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Equipment Discussions >> Mounts

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Motokid600
super member


Reged: 06/27/10

Loc: Berlin, New Jersey
Eq mount load capacity.
      #5639878 - 01/24/13 12:50 AM

As of late ive been looking at EQ mounts for a 11" Edge HD and the Celestron CGEM is looking like its going to be the one. But i have a few questions. It says a load capacity of 40lbs. So the OTA is 28lbs and the counterweight is 17. Thats 45lbs so does that mean i will only have 5lbs to work with? Because I plan to do a side by side saddle setup with a refractor and that can get heavy. Plus imaging equipment. So 5lbs wont cut it.

Also. Is there a way to get these mount without the tripod at a cheaper price? I plan to mount all this on a pier.


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jrcrillyAdministrator
Refractor wienie no more
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Reged: 04/30/03

Loc: NE Ohio
Re: Eq mount load capacity. new [Re: Motokid600]
      #5639918 - 01/24/13 01:31 AM

The rated weight is payload weight; the counterweights don't enter into it. On the other hand, mounts in that class are rated for visual use and folks usually derate them by about 1/3 for imaging use.

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CJK
professor emeritus


Reged: 12/05/12

Loc: Northeast TN
Re: Eq mount load capacity. new [Re: Motokid600]
      #5639919 - 01/24/13 01:32 AM

The load capacities specified by the manufacturers do not include counterweights. (I.e., all you have to worry about in your calculations is whatever equipment you are putting on top of the mount.)

That said, if you're planning on imaging, you probably ought to look at a mount with a higher capacity: generally, you want to keep the weight on the mount around 50% of the rated capacity. The 11" Edge HD would likely work okay, but adding a second scope (plus rings, plates, etc) is going to approach the rated capacity. Performance for imaging will likely suffer.

-- Chris


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Motokid600
super member


Reged: 06/27/10

Loc: Berlin, New Jersey
Re: Eq mount load capacity. new [Re: Motokid600]
      #5639970 - 01/24/13 02:43 AM

Thanks for the info guys I appreciate it. But what about the OTA's weight? You say 50% so 28lbs would already put me over. So if thats the case would anyone be able to recommend a mount thats not much more money then the CGEM? Because ive been looking and after 50lbs prices really rise.


Edited by Motokid600 (01/24/13 02:50 AM)


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neptun2
scholastic sledgehammer


Reged: 03/04/07

Loc: Bulgaria
Re: Eq mount load capacity. new [Re: CJK]
      #5639972 - 01/24/13 02:47 AM

My experience shows that you can use around 75% of the rated payload of the mount for astrophotography without problem. At least this is with my HEQ5 Pro. In you current situation the tube will be ok on cgem but if you add the photographic accessories it will probably be just too much. Maybe the CGEM DX with the additional 10 lbs payload will do the job.

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Motokid600
super member


Reged: 06/27/10

Loc: Berlin, New Jersey
Re: Eq mount load capacity. new [Re: neptun2]
      #5639974 - 01/24/13 02:52 AM

I was looking at the DX. Turns out the only difference is the tripod giving it the extra 10 pounds.

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RTLR 12
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Reged: 12/04/08

Loc: The Great Pacific NorthWest
Re: Eq mount load capacity. new [Re: Motokid600]
      #5639983 - 01/24/13 03:15 AM

Tripod, Counterweight bar (larger diameter), and electronics (more voltage applied to the motors) are different on the DX.

Stan


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: Eq mount load capacity. new [Re: RTLR 12]
      #5640009 - 01/24/13 04:41 AM

used CGE. there is one on the mart for $1950.

I don't think the C11EDGE with its 2800mm focal length can be reliably carried by the CGEM for imaging. I know of one person who does this.. but he has an AO (adaptive optics) unit. The CGEM gears are rough; even in the best case the fast (8/3) non-integer periodic error is 7 arc-seconds. On mine it is 22!

Even Celestron acknowledges that the non-integer gear error is an issue, because in the new AVX they are really talking up the integer-only gear ratios (that can be addressed with PEC). There is some - unconfirmed - talk that the AVX motors will be available for us CGEM owners with 8/3 gearbox problems... at some unknown cost of course. I'd guess $500 range for both motors and a new motor board.

Now if you put the 0.7X reducer on the C11EDGE that would take it down to 2000mm focal length which I think the CGEM can handle fine.

Sadly aside from the (used) CGE there are no other options above the CGEM, except the G11 at $3.6K (note the complaints on here as well..) and the CGE Pro at $5K.

You might want to look at the EQ6 / Atlas. At least it doesn't have the 8/3 gearbox problem, and uses stepper motors, but is otherwise very comparable to the CGEM. Made by the same (Chinese) company too..

As for the tripod.. you cannot buy it without the tripod. Just sell the tripod, you can probably get $200 for it. Or.. buy used and save a bundle.


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mmalik
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Reged: 01/13/12

Loc: USA
Re: Eq mount load capacity. new [Re: Motokid600]
      #5640026 - 01/24/13 05:12 AM

My suggestions:

-Get Mach1GTO...
-Get an APO for imaging while salvaging your 11" if you are not so visually inclined. Thx


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Motokid600
super member


Reged: 06/27/10

Loc: Berlin, New Jersey
Re: Eq mount load capacity. new [Re: orlyandico]
      #5640029 - 01/24/13 05:20 AM

Thanks for the advice I appreciate it. I really would like to stay with celestron so believe it or not I may actually bite the bullet and treat myself to a CGE Pro... Its a lot, but I want something future proof. So with that what kind of imaging performance would I see with about 15 - 20lbs of gear loaded on? ( mounting hardware, Astro Tech 80ed, DSLR ) What kind of exposure times could I achieve? Sorry for throwing the topic out the window, but I can never seem to make up my mind.

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: Eq mount load capacity. new [Re: Motokid600]
      #5640034 - 01/24/13 05:35 AM

15-20 lb? A CGEM will do fine for that. My CGEM does about 2" RMS guiding. Plenty for 500mm focal length. Other CGEMs can get under 1" RMS. The good ones.

Its only at really long focal lengths (>2000mm) where the CGEM struggles.


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: Eq mount load capacity. new [Re: orlyandico]
      #5640056 - 01/24/13 06:08 AM

Mmalik, IMHO if the guy is looking at a CGEM I don't think its relevant to suggest he pony up for a Mach1.

If he said CGE Pro right away then yes it would make sense. Since that's $5000.

OP, if you can spring for a CGE Pro, get the Mach1. Less capacity but far more accurate.

But if your payload is only 20lb and not a C11, both the CGE Pro and Mach1 are overkill...


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jrcrillyAdministrator
Refractor wienie no more
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Reged: 04/30/03

Loc: NE Ohio
Re: Eq mount load capacity. new [Re: orlyandico]
      #5640263 - 01/24/13 09:33 AM

Quote:

used CGE. there is one on the mart for $1950.




Yes. The CGE would be a major upgrade for the least cost increase. Better performance and build quality, and much beefier. I used to run a C11 and a 5" refractor side by side on one.


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bunyon
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Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Eq mount load capacity. new [Re: jrcrilly]
      #5640281 - 01/24/13 09:46 AM

Above we have estimates of 33, 50 and 75% of rated capacity for imaging.

I think they're all far, far too precise. The rule of thumb I'd use is that as you get closer and closer to the rated capacity expect more and more trouble with tracking. But each mount (I mean every individual mount, not just make) will be different. There are people using CG5s with a fair amount of weight on them and 10 minute subs. I wouldn't bet heavily on that, but it can be done.


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terry59
Post Laureate
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Reged: 07/18/11

Loc: Colorado, USA
Re: Eq mount load capacity. new [Re: bunyon]
      #5640327 - 01/24/13 10:12 AM

Quote:

Above we have estimates of 33, 50 and 75% of rated capacity for imaging.

I think they're all far, far too precise. The rule of thumb I'd use is that as you get closer and closer to the rated capacity expect more and more trouble with tracking. But each mount (I mean every individual mount, not just make) will be different. There are people using CG5s with a fair amount of weight on them and 10 minute subs. I wouldn't bet heavily on that, but it can be done.




I'd add that these soundbite numbers don't take into account the type of imaging being done. There is a huge difference between being able to generate quality 3-5 min LRGB type subs and 15-30 min narrowband subs.


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neptun2
scholastic sledgehammer


Reged: 03/04/07

Loc: Bulgaria
Re: Eq mount load capacity. new [Re: terry59]
      #5640383 - 01/24/13 10:40 AM

I completely agree here that these rules are very general and in whole. The length of the scope should also be considered and not only the weight. It also depends on the balance (newtonians are more difficult to balance than the refractors for example due to the location of the focuser and photographic load). The length of the exposures and focal length of the scope are also important. These rules are more of the "don't expect good performance if you put more than that" type. Of course there are exceptions but in general they are true. I personally saw much improvement in tracking accuracy with 5 minute exposures when going from 85% to 75% of maximum load on my HEQ5.

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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Eq mount load capacity. new [Re: neptun2]
      #5641054 - 01/24/13 04:57 PM

This may be a bit of a digression but what is the benefit of doing 15-30 minute subs over 5 minute subs? I can see that there may be less read noise but isn't that a small contribution to the total noise?

I'd rather loose 5 minutes of exposure because a plane flew through the shot than 20 minutes.

Chris


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Motokid600
super member


Reged: 06/27/10

Loc: Berlin, New Jersey
Re: Eq mount load capacity. new [Re: cn register 5]
      #5641072 - 01/24/13 05:08 PM

Better signal-noise ratios with longer subs. But the thing is.. I live in yellow skies. I can just make out the milky way on the clearest of nights. So even with an LP filter would 20 minute subs even be worth it in such polluted skies?

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terry59
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Reged: 07/18/11

Loc: Colorado, USA
Re: Eq mount load capacity. new [Re: Motokid600]
      #5641098 - 01/24/13 05:22 PM

Quote:

Better signal-noise ratios with longer subs. But the thing is.. I live in yellow skies. I can just make out the milky way on the clearest of nights. So even with an LP filter would 20 minute subs even be worth it in such polluted skies?




Long subs (say more than 5 minutes but routinely 10 or more) are essential for narrowband (Ha, OII, SII) imaging. If in a light polluted area, narrowband could significantly enhance the AP experience. There is no free lunch though. Getting into narrowband is more expensive

Edited by terry59 (01/24/13 05:25 PM)


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Motokid600
super member


Reged: 06/27/10

Loc: Berlin, New Jersey
Re: Eq mount load capacity. [Re: terry59]
      #5641150 - 01/24/13 05:51 PM

Well for starters im just going to be using a a 2 inch LP filter for my Canon EoS Rebel. Not the best camera, but it could be alot better with the right hardware. Right now on my Cpc1100 i can do 2 minute guided subs if im lucky. And on top of that the vignetting is horrendous. Its time for me to get serious. I want a telescope/mount setup i can walk away from with confidence. I want something that will just WORK. And work WELL. So far my AP adventure is consisting of nothing, but trial and error... with alot more error then trial.

Idk its a tough call. If im moving up my price range into $6k for mounts then alot of doors open up choice wise. The Mach1GTO does seem really nice. Im just deterred by the amount of needed accessories and switching over to new software. ( Ive become very attuned to NexStar ) But i am confused. .. This GTO mount is $6,415. Yet it can only hold 45lbs of equipment? Yet the Losmandy Titan can hold up to 100lbs for $400 less... so what going on here? Is the GTO THAT much better at tracking? Sadly im not to savy with EQ mounts having never owned one. But i do understand them. Its just alot of these "features" are almost off-putting. As far as narrowband imaging goes... i dont have much ( if any ) interest in it. ( Although i said that about AP when i first bought my CPC1100 for visual use ) Ive also been considering a CCD camera, but... no. I want to stick with DSLR's. There just... easier. And cheaper.


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