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Help! Mount no longer aligns properly

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#1 UncleHoot

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Posted 18 March 2019 - 08:39 PM

Hi all.  I am hoping you can help me troubleshoot this.

 

I have a Sky Watcher EQ6-R Pro mount.  I have had it about a year, without any trouble.  The last couple of times I have tried to use it, it has not been doing a proper 3-star alignment.  By that, I mean it goes through all of the motions, but the stars aren't even close to where it should be.  Normally, by the third star, it's pretty close.  Instead, it's off by about a degree.  

 

I tried using different alignment stars, thinking that perhaps I was looking at the wrong bright star, but I'm getting the same problem.  Oddly, it seems to be repeatable, so if there was something slipping, I wouldn't expect that.  It seems to go to the same places every time, and they are wrong.  Ugh...  And when I tell it to point at something, it ends up being off as well, but again, from what I have seen, it's always in the SAME wrong place.  Yet when I tell it to park the scope, even after sending it all over the sky, it seems to go back to home, just as exact as ever, as far as I can tell.

 

Date/Time latitude and all of those other things are correct (including Daylight savings).  It actually started happening before the time change, so I believe I can safely rule that out.

 

I used it during a couple cold nights (down around 0° F).  Could that have damaged the gears?

 

Other things that might have changed: Voltage is at 14.2, with plenty of amps.  I tried hooking the mount up to a marine battery and blew the fuse and had to replace it, but I am pretty sure I used it without incident after that, and things were fine (replaced with like fuse).  I can't imagine how the voltage would impact it (it's definitely not under voltage), but I'm out of ideas.

 

Did I somehow ruin my mount?  :-(


Edited by UncleHoot, 18 March 2019 - 08:43 PM.


#2 Phil Sherman

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Posted 18 March 2019 - 11:48 PM

I'd start by rechecking for cone error. You don't specify how you are centering the alignment stars. Centering needs to be done using a crosshair eyepiece or a severely defocused star that nearly fills the fov. Aligning using a high power eyepiece with its restricted fov also makes it easier to get the alignment star centered.



#3 Lonnie.H

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Posted 19 March 2019 - 10:53 AM

I have a CGEM-DX that did exactly the same as what is happening with your mount. I checked and double checked everything to no avail.

As a last ditch effort I did a factory reset (in hand controller menu) of the mount and that fixed the problem. Not sure if you can do the same with your mount but it might be worth a try.



#4 UncleHoot

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Posted 19 March 2019 - 08:59 PM

I have a CGEM-DX that did exactly the same as what is happening with your mount. I checked and double checked everything to no avail.

As a last ditch effort I did a factory reset (in hand controller menu) of the mount and that fixed the problem. Not sure if you can do the same with your mount but it might be worth a try.

 

I did that last night, and it seemed to suddenly work.  But then I noticed that it only worked on certain objects.  I had it point to M81 and it was spot on.  I thought it was fixed.  Then I tried the moon, and it was still way off.  I tried Betelgeuse. Bingo!  But another named star was not even close.

 

i am trying it again tonight.  I started taking some pics too, and noticed that M81 seems to be drifting ever so slightly, frame after frame.  The moon is way too bright to have useful pics, but this is just me trying to understand what might be going on.

 

I am no pro at this.  I still consider myself a beginner.  I have had this mount for a year now and recently got an 8” Newtonian, which I had only used a small few times before I began to notice this problem.



#5 UncleHoot

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Posted 19 March 2019 - 09:12 PM

I'd start by rechecking for cone error. You don't specify how you are centering the alignment stars. Centering needs to be done using a crosshair eyepiece or a severely defocused star that nearly fills the fov. Aligning using a high power eyepiece with its restricted fov also makes it easier to get the alignment star centered.

I align using my camera screen, putting the star exactly in the center dot.



#6 UncleHoot

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Posted 19 March 2019 - 09:20 PM

155EE569 2F1D 4982 A394 5245BD890C70
132DE5B2 ACB6 4D36 B9BD 60F8B7A1B7F2

 

These two images were only about 15 minutes apart.  I looked back over my last session as well, from a couple weeks ago, and noticed the same “drift” happening there as well.



#7 emflocater

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Posted 19 March 2019 - 09:48 PM

Are you using sidereal for your tracking speed? Using hand control or EQMOD? Is your Polar alignment which should be done first before anything else being done accurately? Loose Altitude bolts or Azimuth bolts? Tripod level and legs not slowly slipping from the scope and mount weight or sinking into the ground if not on a secure solid surface?

Cheers

Don


Edited by emflocater, 19 March 2019 - 09:48 PM.

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#8 UncleHoot

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Posted 20 March 2019 - 07:58 AM

Are you using sidereal for your tracking speed? Using hand control or EQMOD? Is your Polar alignment which should be done first before anything else being done accurately? Loose Altitude bolts or Azimuth bolts? Tripod level and legs not slowly slipping from the scope and mount weight or sinking into the ground if not on a secure solid surface?

Cheers

Don

I will double-check the sidereal speed, but I think the "factory reset" would have changed that back.

Hand control?  Yes.

 

Polar alignment: I double and triple checked this last night, both with the scope on and off the mount.  After 3 hours, Polaris was still "on the circle," just about exactly where I would have expected it to be.  I also centered Polaris on the polar scope and rotated the axis 180 degrees to make sure that somehow the polar scope didn't get knocked out of alignment somehow.  I also watched Polaris in my camera as I rotated the axis, and it essentially remained stationary, even when I did an extreme digital zoom.  So, the polar alignment, in my opinion, is about as good as I can do it.  Having said that, I remember having a similar problem when I was really new to polar alignments where I had somehow managed to "polar align" on some star other than Polaris.

 

Loose Altitude bolts or Azimuth bolts: They were all tight.

 

Tripod legs slipping/moving: I was setup on my back deck (wood) and while I am aware of slight movements when I walk on the deck, they are in seconds of arc, not minutes or degrees.

Once I completed the 3 star alignment, I seem to be able to send it back to those stars and it seems to line up - at least I think so.  I went through the whole process 3 times, choosing different alignment stars, and the "error" seems to be the same.  If I try to GoTo the moon, it ends up in the same wrong place, shifted about a degree from where it should be.  Trying named stars and other objects gets me sometimes more and sometimes less error, but (I think) it always seems to be the same error for each object, and M81 usually seems to be spot-on (it may depend on the alignment stars, tho).

I also re-checked the collimation last week, and it doesn't seem to have shifted.  It definitely hasn't gone completely out of whack.

It has been below freezing (25-30 F), but I have had it out in much, much colder temps, and never had this problem in the past.  Then again, I may have been using my ED80, which would mean a lot less weight.  Could cold plus weight be the culprit?  


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#9 Phil Sherman

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Posted 21 March 2019 - 01:30 PM

I thought I had good polar alignment with my Atlas and had just over 1 arcsec drift / minute. I finally fixed this with a better polar alignment. Polar scope alignment just isn't good enough for longer exposure imaging.


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#10 UncleHoot

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Posted 22 March 2019 - 01:47 PM

I thought I had good polar alignment with my Atlas and had just over 1 arcsec drift / minute. I finally fixed this with a better polar alignment. Polar scope alignment just isn't good enough for longer exposure imaging.

I have been getting 3+ minute exposures very consistently, even with the 8" telescope, until a couple weeks ago.  My polar alignment may have been a little off, but it doesn't account for that much drift.

 

The best explanation I have at this point is that the cold temps affected the grease which became too stiff.  This last time, I purposely got setup while it was still daylight, so the mount had been outside for perhaps 2 hours before I finished the setup and did the polar alignment.  Maybe the weight of the 8" scope aggravated the problem.  If that's not the answer, I am out of ideas, and I may have to send it off (to somewhere) to get it fixed, even though I can think of no reason that something should have broken, other than using it in the cold.



#11 sg6

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Posted 22 March 2019 - 03:07 PM

What is the situation if you level the mount, polar align and all the rest then just do a 2 star alignment?

Here the 3 star alignment was dropped for some time as it rarely succeeded. If I recall the result that was produced and the tolerance was too tight.

 

Used a CPC 1100 a few months back and that was just 2 star and worked well, different scope and mount but it is a thought.

 

If it is the grease, was notorously thick black stuff, then where would you consider sending it? Just thinking that a recognised Skywatcher service may be required to use the same stuff.

 

Does raise the question of do you know what is in there at present?

Do they give an operating temperature range, is another.

 

What is the power supply?

 

Moon position is calculated and that makes it a not very good object to pass judgement with.

 

Just searched and no operating temperature is given anywhere I can find. Find that a little odd.

One report that at 0C (32F) the handset became sluggish, and that entering information via the keypad had to be performed slower therefore.


Edited by sg6, 22 March 2019 - 03:28 PM.


#12 UncleHoot

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Posted 22 March 2019 - 08:53 PM

I am gathering more data asi type, but at this point it seems pretty clear that it simply isn’t tracking at the right speed.  It is lagging.  

 

The RA doesn’t seem to be working right at all, and I am noticing quite a bit of backlash in the RA when doing the alightment.  The DEC is fine.  

 

I kept the mount inside and warm until the very last minute, quickly got setup outside (30F at the moment) and had the exact same problems.

 

Sigh...  I have only had it for a year, but I think something is wrong.  But what would make it lag?  It isn’t jittery, it simply lags, as if the timing is off.  And yes, it is definitely set to sidereal rate.  But keep in mind that it lags at both high and low speeds.

 

Unless someone has a miracle solution, I am going to have to send it away during the best part of the year.  :-(

 

EDIT: This is my power supply, currently at 13.9v.

https://smile.amazon...duct/B00KZ18LRI


Edited by UncleHoot, 22 March 2019 - 09:19 PM.


#13 UncleHoot

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Posted 22 March 2019 - 09:01 PM

This is a 10 minute exposure.  No, I didn’t expect it to be perfect, but the point is that if I were to take several of these, they would all look basically the same.  It’s not that it isn’t tracking, it’s simply that it is tracking too slowly.  That is, unless someone can prove me wrong.  Please do.  :-)
 
CB34D39A 019A 4F11 81F6 D32DD84EEF83


#14 UncleHoot

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Posted 23 March 2019 - 01:33 PM

So...  here is the point that I admit that at least part of the problem is in my head.  I got some fantastic results last night, with varying exposures up to 3 mins.  That is about all I can hope for with an unguided mount.  I did a 30 minute exposure, and got around 40 arc secs of drift, and the periodic error was also quite noticeable.  If I happened to catch it at the right time, I might be able to get a 6 min unguided exposure.  If I complain about that, I should be shot.  Lol

 

As for the GoTo issues, they are real.  But I started digging into other posts and it sounds like it isn’t that odd with these Synscan mounts.  They do their best to compensate for cone error, backlash, polar alignment error, and whatever other error we introduce, but they may not be quite as accurate once you add a lot of weight.

 

What changed for me?  Probably the alignment stars (too close to the zenith), and new, heavier equipment.  And maybe the backlash is worse than it used to be.  The tracking is okay (or great!) and that is what really matters.  

 

I think I just got too worried and convinced myself I had ruined an awesome piece of equipment. :facepalm:



#15 ThatsMyCoffee

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Posted 24 March 2019 - 04:39 AM

"I also watched Polaris in my camera as I rotated the axis, and it essentially remained stationary, even when I did an extreme digital zoom.  So, the polar alignment, in my opinion, is about as good as I can do it."

 

 

But Polaris isn't the centre point.  If it did not move, your alignment is BAD.  It should be moving in a circle around the NCP.

 

This could explain your problems.



#16 rmollise

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Posted 24 March 2019 - 07:57 AM

So...  here is the point that I admit that at least part of the problem is in my head.  I got some fantastic results last night, with varying exposures up to 3 mins.  That is about all I can hope for with an unguided mount.  I did a 30 minute exposure, and got around 40 arc secs of drift, and the periodic error was also quite noticeable.  If I happened to catch it at the right time, I might be able to get a 6 min unguided exposure.  If I complain about that, I should be shot.  Lol

 

As for the GoTo issues, they are real.  But I started digging into other posts and it sounds like it isn’t that odd with these Synscan mounts.  They do their best to compensate for cone error, backlash, polar alignment error, and whatever other error we introduce, but they may not be quite as accurate once you add a lot of weight.

 

What changed for me?  Probably the alignment stars (too close to the zenith), and new, heavier equipment.  And maybe the backlash is worse than it used to be.  The tracking is okay (or great!) and that is what really matters.  

 

I think I just got too worried and convinced myself I had ruined an awesome piece of equipment. :facepalm:

 

Then goto accuracy of the SynScan controller is inherently limited. The company's Celestron branded scopes did away with the 3-star alignment years and years ago.

 

However, by following the rules in the manual regarding alignment star choice, etc. they are sufficient. 

 

As for your drift? Tighten up your polar alignment and guide. ;)


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#17 UncleHoot

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Posted 24 March 2019 - 08:30 AM

"I also watched Polaris in my camera as I rotated the axis, and it essentially remained stationary, even when I did an extreme digital zoom.  So, the polar alignment, in my opinion, is about as good as I can do it."

 

 

But Polaris isn't the centre point.  If it did not move, your alignment is BAD.  It should be moving in a circle around the NCP.

 

This could explain your problems.

I wondered if someone would misinterpret that.  I purposely centered Polaris in the polar scope so that I could rotate the RA access without it changing position.  This was to rule out the possibility that somehow my polar scope itself had become severely misaligned.


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#18 UncleHoot

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Posted 24 March 2019 - 08:40 AM

Then goto accuracy of the SynScan controller is inherently limited. The company's Celestron branded scopes did away with the 3-star alignment years and years ago.

 

However, by following the rules in the manual regarding alignment star choice, etc. they are sufficient. 

 

As for your drift? Tighten up your polar alignment and guide. wink.gif

I can’t get over the fact that the GoTo had been working perfectly for the last year.  I can only remember a couple of instances where the target was not centered perfectly.  I picked some better alignment stars last night, then tried to point to M81 and I couldn’t even find it on the camera screen.  I did eventually get it on screen and, once again, it tracked fairly well.

 

I may do more troubleshooting  with it this week, but I hate wasting great imaging opportunities.  :lol:



#19 DMRandall

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Posted 24 March 2019 - 10:21 AM

A couple of things to consider. 

 

1. The PA seems to be a recurring question.  Since you have a camera, have you looked at doing a drift alignment?  There are some good youtube tutorials on using PHD2 for drift alignment.  Or, maybe using sharpcap for polar alignment?  

 

2. One thing which may have been affected by temperature is your backlash adjustment.  I found that my Atlas Pro had quite a bit more backlash than I expected after a winter in my observatory.  I think the heating/cooling cycles were the most likely culprit.  http://www.astro-bab...ld/heq5-we1.htm shows you the adjustment process - which should be similar to your mount.  

 

3.  You mentioned you're on your wood deck, so at least it's not likely to sink, but of course ensure the tripod is level, the spreader is snugged up and the legs are stationary (e.g. lift them 1/2" and place them back down to make sure nothing is binding up).

 

Interested to see how it goes..

 

Dave



#20 emflocater

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Posted 24 March 2019 - 11:04 AM

 

I picked some better alignment stars last night, then tried to point to M81 and I couldn’t even find it on the camera screen.

I think I may know whats going on ...is it possible that M81 is moving faster than scientists thought! applause.gif

Cheers

Don


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#21 UncleHoot

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Posted 24 March 2019 - 11:52 PM

A couple of things to consider. 

 

1. The PA seems to be a recurring question.  Since you have a camera, have you looked at doing a drift alignment?  There are some good youtube tutorials on using PHD2 for drift alignment.  Or, maybe using sharpcap for polar alignment?  

 

2. One thing which may have been affected by temperature is your backlash adjustment.  I found that my Atlas Pro had quite a bit more backlash than I expected after a winter in my observatory.  I think the heating/cooling cycles were the most likely culprit.  http://www.astro-bab...ld/heq5-we1.htm shows you the adjustment process - which should be similar to your mount.  

 

3.  You mentioned you're on your wood deck, so at least it's not likely to sink, but of course ensure the tripod is level, the spreader is snugged up and the legs are stationary (e.g. lift them 1/2" and place them back down to make sure nothing is binding up).

 

Interested to see how it goes..

 

Dave

1. I have always had “pretty good” polar alignments.  I have considered doing a drift alignment, but to do it properly would take quite a bit of time, and pretty good has been good enough.

 

2.  I am going to play with the backlash adjustment at some point.  I never noticed much, if any, back lash before, and now it is quite noticeable.  I had thought the GoTo alignment process was supposed to compensate for it, but maybe it just isn’t.

 

3. I checked and rechecked all of that, scope on and off.

 

This week and possibly the next few weeks may present some of the best opportunities of the year, here in Michigan, so I hate to do too much fussing and troubleshooting.  Now that I know it’s tracking okay (it seems), I have relaxed a bit.

 

I managed to get my best M81 pic ever, while doing this troubleshooting, so I may as well share.  :)

M81

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#22 gnowellsct

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Posted 25 March 2019 - 12:01 AM

Well computers are known to get squirrely when the power supply is low.

 

You say you're out observing in the cold.  Maybe your power supply is old and cold and isn't delivering.  In winter conditions I need a big honking battery to keep things running.  The little batteries get cold and poof, everything is squirrely again.  

 

Greg N



#23 UncleHoot

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Posted 25 March 2019 - 07:44 AM

Well computers are known to get squirrely when the power supply is low.

 

You say you're out observing in the cold.  Maybe your power supply is old and cold and isn't delivering.  In winter conditions I need a big honking battery to keep things running.  The little batteries get cold and poof, everything is squirrely again.  

 

Greg N

I have ruled that out as well.  I did a fast slew (rate 9) with both DEC and RA simultaneously, and the voltage barely dropped (from 13.9 to 13.7 or 13.8).  It drops a little more when stopping, but it's still above 13V.  Problems don't seem to develop unless voltage drops somewhere below 12.3V, if I recall.

 

When I first got the mount, I quickly discovered what too little voltage will do.  I heard an ungodly squeal coming from the mount when slewing at high speed. I bought the TekPower TP350 and it has worked like a dream.  It may be overkill, but better over than under.  And the voltage is adjustable.  :)



#24 UncleHoot

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Posted 25 March 2019 - 02:53 PM

I believe my mount has a software backlash adjustment in the Synscan hand controller.  I'm going to mess around with that tonight.  If that helps, perhaps I will do a more permanent gear adjustment at some point, if needed.

 

Now that I think about it, the GoTo can't really adjust for backlash automatically.  It would have no way of knowing.  So if I make the software adjustment (and do a reasonable job), it will probably help the problem significantly.



#25 emflocater

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Posted 25 March 2019 - 06:14 PM

I believe my mount has a software backlash adjustment in the Synscan hand controller.  I'm going to mess around with that tonight.  If that helps, perhaps I will do a more permanent gear adjustment at some point, if needed.

 

Now that I think about it, the GoTo can't really adjust for backlash automatically.  It would have no way of knowing.  So if I make the software adjustment (and do a reasonable job), it will probably help the problem significantly.

Through all your posts I don't think you mentioned what scope you are using to photograph M81. So what scope are you using on the mount?

Cheers

Don




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