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Have I murdered my iOptron CEM25P?

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#1 fewayne

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Posted 17 May 2018 - 01:44 PM

Hoping Bob or another longtime iOptron user might chime in here. I have been struggling with getting KStars/Ekos working reliably with my mount. Sometimes it's just dandy, GOTO working perfectly. Other times, the software apparently gets some hallucination about where the mount is actually pointing, or where the target is, and attempts to get there by driving the RA axis right through the body of the mount. Usually I catch when this is happening, but more than once I've been remoting in and too far away to stop it from getting to some physical limit of travel -- snagged cable or some such -- upon which there's a godawful clacking/grinding noise.

 

Since I also am really struggling getting any kind of consistent guiding, I can't really assess for myself whether the mount is tracking and correcting as it should.

 

So I'm asking y'all: Is that enough to toast the CEM25's legendarily fragile gear train?

 

Thanks for your advice.



#2 jpbutler

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Posted 17 May 2018 - 02:13 PM

I have a cem60 and have been known to drive the mount into the tripod a few times, too.

My understanding is that it is the belts slipping and is not chewing up the gears.

Anyway, that is what I like to believe.

 

John



#3 Salty_snack

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Posted 17 May 2018 - 02:15 PM

Grinding noise isn’t a problem for this mount. The motors are not powerful enough to cam the worm gear if it’s fully engaged.

I can’t comment on the software as I have not used it.

You’ll have to describe your guiding issues in more detail. With a 15 pound load the worst I’ve seen on mine is 1.5 arc sec rms and that’s with horrifically bad seeing. On a really good night with good seeing it gets close to 0.5 arc sec rms which is probably close to the lower limit of my guidescope (0.3 pixels).

#4 mistateo

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Posted 17 May 2018 - 02:25 PM

Grinding noise isn’t a problem for this mount. The motors are not powerful enough to cam the worm gear if it’s fully engaged.

I can’t comment on the software as I have not used it.

You’ll have to describe your guiding issues in more detail. With a 15 pound load the worst I’ve seen on mine is 1.5 arc sec rms and that’s with horrifically bad seeing. On a really good night with good seeing it gets close to 0.5 arc sec rms which is probably close to the lower limit of my guidescope (0.3 pixels).

This is about as good as I get with the Atlas Pro and EQ6-R mounts (with twice the payload, but still).  Are your numbers pretty consistent with others who are using the CEM25P?  If so, I need to get one of these for a grab and go setup for camera only and my 80mm scope.



#5 bobzeq25

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Posted 17 May 2018 - 02:36 PM

Hoping Bob or another longtime iOptron user might chime in here. I have been struggling with getting KStars/Ekos working reliably with my mount. Sometimes it's just dandy, GOTO working perfectly. Other times, the software apparently gets some hallucination about where the mount is actually pointing, or where the target is, and attempts to get there by driving the RA axis right through the body of the mount. Usually I catch when this is happening, but more than once I've been remoting in and too far away to stop it from getting to some physical limit of travel -- snagged cable or some such -- upon which there's a godawful clacking/grinding noise.

 

Since I also am really struggling getting any kind of consistent guiding, I can't really assess for myself whether the mount is tracking and correcting as it should.

 

So I'm asking y'all: Is that enough to toast the CEM25's legendarily fragile gear train?

 

Thanks for your advice.

You stall the stepper motors before breaking anything.  Terrible noise, usually no damage if you're there to fix it.  Can't say what would happen to the motor if it went on for an hour.



#6 xiando

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Posted 17 May 2018 - 03:12 PM

If you want some level of "emergency" protection to over-driving a mount, you can always apply limit switches to cut power to the mount if things go too far. It's better than blowing a motor or otherwise damaging a mount.

 

 

FWIW, are you using the meridian limit feature? I made the mistake of disabling that feature to eek out a few more degrees past meridian and wound up having to purchase a new motor and control board when I dozed ... Needless to say, I turned it back on and leave it that way now.



#7 fewayne

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Posted 18 May 2018 - 12:34 PM

Oh, you guys flatter me, you really do. I appreciate the unstated assumption here that I know what the <bleep> I'm doing. Thank you for that!

 

No, meridian flip is not at issue here, but thanks for suggesting that, I'll be sure to check that setting. Since my best-available dark site is a state park that officially closes at 2300, imaging for that long is rarely an issue! What's happening is that when I use Ekos to GOTO an object, it often sends the mount to seemingly random, wrong places. The hand controller usually does a very good job; Ekos, only sometimes. No idea why. Doesn't seem to correlate with whether or not I do a plate-solve-and-sync, either. I would rather just run everything from my iPad, but maybe I should use the hand controller to get in the neighborhood, plate-solve, and then tell Ekos to fix the result.

 

And some of those journeys are apparently trying to go through upside-down (i.e., RA counterweight shaft pointing up) on the way. Hence the noises: The clacking/grinding from the mount, and the "RACKUM FRACKUM FRAGGING BRACKUM" sounds from the astronomer. Also jumping up and down, and arm-waving.

 

As for my guiding -- let me see if I misplaced a decimal point in my original post -- nope, I didn't mention the values. On this most recent evening I was initially hard-pressed to get RMS values under 15, I say again, one-five seconds of arc. I had the most beautiful little star-trails on my images. Well, the two I managed before my camera battery died, that is. (It was a beautiful and incredibly frustrating night.)

So yeah, that wasn't something needing tweaking, that was something fundamentally dinked. (Though "dinked" was not the word I used. Aloud. Several times. Curiously, on these little soirees I usually wind up with the whole park to myself after awhile. Darndest thing, but I digress.)

 

As it turned out, by powering everything down including the Raspberry Pi, firing back up, running PHD2 instead of Ekos's internal guider, and forcing a recalibration near the celestial equator, I was getting more like 1.5". For me that's a really good night, but I doubt it's the CEM25P that's at fault there.

For reference, meteoblue forecast 1.45" seeing at my location for that time, and the PHD2 Guiding Assistant's high-frequency star motion values were a little under that. So I eventually managed to get RMS values within shouting distance of what the seeing was probably running.

 

I also pinged iOptron about it, assuming that I'd hear from y'all long before they replied. As it happens, they responded immediately, and reassuringly, agreeing with Bob: The noise is just the stepper motor skipping steps, and it doesn't damage anything, at least for short periods. Whew!

 

Thanks again folks. 


Edited by fewayne, 18 May 2018 - 12:36 PM.


#8 the0phrastus

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Posted 22 May 2018 - 10:20 PM

Oh yeah, I've sent my gear into the mount a few times, with belts and gears making ugly noises. It hasn't affected things, but I have had to run out and hit zero on the keypad to stop the mount mid-slew.

 

I use INDI/Ekos/KStars with a Raspberry Pi3 for most of my narrowband imaging. Are you using Ekos to polar align? If so, after you're done, and before you slew anywhere, try clearing your alignment model in the telescope/mount tab as well as under plate solving/alignment. Just clear everything out of the list. It's just a guess, but I think the polar alignment function throws off the alignment model because it's plotting things so close to the meridian.  Another thing to try is to clear the alignment model in the mount, using the handset. If you're using Ekos to plate solve, you shouldn't need to do any aligning in the CEM25P itself. It may be confusing for Ekos or the mount to have competing alignment models stored and used?  I never had issues like this with my Orion Atlas EQ-G. I ended up getting the iOptron adapter for my Polemaster, and that's what I use now for polar alignment. One difference between the CEM25P and the Atlas is Ekos is passing commands through the iOptron handset, which is sort of a black box and may affect things. With the Orion Atlas, Ekos or EQMod are talking directly to the mount over serial. 

 

Let me know if this helps with the Goto issues. I was having similar problems, but I I changed a few steps in my setup process and I haven't had any problems for the last eight months or so.

 

Chris


Edited by the0phrastus, 22 May 2018 - 11:03 PM.

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#9 fewayne

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Posted 31 May 2018 - 04:08 PM

Thanks for your suggestions!

 

Yes, I am using Ekos for PA. I'll try clearing everything out as you suggest the next time I'm out. I actually don't know if the PA assistant in Ekos syncs the mount or not, it could work just by doing the math and displaying the "move star to here" reticle over the image. I don't know if I've even ever run the CEM25P handset's alignment procedures, but it would not surprise me if it had a model lurking in there somewhere!

 

I guess I'll add that to the routine -- align with the scope, do the Ekos PA assistant, clear all models and alignment data I can find, slew to (general vicinity) target, plate-solve, center target for real. I haven't tried the "Mount model" tool on the alignment tab, but I think that's the one you meant to clear anyway.

 

I have to say that I wish you could just enter a target on the alignment tab; if I search for one on the scheduler tab, then go to alignment and tell it to plate-solve and then slew to target, nothing useful happens. If I happen to have a FITS to give it to chew on, that works much better. Usually I wind up using the hand controller to do the actual slewing, but maybe if I've got the models cleared as you suggest I won't have to resort to that.


Edited by fewayne, 31 May 2018 - 04:08 PM.


#10 the0phrastus

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Posted 31 May 2018 - 07:31 PM

...

 

I have to say that I wish you could just enter a target on the alignment tab; if I search for one on the scheduler tab, then go to alignment and tell it to plate-solve and then slew to target, nothing useful happens. If I happen to have a FITS to give it to chew on, that works much better. Usually I wind up using the hand controller to do the actual slewing, but maybe if I've got the models cleared as you suggest I won't have to resort to that.

I have only used the Ekos scheduler a couple times, and I only load a FITS to solve if I'm going back to the same target to get more frames. I usually select a target in KStars, right-click, and tell the mount to slew there. Once you do that, go to the Align tab and hit the Capture & Solve button with Slew to Target selected. That's all you should need to do--Ekos will get your scope's position from KStars and start solving. 

 

Here are the ten or so steps I go through for an astro session. I've done this so much over the last couple years it takes me no more than ten minutes to get going. 

 

1. Set up mount, scope, camera, and other stuff. Connect it all. Power up.
2. Open KStars, Ekos, and start INDI for your mount, camera, focuser, etc.
3. Polar align - I usually start with an app on my phone called Polar Scope Align Pro, but there are a batch of these for iPhone and Android. What's nice about this app is it will show you exactly where Polaris should appear in the reticle when you look through the CEM25's polar scope. Use altitude and azimuth adjustments to move Polaris into the right place.
4. If I'm going to do long exposures--over 120 seconds, I will refine the polar alignment with the QHY Polemaster workflow.
5. Before I start or slew anywhere I usually take a couple shots with my primary camera and another couple with the guide camera, just to make sure everything's working, and to see where I am with focusing.
6. First slew and solve: I will usually pick a target--a bright star to the east. Browse for a star in KStars that's in the middle of the sky to the east, and right-click on it. This opens up a menu identifying the target, along with options your equipment provides. You should see CEM25 listed. Open the submenu under CEM25 and select "Slew".
7. Your mount should get your scope pointed somewhere near the target you selected in KStars.
8. Open the Align tab. Click the radio button next to Slew to Target, and press Capture & Solve. Ekos and KStars are working together so the target you selected will be brought in and solved.
9. Focus. I usually start with Capture to see how close or far I am from focus. If things are close I usually just let Ekos do all the work--with Auto Focus. Otherwise I will set the Step high (depends on your focuser) and then use the Focus In and Focus Out buttons to get close.
10. If I'm going start off targeting stuff east of the meridian I will kick off guiding now, just to let it calibrate and be ready when I slew to the first target I plan to capture.

 

11. Go back to KStars, drag the star field around and zoom in on your fist target, then start again at number 6. After that, it's time to capture some frames.

 

CEM25P Park/Home: I have never been able to get Park to work in Ekos (I believe this is iOptron's issue, because this command works fine with other mounts). Instead, when you're done for the night and you want to return the mount to Home, either go out and use the hand controller for the CEM25P, or bring up the INDI Control Panel from the Setup tab and click Goto Home (something like that). I think it's at the bottom on the Main Control tab or the Options tab.

 

Hope this helps!

 

Chris


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#11 fewayne

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Posted 01 June 2018 - 11:26 AM

Thanks Chris, this is perfect. I was already doing a lot of this stuff but you've cleared up some confusion and misconceptions that I didn't even know that I had. I have been using the handset's graphical depiction for PA but it's necessarily crude, I'll look into the apps.
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