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New iOptron IEQ45 pro arrived : point of view needed on vibration

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#1 tegea

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Posted 17 July 2017 - 04:41 PM

Hi,

 

I've been looking for a while to purchase a new mount for my Mewlon 250, and wanted to find one that would not be too heavy. The iOptron IEQ 45 pro seemed perfect in this regard, with an admissible payload of 20kg, as the mewlon fully equiped (diagonal, binoviewer; tube counterweight) weights around 15kg. I read a lot about this mount on the forum and decided to purchase one.

I mainly use my mewlon for planetary and lunar work (visual and images).

 

The mount arrived 2 weeks ago. It is beautiful and quite sturdy and pairs well with the Mewlon 250.

It is very easy to use and the goto works well as long as I perform some 3 stars alignment, so I overall like it a lot.

 

mewlon_250_1.jpg

 

But I have a problem that I can't solve : Whis moderate to high magnifications, (200, 300x) I observe a periodic pulse in the image at a frequency of 1.2Hz. The amplitude is quite low, but sufficient to soften the image, washing out very fine planetary details. This pulse is coupled with some sort of small ticks coming from the motors.

 

It is not a balancing issue, the scope is perfectly balanced in both RA (using the electronic balancing procedure with the HC) and DEC (done manually by adjusting the dovetail and using the Mewlon 250 counterweight).

 

I tried to add some pads under the tripod, but it changed nothing.

 

So, if some of you have the same mount as me, I would be interested to know if you noticed the same thing, and if you can hear those 1.2Hz ticks in the motors.

And finaly, what do you think can be done to solve that issue ?


Edited by tegea, 17 July 2017 - 04:45 PM.


#2 bobzeq25

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Posted 17 July 2017 - 04:55 PM

Are the ticks fairly loud?  If so, it's very likely the steppers slipping.  They do that, and I can't think of what else would.  Either load or something binding up.  When that happens on my CEM60 though (usually a cable snag) the mount just stops.  It's not slightly inaccurate.

 

Take the scope and the counterweight off.  Still ticking?  What about mounting one of your lighter scopes?

 

After those experiments, I'd email iOptron tech support.


Edited by bobzeq25, 17 July 2017 - 04:57 PM.


#3 tegea

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Posted 17 July 2017 - 05:04 PM

No, the ticks are very discreet, and yes it does the same with a small telescope (Sky 90, 3.5 kg). It does not affect the tracking accuracy.

 

I mailed iOptron one week ago and I'm waiting for their answer.



#4 fmeschia

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Posted 17 July 2017 - 05:22 PM

I don't see that kind of behavior with my 11-kg payload. But I noticed that you use an CW shaft extension, I wonder whether the problem may come from the higher moment of inertia that the solution entails (compared with just more weight on a shorter shaft).


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#5 msl615

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Posted 17 July 2017 - 05:29 PM

OK....that must be annoying and I was just about to write about the moment arm, when I saw the message above come in...I get some bothersome vibrations in the mount itself (Vixen systems), if a have the CWeights way to the outside as in your image. Anti-vibration pads on the ground don't impact this, as the vibration is coming from the mount.

 

Suggestion #1: Heavier CW mass, closer to the center. Remove the extension, if possible. If you don't have extra CWs right now, then pick up some Velco exercise weights, and attach them to the regular CW and get it closer on the shaft.

 

#2.  I  have had very good luck taking one of the Velcro weights and hanging it not below the tray, but rather hanging off of the CW about 4-5 inches. Something about the extra mass on a flexible hanger (neoprene, etc), seems to magically absorb vibrations. 

 

Your mileage will vary, but I for sure would move the weight inwards as a first step, and try these Velcro weights all over the mount. You may not be able to resolve the 1.2hz clicking without working with the OEM, but you may be able to minimize the impact. 



#6 tegea

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Posted 17 July 2017 - 05:54 PM

Yes you're right, I have the CW extension and this might have an influence. I will try tomorrow to move the CW closer to the mount. I have scratch weight as well that I can add on the shaft, and can hang my eyepiece bag under the tripod.

I'll give it a try and tell you.

#7 tegea

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Posted 18 July 2017 - 06:53 AM

For the ones among you who have an IEQ45 Pro : can you hear those 1.2Hz tiny ticks coming from the electronic box/motors when in tracking mode ? (Just put the mount in tracking mode, put you ear in contact with the black plastic RA electronic box and listen)



#8 rmollise

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Posted 18 July 2017 - 09:12 AM

For the ones among you who have an IEQ45 Pro : can you hear those 1.2Hz tiny ticks coming from the electronic box/motors when in tracking mode ? (Just put the mount in tracking mode, put you ear in contact with the black plastic RA electronic box and listen)

 

With stepper motors, sounds like this are quite normal. 



#9 tegea

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Posted 18 July 2017 - 09:36 AM

Well, the 1.2Hz frequency does not seem normal to me and I don't understand at what this frequency corresponds.

 

If I understand correctly the documentation, there is 1 micro step every 0.09 arcsec, and given that the sideral rotation speed is 15 arcsec/s, the step frequency while tracking is 15/0.09=167 Hz, not 1.2Hz.

 

Or am I completely wrong ?



#10 fmeschia

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Posted 18 July 2017 - 10:48 AM

Yes, 1.2 Hz would definitely not be the proper step frequency. If you do have only 1.2 steps/sec, you should clearly see objects wiggle forth and back in RA in an eyepiece, with an amplitude of 12 arcsec at the equator. Is that the amplitude of the pulse you see?



#11 tegea

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Posted 18 July 2017 - 11:44 AM

Oh no, the amplitude is under 2 arcsec



#12 rmollise

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Posted 18 July 2017 - 11:51 AM

Well, the 1.2Hz frequency does not seem normal to me and I don't understand at what this frequency corresponds.

 

If I understand correctly the documentation, there is 1 micro step every 0.09 arcsec, and given that the sideral rotation speed is 15 arcsec/s, the step frequency while tracking is 15/0.09=167 Hz, not 1.2Hz.

 

Or am I completely wrong ?

Well, if you don't think it is normal, best bet is to email iOptron and ask them.



#13 bobzeq25

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Posted 18 July 2017 - 02:06 PM

For the ones among you who have an IEQ45 Pro : can you hear those 1.2Hz tiny ticks coming from the electronic box/motors when in tracking mode ? (Just put the mount in tracking mode, put you ear in contact with the black plastic RA electronic box and listen)

For what it's worth.  If I put my ear right up to my CEM60 I hear a buzz, vaguely like a copying machine.  It warbles a bit regularly, maybe 1.5 HZ.  Not a discrete tick, just a rise and fall in volume.

 

I'm starting to wonder if the slight softening is something else like seeing.  Does it also happen at 1.2 Hz?  What happens if you turn tracking off?



#14 Midnight Dan

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Posted 18 July 2017 - 02:23 PM

I have an iEQ45 Pro and use it with a Celestron Edge 8 HD.  I've seen no such vibration and I've never noticed any ticking like you describe.  If you're sure you're well balanced, I'd definitely follow up with iOptron.

 

-Dan



#15 tegea

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Posted 18 July 2017 - 02:51 PM

When I turn the tracking off, the image gets suddenly stable.

It becomes jerky again when I put the tracking on : small jumps of the image at 1.2Hz..

 

I wrote to iOptron more one week ago, but still no answer.



#16 tegea

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Posted 18 July 2017 - 03:24 PM

Ok Dan, if you don't hear it on your ieq45, then I must have a problem with mine.

Bobzeq25, the noise you hear might have the same origin but sound differently because the mount is different

#17 gotak

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Posted 18 July 2017 - 11:17 PM

I have used the Ieq45 pro and a 3x barlow so 4500mm focal length without seeing this issue imaging.

 

I don't hear this sound out describe not from RA anyhow. The DEC when guiding will make a noise during the pulse. So I would ask how well polar aligned are you? Could this be a DEC tracking issue? Do you know if this wobble is in one of the axis or both? When you say 1 hertz or so this is in real time or is this just from the playback of the capture? Cause if it's play back of a AVI file it would run at what 30fps but your capture rate maybe a lot higher so the oscillation wouldn't be 1 hertz ish. 

 

One thing I found and you would see in my previous thread that this mount potentially needs some work. Both my RA and DEC worm was not well adjusted from smoothness of movement point of view from factory. And even now I have bad enough backlash in DEC to only be able to guide one direction.

 

Also, I found that my dec axis had some play and needed tightening up at the bottom where the counter weight shaft goes in. RA had some play but disappeared after worm mesh adjustments. The DEC worm had some lose end cap that let the worm move about inside the unit a bit and needed adjustments. And the belt tension needed adjusting too.

 

It would be a good idea to email iOptron right away to see what they suggest you try. I didn't find all the communication to be super enlightening but then again my issue isn't as big of a show stopper as your's. 


Edited by gotak, 18 July 2017 - 11:21 PM.


#18 astronz59

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Posted 19 July 2017 - 12:33 AM

You'll need to re-read the sections in the manual that discuss correcting for PE and backlash.Not required for visual use, but definitely factors to be considered when imaging. Telescope.gif fingertap.gif



#19 tegea

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Posted 19 July 2017 - 04:24 PM

Gotak : The polar alignment was correct but not excellent.

I checked again inside the house, and the ticks are emitted by both the RA and DEC axis, same noise, same frequency. I wouldn't have believed this, so thanks for your post !

So now, I don't know which axis is the source of the image jumps, abd it might be the DEC axis and not the RA... I have to wait until the clouds are gone to make another test under the stars.

 

I didn't make any aquisition with a camera, I can see the jumps with my own eyes at a magnification of 200/300x, and I counted the number of jumps during 1 minute to calculate the frequency. So, this is real time. I also counted the ticks and the frequency is exactly the same.

 

I also went through your threads and was thrilled with the problems you had... Seems like I'll have to follow the same way as you.

 

I'm waiting for iOptron's answer for more than one week now, I'll mail them again.

 

astronz59 : My vendor tweaked the PE and measured it under 8 arcsec, and I have nearly no backlash. I only do visual use, mainly planetary, and I also do some planetary imaging, but no DSO imaging. So I'm not concerned with PE and autoguiding. While imaging planets, I just do some manual guiding if I see that the planet apporaches the edge of the field of view of the camera. But I need to have no vibrations, or the sharpness of the image will be ruined.


Edited by tegea, 19 July 2017 - 04:25 PM.


#20 gotak

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Posted 19 July 2017 - 09:58 PM

I would suggest you take a video and share it with iOptron. I am surprised you haven't had an answer for a week. 

 

The video will help a lot as I find they sometimes seems to not get what you are saying in words but a picture or video usually does the trick.



#21 tegea

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Posted 25 July 2017 - 08:47 AM

Still cloudy here so couldn't test anything for the moment. The meteo should be better this week-end...

 

I received an answer from iOptron who tells me to make trials with more counter-weigths and a shorter shaft as fmeschia and msl615 suggested as well as tuning the tension of the belt which are good suggestions.




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