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Losing PA during Imaging Session

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#1 MarinerDNA

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Posted 17 October 2020 - 09:01 PM

I have an EQ6-R Pro, six months old. Mounted on top is a 80mm refractor and DSLR. Until my guiding equipment arrives I've been imaging unguided. I first brought this issue up in the EQ6-R Pro Owners thread but got no takers. I'm feeling a bit panicked. This is an edited copy+paste:

 

Is it possible for the Altitude bolt(s) to slip? By now I've had 7+ successful nights of imaging in a row and I've never seen this happen.

 

Thursday night after slewing to my target (Heart Nebula) and starting the session, my first sub looked like I had taken a picture of multiple satellites. Every star was trailing REALLY bad. The first culprit is usually poor polar alignment? When I checked it, Polaris was nowhere near where I had left it. So I put it back where Synscannit wanted it, Redo the whole process and the same thing happens (bad trailing). I then figure it could be tracking related. So I reduce the exposure down from 180" to 30." This time my stars were eggs. I took 10 min to cool off and came back to check PA. Polaris had moved 1hr up from its last position. I decided to fix it, then check, repeat and take pictures.

 

Each of the pics (inside polar scope) I took was 10-20 minutes apart. Inbetween each pic I put Polaris back where its supposed to be and walked away. On the last attempt I tightened the Altitude bolt (non spring-loaded) so hard I needed a tool to back it off and Polaris STILL moved UP 10 minutes later!

 

-The mount was leveled.
- Tripod was settled
- Ground was stable
- I never bumped anything
- No cables are catching
- I've done 3-5 minutes unguided without issues thus far
- Mount is slewing fine in both RA and DEC
- Azimuth bolts were tighted down firm
- I SPUN RA 360 DEGREES and Polaris DID NOT move. The PA scope came great out of the box
- I did get one 30"sub looking ok within 5 minutes of re-doing a PA. Thats it.
-Neither alt bolt is "unwinding" (I think)

- My Altitude is 45 deg. To get Polaris in view I need to be at 49 deg. This is how it was out of the box

 

I noticed that after the altitude bolt (non spring-loaded) becomes flush with that "tab" that I can continue to turn it all the way around 3-4 times. I dont remember if it could do that before Thursday night - I don't believe so. When I do twist it tight, Polaris will shoot down the screen from 0-6. I tried testing PA using both methods - flush & those extra turns and everything inbetween. Same result. Polaris moves down considerably.

 

During my search I noticed the alt bolts are more of a problem on the EQ6 and that SW improved the issue in the Pro model. I did notice some grease on the end of the bolt and on the tab where it looks coagulated, also some circle gouges. Is that normal? Here's some pics:

 

https://www.flickr.c...teposted-public

 

https://www.flickr.c...eposted-public#

 

https://www.flickr.c...eposted-public/

 

https://www.flickr.c...eposted-public/

 

Thank you for reading my long post



#2 TelescopeGreg

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Posted 17 October 2020 - 09:30 PM

I'm a bit concerned about the "Polaris did not move" comment.  Can you described how you do your polar alignment?



#3 17.5Dob

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Posted 17 October 2020 - 10:18 PM

Trust me...the altitude bolt can't slip......!!!!!

 



#4 ICit2

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Posted 17 October 2020 - 10:37 PM

Admittedly, I've come close to losing my mind one time while imaging but never a PA. grin.gif

But seriously, you might want to check the tripod legs to see if they're securely locked into position.  Also, in light of all the other possibilities you've looked into, perhaps the slippage is occurring in the mount saddle or scope rings.  Yes, unlikely, but worth a look.


Edited by ICit2, 18 October 2020 - 12:42 PM.

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#5 MarinerDNA

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Posted 17 October 2020 - 10:38 PM

I'm a bit concerned about the "Polaris did not move" comment.  Can you described how you do your polar alignment?

This was to check alignment of the Polar Scope. If Polaris moves in a circle (or at all) then the scope needs to be aligned. It stayed still during my test.

 

After I get set up and leveled, I do a rough polar alignment. Then I extend the bar and add counterweight. Next I mount the imaging train and re-check PA to get it perfect according to the Synscaninit app. This method has worked great thus far; I've done it successfully 10+ times in a row.



#6 MarinerDNA

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Posted 17 October 2020 - 10:49 PM

Trust me...the altitude bolt can't slip......!!!!!

 

Thats what I'm afraid Skywatcher will say...and then I've got a mystery on my hands that I need to fix myself. 

 

There are two Alt bolts. The one that does the adjusting is spring-loaded. The other alt bolt is physically identical to the Azimuth bolts and keeps the adjustment you make in place. One of them has to be slipping, allowing the mount to creep down, thus making Polaris move upward in my scope. 

 

I can only see whats going on with the other alt bolt (see pictures). I'd have to take the mount apart to check the spring-loaded bolt which I'm not comfortable doing. I don't know if that grease - or whatever it is - was purposely added there on the tab and the end of the bolt. It's kind of hardened on the tab like rubber.


Edited by MarinerDNA, 17 October 2020 - 10:56 PM.


#7 endlessky

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Posted 18 October 2020 - 03:37 AM

Polaris will move, as time passes, in a circle, around the North Celestial Pole. So, if I understood correctly, I don't think judging its movement inside the Polar scope is an indication of a good polar alignment, or not.

 

If it indeed was the altitude bolt slipping, Polaris would move in a straight vertical line, away from the circle centered on the NCP. But if it moves around the circle (while staying on top of the circle itself) this is perfectly normal.

 

I am afraid that, if you are using a DSLR and no guiding, the only way to check how good your polar alignment is (and if it holds over time) is by adding a guiding system to your setup. I have been shooting "blind" for 9 months, with an old Skywatcher NEQ6 Pro, and I have been able to do up to 2 minutes, unguided, with a 300mm focal length lens. Polar alignment was always done "by eye", looking at my phone app and matching as best as I could Polaris location on the polar scope circle.

 

I recently added a guide-scope and a guide-camera and now, using PHD2 guiding assistant, I can actually see what my polar alignment error is - and fix it, if needed, using the various polar alignment tools PHD2 provides.



#8 MarinerDNA

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Posted 18 October 2020 - 04:01 AM

Polaris will move, as time passes, in a circle, around the North Celestial Pole. So, if I understood correctly, I don't think judging its movement inside the Polar scope is an indication of a good polar alignment, or not.

 

If it indeed was the altitude bolt slipping, Polaris would move in a straight vertical line, away from the circle centered on the NCP. But if it moves around the circle (while staying on top of the circle itself) this is perfectly normal.

 

I am afraid that, if you are using a DSLR and no guiding, the only way to check how good your polar alignment is (and if it holds over time) is by adding a guiding system to your setup. I have been shooting "blind" for 9 months, with an old Skywatcher NEQ6 Pro, and I have been able to do up to 2 minutes, unguided, with a 300mm focal length lens. Polar alignment was always done "by eye", looking at my phone app and matching as best as I could Polaris location on the polar scope circle.

 

I recently added a guide-scope and a guide-camera and now, using PHD2 guiding assistant, I can actually see what my polar alignment error is - and fix it, if needed, using the various polar alignment tools PHD2 provides.

Thanks for the reply. Polaris is indeed moving up vertically. One time during my 8 PA re-do's it moved well out of the circle almost in the upper left corner. Every hour or so Synscaninit would update me on Polaris' position and I'd make the correction, so I was aware of that as well.

 

After the 4th PA re-do I had given up on imaging and went into diagnosis mode. Because of the vertical movement I'm making the assumption its a bolt not setting/slipping or whatever. 

 

Yesterday I spent some time searching the forum on this issue and saw that this only happened to those with an older EQ6 and NEQ6. 3rd party vendors even make a special rail for when that tab gets too gouged. But nothing on the EQ6-R Pro with its improved bolts.



#9 endlessky

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Posted 18 October 2020 - 04:36 AM

Yesterday I spent some time searching the forum on this issue and saw that this only happened to those with an older EQ6 and NEQ6. 3rd party vendors even make a special rail for when that tab gets too gouged. But nothing on the EQ6-R Pro with its improved bolts.

I have an old NEQ6 Pro, that I bought used. However, I cannot really comment on the bolts not being able to do their job, since the previous owner did a lot of heavy modifications to the mount.

 

One of these was replacing the standard bolts the mount originally came with. He bore and threaded larger holes in the mount, and upped the size of the bolts for the altitude adjusments (both of them).

 

Another thing he did was changing the whole counterweight bar / bar holder part of the mount, making it bigger and sturdier.

 

Finally, he replaced the dual Vixen/Losmandy clamp with a Losmandy only, but oversized (200mm long) saddle.

 

I find the bolts very sturdy and able to hold the mount and all the weight on top of it in place. I never noticed Polaris slipping out of position. The pushing bolt (the one closer to the polar scope), though, is very hard to turn, even if I losen by quite a bit the bolt on the other side - and I always do my polar alignment without the telescope setup, so there's no additional weight to push up. I should probably take my mount apart and have a look, maybe the bolts need greasing.



#10 MarinerDNA

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Posted 18 October 2020 - 05:28 AM

I have an old NEQ6 Pro, that I bought used. However, I cannot really comment on the bolts not being able to do their job, since the previous owner did a lot of heavy modifications to the mount.

 

One of these was replacing the standard bolts the mount originally came with. He bore and threaded larger holes in the mount, and upped the size of the bolts for the altitude adjusments (both of them).

 

Another thing he did was changing the whole counterweight bar / bar holder part of the mount, making it bigger and sturdier.

 

Finally, he replaced the dual Vixen/Losmandy clamp with a Losmandy only, but oversized (200mm long) saddle.

 

I find the bolts very sturdy and able to hold the mount and all the weight on top of it in place. I never noticed Polaris slipping out of position. The pushing bolt (the one closer to the polar scope), though, is very hard to turn, even if I losen by quite a bit the bolt on the other side - and I always do my polar alignment without the telescope setup, so there's no additional weight to push up. I should probably take my mount apart and have a look, maybe the bolts need greasing.

Did you buy your mount recently? I remember an ad for a heavily modded NEQ6 not far from me (Portland, OR) 2-3 nonths ago. I almost pulled the trigger but the EQ6-R was only $200 more brand new at the time.



#11 endlessky

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Posted 18 October 2020 - 06:21 AM

Did you buy your mount recently? I remember an ad for a heavily modded NEQ6 not far from me (Portland, OR) 2-3 nonths ago. I almost pulled the trigger but the EQ6-R was only $200 more brand new at the time.

I bought it at the end of January. Also, in Italy... lol.gif



#12 WadeH237

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Posted 18 October 2020 - 09:11 AM

Every mount that I've used adjusts the altitude by using essentially a jack screw.  Due to the way that mechanical advantage works, I can't see any way that this could ever slip, even if you forget to tighten locking bolts.

 

I do have three thoughts that might help.

 

My first thought has been mentioned already:  Polaris moves.  It's not actually on the celestial pole.  Like every other star, it rotates around it once every 24 hours.  I get the sense from your description that you are seeing movement that is bigger than this, though.

 

My second thought is that it's important to finish up the altitude adjustment by turning the screw that raises the altitude.  Some mounts use a single jack screw to raise the altitude and rely on gravity to lower it when you loosen the jack screw.  They then generally have lock screws that clamp the altitude adjustment when you are done.  On a mount like this, settling is possible if you finish the adjustment by lowering the mount (especially if you don't tighten the lock screws - but even that is no guarantee if you finish adjustment by lowering the axis).  Some mounts use two jack screws, one to raise the altitude and another to lower it.  These mounts are secured by squeezing the contact point between the two jack screws.  On a mount like this, you would complete the adjustment by raising the mount to the final altitude and then snugging the other one, but not enough to force the altitude back down again.  I would expect the second type of adjustment to be more resilient against settling. 

 

Finally, my third thought is that, while I've never seen a properly adjusted altitude adjustment slip, I definitely have seen the entire setup shift when the ground underneath the tripod or pier settles.  The ground would need to be pretty soft for this to happen over a short period of time, but it is very common for this kind of thing to happen over, say, a week.  To mitigate this, I never put the tripod or pier feet on bare ground.  I always use something wide to use as pads underneath.  At home, I have paving stones set up for each of the feet.  When I image in the field, I use plywood squares as pads to prevent this.



#13 MarinerDNA

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Posted 18 October 2020 - 09:39 AM

Every mount that I've used adjusts the altitude by using essentially a jack screw.  Due to the way that mechanical advantage works, I can't see any way that this could ever slip, even if you forget to tighten locking bolts.

 

I do have three thoughts that might help.

 

My first thought has been mentioned already:  Polaris moves.  It's not actually on the celestial pole.  Like every other star, it rotates around it once every 24 hours.  I get the sense from your description that you are seeing movement that is bigger than this, though.

 

My second thought is that it's important to finish up the altitude adjustment by turning the screw that raises the altitude.  Some mounts use a single jack screw to raise the altitude and rely on gravity to lower it when you loosen the jack screw.  They then generally have lock screws that clamp the altitude adjustment when you are done.  On a mount like this, settling is possible if you finish the adjustment by lowering the mount (especially if you don't tighten the lock screws - but even that is no guarantee if you finish adjustment by lowering the axis).  Some mounts use two jack screws, one to raise the altitude and another to lower it.  These mounts are secured by squeezing the contact point between the two jack screws.  On a mount like this, you would complete the adjustment by raising the mount to the final altitude and then snugging the other one, but not enough to force the altitude back down again.  I would expect the second type of adjustment to be more resilient against settling. 

 

Finally, my third thought is that, while I've never seen a properly adjusted altitude adjustment slip, I definitely have seen the entire setup shift when the ground underneath the tripod or pier settles.  The ground would need to be pretty soft for this to happen over a short period of time, but it is very common for this kind of thing to happen over, say, a week.  To mitigate this, I never put the tripod or pier feet on bare ground.  I always use something wide to use as pads underneath.  At home, I have paving stones set up for each of the feet.  When I image in the field, I use plywood squares as pads to prevent this.

Thank you for these thoughts. 

 

The EQ6-R has one altitude bolt that both lowers and raises. The other bolt seems to be there to hold the position in place. As with the azimuth bolts, you jave to release one bolt to turn the other. I'll try doing azimuth before I use altitude; maybe that would help? Also I could assist the altitude by physically raising the extension bar to assist this action. This really alarmed me as PA until now took 5 min max. I was out there for hours testing different solutions. If this could happen to a regular EQ6/NEQ6 as people have stated in other threads, couldn't it also happen to the EQ6-R? I dont even know...

 

I use paving stones as well for support. I have another area I could move the mount to to eliminate variables.

 

I just ordered a polemaster (was going to eventually anyways). I figure I could verify all this in real time and move on from there. 



#14 sn2006gy

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Posted 18 October 2020 - 11:06 AM

There is a roller kit for the EQ mounts for those in high altitude that will keep your bolt firm/straight

 

https://youtu.be/hAAxkgWVxZ8



#15 csauer52

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Posted 18 October 2020 - 12:12 PM

Just out of curiosity, are you sure you're looking at Polaris? I can't imagine your tracking would be that bad if you were in the general vicinity of the NCP. 

 

Just a thought.....



#16 Domtbol

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Posted 18 October 2020 - 12:36 PM

Im sure you have already checked this but it has not been mentioned so far , are the tripod legs securley tightened especially the North one , or have they grease or oil on them  then there is a possibility that they will slide on the chrome surface , you might not see that slippage immediately on the level bubble , just a thought



#17 TelescopeGreg

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Posted 18 October 2020 - 05:50 PM

This was to check alignment of the Polar Scope. If Polaris moves in a circle (or at all) then the scope needs to be aligned. It stayed still during my test.

 

After I get set up and leveled, I do a rough polar alignment. Then I extend the bar and add counterweight. Next I mount the imaging train and re-check PA to get it perfect according to the Synscaninit app. This method has worked great thus far; I've done it successfully 10+ times in a row.

I don't have that mount, nor any knowledge of the Synscaninit app, so I'm trying to envision what you're describing and may be totally in the woods here...  Apologies if this is the case.

 

If you're looking through a polar alignment scope, Polaris should be on the big circle, not at the center.  Then, if you have the scope itself properly aligned to the mount, rotating the mount in RA should have Polaris remain on that circle.  But neither test determines that your mount is properly polar aligned.  That requires that the mount be at the right RA angle at the start, so that Polaris lands on the right place along that outer circle's circumference. 



#18 MarinerDNA

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Posted 18 October 2020 - 07:14 PM

Just out of curiosity, are you sure you're looking at Polaris? I can't imagine your tracking would be that bad if you were in the general vicinity of the NCP. 

 

Just a thought.....

I've got the ground marked with stepping stones. The closest star nearby is Alderamin? I can't imagine confusing this. Still, the thought did cross my mind to point of getting out my laser and confirming.

 

Can anyone confirm this? I know for viewing only, PA doesnt have to be perfect. If PA is being lost in the process of taking a sub I'd imagine some trailing would be present. Until now I haven't had this trouble...the only things different are my new modded DSLR (this was my 1st time with that camera modded) and this PA issue.


Edited by MarinerDNA, 18 October 2020 - 07:28 PM.


#19 MarinerDNA

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Posted 18 October 2020 - 07:18 PM

Im sure you have already checked this but it has not been mentioned so far , are the tripod legs securley tightened especially the North one , or have they grease or oil on them  then there is a possibility that they will slide on the chrome surface , you might not see that slippage immediately on the level bubble , just a thought

I wish it was this. I'll check again. Even if its not perfect weather I'm trying again tomorrow.



#20 MarinerDNA

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Posted 18 October 2020 - 07:23 PM

I don't have that mount, nor any knowledge of the Synscaninit app, so I'm trying to envision what you're describing and may be totally in the woods here...  Apologies if this is the case.

 

If you're looking through a polar alignment scope, Polaris should be on the big circle, not at the center.  Then, if you have the scope itself properly aligned to the mount, rotating the mount in RA should have Polaris remain on that circle.  But neither test determines that your mount is properly polar aligned.  That requires that the mount be at the right RA angle at the start, so that Polaris lands on the right place along that outer circle's circumference. 

Polaris should remain in place when I spin the RA, which is what I confirmed. When I start the PA proccess Polaris is always in view and close enough to the circle that alignment takes under 5 min. I would say the fastest I've done it is under 1 minute.



#21 TelescopeGreg

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Posted 18 October 2020 - 08:42 PM

Polaris should remain in place when I spin the RA, which is what I confirmed. When I start the PA proccess Polaris is always in view and close enough to the circle that alignment takes under 5 min. I would say the fastest I've done it is under 1 minute.

Having Polaris stay in place only means that the polar scope is aligned with the mount, not that the mount is properly aligned to the North Celestial Pole.  You can prove this by intentionally misaligning the mount and doing the same test.



#22 WadeH237

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Posted 18 October 2020 - 09:26 PM

The closest star nearby is Alderamin?

Kochab is the classic star to get confused with Polaris, particular in a polar alignment scope.

 

I would go so far as to say that there are two kinds of astrophotographers:  Those who've polar aligned on Kochab, and those who have not...yet.  There are probably more people (myself included) who are in the first group...



#23 17.5Dob

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Posted 18 October 2020 - 10:06 PM

Kochab is the classic star to get confused with Polaris, particular in a polar alignment scope.

 

I would go so far as to say that there are two kinds of astrophotographers:  Those who've polar aligned on Kochab, and those who have not...yet.  There are probably more people (myself included) who are in the first group...

+1..

 

One test shot lets you know you screwed up....even in 20"....

 




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