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CEM40 or CEM60 for EdgeHD 8" with Reducer, OAG, FW w/ cooled Camera

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#1 v3ngence

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Posted 15 December 2019 - 03:09 AM

Right now I am using a CEM 25 which is managing just about 1.0 arc seconds RMS with my 20 lbs of EdgeHD 8" + reducer + OAG + D5300. For a $900 mount at 75% of it's capacity, I really can't complain!

 

But I want to get guiding closer to 0.5" RMS, and I'm getting the new ASI6200mm and a filter wheel so I want to do it justice with an upgraded mount.

 

The CEM 40 is newer, has very similar specs to the CEM60, but is nearly half the weight:

https://www.ioptron....uct-p/7402a.htm

 

Worm Wheel Φ110mm, 216 teeth

Resolution 0.08 arc seconds

Unguided Accuracy / PE <±7 arcsec

Mount weight 15.8 lb

 

The CEM 60 has built-in usb ports, more capacity, better specs, and still pretty light for it's capacity:

https://www.ioptron....uct-p/7200a.htm

 

Worm Wheel Φ146mm, 288 teeth 

Resolution 0.06 arc seconds

Unguided Accuracy / PE < ±5 arcsec

Mount weight 27 lb

 

I'm leaning to the CEM 60, but which would you choose? Anyone getting ~0.5" RMS with a big scope on the CEM 40?



#2 Jeff Smith

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Posted 15 December 2019 - 08:31 AM

I've got a Cem40. I'm wishing I had gotten the Cem60 instead for my Esprit 100. The shorter tube on your 8" Edge should be just fine but if the wight difference isn't that much of a factor to you, go up a level and get the Cem60.


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#3 joseph07081

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Posted 15 December 2019 - 10:03 AM

I purchased my CEM40 as a lighter weight mount to go with my ZS73 and SV102 Access, with thought of using the Edge 8 for visual. The Edge 8 looks absolutely huge on the CEM40. The weather has been horrible since I purchased the mount, so I can't say how steady the combination is, but if I were using the Edge 8 as my main imaging scope, I think I would lean toward the CEM60 for the extra capacity. My opinion may change if the weather ever clears up and I can get that combination out under the stars. 


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#4 OldManSky

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Posted 15 December 2019 - 10:39 AM

I faced nearly the identical choice (have been happily using my CEM25P for a year, but wanted more capacity).

My take was that if going portable, setting up and tearing down regularly, go with the CEM40.  If not, the CEM60.

Since I'm putting in a new pier/flip-top observatory, and won't go portable, I got the CEM60.

Well, I ordered it...won't have it for another week or two.

 

TomK on here is regularly getting 0.5 - 0.6" RMS guiding with his CEM60.  I don't think that will be a problem.


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#5 ChrisWhite

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Posted 15 December 2019 - 12:28 PM

I'm running an Edge 925 on my Cem60 with full mono imaging set.  Guiding is between .4 and .6"/px total RMS with OAG at native focal length.  It's a wonderful combo. 


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#6 joseph07081

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Posted 15 December 2019 - 01:48 PM

I faced nearly the identical choice (have been happily using my CEM25P for a year, but wanted more capacity).

My take was that if going portable, setting up and tearing down regularly, go with the CEM40.  If not, the CEM60.

Since I'm putting in a new pier/flip-top observatory, and won't go portable, I got the CEM60.

Well, I ordered it...won't have it for another week or two.

 

TomK on here is regularly getting 0.5 - 0.6" RMS guiding with his CEM60.  I don't think that will be a problem.

I concur with Paul, my main consideration when choosing the CEM40 was it's light weight and capacity. My needs were light weight and my imaging needs will only extend to my SV102 Access, but mostly be with my ZS73.  If I were going to permanently mount it, the CEM60 would have been my first choice.


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#7 RandallK

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Posted 15 December 2019 - 06:59 PM

I got my CEM40 for the ease of lifting (at 72 years old). My max payload (with another 4.5Kg counterweight) is with my 8" Meade SCT. Seems to be OK but that would be my max.


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#8 DuncanM

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Posted 15 December 2019 - 07:11 PM

Right now I am using a CEM 25 which is managing just about 1.0 arc seconds RMS with my 20 lbs of EdgeHD 8" + reducer + OAG + D5300. For a $900 mount at 75% of it's capacity, I really can't complain!

 

But I want to get guiding closer to 0.5" RMS, and I'm getting the new ASI6200mm and a filter wheel so I want to do it justice with an upgraded mount.

 

The CEM 40 is newer, has very similar specs to the CEM60, but is nearly half the weight:

https://www.ioptron....uct-p/7402a.htm

 

Worm Wheel Φ110mm, 216 teeth

Resolution 0.08 arc seconds

Unguided Accuracy / PE <±7 arcsec

Mount weight 15.8 lb

 

The CEM 60 has built-in usb ports, more capacity, better specs, and still pretty light for it's capacity:

https://www.ioptron....uct-p/7200a.htm

 

Worm Wheel Φ146mm, 288 teeth 

Resolution 0.06 arc seconds

Unguided Accuracy / PE < ±5 arcsec

Mount weight 27 lb

 

I'm leaning to the CEM 60, but which would you choose? Anyone getting ~0.5" RMS with a big scope on the CEM 40?

You might already be atmosphere limited in terms of actual FWHM and your C8@~F7 so don't expect a huge gain in resolution. My CEM60's PE beats the spec quite handily. It's still a fairly lightweight mount and I'd go with it, all else being equal. It is a bit awkward to extract from it's case, but fortunately mine is permanently mounted.


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#9 v3ngence

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Posted 15 December 2019 - 11:54 PM

Thanks for the replies everyone!

 

I concur with Paul, my main consideration when choosing the CEM40 was it's light weight and capacity. My needs were light weight and my imaging needs will only extend to my SV102 Access, but mostly be with my ZS73.  If I were going to permanently mount it, the CEM60 would have been my first choice.

 

I got my CEM40 for the ease of lifting (at 72 years old). My max payload (with another 4.5Kg counterweight) is with my 8" Meade SCT. Seems to be OK but that would be my max.

 

What kind of guiding RMS are you guys seeing with the CEM 40?



#10 PaulE54

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Posted 16 December 2019 - 02:16 AM

Just got my CEM40 (non EC) and so far getting around 1.0 total RMS with guidescope (but that figure includes dithering), using an RC6 so around 8kg total load - so same as your CEM25. Looking at stats reported by other CEM40 owners, this is towards the worst end, some report as low as 0.5 total RMS.

 

I think my figures are a result of poor suburban seeing here in the Manchester UK suburbs, plus still getting to know the mount. Need to work on balancing and getting more counterweights closer in. Looking to try PHD2 Z filter if the clouds ever clear, which may give me worse headline RMS figures but hopefully tighter stars. So very much work in progress.

 

Good luck whatever you decide to get.


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#11 MrRoberts

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Posted 16 December 2019 - 10:26 AM

I just received my CEM40, and placed my Esprit 120 on it. I think its a bit much even for SC's "live stack". I am going to order the CEM60 in the early spring. 

I would suspect it should handle the C-8/E well. But to get numbers others talk about, you might need the EC version.
But if you are planning on any long exposer ap I think you just go ahead and order the CEM60. I to was worried about the weight/age but as I keep mine on a JMI dolly I only have to set it up once or twice a year.

I am planning on taking my CEM40/25 down to Arizona in the spring and put my C-8/E on the 40 and my Esprit 80 on the CEM25P.

I will be training myself with it using my C-6 here in the Chicago area.

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#12 joseph07081

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Posted 16 December 2019 - 12:17 PM

Thanks for the replies everyone!

 

 

 

What kind of guiding RMS are you guys seeing with the CEM 40?

Unfortunately I have only had 2 nights of clear skies since I purchased the mount. First light was my shakedown cruise to try out all of the pieces and parts, the second night I was having issues with the ZWO EAF due to cold weather (I hope fixed with a firmware upgrade).


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#13 SonnyE

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Posted 16 December 2019 - 12:53 PM

Go Big. wink.gif

For Astrophotography, rule of phumb is 1/2 the mounts capacity = maximum load. Makes it real simple that way.

Figure out your weight from the Vixen bar up (Or Losmandy bar), including the bar, and get a mount that can handle twice that weight. Or more.

 

My rig is 13.2 pounds. So a 30 pound capacity mount worked well. (2.2727 to 1 ratio)

I'm replacing my failed mount with a 44 pound capacity mount. (3.3333 to 1 ratio)


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