Are other peoples iOptron GEM45's this good? because I'm blown away!

[Chris]

As a serial kit tester I've owned/used my fair share of mounts including a number of Sky-Watcher and Celestron mounts as well as an Explore Scientific, but I think I may be an iOptron convert after using a GEM45!

Yes, you would expect a 2K iOptron to be better than a 1k Sky-Watcher for example, however, I'm just surprised by how easy the iOptron has made imaging and I'm having a real blast! 

I was looking to jump on the whole ASI Air thing as it does look like an amazing product, though I feel the GEM45 has made this less needed with such a quick and and accurate goto system plus the realisation that periodic error is so low that I don't need to guide! I was getting 5 minute unguided subs @432mm on the California nebula last week, and I'm sure I could have gone longer! I've never seen anything like it!

I know iOptron is one company that states periodic error figures and the standard (Non EC Encoder) GEM45 is stated to have < 7 arc seconds.

I suspect such a post will attract both very good and very bad stories, and perhaps not what's typical? so it may not be possible to see a true picture, I'm just wondering if others have found that they don't need to guide with their iOptrons? 

As always I documented my experience below: 

 

 

 

 

 

 

Edited December 19, 2021 by Chris

[MARS1960]

I can vouch for my CEM26 to be the worst mount I ever owned.

It would track for 60 secs at the most ( I used to get 120 secs from an old, used Celestron GT5) and that was with Ioptrons perfect polar alignment

After one nights use it broke and I found Ioptrons customer service was practically non existent.

In the end I sent it back to the shop I purchased it from and they repaired it for me, It would still only track for 60 secs though.

Now sold and I would not buy one again.

[Chris]

2 hours ago, MARS1960 said:

I can vouch for my CEM26 to be the worst mount I ever owned.

It would track for 60 secs at the most ( I used to get 120 secs from an old, used Celestron GT5) and that was with Ioptrons perfect polar alignment

After one nights use it broke and I found Ioptrons customer service was practically non existent.

In the end I sent it back to the shop I purchased it from and they repaired it for me, It would still only track for 60 secs though.

Now sold and I would not buy one again.

Hey Mark, I know it can be pot luck sometimes can't it. At least your GT5 sounded like a good one, better than the GT5 I had by the sounds of it. I'm sorry to hear your CEM26 broke after just one use and glad the retailor sorted it as they should do, I would always make the retailor your first port of call. 

You also kind of raise a good point about buying goto mounts second hand. It's one astro item I stopped buying on the second hand market as the poor examples naturally get moved on more than good examples, and there is so much to go wrong with a mount compared to say a telescope or eyepiece.    

  

Edited December 19, 2021 by Chris

[ONIKKINEN]

I would assume a mount as good as yours to be extremely rare. Maybe try running PHD2 guiding assistant on it to measure the PE curve? If youre getting away with 5min subs unguided it should be very shallow and even since the stars in your final image are a-ok.

3 hours ago, MARS1960 said:

In the end I sent it back to the shop I purchased it from and they repaired it for me, It would still only track for 60 secs though.

I would assume this is the norm, unguided mounts really are not a thing below the 3k (whatever currency) mark.

My Skywatcher junkpile of a mount (EQM35) gets about 50% success rate with 30s subs on a good day unguided, and towards northern declinations. 0% success rate towards lower declinations guided or unguided. The periodic error also has sharp cliffs that guarantee a failed sub at least once per every worm period even with guiding, as this is too quick for any guide corrections to correct in time. So i think in the china category of mounts (Skywatcher, Celestron, Ioptron) you really cant know for sure what you're going to get.

Also i get periodic error in declination (dont ask).

Treasure that mount, its probably a one of a kind!

[Chris]

1 hour ago, ONIKKINEN said:

I would assume a mount as good as yours to be extremely rare. Maybe try running PHD2 guiding assistant on it to measure the PE curve? If youre getting away with 5min subs unguided it should be very shallow and even since the stars in your final image are a-ok.

Hey, It would be interesting to have some empirical data for the PE curve but my next move will be to grin insanely at the mount as I attempt to go for even longer subs! That will have to wait though as I currently have the dreaded you know what 🤒

 

[ONIKKINEN]

23 minutes ago, Chris said:

Hey, It would be interesting to have some empirical data for the PE curve but my next move will be to grin insanely at the mount as I attempt to go for even longer subs! That will have to wait though as I currently have the dreaded you know what 🤒

 

Could be that longer subs work as well as 5min ones, because the worm period is probably somewhere around 8 minutes. This means 5min subs already go through almost all of the periodic error, so polar alignment limited basically.

And best of luck with the big evil C!

[Al_N]

Owner of a GEM28 here.

My experience with this iOptron mount mirrors that of @Mars1960.

fundamentally, the issue is an apparent lack of quality control at the factory/assembly line.

Issues encountered included:

1. 1. Dec axis improperly bolted to the RA axis;
2. 2. Housing for lower RA bearing was machined oversize - the bearing literally rattled around the pocket.
3. 3. DEC worm carrier had excessive (~.6mm) end clearance - allowing the DEC axis to randomly flop +/- 6-7 arc sec in the lightest of breezes, or as a result of weight shifting during tracking.
4. 4. iOptron customer support fell off the face or the earth after two contacts, without any useful support being rendered.

I couldn't find a decent manual for the mount, so trying to diagnose and fix the issues was really slow - this was my first equatorial mount. After fully disassembling and reassembling the mount with a bit of care, the DEC flop is gone, and a first test showed .4" RMS guiding error in DEC.  Total RMS error was 0.8", which is much better than the 1.5-2.5" prior to these efforts.

Al

[scotty38]

5 minutes ago, Al_N said:

Owner of a GEM28 here.

My experience with this iOptron mount mirrors that of @Mars1960.

fundamentally, the issue is an apparent lack of quality control at the factory/assembly line.

Issues encountered included:

1. 1. Dec axis improperly bolted to the RA axis;
2. 2. Housing for lower RA bearing was machined oversize - the bearing literally rattled around the pocket.
3. 3. DEC worm carrier had excessive (~.6mm) end clearance - allowing the DEC axis to randomly flop +/- 6-7 arc sec in the lightest of breezes, or as a result of weight shifting during tracking.
4. 4. iOptron customer support fell off the face or the earth after two contacts, without any useful support being rendered.

I couldn't find a decent manual for the mount, so trying to diagnose and fix the issues was really slow - this was my first equatorial mount. After fully disassembling and reassembling the mount with a bit of care, the DEC flop is gone, and a first test showed .4" RMS guiding error in DEC.  Total RMS error was 0.8", which is much better than the 1.5-2.5" prior to these efforts.

Al

I keep hanging my nose over an iOptron mount (albeit the CEM70) but how did your dealer react to these issues?

[geeklee]

I've had a CEM26 since the start of November but it appears to be a slight revision as a few things were different to photos / existing mounts.  I hope the QC was part of these changes!

Mine has been imaging for ~20-25 hours (that can't seem right in UK weather!) and so far it's only needed the gear mesh on DEC tweaked (it was too tight).  I think the RA could do with a tweak - I'm still working on this.

My current image scale on this rig is ~3.7"PP.  Typically it'll be well under 1" RMS with the graph having occasional spikes ~2".  It also  recovers from RA and DEC dithers OK.  My image scale is very forgiving so there's no concerns but with something below this, there might be more to investigate/tweak.

[Al_N]

1 hour ago, scotty38 said:

I keep hanging my nose over an iOptron mount (albeit the CEM70) but how did your dealer react to these issues?

My dealer tried to act as a go-between for iOptron and myself. Didn't accomplish much. Dealer just passed the buck to iOptron and wouldn't even discuss return.

So I bought my next scope and mount (Sharpstar 94EDPH and HEQ5 Pro) from a competitor. Then I told him that he lost those sales.

There are four fairly price competitive on-line shops in Canada. I've ruled out purchasing anything else from two of them due to crappy customer service.

Al

[StarryEyed]

"As a serial kit tester I've owned/used my fair share of mounts"

Its possible then that statistically speaking you have gone thought enough mounts to have come across one that works properly. Statistically speaking then all the others had problems and you moved them on.

Whats frustrating about this is all the mounts coming out of the factory should be performing as your's does.

 

Edited December 19, 2021 by StarryEyed

[Chris]

11 minutes ago, StarryEyed said:

" Statistically speaking then all the others had problems and you moved them on.

I think I'd describe myself as someone who likes to try different things rather than someone who went through a dozen mounts looking for one without problems. I.e. I've chose to sell good mounts in the past just to free up money for something I wanted.

As someone who has paid full second hand price for problem mounts on more than one occasion I've chose not to follow suit and just give the problem mounts away or sell them as spare or repair. My last mount went to the local high school to be used manually with a Vixen refractor.   

Edited December 19, 2021 by Chris

[Chris]

27 minutes ago, StarryEyed said:

Whats frustrating about this is all the mounts coming out of the factory should be performing as your does.

 

I think this is where the price thing may come into it to some extent? I am after all lucky enough to be using a 2.2k mount at the moment. 

It might be fairer to compare brands by price, for example how does say the SW HEQ5 compare to the iOptron CEM26 as they are about the same price.

Is the QC and tracking better for one compared to the other?  

 

 

 

 

Edited December 19, 2021 by Chris

[Chris]

2 hours ago, Al_N said:

Owner of a GEM28 here.

My experience with this iOptron mount mirrors that of @Mars1960.

fundamentally, the issue is an apparent lack of quality control at the factory/assembly line.

Issues encountered included:

1. 1. Dec axis improperly bolted to the RA axis;
2. 2. Housing for lower RA bearing was machined oversize - the bearing literally rattled around the pocket.
3. 3. DEC worm carrier had excessive (~.6mm) end clearance - allowing the DEC axis to randomly flop +/- 6-7 arc sec in the lightest of breezes, or as a result of weight shifting during tracking.
4. 4. iOptron customer support fell off the face or the earth after two contacts, without any useful support being rendered.

I couldn't find a decent manual for the mount, so trying to diagnose and fix the issues was really slow - this was my first equatorial mount. After fully disassembling and reassembling the mount with a bit of care, the DEC flop is gone, and a first test showed .4" RMS guiding error in DEC.  Total RMS error was 0.8", which is much better than the 1.5-2.5" prior to these efforts.

Al

Sad to hear but kudos for sorting it out, you're clearly tenacious! Did you shim the 0.6mm end clearance and wrap something around the bearing so it didn't move around? As someone who trained as a CNC machinist from school it's hard to relate to components being passed through inspection which are out of tolerance. The inspectors would be right up in your grill if you were 1/10th of a thou out! A different type of engineering world maybe ?

 

 

[newbie alert]

I've been more than ecstatic with my cem 60, it's never missed a beat ... awesome mount

[Chris]

1 hour ago, geeklee said:

I've had a CEM26 since the start of November but it appears to be a slight revision as a few things were different to photos / existing mounts.  I hope the QC was part of these changes!

Mine has been imaging for ~20-25 hours (that can't seem right in UK weather!) and so far it's only needed the gear mesh on DEC tweaked (it was too tight).  I think the RA could do with a tweak - I'm still working on this.

My current image scale on this rig is ~3.7"PP.  Typically it'll be well under 1" RMS with the graph having occasional spikes ~2".  It also  recovers from RA and DEC dithers OK.  My image scale is very forgiving so there's no concerns but with something below this, there might be more to investigate/tweak.

Thanks for bringing up pixel scale as this needs to be taken into account when looking at tracking performance.

Someone will of course have a much harder time trying to image at 1"/pixel compared to say 4"/pixel.  

I probably should have mentioned that my 5 minute subs were at a pixel scale of 2.3"/pixel. 

p.s. blimey well done for getting 20-25 hours imaging in the last 6 weeks!  

 

[StarryEyed]

1 hour ago, Chris said:

 

1 hour ago, Chris said:

.... 

It might be fairer to compare brands by price

..... 

Is the QC and tracking better for one compared to the other?  

 

Everybody dreads even expects to get a mount that underperforms but hopes to get one like yours that's right on the money. 

Price has nothing to do with it. Even paint does what it says on the tin.

Statically your mount is at the right and edge of the curve. 

Edited December 19, 2021 by StarryEyed

[Chris]

1 minute ago, StarryEyed said:

Everybody dreads even expects to get a mount that underperforms but hopes to get one like yours that's right on the money. 

Price has nothing to do with it. Even paint does what it says on the tin.

Statically your mount is at the right and edge of the curve. 

I probably should point out that I technically don't own the mount, it's on loan so please don't think I'm just hear rubbing in how good my mount is or anything like that, I was just genuinely surprised and wanted to know if others had a similar experience.  

I think we might have to agree to disagree regarding money as I wouldn't expect the same quality or results from a 1k mount compared to a 3k mount,  just like I wouldn't expect the same handling speed performance from a Dacia Sandaro compared to er? an expensive car.....I can't think of one  

 

[Al_N]

57 minutes ago, Chris said:

Sad to hear but kudos for sorting it out, you're clearly tenacious! Did you shim the 0.6mm end clearance and wrap something around the bearing so it didn't move around? As someone who trained as a CNC machinist from school it's hard to relate to components being passed through inspection which are out of tolerance. The inspectors would be right up in your grill if you were 1/10th of a thou out! A different type of engineering world maybe ?

 

 

I don't know what qc processes are in place in whatever factory in China turns these out. I do know that there are many unhappy CEM26 and GEM28 owners around the internet. Plus a few winners of the equipment lottery who are really quite happy with properly assembled mounts from the factory.

Sorry, the .6mm refers to excessive side-play in the DEC worm shaft. I needed to tighten the float adjuster by about 1/4 turn to eliminate side play in the DEC worm. RA worm shaft had been adjusted fairly well at the factory, so I just tweaked it. Unfortunately, you have to remove the entire worm and carrier assembly to get to the float adjuster.

I'm somewhat embarrassed to admit that, in my haste for a fix, I used loctite to secure the bearing, rather than waiting to get shim material to deal with the overbore. That bearing is not coming out again without the application of some heat.

[StarryEyed]

1 hour ago, Chris said:

I probably should point out that I technically don't own the mount, it's on loan..... 

 

So not new out of the box. Well fair enough then. 

Edited December 20, 2021 by StarryEyed

[Chris]

1 hour ago, StarryEyed said:

So not new out of the box. Well fair enough 

 It's one of our customer returns. Does that make a difference?

[newbie alert]

13 hours ago, ONIKKINEN said:

Could be that longer subs work as well as 5min ones, because the worm period is probably somewhere around 8 minutes. This means 5min subs already go through almost all of the periodic error, so polar alignment limited basically.

And best of luck with the big evil C!

The worm period for the gem 45 is 400 secs

[Chris]

10 hours ago, Al_N said:

I don't know what qc processes are in place in whatever factory in China turns these out. I do know that there are many unhappy CEM26 and GEM28 owners around the internet. Plus a few winners of the equipment lottery who are really quite happy with properly assembled mounts from the factory.

Sorry, the .6mm refers to excessive side-play in the DEC worm shaft. I needed to tighten the float adjuster by about 1/4 turn to eliminate side play in the DEC worm. RA worm shaft had been adjusted fairly well at the factory, so I just tweaked it. Unfortunately, you have to remove the entire worm and carrier assembly to get to the float adjuster.

I'm somewhat embarrassed to admit that, in my haste for a fix, I used loctite to secure the bearing, rather than waiting to get shim material to deal with the overbore. That bearing is not coming out again without the application of some heat.

Ah right, I was thinking you meant the worm shaft was 0.6mm too short full stop, as in 0.6mm too short to be adjusted out. That's a bit less shocking but I realise it was still a pain to adjust.

I guess the bearing will only need to come out again if it wears out, and If the bottom bracket bearing of my road bike can take 1000's of miles of abuse I think you should be good for years to come I think iOptron should feel more embarrassed for machining it oversized to begin with! I can only hope that doesn't happen too often! 

 

[pete_l]

14 hours ago, StarryEyed said:

all the mounts coming out of the factory should be performing as your's does

Yes. However, mounts do not perform in isolation.

The OP tells us they have a 3kg OTA plus what seems to be a DSLR on a mount that is rated for 20kg. The focal length (432mm) is also very forgiving.

Edited December 20, 2021 by pete_l

[vlaiv]

What is average FWHM, star eccentricity and number of frames that did not make it into the stack?