AP900 Gto Auto-Guiding woes.


Vince Salfranc
 

Hi,

I have been totally happy with my mount until I decided to move it into a new observatory which gave me a better view of the southern sky.

Now with exactly the same equipment the auto-guiding is bouncy back and forth on both axis.

The polar align seem to be good as I did use Polemaster on 4 or 5 occasion and it came back with exactly the same setting on each case.

I cam get a 4 minutes exposure with no trailing without the auto-guiding.

I use Maxim for the image acquisition and guiding.

When I first start auto-guiding the first 15 minutes everything is working great and then the bouncing start and doesn't seem to stop until I disable the PEM. The auto-guiding is then ok for again maybe 15 minutes and then the bouncing start again. I enable the PEM and everything is ok again for a short while and the whole process starts again.

I have tried unplugging every bits of equipment one by one but nothing seem to cure the problem.

Any idea on what could be affecting the auto-guiding would be great.

Thank you.

Vince


Roland Christen
 

I would start with your calibration parameters. After calibration, do you check to see if the numbers make sense? What is your focal length and pixel scale on the guide camera?
 
Rolando
 
 

-----Original Message-----
From: salfranc@... [ap-gto]
To: ap-gto
Sent: Wed, Oct 12, 2016 1:49 am
Subject: [ap-gto] AP900 Gto Auto-Guiding woes.



Hi,
I have been totally happy with my mount until I decided to move it into a new observatory which gave me a better view of the southern sky.
Now with exactly the same equipment the auto-guiding is bouncy back and forth on both axis.
The polar align seem to be good as I did use Polemaster on 4 or 5 occasion and it came back with exactly the same setting on each case.
I cam get a 4 minutes exposure with no trailing without the auto-guiding.
I use Maxim for the image acquisition and guiding.
When I first start auto-guiding the first 15 minutes everything is working great and then the bouncing start and doesn't seem to stop until I disable the PEM. The auto-guiding is then ok for again maybe 15 minutes and then the bouncing start again. I enable the PEM and everything is ok again for a short while and the whole process starts again.
I have tried unplugging every bits of equipment one by one but nothing seem to cure the problem.
Any idea on what could be affecting the auto-guiding would be great.
Thank you.
Vince



Vince Salfranc
 

Hi,
The focal length of the scope is f6.6 (860mm) and the arc-secs/pixel is 1.28.
Thank you.
Vince


Roland Christen
 

Ok, and what are the parameter numbers after you did your calibration run? I assume that the guide camera has the same 1.28 arc sec/pixel? Do you understand the significance of the calibration parameter numbers?
 
Rolando
 
 

-----Original Message-----
From: salfranc@... [ap-gto]
To: ap-gto
Sent: Wed, Oct 12, 2016 10:40 am
Subject: Re: [ap-gto] AP900 Gto Auto-Guiding woes.



Hi,
The focal length of the scope is f6.6 (860mm) and the arc-secs/pixel is 1.28.
Thank you.
Vince




Vince Salfranc
 

Hi Rolando,
I don't know if I understand the calibration parameters.
All I do is set the calibration time to 15s and the maxim do the rest. I would be grateful if you could clarify them for me.
Thank you.
Vince


Roland Christen
 

Bring up Maxim on your computer. Under the Guide tab click on Guider Settings. Look at the numbers under X Speed and Y Speed and the Angle. Also check the Binning setting. The X and Y speeds are your parameter numbers. The angle should be close to zero or 180 or 90 degrees depending on how close your camera is to the RA and Dec direction.
 
Lets assume that you calibrated at 1x sidereal guide speed. If your binning is 1 and your camera orientation is set close to the X and Y axes (RA and Dec axes), AND you properly calibrated near the celestial equator, then the parameter numbers should be equal to 15 divided by your pixel scale. Or close to it. If they are way different, then calibration is not correct and we have to find out why.
 
Rolando
 
 

-----Original Message-----
From: salfranc@... [ap-gto]
To: ap-gto
Sent: Wed, Oct 12, 2016 12:33 pm
Subject: [ap-gto] Re: AP900 Gto Auto-Guiding woes.



Hi Rolando,
I don't know if I understand the calibration parameters.
All I do is set the calibration time to 15s and the maxim do the rest. I would be grateful if you could clarify them for me.
Thank you.
Vince



Vince Salfranc
 

Hi Rolando,
Many thanks. I will check all of this and report back.
Vince


Vince Salfranc
 

Hi  Rolando,
I have checked the parameters as you indicated and here are the results.
Guiding Chip Arc-sec / pixel = 2.67
X & Y angle = -1.477
x Speed = 5.5793
y speed = 5.773
It seems to me that the calibration is ok so it must be something else.
Vince


Roland Christen
 

Next time you are out guiding, bring up the Guider Graph and take a screen shot during the time that the guide star is bouncing back and forth and post it to the group. Also post the Tracking Log so we can see what the guide corrections are that are being sent to the mount during this time.
 
Check also under Guider Settings/Advanced that the box labeled "Enable simultaneous RA and Dec corrections" is unchecked. Checking this box can lead to instability due to a bug in MaximDL.
 
Rolando
 
 

-----Original Message-----
From: salfranc@... [ap-gto]
To: ap-gto
Sent: Thu, Oct 13, 2016 6:12 am
Subject: [ap-gto] Re: AP900 Gto Auto-Guiding woes.



Hi  Rolando,
I have checked the parameters as you indicated and here are the results.
Guiding Chip Arc-sec / pixel = 2.67
X & Y angle = -1.477
x Speed = 5.5793
y speed = 5.773
It seems to me that the calibration is ok so it must be something else.
Vince



Roland Christen
 

One other thing you can do is to make sure all your cables from the camera and guider are tied to the mount and not hanging down unsupported. Any slight movement of the guider cable can cause large errors in the guide star position.
 
Rolando
 
 

-----Original Message-----
From: chris1011@... [ap-gto]
To: ap-gto
Sent: Thu, Oct 13, 2016 10:14 am
Subject: Re: [ap-gto] Re: AP900 Gto Auto-Guiding woes.



Next time you are out guiding, bring up the Guider Graph and take a screen shot during the time that the guide star is bouncing back and forth and post it to the group. Also post the Tracking Log so we can see what the guide corrections are that are being sent to the mount during this time.
 
Check also under Guider Settings/Advanced that the box labeled "Enable simultaneous RA and Dec corrections" is unchecked. Checking this box can lead to instability due to a bug in MaximDL.
 
Rolando
 
 
-----Original Message-----
From: salfranc@... [ap-gto] gto@...>
To: ap-gto gto@...>
Sent: Thu, Oct 13, 2016 6:12 am
Subject: [ap-gto] Re: AP900 Gto Auto-Guiding woes.



Hi  Rolando,
I have checked the parameters as you indicated and here are the results.
Guiding Chip Arc-sec / pixel = 2.67
X & Y angle = -1.477
x Speed = 5.5793
y speed = 5.773
It seems to me that the calibration is ok so it must be something else.
Vince





Vince Salfranc
 

Hi Rolando,
Many thanks for your help.
I will have a go at making sure the cables are tied to something solid.
Vince


Christopher Erickson
 

Personally I bring the camera cables back along the OTA and then bring them down close to the 900's DEC axis hub.  Minimize any dangling cables from influencing the tracking.
 
A friend of mine with a 1200 does exactly the same thing.
 
 
Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 


From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, October 13, 2016 8:39 AM
To: ap-gto@...
Subject: Re: [ap-gto] Re: AP900 Gto Auto-Guiding woes.

Hi Rolando,
Many thanks for your help.
I will have a go at making sure the cables are tied to something solid.
Vince


Vince Salfranc
 

Hi,
Good idea for the cables. I will do that.
Vince


C. G. Anderson
 

Christopher:

Do you have any example images of your cable routing?  All of my cables are secured to the back end of my OTA/STT-8300. And I mean a lot of cables! I tried routing them along the axis/pier, but didn't have enough slack at that point. As they are now, the can't hang on anything, and can't move or put any strain on any connectors (pigtailed at the connection). But I'd think there has to be a better way. 


Thanks.  Good thread!

CG

PS: Roland, when you say any movement of the guiding cable can result in errors, are you refering to just weight or physical strain on the guider plug?


Roland Christen
 

This may not be the source of your guiding issues, but one thing I see in your setup that can cause problems is that your guide scope is attached to the rings of the imaging scope. The imaging scope will always move slightly inside those rings and you will have differential movement between guider and imaging scopes. I always advise that if you use a separate guide scope that it must be rigidly affixed to the imaging scope itself with its own bracket and ring system.
 
Rolando
 
 

-----Original Message-----
From: chris@... [ap-gto]
To: ap-gto
Sent: Fri, Oct 14, 2016 9:26 am
Subject: [ap-gto] Re: AP900 Gto Auto-Guiding woes.



Christopher:

Do you have any example images of your cable routing?  All of my cables are secured to the back end of my OTA/STT-8300. And I mean a lot of cables! I tried routing them along the axis/pier, but didn't have enough slack at that point. As they are now, the can't hang on anything, and can't move or put any strain on any connectors (pigtailed at the connection). But I'd think there has to be a better way. 


Thanks.  Good thread!

CG

PS: Roland, when you say any movement of the guiding cable can result in errors, are you refering to just weight or physical strain on the guider plug?



Vince Salfranc
 

Hi,
I am not sure how I can better fit the guide scope to the mount. If you could give me a picture or something to show me the best way I would be really happy to modify my setup.
The cables are also showing on the image. I cannot get them any closer to the centre of the imaging scope as they interfere with the CP3 cables when slewing east and west.
Image setup.
Setup-guiding
Thank you
Vince
 


Stuart
 

Vince, you want the guide scope/camera to be fixed relative to the back of your imaging scope. Ideally mounted on the focuser but with your scope that seems impractical. You could try a second pair of rings that are lower profile around the big tube and move them back as far as possible. 

What is the focal length of your imaging scope? AP makes a very elegant guider holder that mounts on the focuser. I'd talk to them about that vs. what you're trying in the photo if that set-up is suffering from flexure.

BTW - I imaged for years with a 350mm focal length Borg 60mm guide scope mounted to the top plate on my AP155. I was able to stabilize it fine and never had an oblong star in all the years I did that. You should be able to do what you're trying but it may need to be more securely attached than what I see in the photo. In my case, I had the guide camera, an ST-402ME, sitting firmly on the top plate of the cradle holding the AP155. The rear ring of the cradle nestled up against the focuser. The front of the Borg 60 was held in a Losmandy 3-point ring and the body of the Borg 60mm was held in a second Losmandy 3-point ring. The three points were tightened down really hard.

I'll try and get a photo of this set-up.

Stuart

On Fri, Oct 14, 2016 at 2:31 PM, salfranc@... [ap-gto] <ap-gto@...> wrote:
 

Hi,
I am not sure how I can better fit the guide scope to the mount. If you could give me a picture or something to show me the best way I would be really happy to modify my setup.
The cables are also showing on the image. I cannot get them any closer to the centre of the imaging scope as they interfere with the CP3 cables when slewing east and west.
Image setup.
Setup-guiding
Thank you
Vince
 





Christopher Erickson
 

I don't have any pics of an imaging setup on my 900 right now so I would have to set up and take some.  These days I mostly image with my Mach1+130EDF-GT+SBIG STF-8300M/FW5/OAG/STi and use my 900+C14 for outreach.  On the Mach1 I route cables internally.
 
Using thin Velcro wraps every so often, I take the 3 cables (USB2+USB2+12VDC) from the cameras on to the focus motor, add that cable to the bundle and then from there go to a small USB+12VDC distribution hub I have mounted off of the OTA dovetail bar, centered over the DEC axis.  From there I drop one USB cable and one PWR cable down past both axes and connect to the rest of my electronics collected in a small Pelican box hanging on the side of the tripod.
I'll try to get some pics and upload them later.
 
I hope my descriptions are helpful.

Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com

 


From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, October 14, 2016 4:26 AM
To: ap-gto@...
Subject: [ap-gto] Re: AP900 Gto Auto-Guiding woes.

Christopher:

Do you have any example images of your cable routing?  All of my cables are secured to the back end of my OTA/STT-8300. And I mean a lot of cables! I tried routing them along the axis/pier, but didn't have enough slack at that point. As they are now, the can't hang on anything, and can't move or put any strain on any connectors (pigtailed at the connection). But I'd think there has to be a better way. 


Thanks.  Good thread!

CG

PS: Roland, when you say any movement of the guiding cable can result in errors, are you refering to just weight or physical strain on the guider plug?


Christopher Erickson
 

The only scope I have ever owned that didn't suffer from differential flexure between a piggyback guide scope and the main scope is my AP 130EDF-GT.  That is why I ONLY use off-axis/radial guiders any more.
 
Over in the Meade Yahoo groups that I haunt (I also have a 16" LX200GPS) I am constantly amazed over how many scope setups I see where there is an under-mounted SCT combined with a small Chinese refractor and a floppy focuser riding on its back.  And not an OTA counterweight anywhere in sight.
 
Of course I rarely see any images taken with those scopes...
 
 
Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 


From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, October 14, 2016 8:44 AM
To: ap-gto@...
Subject: Re: [ap-gto] Re: AP900 Gto Auto-Guiding woes.

Vince, you want the guide scope/camera to be fixed relative to the back of your imaging scope. Ideally mounted on the focuser but with your scope that seems impractical. You could try a second pair of rings that are lower profile around the big tube and move them back as far as possible. 

What is the focal length of your imaging scope? AP makes a very elegant guider holder that mounts on the focuser. I'd talk to them about that vs. what you're trying in the photo if that set-up is suffering from flexure.

BTW - I imaged for years with a 350mm focal length Borg 60mm guide scope mounted to the top plate on my AP155. I was able to stabilize it fine and never had an oblong star in all the years I did that. You should be able to do what you're trying but it may need to be more securely attached than what I see in the photo. In my case, I had the guide camera, an ST-402ME, sitting firmly on the top plate of the cradle holding the AP155. The rear ring of the cradle nestled up against the focuser. The front of the Borg 60 was held in a Losmandy 3-point ring and the body of the Borg 60mm was held in a second Losmandy 3-point ring. The three points were tightened down really hard.

I'll try and get a photo of this set-up.

Stuart

On Fri, Oct 14, 2016 at 2:31 PM, salfranc@... [ap-gto] <ap-gto@...> wrote:

 

Hi,
I am not sure how I can better fit the guide scope to the mount. If you could give me a picture or something to show me the best way I would be really happy to modify my setup.
The cables are also showing on the image. I cannot get them any closer to the centre of the imaging scope as they interfere with the CP3 cables when slewing east and west.
Image setup.
Setup-guiding
Thank you
Vince
 





Stuart
 

Christopher, I agree mostly with what you said. I think in my case, the
rings are old and the felt is pretty much crushed so my 155 isn't moving in
the rings like it might if the felt was thicker/newer.

The main difference between what I'm doing and what most people try is that
I'm not using a small refractor with a cheap focuser for a guidescope. I am
using a Borg guidescope that mounts directly into the ST-402ME. It has NO
focuser. The connection is rock solid. I think droopy focusers on
guidescopes are a bigger problem than flexure of the main scope inside the
rings. My 2 cents - worth every penny!

Like I said, I imaged for years with the set-up I described. 100% round
stars. I "just" put this set-up together again while I do some upgrades to
my primary imaging rig. I'm going to see if they remain attached to this
note but I put them here:
https://groups.yahoo.com/neo/groups/ap-gto/photos/albums/116213838 in case
they are removed by Yahoo.

BTW - like you I use an off-axis guider on my primary rig. A MMOAG. But I
don't have all the fittings to put it into the train on my AP155 and it was
an "impulsive" decision to put the AP155 back into action.

Stuart

On Fri, Oct 14, 2016 at 3:48 PM, 'Christopher Erickson'
christopher.k.erickson@... [ap-gto] <ap-gto@...> wrote:



The only scope I have ever owned that didn't suffer from differential
flexure between a piggyback guide scope and the main scope is my AP
130EDF-GT. That is why I ONLY use off-axis/radial guiders any more.

Over in the Meade Yahoo groups that I haunt (I also have a 16" LX200GPS) I
am constantly amazed over how many scope setups I see where there is an
under-mounted SCT combined with a small Chinese refractor and a floppy
focuser riding on its back. And not an OTA counterweight anywhere in sight.

Of course I rarely see any images taken with those scopes...


Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com


------------------------------
*From:* ap-gto@... [mailto:ap-gto@...]
*Sent:* Friday, October 14, 2016 8:44 AM
*To:* ap-gto@...
*Subject:* Re: [ap-gto] Re: AP900 Gto Auto-Guiding woes.

Vince, you want the guide scope/camera to be fixed relative to the back of
your imaging scope. Ideally mounted on the focuser but with your scope that
seems impractical. You could try a second pair of rings that are lower
profile around the big tube and move them back as far as possible.

What is the focal length of your imaging scope? AP makes a very elegant
guider holder that mounts on the focuser. I'd talk to them about that vs.
what you're trying in the photo if that set-up is suffering from flexure.

BTW - I imaged for years with a 350mm focal length Borg 60mm guide scope
mounted to the top plate on my AP155. I was able to stabilize it fine and
never had an oblong star in all the years I did that. You should be able to
do what you're trying but it may need to be more securely attached than
what I see in the photo. In my case, I had the guide camera, an ST-402ME,
sitting firmly on the top plate of the cradle holding the AP155. The rear
ring of the cradle nestled up against the focuser. The front of the Borg 60
was held in a Losmandy 3-point ring and the body of the Borg 60mm was held
in a second Losmandy 3-point ring. The three points were tightened down
really hard.

I'll try and get a photo of this set-up.

Stuart

On Fri, Oct 14, 2016 at 2:31 PM, salfranc@... [ap-gto] <
ap-gto@...> wrote:



Hi,
I am not sure how I can better fit the guide scope to the mount. If you
could give me a picture or something to show me the best way I would be
really happy to modify my setup.
The cables are also showing on the image. I cannot get them any closer to
the centre of the imaging scope as they interfere with the CP3 cables when
slewing east and west.
Image setup.
Setup-guiding
<https://www.flickr.com/photos/61128796@N08/29693328394/in/dateposted-public/>
[image: image]
<https://www.flickr.com/photos/61128796@N08/29693328394/in/dateposted-public/>
Setup-guiding
<https://www.flickr.com/photos/61128796@N08/29693328394/in/dateposted-public/>
Explore vince236's photos on Flickr. vince236 has uploaded 60 photos to
Flickr.
View on www.flickr.com
<https://www.flickr.com/photos/61128796@N08/29693328394/in/dateposted-public/>
Preview by Yahoo
Thank you
Vince



--
Stuart Heggie
http://www.stuartheggie.com/featured.html <http://www.stuartheggie.com>




--
Stuart Heggie
http://www.stuartheggie.com/featured.html <http://www.stuartheggie.com>


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