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iOptron CEM60 & HC Dead

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45 replies to this topic

#26 medderx

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Posted 24 March 2019 - 11:13 PM

In what direction is the error that causes the AO to run out of range?  Could it be due to polar alignment error?

 

If you are off 2 arcminutes in polar alignment, you can get 30" of accumulated error in 1 hour of time.  And that is very good polar alignment.

Both Ra and Dec, but Ra is usually the first to do it. My brain is breaking to figure the directions out, but objects move up and to the left in the frame no matter the side of the pier it is on. I think....

 

 

Not to mention king vs sidereal. 

Its on sidereal, I have been tempted to try king but my fov is fairly limited so I'm not sure how much of a difference it would make. 


Edited by medderx, 24 March 2019 - 11:13 PM.


#27 gotak

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Posted 25 March 2019 - 06:07 AM

The ioptron encoder mounts needs to be guided because of refraction.

You'd need a modeled mount to avoid that but then you'd be fighting the find the last source of flexure game. Yes some modeling can compensate for sagging of instrument etc but from what I have seen you still have to take fair bit of care to eliminate as much as you can, and cable management needs to be clean.

#28 DuncanM

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Posted 25 March 2019 - 12:25 PM

With my 9.25 the ao can correct up to almost exactly 30 arcseconds. It always reaches that withen an hour but more commonly a half hour. 

 

Yes incoders is an option Ihave been wanting and kinda regret not getting but an additional $1000 seemed like a lot at the time for a mount that should in theory be able to already peform well enough for my setup. 

 

Just to clarify, I'm not intending to trash the CEM60 because I like them a lot, it just seems like mine is a bit of a lemon. There is a point where you get fed up with things and just want to start from scratch.

 

That sounds like mirror shift. I measured the image shift on my 10in SCT at ~.47 arcsecs/min @F6.93 at an altitude of ~48 degrees. Guiding via a guidescope was spot on, but the SCT mirror is the limiting factor.


Edited by DuncanM, 25 March 2019 - 12:32 PM.


#29 rmollise

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Posted 25 March 2019 - 01:09 PM

A g11 is not exactly an upgrade.

Btw while the gm-1000 is good you should read what is involved if your plans is to image without guiding. It seems potentially another source of issues and frustration.

If I where you I'd just ship in the HC first. I am not sure what exactly happened to your HC or mount. Cause usually electronic don't partially break usually it's a binary working or completely not. Especially if you actually have a blown dc-dc convertor chip.

 

I'd say the G11 is certainly an upgrade. In build quality anyway.

 

Be that as it may, OP, if you want to sell the mount, it and its HC will need to be in working condition...



#30 gotak

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Posted 25 March 2019 - 01:15 PM

I'd say subjective quality.

#31 rmollise

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Posted 25 March 2019 - 03:31 PM

I'd say subjective quality.

I wouldn't say so at all. It's machined rather than cast, for starters. And given the posts you see here far less prone to electronic problems. There are a couple of CEM60 threads on that subject right now...



#32 medderx

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Posted 25 March 2019 - 06:19 PM

I'd say the G11 is certainly an upgrade. In build quality anyway.

 

Be that as it may, OP, if you want to sell the mount, it and its HC will need to be in working condition...

Yeah after these issues if I am to sell it I would of course send it in to be serviced unless for some reason someone wanted it as it is. 

 

I see the G11 as a sidestep in mounts but an upgrade for me. Its much higher quality but pretty basic on the electronics side which I'm fine with because maxim dl can take care of that.  

 

 

That sounds like mirror shift. I measured the image shift on my 10in SCT at ~.47 arcsecs/min @F6.93 at an altitude of ~48 degrees. Guiding via a guidescope was spot on, but the SCT mirror is the limiting factor.

I dont think it is, mostly because I have an EdgeHD so I have mirror locks but also because I am almost always imaging at the zenith and the scope does not change its angle that much by the time trees get in the way. 



#33 rmollise

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Posted 25 March 2019 - 06:33 PM

Yeah after these issues if I am to sell it I would of course send it in to be serviced unless for some reason someone wanted it as it is. 

 

I see the G11 as a sidestep in mounts but an upgrade for me. Its much higher quality but pretty basic on the electronics side which I'm fine with because maxim dl can take care of that.  

 

 

I dont think it is, mostly because I have an EdgeHD so I have mirror locks but also because I am almost always imaging at the zenith and the scope does not change its angle that much by the time trees get in the way. 

 

Much depends on your goals. If that is 10-hour Hubble palette exposures, an AP or a similarly expensive mount is the way to go.

 

Otherwise, the Losmandy is a good choice. The Gemini II is actually quite sophisticated with a color touch screen and the ability to interface to a PC with good old serial, USB, OR Ethernet connection (which works very well indeed and is my preference).

 

smile.gif


Edited by rmollise, 25 March 2019 - 06:33 PM.


#34 Michael Covington

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Posted 25 March 2019 - 06:40 PM

Yeah after these issues if I am to sell it I would of course send it in to be serviced unless for some reason someone wanted it as it is. 

 

I see the G11 as a sidestep in mounts but an upgrade for me. Its much higher quality but pretty basic on the electronics side which I'm fine with because maxim dl can take care of that.  

 

 

I dont think it is, mostly because I have an EdgeHD so I have mirror locks but also because I am almost always imaging at the zenith and the scope does not change its angle that much by the time trees get in the way. 

IIRC, near the zenith is almost always where flexure is worst, for any type of mount.

That includes mirror shift as well as other flexure.

 

Near the zenith, the angular rate of change is the same as anywhere else.  But near the zenith, the *direction* of the load changes completely, first pulling one way and then the other.


Edited by Michael Covington, 25 March 2019 - 06:42 PM.


#35 DuncanM

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Posted 25 March 2019 - 06:49 PM

 

 

 

I dont think it is, mostly because I have an EdgeHD so I have mirror locks but also because I am almost always imaging at the zenith and the scope does not change its angle that much by the time trees get in the way. 

All SCTs have mirror shift; they have to because the mirror sits on a flexible cushion to allow for thermal expansion. The mirror locks will reduce shift by locking the mirror cell but they cannot lock the actual mirror.

 

The way to test for this is to guide with a guidescope and take a series of subs and track the movement of the successive images.



#36 rmollise

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Posted 25 March 2019 - 07:09 PM

All SCTs have mirror shift; they have to because the mirror sits on a flexible cushion to allow for thermal expansion. The mirror locks will reduce shift by locking the mirror cell but they cannot lock the actual mirror.

 

The way to test for this is to guide with a guidescope and take a series of subs and track the movement of the successive images.

That is not the reason for mirror shift. The primary is not on any sort of "cushion." What causes mirror flop and focus shift is that the mirror rides on the baffle tube. With only one screw pushing and pulling the mirror forward and back, any lateral movement of the mirror on the baffle tube--and it doesn't take much--due to loose tolerances can cause both problems.

 

The mirror locks will prevent the primary from moving when the scope change attitude, but you will have to undo them for focusing--thus you'll get a little focus shift.


Edited by rmollise, 25 March 2019 - 07:09 PM.


#37 DuncanM

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Posted 25 March 2019 - 07:41 PM

That is not the reason for mirror shift. The primary is not on any sort of "cushion." What causes mirror flop and focus shift is that the mirror rides on the baffle tube. With only one screw pushing and pulling the mirror forward and back, any lateral movement of the mirror on the baffle tube--and it doesn't take much--due to loose tolerances can cause both problems.

 

The mirror locks will prevent the primary from moving when the scope change attitude, but you will have to undo them for focusing--thus you'll get a little focus shift.

If only that were true...but it isn't. The mirror sits in a cell but it is not rigidly attached to the cell and as I explained it cannot be rigidly attached because the cell has to provide for thermal expansion of the mirror and of the cell itself:

 

 There are lots of images of SCT mirror cells showing the method of attachment but apparently I'm not allowed to link to any of them.

 

Here's website showing an SCT mirror cell:

 

http://astroshed.com...aga/c11saga.htm



#38 rgsalinger

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Posted 25 March 2019 - 08:55 PM

I don't see why you can't link to photos or tutorials??? Maybe it's the case that there are two causes for mirrors to flop in an SCT design. Still the problem with them is that they flop and the only way to fix it is to lock down the mirrors. 

 

Getting back to the OP original post I always want to sell things when they break. I don't do that anymore as I figure I'm just as likely to get into worst problems by doing that. I had a terrible experience with a cooled OSC, it broke after 12 months! After having it repaired I got rid of it and got something "better". It wasn't, it was a very difficult camera to use which I only found out the hard way - after my 30 day return window had expired. So, unless it's a real upgrade I'd just bite the bullet and send it in. At least it's not a Paramount MX+. 

 

Rgrds-Ross



#39 DuncanM

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Posted 25 March 2019 - 08:59 PM

I don't see why you can't link to photos or tutorials??? Maybe it's the case that there are two causes for mirrors to flop in an SCT design. Still the problem with them is that they flop and the only way to fix it is to lock down the mirrors. 

 

Getting back to the OP original post I always want to see things when they break. I don't do that anymore as I figure I'm just as likely to get into worst problems by doing that. I had a terrible experience with a cooled OSC, it broke after 12 months! After having it repaired I got rid of it and got something "better". It wasn't, it was a very difficult camera to use which I only found out the hard way - after my 30 day return window had expired. So, unless it's a real upgrade I'd just bite the bullet and send it in. At least it's not a Paramount MX+. 

 

Rgrds-Ross

I'll try to to post this link again:

 

http://www.darkatmos...ic/C11_Project/ (it gave me some kind of"cannot link to this  image" error before)

 

and

Disassembly_13.jpg

 

and in the above photo you can see how the mirror sits on a flexible substrate atop the mirror cell. Locking the mirror cell will help but it will not eliminate mirror movement as Celestron states: 

 

"...Mirror support knobs hold the mirror in place and reduce image shift during imaging..." (my emphasis)

https://www.celestro...l-tube-assembly

 

I've had a front row seat watching a friend rebuild his RASA 11 to reduce mirror shift to minimal levels; locking the mirror via the mirror locks wasn't sufficient. He eventually came up with something along the lines in the first url, above.


Edited by DuncanM, 25 March 2019 - 09:15 PM.


#40 medderx

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Posted 26 March 2019 - 01:14 AM

I would classify that as flexure not flop, I also have a C8 so I am experienced with how drastic the differences are. I will also add that the tracking issues are still there when I am imaging the sun with my itty-bitty 80mm refactor. 

 

I can ask a moderator to change the thread title to "Mirror Flop Argument" if you wish

 

 

 

 

Much depends on your goals. If that is 10-hour Hubble palette exposures, an AP or a similarly expensive mount is the way to go.

 

Otherwise, the Losmandy is a good choice. The Gemini II is actually quite sophisticated with a color touch screen and the ability to interface to a PC with good old serial, USB, OR Ethernet connection (which works very well indeed and is my preference).

 

smile.gif

Yeah browsing around the new G11, Mach1 and JTW OGEM are the ones that I would want that I can afford right now. 



#41 rmollise

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Posted 26 March 2019 - 07:45 AM

If only that were true...but it isn't. The mirror sits in a cell but it is not rigidly attached to the cell and as I explained it cannot be rigidly attached because the cell has to provide for thermal expansion of the mirror and of the cell itself:

 

 There are lots of images of SCT mirror cells showing the method of attachment but apparently I'm not allowed to link to any of them.

 

Here's website showing an SCT mirror cell:

 

http://astroshed.com...aga/c11saga.htm

Nevertheless that is not the cause of mirror flop/focus shift. 

 

If that's your opinion however, well, rock on. wink.gif


Edited by rmollise, 26 March 2019 - 07:46 AM.


#42 medderx

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Posted 01 April 2019 - 07:58 AM

So because the mount now works after having firmware reinstalled, iOptron thinks the firmware crashed which in turn sent a power surge to the hand controller. 

 

For the time being I am just going to send the HC in to get fixed and see how the mount performs from there. 



#43 Michael Covington

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Posted 01 April 2019 - 08:41 AM

So because the mount now works after having firmware reinstalled, iOptron thinks the firmware crashed which in turn sent a power surge to the hand controller. 

 

For the time being I am just going to send the HC in to get fixed and see how the mount performs from there. 

How could a firmware failure send a damaging power surge to the hand controller?  Sounds like a strange way to do voltage regulation.


Edited by Michael Covington, 01 April 2019 - 08:44 AM.


#44 medderx

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Posted 01 April 2019 - 11:10 AM

How could a firmware failure send a damaging power surge to the hand controller?  Sounds like a strange way to do voltage regulation.

No clue, but I have no better ideas on how it fried itself. 

 

Will probably be sending in the whole mount for a check-up after an upcoming star party and after that will decide on keeping it or not. 


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#45 linxx966

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Posted 23 May 2020 - 05:36 AM

Blew mine CEM60 just now, RIP. frown.gif frown.gif

2,3 hours into imaging a nebula, mount stopped moving.

Bad smell on the DC power distribution input, power LED still up, no connection to PC.

Connected with hand controller but no luck either.



#46 DuncanM

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Posted 26 May 2020 - 02:26 PM

Blew mine CEM60 just now, RIP. frown.gif frown.gif

2,3 hours into imaging a nebula, mount stopped moving.

Bad smell on the DC power distribution input, power LED still up, no connection to PC.

Connected with hand controller but no luck either.

IIRC, you'll probably need a new circuit board - contact iOptron and descrbe the problem and they'll sell you the needed part. These are actually quite easy to install as I helped a friend with one.




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