Rainer

As far as I know CEM 120 can not be retrofitted to CEM 120EC or EC2.

19 hours ago, Jkulin said:

Sorry Rainer, but you are wrong my 120EC is guiding at between 0.18 and 0.29RMS now, I think the issue you had was related to the EC2 and was exacerbated by poor dealer support in Mexico, not something I have experienced with UK dealers: -

Hi John,

No, I am not wrong and BTW

 

Quote

and was exacerbated by poor dealer support in Mexico,

there is no dealer of iOptron in Mexico so I have been dealing directly with the poor iOptron support in Woburn, Massachussets, USA.  !
 

and

Quote

... my 120EC is guiding at between 0.18 and 0.29RMS now ...

Good for you and consider yourself over all very Lucky. There are many cases of iOptron  CEM 120EC or EC2 mounts which do NOT work. So do not try to cover up the Sun with a finger.

You know the stories very well ...

have a nice day ...  👍

On 01/06/2020 at 16:10, Datalord said:

Wow, that's a lot of money tied in holding paper down. I really feel for you. The mounts are no good doing regular guided tracking?

Biggest problem is the newest firmware is introducing a periodic error with +-90" arcseconds and it can nor be guided out do I need to use an older firmware and that one does not correct the SDE of the encoders ... SDE = Sub-divisional error ... and iOptron does NOTHING !

Newest firmware dated 191120

Old firmware ( the slight drift in RA = horizontal is normal )

On 31/05/2020 at 13:09, Datalord said:

I should update this thread.

I managed to get myself talked into a GM1000 being the only sane choice, but then I looked at my budget and concluded that I probably shouldn't do anything at all. Until by chance a used GM2000 QCI + upgrade package + tripod for £6k, exactly my budget. So I'm waiting for delivery on that baby.

The GM2000 doesn't have encoders, but it has a 50kg payload and everything tells me it will perform great!

Intelligent decision. CEM 120EC and EC2 still are plagued with encoder problems and that is going on for more then a year. Ask me why I know it. I have two of these CEM 120EC2 paperweights ... and no money to get something decent but that is my goal for next year.Scrap the two CEM 120EC2 and get another reliable brand.

Hi,

A GoTo command with this mount will always use the MAX speed.

More then a year ago several owenrs of CEM 120XXX mounts suggested to iOptron to add a menu feature to set up this speed. No reaction from iOptron.

Hi,

I can not say anything to the size but as you mentioned CEM 120EC2 I would think it twice to take the EC2. If you decide to do it get a guarantee that it will work with EC2. I have two of them and It started all very nice but at full load it does not eprfomr as expected ... and iOptorn is doctoring with firmware since I have them. With encoders I would rate capacity down to maybe 80 to 90 lbs MAX! and not 115 as they say.

I got my mounts in April 2018 and since then I have tested for them 16 firmware versions in 20 months and still I do not see the Silver Lining on the horizon ... I am at the max load of 115 lbs and it just does not work out ...

I just wanted to warn you so you do not wlak the Road to Canossa as I am at the moment ...

Yes I was very enchanted but now I am disenchantent 🤔

regards Rainer

On 25/10/2019 at 01:28, Rusted said:

Many mounts have undersized wormwheels to avoid spoiling the styling or reducing the profit margin.
Lower tooth counts have larger gaps between the wormwheel "teeth" to provide increased backlash.

In mechanical theory, worms should never be jammed into the wormwheel to kill backlash.
There should always be some clearance to avoid high friction and wear.
It also assumes that perfection exists in wormwheel concentricity with the shafts and bearings.
Otherwise there will [inevitably] be loose arcs of rotation and tight arcs.
Under these circumstances an "uphill" drive bias may be all one can possibly hope for.

Interesting and OK I accept your point of view. We are talking heere of worm and worm wheel gears which most of the time have a speed of 1 revolution in 24 hours.

Backlash in our case is more annoying then any friction and wear we will have all over the time we use our mounts.

So as far as I know there are some " Premium " mount producers which do lap the worm against the worm wheel. They do not adjust the gear for having backlash. 🤔

I used to have two Losmandy G11 and had too adjust the worm gear at night after having adjusted it for Sun imaging and that is a total NO NO. So I made a custom floating worm with springs and since then I did not have to adjust them anymore. I also lapped my worm and worm wheel.

The newest mounts from any brand are now using spring loaded worm assemblies pushing against the worm wheel ¿ why ?

But OK, we can adjust our mounts as we think we need them, but my problem is now that I can not adjust my mount to have backlash 

Have a nice week 👍

1 hour ago, Rusted said:

To add to the confusion it is considered wise in imaging circles to have a slight imbalance which ensures the telescope must be constantly lifted "uphill."
This ensures that only one side of the teeth of the drive wormwheel remain in constant contact with the worm.
Were the telescopes perfectly balanced the wormwheel could rock between teeth where it meets the worm due to wind gusts.

Great explanation except the famous slight imbalance is only necessary for mounts with backlash. When you have a mount with no backlash then slight imbalance can even develop to be a problem.

19 hours ago, wornish said:

What magical physics is going on?

None. The motors do not have much to do when it is very well balanced. I do not say perfect as perfect balancing is nearly impossible.

It gets critical when you do auto guiding and need to move it fast for- and backward and there is where the Magic of the " Moment of Inertia " gets into our way.

When setting guide commands very often then the mount can get into a resonance state and you will never get it out of it due to the pendulum effect ...

And so we get now into the discussion of many more variables but this is not the main topic of this thread ...

3 hours ago, Kev M said:

Sorry to abuse your picture.....

 

I missed the first point you raised above, I was looking at the balance between the equipment & the counterweights, but forgot the equipment itself....

I am assuming that your equipment is balanced above and below the Blue line I have added.....

Mine has the guidescope off to one side and it is this that is dragging it down.

It will balance horizontal but when moved up or down will return there as the centre of gravity is no longer at the pivot point ( yes i googled that bit ).

With the guidescope mounted directly above the Main scope it stays at what ever angle it is placed at ( RA only ....still need to balance it for Dec, may need a longer dovetail )

I had the guidescope there so I could fit a widefield camera the other side...when I do that I may have to rebalance it again.

Thanks again...for helping a thicko  😳

I took some images of my other set up but it is the same game.

As you can see the heavier side e.g. the two Takahashi scopes are nearer to the center line then the AstroTech 8" RC

2 hours ago, Kev M said:

 

 

 

Sorry to abuse your picture.....

 

I missed the first point you raised above, I was looking at the balance between the equipment & the counterweights, but forgot the equipment itself....

I am assuming that your equipment is balanced above and below the Blue line I have added.....

Mine has the guidescope off to one side and it is this that is dragging it down.

It will balance horizontal but when moved up or down will return there as the centre of gravity is no longer at the pivot point ( yes i googled that bit ).

With the guidescope mounted directly above the Main scope it stays at what ever angle it is placed at ( RA only ....still need to balance it for Dec, may need a longer dovetail )

I had the guidescope there so I could fit a widefield camera the other side...when I do that I may have to rebalance it again.

Thanks again...for helping a thicko  😳

 

 

No Problem.

Quote

I am assuming that your equipment is balanced above and below the Blue line I have added.....

That is correct. And the balance there you achieve with the method below.

Sometimes it is easier to balance a side by side set up as you have the freedom to move the assembly left or right and so find the correct balance when the CW shaft is vertical.

Somewhere I recommended to make a simple side by side set up e.g.  turn the DEC saddle 90° and even if you only have on scope then you have the freedom of sliding the scope left or right and so get vertical balance ... That even gives you the freedom to have you accessories in the orientation you like best  ...

So you balance first with CW shaft horizontal. Then you put it vertical and move the scope left or right and then, I do it that way I balance the DEC axis.

Simple as that.

Many people say balancing side by side is a 3 axes balancing. Well yes, but a normal scope set up also needs that either by adding weights ( 3rd axis) or by rotating until the whole scope weight is 50/50 over the vertical axis e.g. CW shaft ...

Balancing means I have always 50/50 of the weight of each side of the rotation axis. RA has a rotation axis and DEC also has a rotation axis.

49 minutes ago, Kev M said:

That sounds ideal, I want to get mine balanced the same

This sounds like you do not get it balanced. Can you post some pics ?

And now that I am writing this yes it is possible that when you have balanced in horizontal and you put it in another angle that you setup could move to some side.

You can check this after having it balanced in horizontal and then put the whole set up in vertical position, If it stays there then you have it well balanced but if it starts to move to one side that means that you have an asymmetric weight distribution on the telescope side, which could be a finder scope, or a motor focuser, ot the filter wheel of the camera, etc. or whatever. if you see this then you have to add some weight on the opposite side to which it moves or rotate the scope in its rings, if possible, to get a symmetric weight ratio through the vertical line. Once you made that you will need to check balance in horizontal position again.

You can even have an asymmetric balan on the counterweight side just by putting the knobs for tightening not directly over the shaft but to one side or the other ... of course it depends on how well or easy the RA shaft rotates. If the mounts has ball nearings then this is easily measurable. If there ar no ball bearing then this can be a source of stiction and balancing gets difficult as the stiction can hold up some wight distribution.

50 minutes ago, Kev M said:

So at an angle of 45 degrees if you let it go it stays there and doesnt return to the horizontal ?

 

Yes that is correct. Once you have balanced in horizontal the Center of Gravity will remain the same for both sides ...

The length of the lever arm is equal to the position of the center of gravity and so in any position it will remain without moving. In the moment you have done it in real life then you will understand it.

6 minutes ago, Rainer said:

No, that is not correct as the center of gravity has to be the same ...

I have 54 kg of counterweights on my mounts but know that my equipment just weighs maybe 42 or 43 or 44 or 45 kg and it is perfectly balance out with 54 kg of counterweights ...

¿ why ? Very easy

54 kg counterweights at let me say at a Center of Gravity  of 35 cm will perfectly balance out 43 kg at ~ 44 cm Center of Gravity.

Lever arm law ... as I posted a link above

 

Look here at one of my mounts and yes that is most upper position of my counterweights as if the RA runs the most upper CW passes with a clearance of 1 mm from the mounts body. If I take off one of the 12 kg upper counterweights everything would be at the lower end.

29 minutes ago, Kev M said:

In my opinion the only way to get it to be balanced at any angle is for counter wieghts to be used that exactly match the wieght of the equipment and for these weights to be placed at the same distance as the centre of mass of the equipment.

No, that is not correct as the center of gravity has to be the same ...

I have 54 kg of counterweights on my mounts but know that my equipment just weighs maybe 42 or 43 or 44 or 45 kg and it is perfectly balance out with 54 kg of counterweights ...

¿ why ? Very easy

54 kg counterweights at let me say at a Center of Gravity  of 35 cm will perfectly balance out 43 kg at ~ 44 cm Center of Gravity.

Lever arm law ... as I posted a link above

On 21/10/2019 at 06:24, newbie alert said:

Not always just weight but focal length to consider

Here applies again the Moment of Inertia Law and less the weight itself of the telescope
 

18 hours ago, Stu said:

The counterweights don't count towards the load on the mount so that doesn't affect the decision. I believe it is to do with wanting to reduce the moment of inertia. A smaller weight further from the mount is more likely to suffer flex and vibration in the counterweight shaft, and take longer to settle down. General advice would be to have more weight closer to the axis of rotation. Some discussion on it here:

http://www.iceinspace.com.au/forum/archive/index.php/t-135463.html

Stu, that is correct and the only reason is Moment of Inertia. Some builders DO restrict the amounf ot Counterweights and Urban Myth more or less developed to the believing that the amount of counterweights is equal to the carrying capacity but that will never make you happy ...

The key word here is moment of inertia and let us make a simple calculation.

You balanced your mount with a 10 kg weight at 40 cm away from the RA rotation center.  This gives you then a factor of 400

Ok, you can also balance your mount using 2x 10kg weights at 20 cm away from the RA rotation center which gives you a factor of 400

https://en.wikipedia.org/wiki/Lever#targetText=This is the law of,lever amplifies the input force.

That is for balance.

Now Moment of inertia is calculated Mass x Radius² and that means for

case 1 = 10 x 40² = 10 x 1600 = 16,000 Moment of Inertia

case 2 = 20 x 20² = 20 x 400 = 8,000 Moment of Inertia

https://en.wikipedia.org/wiki/Moment_of_inertia

¿ Which case is easier to " change direction of movement " ? Like we do when autoguiding ...

23 hours ago, msacco said:

 

Thanks for the comment guys, I actually had a similar discussion in cloudynights, and EVERYONE was saying that the CEM60 is bad and that the G11 is much better.
Any opinions?

Yes, G11 is plagued with backlash and you will tinker after tinker month by month, as the temperature changes.  I used to own two G11 and 14 years ago I developed a floating worm system. The available floating worm system which is offered by Losmandy still does not cope with the problem as it should.

Now that I retired from my day job I did not want to continue with the daily tinkering and got two CEM 120. I know it is not CEM 60 but is the same technology ...

CEM 60 has no backlash as it has a floating worm.

12 hours ago, alan potts said:

They need to be charged with electricity for tricks like that Rainer.

Alan

Hi Alan,

Just hink about it as the Payload of a carrier is fixed. So would you carry Polystyrene for the same price as Steel ? Volume against weight ...

Does it no bother you when you transport a tree in your car or your mount that space is missing or left ?

🤣

No, I do not have a transportation company 🤔

3 hours ago, alan potts said:

the cost of shipping a Televue zoom from here to Finland 37.50, weighing in at 300g I would love to hear an explanation of that costing.

Hi Alan,

Thc ourier have a way to calculate wither by weght or volume. There is a Volume/Weight factor . If the weight is bigger then the volume then they charge by weight and if the volume is bigger then the weight they charge by volume.

1 hour ago, x6gas said:

As I say, Rainer, I haven't got as far as definitively eliminating user error but once I have I will indeed get in touch with iOptron support.  Sadly they weren't as helpful in my most recent communications with them as they had been in the past and I note that there does appear to have been an update to the main board and RA board at the end of April this year and I can't 100% recall if I have this version installed...

But otherwise, I completely agree and gave a lot of feedback on the firmware of the mount in the first months after release.

I can feel you pain as I have had it for the last 10 months with my two ( not only one) CEM 120EC2. I knew I was buying an unproved thing but OK, I have spent a lot of time and do not regret and now after 10 months I can say it is working more or less as expected, nothing will work perfectly even some say so but that is OFF TOPIC.

iOptron has been responsive but what [removed word] me off mostly was their dishonesty. I might be stupid but not yet stupid enough in order not to see what BS they sometimes were writing and that is what makes me angry.

On the other side there is no mount in this carrying class for that price including encoders (which now work) ... All similar products cost at least double and upwards ... and honestly I see no reason to buy that just for maybe a 5% improvement ? All have problems and that is proven ... OK I will finish here so souls33k3r doe snot need to say to stay on topic  🤣 🤣 🤣 🤣

9 hours ago, x6gas said:

I'm very interested in this thread...

I returned to imaging this year after a bit of a hiatus and my trusty CEM60-EC - which I have been very happy with and which pretty much delivered nice round stars - has been causing me problems too.  I wasn't sure if it was because the mount hadn't been used for a couple of years or if it was because I'd done a better job of polar alignment (the RA guiding isn't bad but it's significantly worse than the Dec, ruining the star shape).  However, I was just beginning to suspect that it was the firmware (I upgraded to the newest version when recommissioning the mount) but my new CEM40 arrived before I could properly test this and I've been playing with the new mount since...

I strongly suspect that the firmware upgrades have significantly improved unguided performance but caused interference with guiding.  I have older versions of the firmware archived so can revert and I will be checking to see what the outcome is.  I really don't know why iOptron have never implemented a firmware option to disable the encoder - that was a request pretty much from launch.

The CEM40 is a lovely bit of kit, by the way.  Nice looking thing (CNC machined, anodised ali), light, USB connectivity and it's delivering nice tight stars out of the box with default PHD2 settings albeit I've only tried it imaging at 450mm f/l so far.

¿ Have you reported you problems to iOptron ? The more people draw the attention of iOptron to this the faster they can react and make corrections on the firmware. Well at least that is what I saw with my problems with both of my CEM 120EC2 ...

Reporting it to you dealer is useless as the dealer does not write the firmware and perhaps what the dealer reports to iOptron could be only the half of it ... " Broken Phone " game ...

1 hour ago, souls33k3r said:

Can stay on topic please?

Sorry and deleted my OT answers 

😊

Take a look here

https://www.timeanddate.com/worldclock/

15 hours ago, ollypenrice said:

It's perfectly true, I promise. One of them has been plugged and played for 7 years, the other only about three.

Olly

My answer was OFF TOPIC