New mount suggestions

[RolandKol]

22 minutes ago, Jkulin said:

Hi Roland,

I would seriously doubt that DF have ever had a CEM60EC in for hypertuning, when I looked at your link they just said iOptron, maybe I missed something, and if I have then will stand corrected.

I never disabled anything with mine, there was never any need.

This is exactly what I wrote...

CEM60EC  is not in the list for Tuned mounts, but a simple CEM60 is... However, - not sure about the dates of their tests and tunes.... The link they shared in the top of the web, has data from 2014

Edited April 24, 2019 by RolandKol

[Jkulin]

2 hours ago, cotak said:

And there are people talking about issues with CEM120s.

Indeed as I have said there were some issues with the 120EC and these were resolved to useable levels with work still in progress, there were a couple of big issues with random slews and spikes in DEC, these were resolved and it's now down to iOptron to get the guiding even tighter which I am sure they will.

[RolandKol]

Just received a message on FB confirming, DF never had EC version of CEM60, but a simple CEM60 was tuned to reduce PE

Edited April 24, 2019 by RolandKol

[cotak]

1 hour ago, Hicks said:

When it comes to the CEM60 it was said that PPEC is (or should be) disabled when guiding. Seems to be a common suggestion with many mounts to avoid fighting. What about the CEM60-EC though? Are the corrections due to the encoder (RA only?) always applied? Or are they ignored when guiding or optionally disabled?

PPEC as implemented doesn't work with guiding on iOptron mounts period. What you'd see if the mount doing it's own thing and completely ignoring guide inputs. And its you ask them iOptron would say well why would you want to use both guiding and PPEC?

The EC on the other hand works like live PEC but when set to accept guide pulses it ignores the encoder for the duration of the guide pulses and executes the guiding instruction instead. This very simple implementation means under certain conditions if you try to guide too aggressively, you end up seeing oscillation as the two systems fight.

Edited April 24, 2019 by cotak

[vlaiv]

28 minutes ago, cotak said:

PPEC as implemented doesn't work with guiding on iOptron mounts period. What you'd see if the mount doing it's own thing and completely ignoring guide inputs. And its you ask them iOptron would say well why would you want to use both guiding and PPEC?

The EC on the other hand works like live PEC but when set to accept guide pulses it ignores the encoder for the duration of the guide pulses and executes the guiding instruction instead. This very simple implementation means under certain conditions if you try to guide too aggressively, you end up seeing oscillation as the two systems fight.

I'm not following the argument here.

In my mind both PEC/PPEC and encoders work together with guiding rather than "fighting" each other. I'm aware that you are only quoting what you've heard before, and even directly from iOptron, but I would argue that if it is indeed the case - their system is somehow flawed.

PEC/PPEC will correct some major worm period cycles. What is left is error that is not harmonic of worm period, but there is still error left. PEC does not know anything about guiding - it just alters "mechanics" of the mount, or rather alters periodic error signature. For all intents and purposes you can either view it as variable speed of tracking, or constant speed of tracking in "variable time" (makes no difference).

Guide pulses offset current position, what ever that may be. Those two can be superimposed on top of each other and I just fail to see how would they end up "fighting".

With encoders, a lot depends on their resolution. They are in fact very good "guiding" system where mount is not guided on actual star, but it's rather guided where it supposed to be mechanically. One still needs to guide for other factors, like mentioned above.

Encoders should make tracking smooth if implemented properly - if they have enough resolution and if underlying mechanics of the mount is smooth as is. They have advantage over regular guiding because seeing and wind and other things that impact regular guiding don't have effect on it.

I also wonder if difference in performance is significant between regular CEM60 and CEM60EC. As far as I know, CEM60EC has encoder only on RA? But still DEC guiding with added seeing is often as low as 0.3"?

Whole thing with PPEC being turned off when guiding is very confusing.

For a moment I was also looking at CEM60 as an upgrade over my HEQ5. Now I'm not sure any more, I might avoid doing multiple upgrades and just wait until I can afford Mesu 200.

[DaveS]

3 hours ago, pete_l said:

ISTM that the RMS accuracy of the encoders will easily outperform the variation in star position due to seeing. The encoders should also correct for things like cable drag on the mount, too.

The effect of atmospheric refraction won't be corrected by encoders. We are told that +/- 45° from the zenith, this refraction is about 1 arc-min. as a worst case. So starting with an object 45° in the east and imaging until it gets to 45° west, that comes to 120 arc-sec movement from the theoretical position in 6 hours of imaging. On average, 1 arc-sec per 3 minutes of exposure. Though at the zenith there is none and it increases as the object is lower in the sky. Down to about 5 arc-min at the lowest practical limit for imaging. So if you rely on encoders for tracking, even with a perfect PA, you will still see some elongation if you take multi-minute exposures and target objects that are lower in the sky.

 

I think I've just talked myself out of buying a mount with encoders. How did that happen? ?

Which is where ASA score with their DDM mounts. In addition to a whole sky model (Which can be as many as 120 points) the mount will run and solve a local model (They call it MLPT) along the track of the imaging run. I've seen an uncorrected error of 3-5' reduced to essentially 0" over a 2 hour period. No guiding needed even for 600 sec subs. And no problem with wind gusts or losing the guide star either, with 0.02" ticks and 100Hz feedback gusts never get the chance to create problems. The MLPT takes less time than PHD2 takes to calibrate.

[cotak]

2 hours ago, souls33k3r said:

Yes guiding will never be out of the equation and it was never going to be in the first but even so if the mount can achieve those very low RMS values with the EC version, it should really make a hell of a difference. The only question is, are encoders going to be up for the job with a heavy payload (20kgs) at higher FL and 10 minute subs at least with near perfect pin point stars?

So you have the CEM60 on a pier or on a tripod? Because i think one way of (so far that i have seen) to get good RMS values from any mount is to have it on a pier (which by the way mine will be going up during this summer). I can stretch my limit but it will be a stretch if that is i am completely happy with it in the long run and it just performs as is. @Jkulin mentioned this as well and that has sit down well with me is that there has hardly been a reported case (in my knowledge) that someone had to send in their iOptron mount  (especially the CEM60's) for hypertuning so maybe it doesn't require any?

It's on a pier. The pier is the only way I got the ieq45 Pro down to 0.38 RMS on RA one very good seeing night, or was the right temp for the mount to operate in the sweet spot?

My pier is a 8 inch 36 inch tall skyshed pier bolted onto a 24 inch diameter concrete pillar sunk 4 feet into the ground, and filled with sand as recommended. 

[cotak]

26 minutes ago, vlaiv said:

I'm not following the argument here.

In my mind both PEC/PPEC and encoders work together with guiding rather than "fighting" each other. I'm aware that you are only quoting what you've heard before, and even directly from iOptron, but I would argue that if it is indeed the case - their system is somehow flawed.

PEC/PPEC will correct some major worm period cycles. What is left is error that is not harmonic of worm period, but there is still error left. PEC does not know anything about guiding - it just alters "mechanics" of the mount, or rather alters periodic error signature. For all intents and purposes you can either view it as variable speed of tracking, or constant speed of tracking in "variable time" (makes no difference).

Guide pulses offset current position, what ever that may be. Those two can be superimposed on top of each other and I just fail to see how would they end up "fighting".

With encoders, a lot depends on their resolution. They are in fact very good "guiding" system where mount is not guided on actual star, but it's rather guided where it supposed to be mechanically. One still needs to guide for other factors, like mentioned above.

Encoders should make tracking smooth if implemented properly - if they have enough resolution and if underlying mechanics of the mount is smooth as is. They have advantage over regular guiding because seeing and wind and other things that impact regular guiding don't have effect on it.

I also wonder if difference in performance is significant between regular CEM60 and CEM60EC. As far as I know, CEM60EC has encoder only on RA? But still DEC guiding with added seeing is often as low as 0.3"?

Whole thing with PPEC being turned off when guiding is very confusing.

For a moment I was also looking at CEM60 as an upgrade over my HEQ5. Now I'm not sure any more, I might avoid doing multiple upgrades and just wait until I can afford Mesu 200.

It's not what iOptron said. It's what I have seen. And if you ask their support initially they seem very unfamiliar with the reaction, when you ask again they'll say there's no reason to want to use PPEC and guiding together. It's true of the ieq45 pro and cem60 which basically uses the same electronics. 

The encoders on the other hand operates by doing what the guider asks for and ignoring the encoders. It's different from PPEC implementation for iOptron.

Now what iOptron says about PPEC vs guiding is not that far to left field. The non-EC mounts still have a +/-5" PE spec and the mounts guides quite well so with seeing induced star motion and flexure etc, I do see why PPEC is of limited value. 

I did consider mesu as well but it would cost 2x the CEM60EC, and I would not be able to max it out because in my 6x6 ROR there's no room for larger OTAs that need such payload ratings. And there's zero percent chance of being able to rebuilt for a larger ROR as the planning mistress already thinks the ROR looks like a chicken coop :P.

Edited April 24, 2019 by cotak

[Rainer]

1 hour ago, cotak said:

but when set to accept guide pulses it ignores the encoder for the duration of the guide pulses

Hi cotak,

This has not been denied nor confirmed by iOptron. I did ask and they just keep silent about it ...

¿ from where did you get the information or is it based on an ancient post in Cloudy Nights forum ?

¿ or is it an assumption from your side ?

Sorry, but I think it is time to put down facts and not guessing or assumptions or I have heard from somebody ...

regards Rainer

[souls33k3r]

As luck would have it, there's a delay in CEM60 family mount production ? 

As an impulse buy, i could've gone for a Mesu 200 but then that's out of stock as well ?

Is the universe trying to tell me something? ?

[RolandKol]

yep... it tells,

you should be happy with this one!

[RolandKol]

P.S.

and MESU are not out of stock... There are none of them at all.

Mesu 200 Ver2 is at the final stage of development at the moment and no old versions are produced

So... No one yet knows the date of the new release

Edited April 25, 2019 by RolandKol

[souls33k3r]

Just now, RolandKol said:

P.S.

and MESU are not out of stock... There are none of them at all.

Mesu 200 Ver2 is at the final stage of development at the moment and no old versions are produced

So... No one yet knows the date of a new release

Yeah i've been following the MKII thread and have also heard that the pricing is going to be the same which means Mesu MK1 mounts might be on sale very soon ?

[fwm891]

3 hours ago, souls33k3r said:

As luck would have it, there's a delay in CEM60 family mount production ? 

Well I for one am not happy about the iOptron CEM60 problems - been waiting 6-7 weeks now. My iEQ45 Pro guided extremely well whether I used a separate guide scope or OAG, it's only that I want to put a heavier scope on a mount and tandem mount two smaller scopes that I'm going for the CEM60. I've seen a friends results directly with his CEM60, OAG guided with a 9.25" Edge HD on board and the results are superb - one reason I hit the buy but with FLO for a CEM60 - come on iOptron fix it quick.

Seems TS have the EC version in stock...

Edited April 25, 2019 by fwm891
text added

[souls33k3r]

48 minutes ago, fwm891 said:

Well I for one am not happy about the iOptron CEM60 problems - been waiting 6-7 weeks now. My iEQ45 Pro guided extremely well whether I used a separate guide scope or OAG, it's only that I want to put a heavier scope on a mount and tandem mount two smaller scopes that I'm going for the CEM60. I've seen a friends results directly with his CEM60, OAG guided with a 9.25" Edge HD on board and the results are superb - one reason I hit the buy but with FLO for a CEM60 - come on iOptron fix it quick.

Seems TS have the EC version in stock...

That's exactly what's making me go towards the iOptron route.

But like i also said, if there was a second hand Mesu or a smaller version of Mesu (even in the pipeline) i would've gone for it straight away. Tried to call Modern Astronomy to find out but their phones are constantly busy.

[Rainer]

1 hour ago, fwm891 said:

Well I for one am not happy about the iOptron CEM60 problems - been waiting 6-7 weeks now.

Hi,

What problem do you mean ? Electrical, Electronic or mechanical problems ...

... or waiting time until delivery ?

If it is waiting time, then well that means something and interesting that people having bought a iOptron get upset about waiting time ...

Take it as a good sign because that means iOptron is not a mass produced product anymore ? or is it ?

... but there are also people who are very proud for waiting a year or more after buying a certain mount brand ... Do the Bells ring ? ?

SARCASM OFF

a bit of fun must be ...

Have a nice day

Rainer

[Hicks]

I think this thread has left me even more unsure about whether the extra cost of the CEM60-EC is worth it when guiding. I've gone from planning to get the CEM60 to getting the CEM6-CE to no longer being sure which Interesting discussions though.

Edited April 25, 2019 by Hicks

[souls33k3r]

8 minutes ago, Hicks said:

I think this thread has left me even more unsure about whether the extra cost of the CEM60-EC is worth it when guiding. I've gone from planning to get the CEM60 to getting the CEM6-CE to no longer being sure which Interesting discussions though.

I'd say, soak in all the information provided within this thread and then see what people's experience has been. So far i'm only hearing positive things so it shouldn't leave you in any doubt The other thing is, there is no other mount within this price point that can do all of this. The next step down from CEM60 or the EC version is the EQ6-R which don't get me wrong is a good mount but then it's got the Skywatcher badge on it which comes with it's own set of issues.

[Rainer]

24 minutes ago, Hicks said:

I think this thread has left me even more unsure about whether the extra cost of the CEM60-EC is worth it when guiding. I've gone from planning to get the CEM60 to getting the CEM6-CE to no longer being sure which Interesting discussions though.

Hi Hicks,

I understand it but main reason for people reluctant to understand the advantage of an encoder is mainly because of the additional price for them and other people who do not have it can not understand the advantage and that is why they say " OH, if you are going to guide anyway, save the money " OK, yes but I think I have written my fingers wound trying to explain the advantage of encoders ... but looks like nobody understands it or do not read it ? ...

Again ... see my message posted yesterday at 10:16 Mexican time

Quote

With encoder you mainly correct for drift and atmospheric refraction over a long period and perhaps the one or other sum up of seeing and a bit of rest PE. In reality it is not PE but it is more a summing up of different error and that is what you guide out from time to time but mostly drift and atmospheric refraction.

Without encoders you add the PE for guiding out and that is compared to drift and Atmospheric refraction a quick changing error whereas drift and atmospheric refraction are a slow changing error and are constantly moving only in one direction. PE is moving backwards and forwards and even can have additional peaks or valleys overlaid over the sinusoidal curve.

 

[souls33k3r]

1 minute ago, Rainer said:

Hi Hicks,

I understand it but main reason for people reluctant to understand the advantage of an encoder is mainly because of the additional price for them and other people who do not have it can not understand the advantage and that is why they say " OH, if you are going to guide anyway, save the money " OK, yes but I think I have written my fingers wound trying to explain the advantage of encoders ... but looks like nobody understands it or do not read it ? ...

Again ... see my message posted yesterday at 10:16 Mexican time

 

I for one am totally seeing the benefit for it Rainer

[RolandKol]

I am completely sure EC is the way forward from NEQ6... But I will make it even worse...

CEM6EC or CEM120 non EC  ????

Edited April 25, 2019 by RolandKol

[Rainer]

18 minutes ago, RolandKol said:

CEM6EC or CEM120 non EC  ????

Hi Roland,

That is a budget problem right ? as usual ... 

CEM 120EC2 is the way to go ? unless you will never fill the mounts capacity but on the other side one can be never over mounted ...

[Hicks]

double post.

Edited April 25, 2019 by Hicks
double post.

[Hicks]

2 hours ago, Rainer said:

Hi Hicks,

I understand it but main reason for people reluctant to understand the advantage of an encoder is mainly because of the additional price for them and other people who do not have it can not understand the advantage and that is why they say " OH, if you are going to guide anyway, save the money " OK, yes but I think I have written my fingers wound trying to explain the advantage of encoders ... but looks like nobody understands it or do not read it ? ...

Again ... see my message posted yesterday at 10:16 Mexican time

 

I guess my current reservation is the extra grand for the RA encoder. As my scope is a 8" LX90 which would be 1270 focal length (1.04"/pixel) or 2000 if I ran without focal reducer, I'm trying to decide if the non EC version is already good enough to achieve consistent nights of trouble free exposures (seeing and other non mount caused issues aside).

The other factor is that at least from the way the specs are written, it sounds like the EC version is more likely to have a low/smooth periodic error (< 0.5" over 5min), where as the non-EC just has the peak to peak spec. If it's possible they'd ship a non CE mount with a PE change that meets the p2p spec, but has a few sharp spikes that could be tricky to guide out, I'd lean more towards the EC for that peace of mind. So far though, everyone's factory graphs I've seen have been reasonably smooth changes across the peak.

Edited April 25, 2019 by Hicks

[vlaiv]

1 hour ago, Rainer said:

Hi Roland,

That is a budget problem right ? as usual ... 

CEM 120EC2 is the way to go ? unless you will never fill the mounts capacity but on the other side one can be never over mounted ...

I would say that it's quite questionable - since CEM120EC2 is in Mesu 200 territory price wise. I'm not entirely sure I would go for CEM120EC2 over Mesu 200