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iOptron ZEQ25, initial impressions

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#751 DesertCrawler

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Posted 20 October 2013 - 11:48 AM

As an update, I removed the washers previously used to shim the RA tensioner spring, and instead installed a spring to augment the iOptron spring.

The spring I used is Serva Lite #71XAU. I purchased it from a local Ace Hardware. Here it is just for reference albeit incorrectly listed as an extension spring: http://www.amazon.co...r/dp/B000VYFKMI

I snipped a 13-14mm length off each end of the spring and placed one inside each of the RA and DEC axis tension springs. This seems to work well but have not star tested it.

#752 Bluejay08

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Posted 20 October 2013 - 12:26 PM

If the payload is well balanced, shouldn't the spring have minimum effect?

Jay

#753 tango13

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Posted 20 October 2013 - 01:45 PM

I want to like and recommend this mount without reservation. However, most people are probably not prepared to treat it like a kit, nor should they be expected to do so. For those willing and able to spend the time to get it working correctly, it can be a great instrument. It would appear that some combination of design and manufacturing process needs to be adjusted. Either way, iOptron need s to take care of those that shelled out nearly $1,000 for the mount yet remain unable to use it the way it was intended.

I most definitely second this.

#754 Hunlon

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Posted 20 October 2013 - 03:14 PM

If the payload is well balanced, shouldn't the spring have minimum effect?

Jay


The spring actually is quite critical. It is there to apply a force on the worm drive screw against the worm gear - too little force and the engagement is not complete, too much force and you risk RA over-current due to motor overload. The evidence points to iOptron supplying springs that are too weak. In my case I couldn't get the "play" out of the RA even when it was screwed right down. I measured the PE at 65 arc seconds P-P which really is quite poor. As an aside when I reported the figures to iOptron they replied that I should not fully screw down the tension, it may be just that they are working from a script having been burnt from their first batch.

I too have gone down the replacement spring route. The springs I have sourced are the Century C500 and C510. I have been able to do the static tests that Paul has described and get a trip point of 3 1/2 turns with both springs and about 2 turns with just the C510. The mount appears to be much tighter now but I have not been able to perform any empirical tests yet due to lack of stars. Due to the fact that I would have to screw out the tensioner further with both springs than with a single spring, I think I may just go with one C510 spring as it should provide the same results.

I agree with the sentiments voiced in this thread regarding the design of the mount - sadly I have to concur as well regarding the quality control.

Good luck to all and clear skies,
Hunlon.

#755 RandyC

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Posted 21 October 2013 - 08:40 AM

Mine worked out of the box. Yes, there was play in the RA axis and I was skeptical too. But when the motor boards started working, the play disappeared. Sometimes it takes a little time before it is totally gone and I am not sure what the firmware algorithm is. They have designed the system so there is protection of the motors. It doesn't necessarily disappear right away, only after some running or maybe after alignment. I have never found the play to interfere with goto accuracy or tracking. I am not sure what the exact algorithm is and maybe Ioptron would share. The only inaccuracy is after a meridian flip or spring slippage.

#756 DesertCrawler

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Posted 21 October 2013 - 07:38 PM

Mine worked out of the box. Yes, there was play in the RA axis and I was skeptical too. But when the motor boards started working, the play disappeared. Sometimes it takes a little time before it is totally gone and I am not sure what the firmware algorithm is. They have designed the system so there is protection of the motors. It doesn't necessarily disappear right away, only after some running or maybe after alignment. I have never found the play to interfere with goto accuracy or tracking. I am not sure what the exact algorithm is and maybe Ioptron would share. The only inaccuracy is after a meridian flip or spring slippage.


It sounds as though we are observing different symptoms. The issue that I and some others have or had experienced is quite clearly mechanical and not something firmware would impact one way or the other. It is good to hear yours is doing what it is supposed to do. After some tuning thankfully mine does as well.

A properly balanced payload on this mount should not induce any slippage of the gears. Excess force applied to a well balanced axis would be expected to induce slippage. That's where the tensioner comes in.

When my mount arrived, the slippage could be induced with very small amount of force. The tensioner had almost no effect on limiting the tolerance to imbalance. Play was severe with small or modest well balanced payload. The RA axis had so much slop that when disassembled, the motor assembly could be wiggled on its hinge easily over 1/8 of an inch with two fingers. The motor should not move at all in relation to the hinge, but rather should pivot on the hinge as limited by spring tension.

#757 Seanem44

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Posted 22 October 2013 - 06:34 AM

I just took mine out for a longer AP session two nights ago.

The only alteration to mine was adding electrical tape on the encoder caps.

I set it up, polar aligned, and aimed at M31. I set my D800's intervalometer for 30 2minute exposures, left it and went to watch TV. When I got back, I had 30 perfectly tracked exposures. No signs of trailing and M31 stayed in the exact place throughout all exposures.

I will caveat and say I believe mine is a more recent build, as I had purchased it in September and had a little wait time for it to come in.

No problems with my tension knobs. No slippage. Still have cross-talk every now and then, but while outside I can barely hear it.

I am happy with my choice of this instead of the AVX, which seems to have just as many issues. For me, the selling point is the polar alignment, which is by far the easiest I have ever seen.

#758 DesertCrawler

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Posted 22 October 2013 - 08:53 AM

I just took mine out for a longer AP session two nights ago.

The only alteration to mine was adding electrical tape on the encoder caps.

I set it up, polar aligned, and aimed at M31. I set my D800's intervalometer for 30 2minute exposures, left it and went to watch TV. When I got back, I had 30 perfectly tracked exposures. No signs of trailing and M31 stayed in the exact place throughout all exposures.

I will caveat and say I believe mine is a more recent build, as I had purchased it in September and had a little wait time for it to come in.

No problems with my tension knobs. No slippage. Still have cross-talk every now and then, but while outside I can barely hear it.

I am happy with my choice of this instead of the AVX, which seems to have just as many issues. For me, the selling point is the polar alignment, which is by far the easiest I have ever seen.


Had mine worked out of the box I would be saying the same thing. I am still happy with the mount, but there's a bit of an after taste, unfortunately.

I have wondered if there was a bad run, or if it took a few runs to sort out the issues. Mine was purchased at the end of May 2013 and was either the last of the previous shipment, or the first of a new shipment, it is not clear. I had presumed it was a newer one due to the shorter springs since earlier ones had a longer spring.

Either way, it should be good news to prospective buyers if recent versions are working without modification.

While I have not yet enjoyed your level of performance, I am satisfied with what I am getting and am now confident that it will improve. Part of my issue has been environment. Vehicles driving down the street cause movements the camera can see but the eye cannot.

So, the whole cross talk issue is interesting and perhaps another thread. Cross talk is when the electrical activity of one circuit has an unintended effect on another electrical circuit. My mount does not exhibit that behavior as far as I have seen so far. I do observe the mount dithering fairly frequently. When this happens there is a singing sound from the motors which can vary in intensity even if the mount is at rest. I wonder if this is what people have referred to as cross talk. I would expect true cross talk to manifest itself in erratic and unpredictable movement in one or more axis. Dithering may cause minute changes in position but only on those axis affected, which could be both concurrently. Bumping the position with the hand controller could make the dithering stop.

Closed loop servo systems can exhibit this issue. The iOptron support party line seems to be that all closed loop systems dither. This is not true. There are ways to eliminate dithering but that would require appropriate decisions to be made early in the design process, decisions that no doubt would increase the price of the mount.

I am used to the dithering noise and, since it does not impact tracking or slewing accuracy, I have decided not to worry about it. I would prefer the mount to be quiet, however.

Anyway, I am glad yours works for you. Hopefully this is a trend for what appears to be an otherwise solid design.

#759 Seanem44

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Posted 22 October 2013 - 09:12 AM

I guess it is what you refer to as dithering then. Sounds like electronic beeps, kind of like a dial up connection or something.

#760 ramasule

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Posted 22 October 2013 - 06:42 PM

I believe its from the loose caps on the encoder bouncing on the encoder shaft causing it to flutter.

Load the encoder.shaft with a spring, fill in some of the encoder cap with epoxy, shave some of the edges of the encoder cap for tighter fit, tape the encoder cap down hard.

All those options work if, pick your poison, I taped mine.

If street traffic vibrates your mount this is likely your problem, true crosstalk as you stated is due to induced emf on cables via pulsing of stepper motors. However he encoder bouncing simulates he same thing... almost.

#761 DesertCrawler

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Posted 22 October 2013 - 09:10 PM

I guess it is what you refer to as dithering then. Sounds like electronic beeps, kind of like a dial up connection or something.


Yes, that's it. This occurs when the sensor on the encoder cannot tell the difference between one interval and the next. It basically gets stuck between transitions and the controller gets confused. Besides occasional dithering, my mount has so far been quite silent during use.

#762 Seanem44

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Posted 23 October 2013 - 03:05 PM

I taped my endcaps a while back. While it didn't eradicate the noise I think it may have helped a tiny bit. I really can't tell because while I'm outside the ambient noise drowns the sounds out for the most part.

#763 iOptron

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Posted 23 October 2013 - 11:02 PM

The ZEQ25 mount uses springs to load the worm shaft onto the wheel (ring gear) in order to eliminate/minimize backlash and protecting the motors. Any excess force to rotate the wheel would push the worm backed off or disengaged. If the force is strong enough, a “slippage” or “gear jumping” would occur. This is the mechanism to protect the gear system. When a mount is at a perfect balanced state, there should be no force applied to the worm gear and therefore no slippage should ever happen at all.

It seems there were some confusions between a “play” (gear free move) and the normal worm retreat due to a external force, such as swing the CW shaft or wiggling the dovetail saddle. We’ve posted a file in iOptron Yahoo Group file section to explain how to determine if the movement of your mount/scope is a play or just simply the gear is forced to move. The file is also attached here.

CS!

iOptron

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#764 Bill McNeal

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Posted 23 October 2013 - 11:41 PM

Thank you for this document. It is greatly appreciated. The included pictures are very helpful.

#765 Bill McNeal

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Posted 24 October 2013 - 12:21 AM

Can you specify which is the "hinge locking screw" in item 7 and which is the "worm end caps" in item 8?

#766 iOptron

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Posted 24 October 2013 - 08:38 AM

There will be another file for play adjustment. Send a request to support@ioptron.com for a copy if you want to adjust the play. They are also mentioned in Paul's video.

iOptron

#767 DesertCrawler

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Posted 24 October 2013 - 08:59 AM

Good stuff. Thank you for the official explanation. It, along with Paul's instructional video, should go a long way to help those people having issues with these mounts.

My mount'S RA AXIS suffered from the descriptions in 7 and 8 referring to the attached document. Both the RA and DEC axis still have a little play from item 8 that I have yet to address, but it doesn't impact me enough to make me disassemble the mount again. Maybe this weekend.

#768 Astronewb

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Posted 24 October 2013 - 09:42 AM

Can you specify which is the "hinge locking screw" in item 7 and which is the "worm end caps" in item 8?


With the cover removed, and the belt, pulley and encoder motor removed, you can access the worm mesh, worm and hinge adjustment screws.

This is an image of the housing disassembled with annotations:

The worm end caps can be adjusted without disassembly, just with the cover removed.

You can use a small pocket screwdriver to nudge the brass worm nut tighter or looser.

Snug the brass worm nut up against the worm only enough to remove side to side play on the worm, do not over-tighten the brass nut.

In terms of force applied, imagine tightening it with your fingernail until play is removed.

Hope the image helps,

Paul

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#769 ramasule

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Posted 25 October 2013 - 11:01 PM

Paul how many times have you taken that damn thing apart now?

#770 gramaglia

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Posted 26 October 2013 - 04:23 AM

I don't know how many times Paul taken is mount apart but I just finished fine tuning number 7. It's working really well but still not as well as Pauls. Guess my mechanical skills are substantially worse than his. My max error is about 1/2 pixel which is about 6 arc seconds when guiding. Which is still amazingly good for an 800$ mount. But I still believe with more fine tuning I should be able to get it lower. In various test I ran when I couldn't image because of intermittent clouds, I noticed that the mount is extremely sensitive to balancing a couple of ounces off and the error pretty much doubles. Don't know if that's true for all equatorial mounts as this is my first one.

#771 boandpokey

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Posted 26 October 2013 - 07:00 AM

lost my RJ 11 cable in the dark. dumb question.. can I use any RJ 11 cable for the DEC port?w

#772 Astronewb

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Posted 26 October 2013 - 08:33 AM

lost my RJ 11 cable in the dark. dumb question.. can I use any RJ 11 cable for the DEC port?w


You can use any RJ11 cable, but the connectors have to be 'straight pinned'.

Ie, when holding the connectors side by side, with the locking tabs up, all the colors should match in both connectors from left to right.

You can get a RJ11 crimper and some RJ11 connectors at a local electronics store (Radio Shack)and do it yourself?

Using a normal RJ11 with reverse pinned connections will fry something....!

You can also e-mail iOptron support and purchase another cable (or two).

Best..Paul

#773 Astronewb

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Posted 26 October 2013 - 08:41 AM

I noticed that the mount is extremely sensitive to balancing a couple of ounces off and the error pretty much doubles. Don't know if that's true for all equatorial mounts as this is my first one.

That doesn't sound right? Do not balance perfectly, that will only cause the worm to bounce back and forth on the ring endlessly.

Always balance a little heavy in both axis. My mount, for imaging, likes to be ota nose heavy in DEC, and scope heavy in RA for imaging in most cases.

The imbalance keeps the worm in mesh against one side of the ring and will smooth out your guiding. Your ota becomes a 'damper' against any movement (wind) that would cause the worm to lose contact with the ring gear.

Of course, a re-balance is necessary after a meridian flip, to just the opposite.

Cheers...Paul

#774 Astronewb

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Posted 26 October 2013 - 08:44 AM

Paul how many times have you taken that damn thing apart now?


Hi, I haven't counted, but I can have both axes dis-assembled completely in about 20 minutes...:)

The mount is really quite simple, and really well-engineered.

Regards...Paul

#775 Seanem44

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Posted 26 October 2013 - 08:54 AM

Paul, you could probably start a semi lucrative side job tuning these things for people... Lol.

I can see it now, "I have an Astronewb modified ZEQ"






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