in the different PE runs. PEMPro is a very powerful tool that allows you to not only do a curve for your mount, but it also lets you analyze the performance of the RA tracking. You can then monitor that over time to see if there are any changes.

Roland Christen
Astro-Physics Inc.


-----Original Message-----
From: 'Tony Benjamin' tonybenjamin@... [ap-gto] <ap-gto@...>
To: ap-gto
Sent: Tue, Sep 5, 2017 11:09 am
Subject: RE: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?



Hi Chris,
 
Thank you for the information.
 
I will do 2 x 5 min unguided subs (one with PEC on and one with PEC off) with the aggressiveness turned down to “0” on the RA and Dec in PHD2. I guess I could just uncheck the “Enable mount guide output” on the guiding tab of advanced setup as well – that would amount to the same thing?
 
Yes, my seeing isn’t usually bad around here – averaging 2.0 – 2.5. I am using an OAG. It’s a SX attached directly to the SX filter wheel, so quite solid/rigid. Guide camera is a SX Ultrastar.
 
I have zero experience with PEMPro, so unfortunately the six cycles did not lay on top of each other (guess I didn’t have the “Adjust Drift” boxes checked. I just looked for this box and cannot see it as an option under the “Acquire Data” Tab? I will keep looking for it. I did have PE turned “Off”.
 
No, I didn’t do a run in PEMPro with the new curve to see the difference – I just went and uploaded it to the mount.
 
I will get on this ASAP – but of course the wx has turned now and no clear nights in the forseeable future.
 
 
Thanks Again
 
Tony
 
 
 
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Tuesday, September 05, 2017 7:44 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?
 
 
 
Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??
 
A PE curve cannot be that bad to affect a guided image. I suggested that you do an unguided image but monitor your guider graph. Unguided means turning the aggressiveness to zero, but you still get to see what the guider is doing. You can turn PE on, and see what you get, then turn PE off and compare the results. Without knowing this data, you will never know anything about your system, and anything you do will be like shooting in the dark.
 
You say that your image scale is .28 arc seconds per pixel. That is rather severely oversampled, since the atmosphere rarely if ever lets you achieve 1.5 arc sec FWHM resolution. You also don't specify how you guide. Off-axis guider or separate guide scope? That makes a huge difference.
 
When you did the PE run in PEMPro, did the 6 cycles all lie on top of each other with the Adjust Drift boxes checked? Did you make sure that the run was made with PE turned OFF? Then did you do one last run with PE turned ON to check the improvement (Important: do not download this curve!).
 
Roland Christen
Astro-Physics Inc.
 
 
-----Original Message-----
From: 'Tony Benjamin' tonybenjamin@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Mon, Sep 4, 2017 10:37 am
Subject: RE: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?
 
Hi Chris,
 
Thank you for the info below, it is appreciated.
 
My mount (as far as I know) has the newest gearboxes, it is a GTOCP4 so I don’t think I need to re-mesh. I have checked/rechecked to make sure the boxes are tight and the backstops are tight. There is no play in either axis if I push on them externally. Everything looks good.
 
I confirmed that all items (AP V2 ASCOM driver/APCC/PHD2 are all at 1.0x sidereal rate.
 
I have done all PHD2 calibrations at the recommended position of +/- 20 degrees of the celestial equator and within an hour of the meridian.
 
I very recently did adjust my collimation as I did have a slight out of collimation issue. It has been reposted by Gold Focus as being very good now and my recent photos show it – prior to this issue.
 
“One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.”
 
How do you turn off the guiding? – just turn the aggressiveness down to “0” on both RA and Dec? PEC will be on for this?
 
Last night I got fed up with things (I lost a lot of subs - 50% of 1 min exposure due to these oval stars). I had never updated the AP factory set PEC curve – I bought the mount brand new and have had it for over a year now. So I went ahead and tried PEMPro for the first time. I muddled through the help file while trying to get a new curve (the help file is not the most intuitive with a lot of X and Y stuff I’m not sure on). Anyway in the end I did get a new PEC – I let PEMPro run for 6 cycles – and uploaded to the mount. I then took about 20 x 1min exposures with this new PEC curve and 18 of the 20 were perfect and the two that were tossed may have been me moving around in the observatory or a result of an AF run. Also the RMS numbers were now lower both at or slightly below .5 arcsec with the Total RMS error around .6 arcsec – so definite improvement.
 
I have the settle factors at 2.0px for 6 sec – is that enough or should I increase the time? I’m at 2800mm FL @ .28 image scale?
 
So I guess for now I will keep things as they are and see if the nice stars continue?
 
Would a bad PEC curve cause the out of round stars even on these very short exposures or am I out to lunch hoping this new curve was what was needed??
 
 
Thanks Chris
 
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Monday, September 04, 2017 7:52 AM
To: ap-gto@...
Subject: Re: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?
 
 
 
Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
Hello,
 
If you have one of our original gearboxes, then re-meshing is quite simple and wouldn't hurt. However, I don't think that this will do anything to your guiding. As you noted above, you are getting .7 in RA. That axis is not affected whatsoever by gear mesh since the action of guiding in RA does not involve reversal of the axis, it just speeds up or slows down in response to guide signals. It is generally the Dec axis that is most affected by gear mesh, in that it takes longer to reverse if the mesh is loose.

IMPORTANT:  You may be trying to calibrate and guide at a speed other than 1x sidereal. Please check and make sure that all your calibration is done at 1x, and guiding also! This is important, especially for the Dec axis. Reversal takes way too long at the slower guide rates. Calibrate at the celestial equator near the meridian in order to get the best cal numbers. You can use those setting anywhere in the sky.
 
Your other observation that stars are a bit out of round even in short exposures hints at something else besides guiding. Typically if stars are out of round in a very short exposure, you have astigmatism in the optical system. You can verify this by taking a 1 second exposure of a suitable bright star and checking the roundness. Sometimes an optical system will show tight round stars when you are at perfect focus, but show slightly oval stars when you are slightly out-of-focus. An out-of-focus guide star also affects guiding negatively.
 
With PHD you have all the resources to determine if the mount's gear mesh (Dec Axis) is good or not. You might want to run this test to see what you get. Doing a gear mesh on the original gearbox is as simple as loosening two screws, wiggling the gearbox to make sure that the springs are pushing the gears into mesh, and then tightening the screws back again (see you manual or our website on gear mesh). You can tell if the mesh is tight by pushing gently on the end of your tube assembly back and forth and noting if you can feel any looseness. One trick that i have discovered on the original gearbox is to tighten fully just the right side screw, then check the mesh by moving the scope back and forth. If it feels tight and you cannot feel any movement, your mesh is correct, and now simply turn the other screw until it touches the end, but do not tighten it fully. This will allow the springs to keep the gearbox in full mesh all the way around the gearwheel.
 
The same can be done with the RA axis, and you can check the mesh by pushing on the counterweight shaft gently back and forth to see if there is any looseness (be sure to have the counterweight shaft fully screwed in!).
 
One thing I always do before guiding is to judge the steadiness of the atmosphere. I start guiding on a reasonably bright guide star but turn off the guiding signals to the mount. I then monitor the drift in both axes for a short time just to get a feel for the RMS values that are due only to the atmosphere. This is especially applicable to declination since there is no action at all by the Dec motor, and any movement of the guide star in the Dec line will be strictly due to atmospheric motion. You guider graph is your friend, always have it up during guiding so you can monitor any abnormalities.
 
I know this is a long post, but please read it and note the points above. Use the tools in your PHD program to help you troubleshoot any issue. They are quite powerful and can tell you a lot.
 
Roland Christen
Astro-Physics inc.
 
 
-----Original Message-----
From: dvuolhhr6nx4a532a3phnju3zs6lzvlgxdl2wzaf@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Sun, Sep 3, 2017 9:38 am
Subject: [ap-gto] AP 1100GTO Can't Calibrate in PHD2 All of a Sudden?
 
I am wondering if I may have an issue with my AP 1100 GTO mount.
I’ve had it for a little over a year now and it has worked without issue. I am using it for astrophotography with a C11 Edge @ 2800mm with an Ultrastar guide come on a COAG. PHD2 is my guiding software and normally my guiding has me around .3/.4 RMS in both RA and Dec. I have noticed lately that the numbers were getting a bit higher but just assumed it was atmospheric conditions. Although I had also noted that of late my stars have been a bit out of round even on short 30 sec subs.
Last night I was getting around .7 Ra and .5 Dec with a Total RMS near 1.0 arc/sec. I decided I would run a new calibration just to try and tighten things up. Unfortunately I could not get a successful calibration. PHD2 would be complaining about RA and Dec guiding rates differing by too much.
I started a post on Cloudy Nights (https://www.cloudynights.com/topic/590415-help-with-phd2-guiding-cant-calibrate/#entry8082854) before posting this issue here.
I haven’t changed anything in my routine and the only thing I did different was to run a calibration last night. I also made sure my PA was accurate, and it is, as you can see in the pics at Cloudy Nights.
It was suggested that I may need to remesh the gears? Any other thoughts on what may be causing this?