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Celestron CGEM capacity?

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#1 Chet Biggerstaff

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Posted 23 October 2009 - 10:56 AM

I am a bit confused. Ive watched Celestrons videos of the mounts at the trade show and they said the Pro mount has a 90lbs capacity ON THE SCOPE (not on the mount) not including counter weights. Then they say the weight limit on the CGEM is 40lbs but dont say wether thats on the mount or on the scope or wether it includes the counter weights or not. What I want to know is what is the REAL weight capacity of the CGEM mount without counterweights or a tube on it. How much can I put on the mount without running into major issues with AP?

#2 t.r.

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Posted 23 October 2009 - 11:40 AM

40# is the weight limit on the saddle, ie. scope,rings,eyepieces and accessories not to include counter weights. This would be the max I would say, for visual observing with reasonable damping times. For imaging, the rule of thumb is half the weight capacity for Celestron mounts.

Vixen rates their mounts, or did at least, for total weight with counter weights included in the figure.

Astro-physics is by far the most conservative in their mount capacity guidelines. Use their figures and you have solid as a rock!

#3 Christopher Erickson

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Posted 23 October 2009 - 12:38 PM

Just an FYI,

Currently Vixen's mount OTA weight specifications do not include the weight of the counterweights.

#4 Chet Biggerstaff

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Posted 23 October 2009 - 02:10 PM

So that means that they rate the CGE pro differently? Or was the guy in the video wrong?

#5 jrcrilly

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Posted 23 October 2009 - 02:17 PM

So that means that they rate the CGE pro differently? Or was the guy in the video wrong?


The top mount vendors (Astro-Physics, Takahashi, Mountain Instruments, etc.) are more conservative in their ratings than the middle grade gear (Losmandy, Celestron, etc.). The CGE Pro is rated to carry 90 pounds, and it'll do it - but most folks would choose to derate it some for imaging use. An AP or Takahashi mount would be expected to be used for imaging at the rated load or perhaps even a little more.

#6 Chet Biggerstaff

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Posted 23 October 2009 - 02:29 PM

i understand but as $ wont allow one of thoose mounts ill have to stick with the Gem Pro and Cgems i have but looks like ill use the pro for AP instead of the Cgem (although the Cgem does do a great job on the shots ive seen so far)

#7 jrcrilly

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Posted 23 October 2009 - 02:36 PM

i understand but as $ wont allow one of thoose mounts ill have to stick with the Gem Pro and Cgems i have but looks like ill use the pro for AP instead of the Cgem (although the Cgem does do a great job on the shots ive seen so far)


What's your proposed load? The CGE Pro is a big, beefy package and a little pricey so I'd stay with the original CGE unless your load will be over 45 pounds or so.

#8 Chet Biggerstaff

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Posted 25 October 2009 - 09:04 AM

My load will be an 11" hd and some sort of 80mm acromat for guide scope along with Sbig 2000 color with AO8 and a 10 spot wheel. option 2 is 11" HD with same spoter scope with dastar lens and my Sony A900 DSLR or Sbig cammera. The Cgem will handle the weight for regular viewing but dont know about AP which is why im currious

#9 Stew57

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Posted 25 October 2009 - 12:28 PM

I have a CGEM 1100HD. It does not look to be stable enough for ap work. It seems a little shakey to me, even with no wind. Maybe an 8" would be better. I am not setup for imaging yet so this is just visual. I will be looking into a pier to help with the shakes. The ota is fantastic just wish I could have afforded the CGEpro.

#10 Chet Biggerstaff

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Posted 28 October 2009 - 08:44 AM

I have an old C8 on ther enow and its stable as a rock. Still waiting on my HD11 to ship from store (they say they havent recived their 1st shipment yet and im 5 on the list) I was wondewring how people got the EdgeHD series if they are not shipping yet? Why cant I get one but others can? What did I miss?

#11 GaryGray

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Posted 15 June 2010 - 06:32 PM

So if one wants to use an 11" EdgeHD on a CGEM mount for AP what can he/she expect. My projected set-up including camera, guidescope, ect. totals about 35 lbs. Five lbs under the stated limit for this "AP Optimize" OTA, but way over the "rule of thumb." So what will work? Probably not 10 minute exposures at f10. How about three or two minutes? Will a FR be required to do anything? Is Hyperstar the only option? Or is even that out the question? Should I just bag the whole idea and look at pretty pictures on the internet?

#12 Richard Turner

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Posted 15 June 2010 - 06:51 PM

I have a Nexstar 11 GPS and also a CGEM mount. I've been thinking about deforking the C11 tube and trying it out on the CGEM mount to see what I can accomplish for deep-sky astrophotography. As a guess--perhaps successful 2-minute guided exposures at f/6.3. It will be interesting to see how the images turn out.

#13 mclewis1

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Posted 15 June 2010 - 06:59 PM

Richard, You all read up on de forking your NS11? If not PM me, I have a few observations from when I did it.

#14 Richard Turner

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Posted 15 June 2010 - 07:02 PM

Mark, yes, I've done it before a time or two. Thanks.

#15 jrcrilly

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Posted 15 June 2010 - 08:34 PM

I have a Nexstar 11 GPS and also a CGEM mount. I've been thinking about deforking the C11 tube and trying it out on the CGEM mount to see what I can accomplish for deep-sky astrophotography. As a guess--perhaps successful 2-minute guided exposures at f/6.3. It will be interesting to see how the images turn out.


I'd expect the NX11GPS (suitably wedged) to be a much better imaging platform than the CGEM. The NX11GPS mount has nice drives and bearings.

#16 PhilCo126

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Posted 14 June 2013 - 02:35 AM

CGEM load capacity = 20 kilograms
CGEM DX load capacity = 22.7 kilograms
1) The CGEM DX has a 1-1/4” counterweight shaft versus ¾” and correspondingly bigger counterweights.
2) The CGEM DX has a heavier, bigger tripod. It uses the same tripod as the CGE Pro.
3) The CGEM DX has an adapter bell to hold heavier payloads on the tripod.
Both mounts use the same motors, motor boards and the same gear box.

Maximum load capacity refers to "visual use" ... for astro-photography divide by 2 :doah:

#17 Patrick

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Posted 14 June 2013 - 09:27 AM

For imaging, the rule of thumb is half the weight capacity for Celestron mounts.



I'm not sure I totally agree with the 'rule of thumb' approach, mainly because the length of the OTA, position of the camera on the scope, and the focal length plays a bigger role than just the weight itself. For instance, placing a heavy DSLR camera package at the end of a 127mm f/7 refractor is not the same as putting the same camera on the end of an 8" SCT, although the weight is similar.

Some of my best work to date has been on a CG5 mount with a 35 lb weight rating carrying a 25 lb payload (70% of stated capacity). However, the mount was balanced very carefully, and the imaging scope had a shortish focal length.

So, the bottom line is that all these things combined don't fit well within a gerneralized 50% rule of thumb scheme, to the point in my mind that it is meaningless.

One other thought while I'm on the subject. Weight aside, the mount gear train is going to have native PE. Adding balanced weight to the setup is not going to change that much since the motors still see the same load. Usually a heavier setup also means the scope has a larger aperture and longer focal length. I think those factors are more important than the weight itself.

Patrick

#18 corpusse

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Posted 14 June 2013 - 09:53 AM

I don't use this combination anymore but with a cgem and 50mm guidescope (big mismatch) I was able to get 2 minute guided exposures most of the time. Sometimes 3. This is at F10

Incidentally with a CGE and C11 and 66mm refractor, guiding has not substantially improved. I am getting about 3 minutes although I believe most of the problems in this setup are flexture based. The CGE certainly can handle the weight a lot better and the phd graph looks much improved. On the CGEM everything had to be perfectly balanced where as on the CGE there is a little more margin for error.






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