Spurious guider move command?


Lloyd Smith
 

I'm curious to know if anyone else has experienced strange guider movements.  Description:  at various points in imaging sessions 'something' is telling the mount to go on an expedition of sorts which results in a distinct pattern (seen in the attached snip). The guide star, normally centered in the track box, seems to be deliberately moved 12 to 15 pixels from the center and then slowly guided back to the middle.  Has anyone seen and solved this before?  I at first suspected a bad gear mesh, but now believe it's a commanded moved by something in the software stack.  Configuration:  Mach1, FSQ, QSI, Lodestar, APCC, A-P v2 (latest), Maxim 5.24, CCDAP, TSX (latest build), guider relays set in Maxim with cable.  Thanks for any insights. 


Lloyd Smith
 

Strange Guiding

Forgot to attach link to image


Roland Christen
 

1) you can't attach in this newsgroup.
 
2) as for possible things that can cause guider movements, sometimes you can get a cosmic ray hit that is very bright. This will cause the guider to send a command to center that bright spot, ignoring the guide star. If your guide box is too big, it can be many pixels. If your max Move setting is too large, the guide software will send a very large move command.
 
How to fix this? First, make the guide box as small as possible. I usually set mine to 16x16, never larger than 32x32. Second, I set my max move command to 0.3 to 0.5 depending o the focal length of the scope. That way the guider cannot send more than about 7 arc sec or less move when an anomaly occurs. Finally, use as bright a guide star as possible. A faint guide star or long exposure of more than 5 seconds will increase your chances of getting a cosmic ray hit.
 
To see how many cosmic ray hits you receive, just take a 15 minute dark frame with your 683 chip. Then notice all the bright squiggles. You will see a hundred or more on your exposure on a typical night. Some nights are worse than others.
 
Rolando
 
 

-----Original Message-----
From: sixburg@... [ap-gto] <ap-gto@...>
To: ap-gto
Sent: Fri, Aug 7, 2015 10:28 am
Subject: [ap-gto] Spurious guider move command?



I'm curious to know if anyone else has experienced strange guider movements.  Description:  at various points in imaging sessions 'something' is telling the mount to go on an expedition of sorts which results in a distinct pattern (seen in the attached snip). The guide star, normally centered in the track box, seems to be deliberately moved 12 to 15 pixels from the center and then slowly guided back to the middle.  Has anyone seen and solved this before?  I at first suspected a bad gear mesh, but now believe it's a commanded moved by something in the software stack.  Configuration:  Mach1, FSQ, QSI, Lodestar, APCC, A-P v2 (latest), Maxim 5.24, CCDAP, TSX (latest build), guider relays set in Maxim with cable.  Thanks for any insights. 


Roland Christen
 

What direction is that? Does not look like cosmic ray hit, which would be in one direction only.
 
Rolando
 
 

-----Original Message-----
From: sixburg@... [ap-gto]
To: ap-gto
Sent: Fri, Aug 7, 2015 10:37 am
Subject: [ap-gto] Re: Spurious guider move command?



Strange Guiding

Forgot to attach link to image


Bob Benamati
 

Hmm--you might want to upload/post the CCDAP log file too....  Maybe something in there that can tell the tale...


Geoff Smith
 

I had something similar a while ago. Nice guiding for a few minutes, then a sudden blip. Replacing the usb cable from the lodestar fixed the problem.
Geoff


Greg Bradley
 

Are you using Protrack? There is a thread about some odd PE spikes caused by that. I am not seeing it currently but I did see the odd spurious PE spike using a Protrack tracking corrections enabled TPoint model a few weeks ago on another mount. So is a friend seeing a randow spike.


My money is the source is your Sky X. Is it the latest daily build? Sometimes they have bugs that get ironed out after a few weeks.


Greg.


Dave Goodyear <dave@...>
 

I believe protrack does not work with non-bisque mounts.  That function is grayed out unless that has changed in recent builds.

 

Dave

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, August 07, 2015 2:12 PM
To: ap-gto@...
Subject: [ap-gto] Re: Spurious guider move command?

 

 

Are you using Protrack? There is a thread about some odd PE spikes caused by that. I am not seeing it currently but I did see the odd spurious PE spike using a Protrack tracking corrections enabled TPoint model a few weeks ago on another mount. So is a friend seeing a randow spike.

 

My money is the source is your Sky X. Is it the latest daily build? Sometimes they have bugs that get ironed out after a few weeks.

 

Greg.


Greg Bradley
 

Hi Rolando. I was surprised by your max move settings. I have been using .01 min and 3.0 max and when I used the CCDware min/max calculator I got .5min and 2 max.


So with guiding a Honders on an AP1600 what would you recommend for guide exposure lengths, backlash, aggressiveness setting and min max settings?


If you make your guide frame smallish does that mean you do shorter calibration times for the autoguider?


Is it best practice to calibrate near the meridian and does mean you need to reverse X commands after a meridian flip if you do that?


Greg.


Greg Bradley
 

I used to have that problem with the Lodestar as well. I was using CCDsoft. The Lodestars I had (2 of them) both had a bad bias where one had a bright line at the top of the image and the replacement one was worse with an even brighter white line down one side. I am not sure but I think the latest models have had a firmware tweak to stop this.


This was not a problem if you could do an autodark subtract. CCDSoft however needed it to have a shutter to do this and would not apply library darks to autoguiders. I believe Maxim does.


So it would be fine for many images and then wham it would pick the white line as the guide star and issue a 15 arc sec error correction. When I subframed the white edge came with it.


Hot pixel suppression helped a bit. But ultimately I found it was not compatible with CCDsoft and needed the library dark subtract to work. Again this may have been fixed with later models and this was 1.5 years ago.


Are you getting bright white edges on your guide images or a sudden random hot pixel? Some hot pixels are brighter than dimmer guide stars.


Greg.


Ross Salinger <rgsalinger@...>
 

Maxim will do a full calibration if you ask it to. I built a dark library for my Lodestar X2, but I’ve never seen the problem you’re having.

Rgrds-Ross

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, August 7, 2015 2:29 PM
To: ap-gto@...
Subject: [ap-gto] Re: Spurious guider move command?

 

 

I used to have that problem with the Lodestar as well. I was using CCDsoft. The Lodestars I had (2 of them) both had a bad bias where one had a bright line at the top of the image and the replacement one was worse with an even brighter white line down one side. I am not sure but I think the latest models have had a firmware tweak to stop this.

 

This was not a problem if you could do an autodark subtract. CCDSoft however needed it to have a shutter to do this and would not apply library darks to autoguiders. I believe Maxim does.

 

So it would be fine for many images and then wham it would pick the white line as the guide star and issue a 15 arc sec error correction. When I subframed the white edge came with it.

 

Hot pixel suppression helped a bit. But ultimately I found it was not compatible with CCDsoft and needed the library dark subtract to work. Again this may have been fixed with later models and this was 1.5 years ago.

 

Are you getting bright white edges on your guide images or a sudden random hot pixel? Some hot pixels are brighter than dimmer guide stars.

 

Greg.


Mlooker
 

Correct!!

Tom

On 8/7/2015 2:16 PM, Dave Goodyear dave@... [ap-gto] wrote:
I believe protrack does not work with non-bisque mounts.


Roland Christen
 

Yes, the Lodestar cable is super sensitive. I looped mine up and back, then tied it with a tiewrap to the Lodestar body before descending down to the PC. Even then it is touchy, if you yank on it even slightly it loses contact.
 
Roland
 
 

-----Original Message-----
From: ghsmith45@... [ap-gto]
To: ap-gto Sent: Fri, Aug 7, 2015 4:00 pm
Subject: [ap-gto] Re: Spurious guider move command?



I had something similar a while ago. Nice guiding for a few minutes, then a sudden blip. Replacing the usb cable from the lodestar fixed the problem.
Geoff



Roland Christen
 

 
Response below:

Hi Rolando. I was surprised by your max move settings. I have been using .01 min and 3.0 max and when I used the CCDware min/max calculator I got .5min and 2 max.
 
0.5 min is wrong. 0.5 means that the guide star can move 7.5 arc sec (0.5x15=7.5) before a guide correction is sent to the mount Clearly wrong. 2 Max means that you are allowing the mount to go 30 arc sec correction, which is wildly excessive. Why would you ever want any software to send such a huge correction signal to the mount?

So with guiding a Honders on an AP1600 what would you recommend for guide exposure lengths, backlash, aggressiveness setting and min max settings?
 
Min setting of 0.01 to 0.03 depending on how well polar aligned you are and the steadiness of the sky.

If you make your guide frame smallish does that mean you do shorter calibration times for the autoguider?
 
Small guider frame has zero to do with calibration. They are not related.

Is it best practice to calibrate near the meridian and does mean you need to reverse X commands after a meridian flip if you do that?
 
Meridian flip always requires checking the reversing box. Unless you go thru the trouble of re-calibrating on the other side.

Greg.



Roland Christen
 

So with guiding a Honders on an AP1600 what would you recommend for guide exposure lengths, backlash, aggressiveness setting and min max settings?
 
Min setting of 0.01 to 0.03 depending on how well polar aligned you are and the steadiness of the sky.
 
Forgot to add max Move of 0.3 to 0.5 sec, backlash setting = 0, guide exposure lengths of 2 to 8 seconds. Agressiveness depends on your seeing, up to 10 in pristine seeing conditions, down to 6 in poor seeing.
 
Rolando
 
-----Original Message-----
From: chris1011@... [ap-gto]
To: ap-gto
Sent: Fri, Aug 7, 2015 5:05 pm
Subject: Re: [ap-gto] Re: Spurious guider move command?



 
Response below:

Hi Rolando. I was surprised by your max move settings. I have been using .01 min and 3.0 max and when I used the CCDware min/max calculator I got .5min and 2 max.
 
0.5 min is wrong. 0.5 means that the guide star can move 7.5 arc sec (0.5x15=7.5) before a guide correction is sent to the mount Clearly wrong. 2 Max means that you are allowing the mount to go 30 arc sec correction, which is wildly excessive. Why would you ever want any software to send such a huge correction signal to the mount?

So with guiding a Honders on an AP1600 what would you recommend for guide exposure lengths, backlash, aggressiveness setting and min max settings?
 
Min setting of 0.01 to 0.03 depending on how well polar aligned you are and the steadiness of the sky.

If you make your guide frame smallish does that mean you do shorter calibration times for the autoguider?
 
Small guider frame has zero to do with calibration. They are not related.

Is it best practice to calibrate near the meridian and does mean you need to reverse X commands after a meridian flip if you do that?
 
Meridian flip always requires checking the reversing box. Unless you go thru the trouble of re-calibrating on the other side.

Greg.





Greg Bradley
 

Well that is gold - thank you.


Greg.


Greg Bradley
 

With the minimum move of .01 to .03 depending on seeing that would be .03 for good seeing and .01 for poor seeing?


Guide rate is 1.0X?


Greg.


Greg Bradley
 

Sorry, another question.


These guide settings and min/max move are for pulse guiding? I see the CCDware calculator gives completely different results for direct guide versus relays. I am using pulse guide in Sky X. I am not sure if this is similar to Software Bisques direct guide or not.


Greg.


Roland Christen
 

Just the opposite.
 
Rolando
 
 

-----Original Message-----
From: bradgregley10@... [ap-gto]
To: ap-gto
Sent: Fri, Aug 7, 2015 5:24 pm
Subject: Re: [ap-gto] Re: Spurious guider move command?



With the minimum move of .01 to .03 depending on seeing that would be .03 for good seeing and .01 for poor seeing?

Guide rate is 1.0X?

Greg.



Roland Christen
 

There is no difference between using the guider port or software guiding. Use the same settings.
 
Don't know what you mean by pulse guiding.
 
Rolando
 
 

-----Original Message-----
From: bradgregley10@... [ap-gto]
To: ap-gto
Sent: Fri, Aug 7, 2015 5:34 pm
Subject: Re: [ap-gto] Re: Spurious guider move command?



Sorry, another question.

These guide settings and min/max move are for pulse guiding? I see the CCDware calculator gives completely different results for direct guide versus relays. I am using pulse guide in Sky X. I am not sure if this is similar to Software Bisques direct guide or not.

Greg.