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Losmandy G11-G2 or iOptron CEM60 or ??

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#1 Pak

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Posted 07 July 2014 - 11:54 AM

I have a 11"EdgeHD and all told with my imaging gear I have an instrument weight of about 40lbs. I am looking for a mount that is as light weight as possible that also has more than enough capacity to handle the 40lbs. I would like to stay under $5,000US for the mount with tripod and weights and I would prefer that the mount not be really noisy. For the longest time I've had my mind set that I would get a used Mach1GTO or even AP900 but having been around some of the newer mounts that are belt driven and very silent, I have started to think about the CEM60. I have been following the CEM60 thread and it really does not look like that mount is ready at all. The G11 seems like a good choice too. While it isn't belt driven, not too many people complain about how loud it is. The G2 system seems to be coming along and with the OPW I guess the PE is pretty darned low. I considered the Avalon Linear mount but I don't like that I have to have a computer to use it.

So this is a breakdown of what I need.
Lightweight and easy to transport for club events and camping trips.
45lb instrument weight capacity for long exposure photography.
Does not need a computer system to align and do go-tos
Quiet slews
Low and smooooooth PE. Easily guided
Great alignment system for very accurate go-tos
Excellent support and reliability
Less than $5,000US out the door.

Used Mach1GTO (but noisy)
New CEM60 or CEM60EC if they can fix the bugs?
New Losmandy G11 with G2 (but get the OPW?)
????

Please offer up some suggestions and advice. I plan to buy later this month.

Thank you.

#2 blueman

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Posted 07 July 2014 - 01:51 PM

I am not sure about the noise levels in Mach1 mounts. But I think if you slow it down to 600 or 800 the noise levels will drop significantly.
My AP900 is VERY quiet, you can hardly hear it slew during a flip.

The G-11 at 40 lbs + will be working hard. It can probably do it but maybe not every sub. The G-11 worked fairly hard with the AT8RC and a camera and that was not 40 lbs.

I have no personal experience with the Ioptron mounts. The CEM60 at only 27 lbs seems a bit optimistic for a payload of 60 lbs, but hey, maybe it can do it.
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#3 orlyandico

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Posted 07 July 2014 - 02:37 PM

Mach1. Yes it's noisy. 600X slew will quiet it down.

But the reality is if you are imaging you'll be doing only a handful of slews every night. So you can live with the occasional noise. Tracking is silent.

#4 urbanMark

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Posted 08 July 2014 - 03:21 AM

Hard to beat the Mach1 - and it is quite portable. And as orlyandico point out, slews are pretty rare when imaging. But for bang for the buck, a used G11 with some upgrades (G2, OPW, re-grease and inspect, etc)takes the cake. Imaging with the 11" EdgeHD on a G11 should be no problem. Remember the C11 was the original payload for the G11, and the mount has improved significantly since then. I'm sure some G11 users that image with large payloads will chime in shortly....

#5 WebFoot

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Posted 08 July 2014 - 10:18 AM

For a similar price, I chose a new CEM60 over any used G11.

Just me, but I wouldn't image with either at long focal length without an AO device of some sort or other, so I was charmed by newer technology.

I haven't yet imaged with my CEM60, but I've been out with it a couple of times, and it's a fine mount. And you can't beat a 27 pound head with that weight capacity.

#6 moligpy

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Posted 08 July 2014 - 10:49 AM

I would recommend CEM60, it is very quiet even at maximum slewing speed. "Maybe" EC edition have "SDE" problem(I also see some EC owners takes some very beautiful pictures when guiding, so I am thinking the "SDE" problem may be not big enough to take negative impact to guiding). In the other hand, the standard version seems to work perfectly so far.

#7 Mr Greybush

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Posted 08 July 2014 - 03:01 PM

+++++++1 for G11's

#8 Phil Cowell

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Posted 09 July 2014 - 05:08 AM

+1

For a similar price, I chose a new CEM60 over an G11.



#9 Peter D.

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Posted 09 July 2014 - 07:42 AM

I was just faced with the same decision. The price for a new (standard) CEM60 is similar to that of a new G11-G2, considering the considerable additional cost of the CEM60 tripod. The G11 is heavier and uses older technology in its controller, but is very well supported and has a very good reputation. There are many G11's available used in various forms, mainly from users that needed greater capacity, and many priced less than half the cost of a new G11-G2 or CEM60.

After extensive research on forums for both the G11 and CEM60, I decided that considering the great support from Losmandy and the excellent reputation of all G11s the risks associated with purchase of a used G11 were minimal.

I purchased a used G11-G1 with upgrades, and it works great! I have been very happy with the big step up in solidness and tracking performance as compared to my Atlas and CG5-ASGT. I haven't even set up the PEC yet, and stars are pinpoint in guided 5 minute images at 800 mm fl with my SN8, and I have noticed that with a good polar alignment (easy with the G11's excellent PA scope and a quick drift align) guiding is not needed for the 1 to 2 minute subs that I typically use under my light-polluted Bortle 19.7 skies.

The only issues I have encountered relate to the normal learning curve for the controller; I'll certainly become more proficient with experience, but right now Celestron still gets the nod for best controller.

#10 Pak

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Posted 09 July 2014 - 03:33 PM

Yes I agree with everything you said. I am just so worried about buying the G11-g2 and then iOptron suddenly pulls out a win with the CEM60 and gets the bugs squashed and I'm stuck with an older tech spur gear driven mount when I could have a sleek light weight belt driven magnetic worm riding attractive mount with an innovative hand controller.

So its the mount I know will just work and is easy to upgrade and tinker with or a mount that has a lot of potential for the future. I really love the usb and power ports in the saddle. I love iOptrons polar scope too.

So frustrating. Come on iOptron, get these bugs worked out!

#11 cloudywest

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Posted 09 July 2014 - 05:16 PM

If you had so much hesitation, either way would not be wrong too much. If I were you, I would go for the CEM60. So far I have not seen any hardware issue reported except their beta units. You would not miss any new improvement by software/firmware upgrade. There were some discussions about SDE issue on the high precision encoder version, which I personally believe it was exaggerated by magnitude and misleading. Theoretically, the SDE by two orthogonal sin/cos waves is less than 0.1 arcsec, why worry then?

#12 austin.grant

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Posted 09 July 2014 - 05:42 PM

If you had so much hesitation, either way would not be wrong too much. If I were you, I would go for the CEM60. So far I have not seen any hardware issue reported except their beta units. You would not miss any new improvement by software/firmware upgrade. There were some discussions about SDE issue on the high precision encoder version, which I personally believe it was exaggerated by magnitude and misleading. Theoretically, the SDE by two orthogonal sin/cos waves is less than 0.1 arcsec, why worry then?


Curious to know why you think the SDE data was exaggerated and misleading? The fact that the spikes exist (in reported data) and their magnitude seemed fairly straightforward. Whether SDE is the cause is unproven, I suppose, but something caused it.

#13 Raginar

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Posted 09 July 2014 - 08:30 PM

For 5k you can find a used Titan, a Mi-250, or a Temma. I'd skip the chinese mount that doesn't seem to have a very good track record (read the thread, skip the fans who don't own/use it for what you're doing with it).

#14 Dan Finnerty

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Posted 10 July 2014 - 12:05 AM

For 5k you can find a used Titan, a Mi-250, or a Temma. I'd skip the chinese mount that doesn't seem to have a very good track record (read the thread, skip the fans who don't own/use it for what you're doing with it).


Pak,

I have been holding my peace while others comment on the CEM60 but your post has convinced me it is time to speak up. I have had a Losmandy G11/G2 for several years. It has some tracking issues that I know I could resolve if I put the time into tuning it up, but I've not spent the time. I have been frustrated by obtuse, quirky and (fortunately mostly in the past) buggy behavior of the G2 software.

I recently got the CEM60 hoping it could replace the G11 and be a more functional platform for getting into astro photography even though I suspected it would not have quite the payload capacity of the G11.

Two weeks ago I had the CEM60 at a star party and was very disappointed with its performance. Over several nights I used it with both my C11 Edge and AP155 EDFS. They both weigh in at about 30 pounds. Whereas the G11 could damp quickly after focusing (one second or less), the CEM60 would sometimes take 4 to 6 seconds to damp out. It was infuriating to use visually. I dreaded having to refocus. I have the 2 inch tripod which I conclude is not robust enough for the mount, but I don't think the problem is caused by the tripod. A more robust tripod might incrementally improve mount performance, but only incrementally.

Using the AP155 during daytime with a solar filter, even small breezes would jiggle the the scope by a half a solar diameter, and take multiple seconds to settle down.

In my opinion, after using these scopes on both mounts, the advertised weight capacity of the CEM60 is exaggerated by a factor of two. And I'm not basing that on only one CEM60.

The original mount I ordered has a serious problem with the RA axis siezing up during slews. iOptron tech support was very good. They sent me a replacement mount so I could have something working for the star party with a postage paid return label for the old mount. It turns out that the original mount had a problem with improper belt tension.

Both mounts exhibited the same level of instability with both the C11 and the AP155, so there is not likely to be any mount-specific problem there. It just can't handle the payload.

Now I've seen the videos Astronewb has put out with large heavy scopes slewing on it, and indeed it slews just fine. And it tracks well and I'm sure is able to take good guided astro photos (up to some TBD weight/tube-length limit), but it is a very delicate thing and is very inferior to the G11 capacity-wise.

At this point I am not sure what I am going to do about the mount. Its weight performance is poor and it cannot replace the G11. However, it tracks well and the software is more robust and trustworthy than the G2 software.

Frankly I am surprised no one else has complained about the CEM60 mount stability. Maybe they just don't have any experience with another 60 pound rated mount to compare it to.

#15 andysea

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Posted 10 July 2014 - 12:09 AM

Why not get an AP and be done with it? You know it will work.

#16 blueman

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Posted 10 July 2014 - 12:37 AM

I learned after buying 4 mounts, that the AP mount was the answer. I bought one finally and now no problems.
Blueman

#17 tazer

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Posted 10 July 2014 - 07:47 AM

Frankly I am surprised no one else has complained about the CEM60 mount stability.


It's definitely not as stable as one would expect. With my 20lbs of gear on it I can tap the scope in RA and see it move/vibrate. Mine had the same RA freezing issue as yours. iOptron didn't send me a new mount, instead I had to fix it myself (per their "instructions.") As far as autoguiding, I have yet to get it to work as well as my CG5. The mount has definite issues and it sounds like I'm not just an outlier.

#18 Peter D.

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Posted 10 July 2014 - 08:38 AM

Frankly I am surprised no one else has complained about the CEM60 mount stability. Maybe they just don't have any experience with another 60 pound rated mount to compare it to.

Dan, yours is not the first post that I've read regarding the CEM60's mediocre stability. I'm now very satisfied that I made the correct decision in purchasing my G11 instead.

It's important to make distinctions between Stability, Tracking, and Pointing; they're related in some ways, but not in others. Stability relates to how tolerant the mount is to an external force; Tracking relates to how accurately the mount follows the motion of the stars; Pointing relates to how accurately the mount can "goto" a specifiied point in the sky.

My new (used) G11-G1 may not excel at Pointing, but it's Stability and Tracking performance are top-shelf in its weight class; it's just solid in the old-fashioned AMERICAN way (that's shared by most of the expensive high-end mounts). I can deal with mediocre Pointing, but it's hard to improve Stability beyond what's possible through a solid pier mounting.

It's also possible to have good Stability and Pointing with poor Tracking: case in point, my RCX400 (before it died) on its massive alt-az fork mount and tripod. It was a great rock-solid scope visually, with excellent Pointing, but the tracking was so bad you could SEE the stars wiggle back and forth at 200x: forget about imaging (even with guiding, a wedge and a pier; as bad as my CG5-ASGT is with its flaky DEC axis it tracked better than the RCX400).

I suspect that the CEM60's weak link is the feature that makes its Tracking so good: its magnetic worm loading. That innovative feature may eliminate most of the backlash, but can soften the coupling between the worm and the ring gear; making it vulnerable to modest external forces. Build quality may be an issue also, but that can be remedied at the factory and through good support.

#19 cloudywest

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Posted 10 July 2014 - 09:28 AM

[quote
Curious to know why you think the SDE data was exaggerated and misleading? The fact that the spikes exist (in reported data) and their magnitude seemed fairly straightforward. Whether SDE is the cause is unproven, I suppose, but something caused it. [/quote]
You mean the data of 4 arcsec? It must be something beyond SDE, must be a broken encoder. An encoder without subdivision (interpolation) can do better than 4 arcsec. There were convincing images and data of CEM60EC without auto guiding (iOptron CEM60, First Impressions, Page 34, near the top, by Astronewb). He held the DEC slew button depressed in speed 2 while exposed for 60 seconds to check for RA 'ripple' or saw tooth patterns. The lines were almost perfectly straight, even at 300% blow up. Several people agreed the straight lines. However, some could see 11 ripples and concluded about 3-4 arcsec SDE from the same straight line. I was lost from there. We will see when more data is available and time will tell.

#20 moligpy

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Posted 10 July 2014 - 09:52 AM

Frankly I am surprised no one else has complained about the CEM60 mount stability. Maybe they just don't have any experience with another 60 pound rated mount to compare it to.

Dan, yours is not the first post that I've read regarding the CEM60's mediocre stability. I'm now very satisfied that I made the correct decision in purchasing my G11 instead.

It's important to make distinctions between Stability, Tracking, and Pointing; they're related in some ways, but not in others. Stability relates to how tolerant the mount is to an external force; Tracking relates to how accurately the mount follows the motion of the stars; Pointing relates to how accurately the mount can "goto" a specifiied point in the sky.

My new (used) G11-G1 may not excel at Pointing, but it's Stability and Tracking performance are top-shelf in its weight class; it's just solid in the old-fashioned AMERICAN way (that's shared by most of the expensive high-end mounts). I can deal with mediocre Pointing, but it's hard to improve Stability beyond what's possible through a solid pier mounting.

It's also possible to have good Stability and Pointing with poor Tracking: case in point, my RCX400 (before it died) on its massive alt-az fork mount and tripod. It was a great rock-solid scope visually, with excellent Pointing, but the tracking was so bad you could SEE the stars wiggle back and forth at 200x: forget about imaging (even with guiding, a wedge and a pier; as bad as my CG5-ASGT is with its flaky DEC axis it tracked better than the RCX400).

I suspect that the CEM60's weak link is the feature that makes its Tracking so good: its magnetic worm loading. That innovative feature may eliminate most of the backlash, but can soften the coupling between the worm and the ring gear; making it vulnerable to modest external forces. Build quality may be an issue also, but that can be remedied at the factory and through good support.


I must say some of you misunderstand the stability of CEM60. If the CEM60 cannot even have a payload of 20lbs, that is ridiculous. The CEM60 is more sensitive than many other mounts. You may try to put minimal weight on the mount, and tap on the RA axis to feel the sensitive. This is the advantage over many mounts, not the disadvantage. This can make sure you to put the mount into a more balanced position.

#21 tazer

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Posted 10 July 2014 - 10:18 AM

I must say some of you misunderstand the stability of CEM60. If the CEM60 cannot even have a payload of 20lbs, that is ridiculous. The CEM60 is more sensitive than many other mounts.


Where was it stated that the CEM60 couldn't have a payload of 20lbs? _I_ stated that with a 20lb payload I can press lightly along the RA axis and see the mount move, and that if I tap the scope I can watch it (not a star through the eyepiece, but the scope itself) vibrate. That translates to a frustrating experience when observing. Perhaps it gets better with more weight?


You may try to put minimal weight on the mount, and tap on the RA axis to feel the sensitive. This is the advantage over many mounts, not the disadvantage. This can make sure you to put the mount into a more balanced position.


I think you've misunderstood what I was saying. You can't balance the CEM60 with the gears engaged, which is where I'm seeing the issue. Of course once they're disengaged it's a near frictionless balancing environment that allows you to achieve near perfect balance. The play/stability in the RA axis has nothing to do with how well the mount can be balanced.

#22 Nebhunter

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Posted 11 July 2014 - 01:15 AM

Here is my photographic load for the G11 - actually the Celestron version. Updated with one piece block and HP worm. Click the mouse on the picture and it will take you to the gallery with more pictures visible. View in Original size by scrolling below the picture. Film exposures of over 60 minutes guided with an ST-4 using 7 second iteration. Good conditions would give strings of zero adjustments RA consistently 5 to 10 in a row. Any time a +1 adjustment was made in RA it was usually followed by a -1 right after. This mount is 11 years old and going stronger than ever.

http://www.pbase.com...image/146029764

#23 gdd

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Posted 11 July 2014 - 01:50 AM

Hi Nebhunter,

I looked at the other pictures on your site and see you have a 55 pound instrumentation and image at up to 980mm with a large 140mm F/7 refractor. Wonderful images.

Gale

#24 OzAndrewJ

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Posted 11 July 2014 - 08:18 AM

Gday Cloudywest

Theoretically, the SDE by two orthogonal sin/cos waves is less than 0.1 arcsec, why worry then?



Because in practice, fabrication/software tolerances have a real world effect on the "orthogonality" of the data and the accuracy of shape of the interpolated sine waves ;).
So far three users have provided raw data that shows there is a definite SDE error of around 2-4 arcsec pk-pk. This is real world measured data, not theoretical postulations on what is possible.
All that is in consideration at present is if that error will affect imaging at the arcsec/pixel used, and can IOPtron reduce it.

Andrew Johansen Melbourne Australia

#25 gnowellsct

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Posted 11 July 2014 - 06:26 PM

I try not to buy things made in China: Not my dog's food not my telescope stuff. Too many qc/qa issues (to put it mildly, there was poison the exported dog food). My own G11 is the stepper motor kind.

I recently had it set up on HD tripod with the 5" GT130 and one of the people at a star party asked me if the cope wasn't overmounted.

I replied no this is what properly mounted is like the scope doesn't budge when you focus and the stars just sit in the fov as if it were a limpid pool, and wind and even people kicking the tripod just doesn't do a thing.

All that said, I used the G11 with a C14 for a while, it had more load flex than with the 5" refractor, but was still pretty good.

Anyhow go-to systems are quite a bit more finicky than push to systems with steppers but go-to dominates the market by a wide margin. For my part, if and when I get a go-to, it is likely to be an AP1100.

I spent some time with a number of different mounts and consider the G11 the minimum entry point for good visual observing. The tripod is really a fine piece of engineering I don't think there is anything else as solid for the price. I sometimes mount my 900qmd GEM to the tripod (there is an adapter) and use it with my f/6 ten inch Newt.

FWIW,

GN

Greg N






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