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CEM25p issues alignment issues and frustration

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#1 krenyi

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Posted 15 August 2019 - 10:38 PM

So I’m going to outline what I did and what is going wrong with each...

1. I polar align with the polar scope, around this time Polaris is around 10 o’clock position (iOptron style polar scope). So I align it to the best of ability.

2. I lock DEC and RA ALT/AZ control knobs as tight as I possibly could.

3. I do 2 star alignment. Vega, wayyyyyy off in both axis (RA and DEC), I can’t even find it on my camera.

4. So I thought my polar alignment is off. I return the mount to home position, check the polar scope, Polaris magically moved to 930 position and way in to the circle.

5. I repeat the polar alignment process, making sure the ALT/AZ axis can’t move

6. 2 star alignment again, still the same, Polaris Vega wayyyyyyy off.

7. Check polar alignment, Polaris moved to a totally different position again.

8. I check settings. Location and time are all corrects

Like I know Polaris should move over time, but it shouldn’t move 10+ degrees and not even moving along the circle in not even a minute right? What in the hell is going on????


Edited by krenyi, 15 August 2019 - 10:58 PM.


#2 rgsalinger

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Posted 15 August 2019 - 10:42 PM

The most likely problem is that you are doing the polar alignment using the DEC and the RA controls rather than the ALT and AZ controls. That would lead to precisely what you are seeing. Check carefully in the manual. If that's not it, then I'm not sure what you could be doing wrong.

Rgrds-Ross



#3 krenyi

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Posted 15 August 2019 - 10:55 PM

The most likely problem is that you are doing the polar alignment using the DEC and the RA controls rather than the ALT and AZ controls. That would lead to precisely what you are seeing. Check carefully in the manual. If that's not it, then I'm not sure what you could be doing wrong.

Rgrds-Ross

Okay, so I polar align with control knobs (pretty sure it's the ALT/AZ) through the polar scope and I do the 2 star alignment with the hand control (which moves DEC and RA). Is that not how you suppose to do it?



#4 scadvice

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Posted 15 August 2019 - 10:57 PM

Check your location coordinates. Day light savings off. Corrected local time and date. Finally that you have the gear tension  correct ...too tight can cause the motors to miscount steps. Recheck and reset "zero position". 



#5 scadvice

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Posted 15 August 2019 - 11:00 PM

Okay, so I polar align with control knobs (pretty sure it's the ALT/AZ) through the polar scope and I do the 2 star alignment with the hand control (which moves DEC and RA). Is that not how you suppose to do it?

yes, in your manual they are pointed out as the "Lat. Adj. Knob" and the "Azj Adj. Knob"  on Page 8 , 2.2


Edited by scadvice, 15 August 2019 - 11:05 PM.


#6 scadvice

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Posted 15 August 2019 - 11:04 PM

A little more info.

 

"Finally that you have the gear tension  correct ...too tight can cause the motors to miscount steps". Review page 17 fig. 14 of the manual the "Tension Adjusters" control the gear tension. Try backing off 1/4 turn.



#7 rgsalinger

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Posted 15 August 2019 - 11:05 PM

First, If daylight savings is incorrect then you will find that you are 15 degrees off in RA. Same with time zones each hours is 15 degrees off. It doesn't sound like that's what you are seeing. So that seems unlikely given what the OP has posted. 

 

If the OP is confident that the correct controls are being used,  then my next question is "What is the system resting on?" If Polaris is moving that fast in the polar scope then the entire mount must be moving. I can't see what else would explain a movement in the polar scope.

 

Improper gear tension will only cause the system to slew incorrectly, that error cannot result in the polar scope moving away from Polaris.

 

Rgrds-Ross



#8 krenyi

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Posted 15 August 2019 - 11:54 PM

First, If daylight savings is incorrect then you will find that you are 15 degrees off in RA. Same with time zones each hours is 15 degrees off. It doesn't sound like that's what you are seeing. So that seems unlikely given what the OP has posted. 

 

If the OP is confident that the correct controls are being used,  then my next question is "What is the system resting on?" If Polaris is moving that fast in the polar scope then the entire mount must be moving. I can't see what else would explain a movement in the polar scope.

 

Improper gear tension will only cause the system to slew incorrectly, that error cannot result in the polar scope moving away from Polaris.

 

Rgrds-Ross

The mount was in the middle of my yard, I couldn't even move the ALT/AZ with my hand when tightened. I have encountered this once before, I just skipped the alignment and used it like a tracking mount...



#9 Tom3

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Posted 16 August 2019 - 12:06 AM

Could the polar scope reticle be loose?  Do you have a finderscope, Telrad, red dot finder to see how far off you are?  How about trying a long focal length eyepiece instead of your camera.

 

Tom



#10 Chuckwagon

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Posted 16 August 2019 - 12:39 AM

Are you starting this process before the GPS has locked on?  I have noticed that if the GPS isn't locked, your time, DST and location setting will be off, even though they seem correct.  Wait until it beeps to let you know the GPS is locked, then go to settings and verify the time, location, and DST settings, hit enter and then start your aligning process.


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#11 Chuckwagon

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Posted 16 August 2019 - 01:33 AM

Also, are you talking about the "Polar Iterate Alignment" process in the hand controller, or the regular "goto" alignment process that has the 1 or 2 star, etc. alignment?  The "Polar Iterate Alignment" is a bust, and it'll mess up your zero position, so if it was that process, that's likely the problem.  Don't use it.  :)



#12 rgsalinger

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Posted 16 August 2019 - 01:39 AM

If, as the OP describes, Polaris is at substantially different positions within a 15 minute span then either the polar scope is moving or the ground is not solid under the system. I use a set of patio bricks when I image in my backyard. If I didn't do that it would never hold polar alignment. Even if the goto is way off (and we have no knowledge of his FOV at this point), if you don't move that alt and az controls Polaris is just going to slowly rotate in the polar scope.

 

Rgrds-Ross



#13 sg6

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Posted 16 August 2019 - 01:43 AM

So I’m going to outline what I did and what is going wrong with each...

1. I polar align with the polar scope, around this time Polaris is around 10 o’clock position (iOptron style polar scope). So I align it to the best of ability.

2. I lock DEC and RA ALT/AZ control knobs as tight as I possibly could.

3. I do 2 star alignment. Vega, wayyyyyy off in both axis (RA and DEC), I can’t even find it on my camera.

4. So I thought my polar alignment is off. I return the mount to home position, check the polar scope, Polaris magically moved to 930 position and way in to the circle.

5. I repeat the polar alignment process, making sure the ALT/AZ axis can’t move

6. 2 star alignment again, still the same, Polaris Vega wayyyyyyy off.

7. Check polar alignment, Polaris moved to a totally different position again.

8. I check settings. Location and time are all corrects

Like I know Polaris should move over time, but it shouldn’t move 10+ degrees and not even moving along the circle in not even a minute right? What in the hell is going on????

I am a little puzzled by point 4.

You do not alter the polar setting during use at all. The mount is polar aligned and then iy is not moved it remains fixed. You move the scope but not the mount alignment. There should be no need to return the mount to the "home position".it should never have moved from the polar alignment position.

 

So I have the impression that somewhere you have moved the scope by moving the core setting of the mount



#14 astronz59

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Posted 16 August 2019 - 01:54 AM

The polar alignment procedure using the polar scope assumes that the RA and Dec axes are orthogonal. Have you checked for cone error? This could be responsible for the Polaris 'drift' you are seeing.

 

You can check cone error by moving manually (using the slew controls) to any prominent star near the celestial equator and the meridian. Note the time and RA reading (with the telescope on the W side of the mount). Slew to the eastern side of the mount and center the same star again. Read time and RA. If the difference in the two RA readings minus 12 hours differs from the time interval between the two readings,the telescope is not at right angles to the Dec axis. If the difference is greater than the time interval then, the telescope E, the objective must be moved away from the mount (place a shim under front tube ring). Shim the rear tube ring if the difference is less than the time interval.



#15 Waldemar

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Posted 16 August 2019 - 10:54 AM

The mount was in the middle of my yard, I couldn't even move the ALT/AZ with my hand when tightened. I have encountered this once before, I just skipped the alignment and used it like a tracking mount...

As far as i know, all iOptron mounts have nylon washers under the azimuth as well as under the latitude adjustment bolt heads. Those washers tend to deform and not stay in place when the bolts are tightened after alignment and take the mount off alignment...

The way to get rid of that problem is to use stainless steel washers between the nylon washers and the mount, or get rid of the nylon washer totally and only use ss washers. Maybe that will help.


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#16 rgsalinger

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Posted 16 August 2019 - 01:58 PM

The OP's problem is not cone error. Cone error does not result in Polaris moving off it's spot. It results in bad goto's on one side even though they can be perfect on the other side of the sky. Waldemar is on the right track, something is moving. My own bet is that the system is set on grass but I have not seen a picture of the configuration to prove that's the problem here.

Rgrds-Ross



#17 mewmartigan

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Posted 16 August 2019 - 08:11 PM

I know spending more money isn't always the answer you want to hear but the iPolar may work great for you. You remove the polar scope, use iPolar and then you can even leave it up all night to see if your polar alignment has shifted.

 

When I had the CEM25p the polar alignment would occasionally shift during a goto but not to the extent you are describing. I assume I didn't crank the adjustment knobs and locks down hard enough. Either way, seeing the crosshair on the screen let me easily adjust after the goto. 

 

iPolar will also remove your cone error and ensure you are aligning on Polaris and not some other star.



#18 MaciekGroch

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Posted 17 August 2019 - 12:29 PM

Stupid question but : are you sure that you really saw Polaris, not aligned some other star? Fov of this polar scope is about 7deg. Try Sky Safari (or other program), create crosschair 7deg, flip it in both axis and compare with what You saw through polar scope.

 

 Other things :

1.

I am a little puzzled by point 4.

You do not alter the polar setting during use at all. The mount is polar aligned and then iy is not moved it remains fixed. You move the scope but not the mount alignment. There should be no need to return the mount to the "home position".it should never have moved from the polar alignment position.

 

So I have the impression that somewhere you have moved the scope by moving the core setting of the mount

He had to back to zero position to check actual position of the Polaris because polar scope dial rotates when Ra is rotating, so when hand controler shows actual position of the Polaris You have to compare it with polar scope dial in proper position.(zero position) 

 

2. Did You level the mount? Leveled mount =proper position of the polar scope dial (assuming that it is good centred in fabric) 

 

3. Did you SET the zero position in hand controler after polar aligment? 

Tip :clear aligment data before observation 

 

4. "I do 2 star alignment. Vega, wayyyyyy off in both axis (RA and DEC), I can’t even find it on my camera".   Vega was way of in both axis after you successfully did 2 star aligment? Or Vega was first star to align and you did not see Vega in your eyepiece? 

 

5. Did you tight the center rod knob after operating the azimuth knobs? 


Edited by MaciekGroch, 17 August 2019 - 01:08 PM.



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