56 replies to this topic

[Rac19]

When operating at high f ratios (say f/25) and slow speed (<= 3) to fine tune the centering of a planet, slewing can become quite erratic and basically refuse to go to desired position. The planet (or star) will jerk around on the screen and, if I am outside, a clunk can be heard.

 

The clunk makes it seem to be obviously a mechanical problem but I am not so sure, it could be a software issue (possibly)

 

Last night, I was using CPWI with a game controller for manual slewing. The 'scope attempted to move where I wanted it to go but would "snap" back to the starting position, with clunk. The clunk even happened when I pressed the "X" button on the game controller, to switch to slow speed. On this occasion the CPWI on screen buttons seemed to work correctly, but I have experienced the problem when using the CPWI screen buttons, so it's not just just a game controller issue. I had also seen this happen with FireCapture auto-guiding, connected via CPWI.

 

Slewing at a higher speed seems to fix the problem, but that is not something that you want to do when zeroing in on target.

 

I am curious to know whether or not anyone has experienced this issue. It can be very frustrating.

 

 

[skaiser]

Hi Richard  

 some questions to help clarify.

Was the mount working ok up until recently

did this  Suddenly start to happen or a gradual change 

are you using a wedge 

can you tell what axis is causing the clunk

will it clunk if the scope is not on the mount?

Take care

Edited by skaiser, 29 July 2021 - 06:50 AM.

[Rac19]

Hi Richard  

 some questions to help clarify.

Was the mount working ok up until recently

did this  Suddenly start to happen or a gradual change 

are you using a wedge 

can you tell what axis is causing the clunk

will it clunk if the scope is not on the mount?

Take care

It has been happening on and off for a year or more. I can't be absolutely sure, but it could be since I have started using CPWI.

 

I am using a wedge at the moment, which meant to mention.The wedge obviously puts stresses on the drives that they were designed for.  I am pretty sure that it has been happening in Alt/Az model though. 

 

At one point, I thought it was possibly happening near the zenith, I think in Alt/Az mode. One possible cause is that if the Alt axis is at a tipping point (at the zenith), when a very small slew command is issued, the weight shifts to to the other gear face causing a much bigger move than was requested. The motor controller might pick this up from the encoder and attempts to correct it.

 

Now that I am using a wedge, it's a little more complicated. At my latitude, 33.75 Deg South, the the mount base is tilted at 66.25 degrees. There could be a similar weight shift as the mount fork goes "over the top" to point to target in the East, I will take note of this next time.

 

EDIT: Thanks for your reply by the way. I don't necessarily expect a neat solution to this, but understanding what is happening can be helpful.

 

EDIT: It might be more that feedback from the encoder indicates that the movement is too bast rather than too far. The problem only seems to occur at low speeds.

Edited by Rac19, 29 July 2021 - 07:36 AM.

[Notdarkenough]

Hi Richard.  I have had similar experiences. I am visual only, so no wedge or extra camera weight. When the occurrence was most frequent, I was also using CPWI with an Xbox controller. Most memorable to me was in the spring when I was trying to see the whirlpool galaxy. I stopped using CPWI (for a different reason) and I don't remember this happening since. Maybe it had nothing to do CPWI; I have a very spotty memory!

If I were to describe what happened to me, I would say this: when trying to slew to my final observing target, I selected a very low speed slew, and proceeded to attempt the final-slew-right-then-up procedure recommended, I moved the Xbox controller (using CPWI and USB connection to Evo) stick to the right. The visual field shifted to the right as normal. However, when I let the controller stick spring back to normal, the visual field snapped back as well. I tried this several times. I then moved my 'centering box' into a rectangle, coming at the target from further away horizontally and closer vertically. After several permutations of approaching, I found my target and had a very nice time. Due to health problems I haven't been out observing for several months, so I don't have any recent reports.

 

Thanks for posting this!

Mike 

[ButterSmooth]

Just a confirmation; My 9.25 NexStar Evo does the same thing.  I'm also using CPWI, Xbox controller and a USB Cable to the hand controller.  It also exhibits this behavior when using the keyboard arrows on my blue tooth keyboard.  Recently I've been experimenting with the backlash settings, but can't confirm if they help.

 

The mount only does it when the scope tube is mounted.  My rig is very nose heavy to provide clearance for a camera.

 

If it does it next time out, I've got weights ready to see if balance makes a difference.

[Rac19]

Thanks for replies #3 and #4, it's good to know that I am not alone and not imagining things.

 

I have my OTA as far forward as possible for backend clearance so it is always nose heavy, regardless of cameras etc. I do wonder though whether or not a balanced OTA is such a good thing. At the tipping point, the OTA would be floating between the two gear faces and I am not sure how much better that would be when zeroing in on a target with small, slow slew commands. At least it wouldn't flop over quite so heavily I guess.

 

I suspect that with the wedge, the problem is more likely to happen on the Az axis, especially at low latitudes, notwithstanding the other unique forces (not designed for) that the mount experiences when fitted to a wedge. Also, when on a wedge, the centre of gravity and tipping point are less obvious than Alt/Az mode, and actually dynamic.

 

With regard to CPWI, I know that I first reported the issue to the CPWI Team Celestron thread and had some discussion with Derik about it. He introduced a user defined dead zone for the game controller joystick in a later release to hopefully address bounce issues. I have increased the dead zone from 10% to 15% but I didn't feel that it was. joystick bounce problem the other night. As I said, I have seen the same thing happen with FireCapture auto tracking (connected via CPWI).

 

It is really strange the pressing (and releasing) the X button for slow speed on the game controller seems to induce the problem.

 

At the moment, I am beginning to suspect an inappropriate corrective action to a "micro" runaway, during a slow speed slew, when there is a weight shift.

Edited by Rac19, 29 July 2021 - 04:56 PM.

[ButterSmooth]

...

It is really strange the pressing (and releasing) the X button for slow speed on the game controller seems to induce the problem.

...

I've noted that same behavior also -- the X button with no joystick deflection produces a jump and jump back event.

 

Looking for weight shift as a cause may be the wrong path.  Mine is alt/az and there is no weight shift or cable drag issue when the jump occurs.  If I do a larger movement (not letting up on the joystick), it will jump, jump back and after a delay, it will begin to move correctly.

[Rac19]

I've noted that same behavior also -- the X button with no joystick deflection produces a jump and jump back event.

 

Looking for weight shift as a cause may be the wrong path.  Mine is alt/az and there is no weight shift or cable drag issue when the jump occurs.  If I do a larger movement (not letting up on the joystick), it will jump, jump back and after a delay, it will begin to move correctly.

Weight shift is certainly only one possible explanation. It is starting to look like CPWI itself, could also be the culprit. As I said, the first the I reported it was on the Team Celestron CPWI forum. I have been using CPWI for a few years now and maybe it has only ever happened when CPWI is in the loop.

[Noah4x4]

I have never experienced this as I rarely image at high f/ratios nor use ultra-slow slew speeds, but I suspect it is simply a natural consequence of the stepped motion of an Alt-Az. Then, a bit like hitting a pothole in a car, the tyre thump is more noticeable at slow speeds than at higher. Seems to be very common, so I wouldn't get too worried about it.

[Rac19]

I have never experienced this as I rarely image at high f/ratios nor use ultra-slow slew speeds, but I suspect it is simply a natural consequence of the stepped motion of an Alt-Az. Then, a bit like hitting a pothole in a car, the tyre thump is more noticeable at slow speeds than at higher. Seems to be very common, so I wouldn't get too worried about it.

Given the discussion so far, it would seem to be to be a waste of time sending the 'scope in for a check up. I have considered doing so, but now I won't bother.

 

It is actually a problem though, because the problem always seems to crop up at the point of final target alignment and can be quite frustrating.

 

EDIT: It also means that FireCapture auto-tracking can't be used.

Edited by Rac19, 30 July 2021 - 01:37 AM.

[skaiser]

From the discussions it sounds as if the scope is not balanced ( to give clearance for camera)

for most mounts, it is always very important to have a closely balanced scope .

the more off balance the scope, the more likely you will have move/ tracking problems.

it would likely help to add some counter weight to front of scope for closer balance.

 

I’m also a little suspicious of the Xbox control interface stability.

might try fine adjustments using hand control to see if problems still occur 

 

Take care

[ButterSmooth]

From the discussions it sounds as if the scope is not balanced ( to give clearance for camera)

for most mounts, it is always very important to have a closely balanced scope .

the more off balance the scope, the more likely you will have move/ tracking problems.

it would likely help to add some counter weight to front of scope for closer balance.

 

I’m also a little suspicious of the Xbox control interface stability.

might try fine adjustments using hand control to see if problems still occur 

 

Take care

I'd have to add close to 5# to the rear of the scope to get close to balanced and that would exceed the mount capability, potentially causing a new set of tracking/pointing issues.

 

The jump behavior also occurs when using the CPWI slew panel on the laptop, so it's not the Xbox controller.

[whizbang]

I'm curious what firmware revision you thumpers are running.

 

About two years ago, there was a firmware revision that caused the mount to thump and jump, even when using just the hand control.  It was a total hassle, especially since Celestron did not have a fix for several weeks.  Those of us with thumping mount had to back roll an old revision.  It was quite the headache.

 

I wonder if this problem is more of the same???

[Rac19]

I'm curious what firmware revision you thumpers are running.

 

About two years ago, there was a firmware revision that caused the mount to thump and jump, even when using just the hand control.  It was a total hassle, especially since Celestron did not have a fix for several weeks.  Those of us with thumping mount had to back roll an old revision.  It was quite the headache.

 

I wonder if this problem is more of the same???

I updated all firmware recently.

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[ButterSmooth]

I'm curious what firmware revision you thumpers are running.

 

About two years ago, there was a firmware revision that caused the mount to thump and jump, even when using just the hand control.  It was a total hassle, especially since Celestron did not have a fix for several weeks.  Those of us with thumping mount had to back roll an old revision.  It was quite the headache.

 

I wonder if this problem is more of the same???

My firmware was about ... 2 years old.  I just updated today so, we shall see...

[Notdarkenough]

I check mine monthly. I stopped using CPWI and it has yet to reoccur. 

[skaiser]

If you try fine control jog using the hand control you bypass anything to do with the CPWI software.

that would help narrow down where issues might come from.

 

Adding the balance weight puts a lot less stress on drive train.

Trying this is another step in eliminating possible causes of problem.

I remember the software issue caused by a update.

 

good luck finding a fix

take care

[Rac19]

Frankly, I am beginning suspect that CPWI is the culprit. I first reported the issue after I started using CPWI.

 

I have seen enough in the above replies (which are much appreciated) to think that it is not a mechanical problem, so I don't need to waste time sending it in for repair.

 

The things that I like about CPWI include reading time and location from the PC, running StarSense Auto Align from the PC and the gamepad interface (which could be suspect). I actually prefer Cartes du Ciel as sky charting software (the name says it all).

 

The thought of going back to the StarSense HC and GPS isn't appealing but it looks it might come to that.

 

I might first ditch the wedge. I think that it is useful near the zenith, where field rotation is at it's maximum, but it does introduce mechanical forces for which the mount was not designed. Without, it there is only one axis for which balance needs to be considered although, due to backend clearance considerations, I think that my OTA is always going to be nose heavy.

 

Thanks again for all the replies.

Edited by Rac19, 31 July 2021 - 10:03 PM.

[Rac19]

Further to Post #18, this is another potential "nail in the coffin" for CPWI....

 

https://www.cloudyni...in-mid-session/

 

Now that I have a permanent mount, I expect to be able save alignment and park, but all of that is lost if CPWI is going to lose the alignment model in mid session.

 

If save alignment and park works better with the StarSense HC, at least I shouldn't have to do it very often, although I don't know whether location would be preserved and time would definitely not be preserved.

 

Would hibernate be a better option, after manually parking?

 

Does anyone know of a way to load PC location and tine into the HC? I think that I read something, somewhere, sometime.

 

EDIT: Actually, for now I might just learn to live with it. I have found hearing of others similar experiences to be very helpful though.

Edited by Rac19, 01 August 2021 - 04:26 AM.

[skaiser]

May I ask which version of cpwi you are using?

beta or final released?

If control was stable in the past and these issues have gotten progressively worse , I would suspect windows updates introducing problems.

take care

[ButterSmooth]

2.3.5

 

May I ask which version of cpwi you are using?

beta or final released?

If control was stable in the past and these issues have gotten progressively worse , I would suspect windows updates introducing problems.

take care

[Rac19]

May I ask which version of cpwi you are using?

beta or final released?

If control was stable in the past and these issues have gotten progressively worse , I would suspect windows updates introducing problems.

take care

I'm using the very latest beta release (2.4.0) but the problem has existed for 2 years, over many releases. I first reported it on Team Celestron in August 2019.

[Centaurus Curiosus]

I have noticed the same behavior. I do not use a wedge. Nor do I use CPWI software, instead I use the SkyPortal app. I don't know if this happens without SkyPortal connection, but with SkyPortal app connected it happens both when moving via the app and via the HC. It happens in both axes.

 

For me it has nothing to do with the F ratio, it happens with and without Barlow lens, with camera and also with eyepieces.

 

I can work around it in a pinch, it's not that bad, but the clunk noise sounds quite unhealthy and raises concern for me. I would really like to know what exactly causes the noise and if it will harm the mount in the long run. Of course, a solution to the actual problem would be even better.

[mlord]

Open it up and have a look at the gears.  Sometimes they work loose from the factory.

[Rac19]

I have noticed the same behavior. I do not use a wedge. Nor do I use CPWI software, instead I use the SkyPortal app. I don't know if this happens without SkyPortal connection, but with SkyPortal app connected it happens both when moving via the app and via the HC. It happens in both axes.

 

For me it has nothing to do with the F ratio, it happens with and without Barlow lens, with camera and also with eyepieces.

 

I can work around it in a pinch, it's not that bad, but the clunk noise sounds quite unhealthy and raises concern for me. I would really like to know what exactly causes the noise and if it will harm the mount in the long run. Of course, a solution to the actual problem would be even better.

I think that the only correlation with high f ratios is that at f/25, for example, you often find yourself making small, very slow speed slews to centre the target, and that's when it tends to happen.

 

Interesting to hear that it happens even with the HC, it saves me from investigating that possibility. Also, from previous posts, I don't think that I will bother to send it in for "repair".

 

It is possible to live with it (do we have a choice?). It does mean that I can't use Firecapture auto-guiding though. I used it the other night and when the 'scope got the "thumps", the target was completely lost, in mid capture. I am thinking of using auto-framing (which automatically moves the ROI, not the 'scope), but that can only correct so far.

 

Because it only happens at slow speed, I really do wonder if it could be an over-reaction to what looks like over-speed (fed back from the encoders) when there is a weight shift in the gear loading. That seems unlikely to happen on the Az axis when not using a wedge though.

 

EDIT: The problem has never occurred with PHD Autoguiding. I only use it for DSO image capture, with a much lower f ratio, f/2 to f/6.3. As mentioned earlier, it's not so much that type lower f ratio has a direct bearing, but it could be that relatively high slewing speeds (though still quite slow) are used for guiding with the wider image scale.

Edited by Rac19, 08 August 2021 - 03:49 AM.