Date   

Re: Mach 1: Checking for debris in RA worm gear.

Christopher Erickson
 

Last night I was tempted to shout "cables!" but since it was a Mach1 I assumed that all of the cables were routed through the inside of the mount!
 

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

 



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, August 13, 2015 7:40 AM
To: ap-gto@...
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.

I'm posting this for those who have experienced some tracking issues where the guide star seemed to jump in RA or Dec by several pixels during a normal run. I experienced this last night after a 4 hour imaging session where tracking was on the order of 1/4 pixel. Traced it down to the camera cable rubbing on the pier strut. Just touching the cable actually sent the guide star back and forth by several pixels in both RA and Dec.

It turns out that while the mount is slowly advancing in RA the cable was slowly dragging across the pier strut in a stick-slip mode. This was enough to move the guide star by as much as 5 pixels. Since the mount is always moving in RA, this is the direction that the cable is being pulled and this is why the guide star moves primarily in RA.

In the attached screen shot you can see the first RA guide star anomaly marked by a red 1 arrow. The second one occurred about 5 minutes later (red 2 arrow). When I saw that I went to the mount and gently touched the heavy power cable coming from the STL11K camera. The guide star jumped around 5 pixels as marked by the green 3 arrows. Even though the camera, focuser and scope were properly tightened down, still a loose cable dragging will cause the guide star to jump around by several arc seconds.

So, the advice I have for imagers is to not hang the cable down. Rather tie it securely to the mount Dec axis before looping it down to the ground. Either that or run it inside the mount, but again secure it to the scope body so that it cannot tug at all on the camera body. 
 
 The anomaly:
 
 
Here is the setup:
 
 
Rolando
 
 
-----Original Message-----
From: chris1011@... [ap-gto]
To: ap-gto
Sent: Thu, Aug 13, 2015 3:45 am
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



To all of you who are experiencing guiding issues, i.e. jumps of the guide star by 5 pixels or thereabouts:
I went to our observatory tonight and did a 5 hour imaging run, looking specifically for jumps in RA or Dec during my exposures. Sure enough at about 2 am I experienced several jumps in RA and a couple in Dec. Since I was at the mount I was able to see exactly what caused it. I will post the results tomorrow since it is almost 4 am and I need to get some sleep. Suffice to say it was nothing mechanical or electronic in the mount.
Rolando
-----Original Message-----
From: g.kurczveil@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Wed, Aug 12, 2015 6:03 pm
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



Alright, I'll take a look.

Btw, the previous owner did use the original shipping box, but there was no protection between the mount and the packing peanuts. This in turn resulted in numerous crushed peanut pieces, which were a pain to remove from the shafts.




Re: Mach 1: Checking for debris in RA worm gear.

Roland Christen
 

I'm posting this for those who have experienced some tracking issues where the guide star seemed to jump in RA or Dec by several pixels during a normal run. I experienced this last night after a 4 hour imaging session where tracking was on the order of 1/4 pixel. Traced it down to the camera cable rubbing on the pier strut. Just touching the cable actually sent the guide star back and forth by several pixels in both RA and Dec.

It turns out that while the mount is slowly advancing in RA the cable was slowly dragging across the pier strut in a stick-slip mode. This was enough to move the guide star by as much as 5 pixels. Since the mount is always moving in RA, this is the direction that the cable is being pulled and this is why the guide star moves primarily in RA.

In the attached screen shot you can see the first RA guide star anomaly marked by a red 1 arrow. The second one occurred about 5 minutes later (red 2 arrow). When I saw that I went to the mount and gently touched the heavy power cable coming from the STL11K camera. The guide star jumped around 5 pixels as marked by the green 3 arrows. Even though the camera, focuser and scope were properly tightened down, still a loose cable dragging will cause the guide star to jump around by several arc seconds.

So, the advice I have for imagers is to not hang the cable down. Rather tie it securely to the mount Dec axis before looping it down to the ground. Either that or run it inside the mount, but again secure it to the scope body so that it cannot tug at all on the camera body. 
 
 The anomaly:
 
 
Here is the setup:
 
 
Rolando
 
 

-----Original Message-----
From: chris1011@... [ap-gto]
To: ap-gto
Sent: Thu, Aug 13, 2015 3:45 am
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



To all of you who are experiencing guiding issues, i.e. jumps of the guide star by 5 pixels or thereabouts:
 
I went to our observatory tonight and did a 5 hour imaging run, looking specifically for jumps in RA or Dec during my exposures. Sure enough at about 2 am I experienced several jumps in RA and a couple in Dec. Since I was at the mount I was able to see exactly what caused it. I will post the results tomorrow since it is almost 4 am and I need to get some sleep. Suffice to say it was nothing mechanical or electronic in the mount.
 
Rolando
 
 
-----Original Message-----
From: g.kurczveil@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Wed, Aug 12, 2015 6:03 pm
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



Alright, I'll take a look.

Btw, the previous owner did use the original shipping box, but there was no protection between the mount and the packing peanuts. This in turn resulted in numerous crushed peanut pieces, which were a pain to remove from the shafts.




Re: Mach 1: Checking for debris in RA worm gear.

Roland Christen
 

To all of you who are experiencing guiding issues, i.e. jumps of the guide star by 5 pixels or thereabouts:
 
I went to our observatory tonight and did a 5 hour imaging run, looking specifically for jumps in RA or Dec during my exposures. Sure enough at about 2 am I experienced several jumps in RA and a couple in Dec. Since I was at the mount I was able to see exactly what caused it. I will post the results tomorrow since it is almost 4 am and I need to get some sleep. Suffice to say it was nothing mechanical or electronic in the mount.
 
Rolando
 
 

-----Original Message-----
From: g.kurczveil@... [ap-gto]
To: ap-gto
Sent: Wed, Aug 12, 2015 6:03 pm
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



Alright, I'll take a look.

Btw, the previous owner did use the original shipping box, but there was no protection between the mount and the packing peanuts. This in turn resulted in numerous crushed peanut pieces, which were a pain to remove from the shafts.


Re: Mach 1: Checking for debris in RA worm gear.

Geza Kurczveil
 

Alright, I'll take a look.

Btw, the previous owner did use the original shipping box, but there was no protection between the mount and the packing peanuts. This in turn resulted in numerous crushed peanut pieces, which were a pain to remove from the shafts.


Re: Mach 1: Checking for debris in RA worm gear.

Roland Christen
 

The gear is a worm gear, not a spur. Yes, if the mount had a spur gear then debris could wedge itself between the teeth. In a worm gear there is a sideways wiping action as the driving worm turns, so it is virtually impossible for any debris to lodge itself in between the teeth. That is what makes worm gears so suitable for precision clock drives. The constant wiping action also wears the teeth more smooth and uniform over time.
 
The best clue that you gave is that the mount was sent to you by another person, and possibly it was not packed very well. In those cases we have found that rough handling during shipping can wedge the motor box tightly into mesh and cause erratic performance during tracking.
 
Rolando
 
 

-----Original Message-----
From: g.kurczveil@... [ap-gto]
To: ap-gto Sent: Wed, Aug 12, 2015 4:08 pm
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



I'll do that.

Given your answers and your aversion of my main question (how do I check for debris?), can I assume that the internals of the mount are so resilient against foreign objects that even if the mount were to be exposed to a dusty environment I would not have to worry about those particles finding their way into the gear?


Re: Mach 1: Checking for debris in RA worm gear.

Geza Kurczveil
 

I'll do that.

Given your answers and your aversion of my main question (how do I check for debris?), can I assume that the internals of the mount are so resilient against foreign objects that even if the mount were to be exposed to a dusty environment I would not have to worry about those particles finding their way into the gear?


Re: Mach 1: Checking for debris in RA worm gear.

Roland Christen
 

Also, make sure that the two motor boxes are properly meshed. Whenever a mount is sent second hand and not properly packaged, the gearbox can be caused to work its way into hard mesh due to rough handling and vibrations during shipping. This can cause the motor to labor and possibly not track properly. Loosen the screws that hold the gearbox to the mount axis and allow the springs to press the worm properly into mesh. Then tighten them. On our website are full instructions for meshing the worm gears.
 
Rolando
 
 

-----Original Message-----
From: g.kurczveil@... [ap-gto]
To: ap-gto
Sent: Wed, Aug 12, 2015 12:19 pm
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



1. I've worked on this and not seen an improvement.
2. I see this even when I am not guiding, just taking looping exposures, so I'd like to dismiss this idea.
3. Cables are routed externally.
4. See Point 2 (I am not guiding). I can clearly see all stars move in RA even though the guider is not sending a command.
5. The stars eventually always move back to their original position, so I don't think anything is loose.
6. See Point 5. When not sending guide commands, the stars move in RA for a few seconds, but then caom back to their original positions.

I should elaborate. I bought the mount second hand and the original owner didn't do a stellar job of packaging the mount. There were some crushed packing peanuts that I had to fish out of the mount. I am thus thinking if it is not possible that some smaller debris found its way onto the RA worm drive.


Re: Mach 1: Checking for debris in RA worm gear.

Roland Christen
 

Check one more thing. Turn off PEM in the keypad. There may be some bogus data in the PE memory.
 
Rolando
 
 

-----Original Message-----
From: g.kurczveil@... [ap-gto]
To: ap-gto
Sent: Wed, Aug 12, 2015 12:19 pm
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



1. I've worked on this and not seen an improvement.
2. I see this even when I am not guiding, just taking looping exposures, so I'd like to dismiss this idea.
3. Cables are routed externally.
4. See Point 2 (I am not guiding). I can clearly see all stars move in RA even though the guider is not sending a command.
5. The stars eventually always move back to their original position, so I don't think anything is loose.
6. See Point 5. When not sending guide commands, the stars move in RA for a few seconds, but then caom back to their original positions.

I should elaborate. I bought the mount second hand and the original owner didn't do a stellar job of packaging the mount. There were some crushed packing peanuts that I had to fish out of the mount. I am thus thinking if it is not possible that some smaller debris found its way onto the RA worm drive.


Re: Mach 1: Checking for debris in RA worm gear.

Geza Kurczveil
 

1. I've worked on this and not seen an improvement.
2. I see this even when I am not guiding, just taking looping exposures, so I'd like to dismiss this idea.
3. Cables are routed externally.
4. See Point 2 (I am not guiding). I can clearly see all stars move in RA even though the guider is not sending a command.
5. The stars eventually always move back to their original position, so I don't think anything is loose.
6. See Point 5. When not sending guide commands, the stars move in RA for a few seconds, but then caom back to their original positions.

I should elaborate. I bought the mount second hand and the original owner didn't do a stellar job of packaging the mount. There were some crushed packing peanuts that I had to fish out of the mount. I am thus thinking if it is not possible that some smaller debris found its way onto the RA worm drive.


Re: Mach 1: Checking for debris in RA worm gear.

Roland Christen
 

It would not likely be PEC data. Some things that can cause sudden loss of guiding: 1) cable dragging and snagging on something. 2) USB connector on the guide camera not making perfect contact - I have this issue with my miniature USB connector on the Lodestar. 3) if you use internal cabling running thru the mount, the cable might be too tight as it goes around the bend inside the RA/Dec junction, which causes some friction. 4) cosmic ray hit on the guider chip - make the guide box as small as possible, 16x16 or 32x32 pixels. 5) loose camera connection to the focuser drawtube. 6) possibly focuser drawtube sagging or shifting during the night.
 
Rolando
 
 

-----Original Message-----
From: g.kurczveil@... [ap-gto]
To: ap-gto
Sent: Wed, Aug 12, 2015 9:32 am
Subject: Re: [ap-gto] Mach 1: Checking for debris in RA worm gear.



Wouldn't bad PEC data show up as a periodic error every 7 minutes? Instead I see an error of ~20 arcseconds ever 2-4 hours.


Re: Spurious guider move command?

Roland Christen
 

After you do that, please check with George or Howard at Astro-Physics and let us know what the results are. You can email them thru our website. We want to keep track of customer mount issues so we can follow up with solutions. Meanwhile I will be testing mounts for this here at our AP Observatory.
 
Rolando
 
 

-----Original Message-----
From: Lloyd Smith sixburg@... [ap-gto]
To: ap-gto
Sent: Wed, Aug 12, 2015 7:59 am
Subject: [ap-gto] Re: Spurious guider move command?



My guide cam is NOT lined up with X/Y to RA.  Fantastic.  I’ll make that adjustment, note any changes and close the loop with this group. Very helpful.  Thank you.
Lloyd L. Smith
678.427.6341



Re: Mach 1: Checking for debris in RA worm gear.

Geza Kurczveil
 

Wouldn't bad PEC data show up as a periodic error every 7 minutes? Instead I see an error of ~20 arcseconds ever 2-4 hours.


Re: Spurious guider move command?

Lloyd Smith
 

My guide cam is NOT lined up with X/Y to RA.  Fantastic.  I’ll make that adjustment, note any changes and close the loop with this group. Very helpful.  Thank you.

Lloyd L. Smith

678.427.6341

sixburg@...

www.deepskywest.com

www.remotetelescopes.com

www.astrobin.com/users/sixburg


Re: Mach 1: Checking for debris in RA worm gear.

christian viladrich
 

Hi,

You can also check if it is a problem with corrupted PEC data. Just switch off the PEC and check if the problem is still there.

Best regards

Christian


Le 12/08/2015 04:33, g.kurczveil@... [ap-gto] a écrit :
Hi all,

I'm a newbie to the group, but a long time imager/observer.

Setup: Mach 1, TV127is, STF8300, Orion 50 mm guider.

I have a Mach 1 which occasionally (once every 10-20 frames) gives spikes in the RA axis. I am certain that it has nothing to do with the guider (or cosmic ray hits) as I can see this movement even when the autoguider is not sending commands (i.e. I am just doing looping exposures). I am also confident that this is not caused by flex or cables. In addition, the weights are always biased such that the mount is working against gravity. I am suspecting that there is some debris on the worm gear but not on the worm itself as I don't see any periodic issues.

Is there a pdf that shows how to disassemble to mount to allow me to inspect the worm gear?

I've worked on CG5 and GM8 mounts, so I think I would be comfortable inspecting the insides of the Mach 1 too.

Thanks,

Geza.


Mach 1: Checking for debris in RA worm gear.

Geza Kurczveil
 

Hi all,

I'm a newbie to the group, but a long time imager/observer.

Setup: Mach 1, TV127is, STF8300, Orion 50 mm guider.

I have a Mach 1 which occasionally (once every 10-20 frames) gives spikes in the RA axis. I am certain that it has nothing to do with the guider (or cosmic ray hits) as I can see this movement even when the autoguider is not sending commands (i.e. I am just doing looping exposures). I am also confident that this is not caused by flex or cables. In addition, the weights are always biased such that the mount is working against gravity. I am suspecting that there is some debris on the worm gear but not on the worm itself as I don't see any periodic issues.

Is there a pdf that shows how to disassemble to mount to allow me to inspect the worm gear?

I've worked on CG5 and GM8 mounts, so I think I would be comfortable inspecting the insides of the Mach 1 too.

Thanks,

Geza.


Re: Spurious guider move command?

Roland Christen
 

Yes, bias the counterweight to be heavier.
 
Rolando
 
 

-----Original Message-----
From: bmegdal@... [ap-gto] To: ap-gto
Sent: Tue, Aug 11, 2015 10:06 pm
Subject: [ap-gto] Re: Spurious guider move command?



I too see this type of small motion in RA on about 1 out of 5-10 subs (20 minutes each).  Mount is a 1600 with encoders.

I can and will check the RA gear mesh, but want to clarify if always biasing in the direction of a heavier counterweight helps even when imaging to the West?  The observatory is remote, so I can't change the weight bias after a flip.

- Barry



Re: Spurious guider move command?

Barry Megdal
 

I too see this type of small motion in RA on about 1 out of 5-10 subs (20 minutes each).  Mount is a 1600 with encoders.

I can and will check the RA gear mesh, but want to clarify if always biasing in the direction of a heavier counterweight helps even when imaging to the West?  The observatory is remote, so I can't change the weight bias after a flip.

- Barry


Re: Spurious guider move command?

Stuart Heggie <stuart.j.heggie@...>
 

Harsh perhaps. But, when I need a laugh I think of a question and go to Yahoo Answers where EVERY answer seems to start with "I don't know but this is what I think anyway...." Kills me every time.

Stuart

On Tue, Aug 11, 2015 at 12:55 PM, Dave Goodyear dave@... [ap-gto] <ap-gto@...> wrote:
 

Getting "answers' on a public forum is an oxymoron. You only get opinions on forums, not answers.   One of those opinions might be the "answer" but its still an opinion. 

Dave Goodyear


On Aug 11, 2015, at 9:07 AM, look-up1@... [ap-gto] <ap-gto@...> wrote:

 

Why get touchy, folks are just trying to help, they don't know you have a clue with this stuff.  You posted an issue on a public forum and your getting answers.

Tom

On 8/11/2015 5:42 AM, Lloyd Smith sixburg@... [ap-gto] wrote:
Contrary to the implications in other posts I do have a clue as to what I’m doing and have 3 other very similar





Re: Spurious guider move command?

Dave Goodyear <dave@...>
 

Getting "answers' on a public forum is an oxymoron. You only get opinions on forums, not answers.   One of those opinions might be the "answer" but its still an opinion. 

Dave Goodyear


On Aug 11, 2015, at 9:07 AM, look-up1@... [ap-gto] <ap-gto@...> wrote:

 

Why get touchy, folks are just trying to help, they don't know you have a clue with this stuff.  You posted an issue on a public forum and your getting answers.

Tom

On 8/11/2015 5:42 AM, Lloyd Smith sixburg@... [ap-gto] wrote:
Contrary to the implications in other posts I do have a clue as to what I’m doing and have 3 other very similar


Re: Spurious guider move command?

Roland Christen
 

I think I know why your guide errors are what they are. I believe your guide camera (and probably your imaging camera) is oriented at an angle to the RA. Check your parameter number for the angle. If it is not either 0 or 180 or thereabouts, then you will not get any correlation between the guider correction numbers and the error numbers in your guider log. It is always best to orient the guide camera so that the X and Y axes line up with RA/Dec.
 
Rolando
 
 

-----Original Message-----
From: Lloyd Smith sixburg@... [ap-gto]
To: ap-gto
Sent: Tue, Aug 11, 2015 7:42 am
Subject: [ap-gto] Re: Spurious guider move command?



John D…
Your photo is very similar to mine with the exception of the direction of the star trail error.  I need to confirm whether or not the movement is only in RA.  The mount is purposely imbalanced a bit as Roland suggests.  I’m doubtful of wind being the issue in my case as wind is monitored by two different instruments and in the logs there are no winds over 3 mph during the capture of the “ruined” subs.  Over the course of a night perhaps 1 maybe 2 subs are ruined.  Contrary to the implications in other posts I do have a clue as to what I’m doing and have 3 other very similar A-P based systems in the same remote observatory all operating flawlessly except this one (only differences are the OTA and camera) All other systems are on non-A-P mounts and have never shown this behavior.  Ergo, my first hypothesis focused on the mount (i.e, gear mesh), but that didn’t fix it.   I’m going to test with another guider.  It seems to me a spurious signal from the guider could be a cause. 
Lloyd