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Equipment Discussions >> Mounts

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gnowellsct
Postmaster
*****

Reged: 06/24/09

Re: Servo vs Stepper new [Re: photodady]
      #5404121 - 09/04/12 11:21 PM

Quote:


The tradeoff here is, of course, CASH. So for the money the CGEM (or Orion Atlas) is as good as it gets - for the money. The Losmandy G-11 with an upgraded worm gear (and twice the RA gear diameter) will cost upwards of four thousand US dollars, the Celestron pro more than that.

Again, thanks for using the link to my site and I wish upon all – clear and dark seeing.

If there is something here that I am missing please don't hesitate to correct and/or educate me.




Well, $3800 unless you're counting shipping. ($3300 plus $500 for an Ovision).

A lot of top high end work is done on planets with lower end mounts.

There is something to your argument; in fact, I think it's right. Nonetheless, the selection bias in saying this is what the people who are in the magazines use is apparent. There is a certain class of people who have the wherewithal to go high end on everything which makes their choices easy. The best CCD systems, Peltier coolers, best optics, best software, one can go north of $100k without much effort, but in any case, $20 to $50k.

The people working on the less expensive mounts have also made other decisions which may make them less competitive in high end astrophotography.

Many, however, are doing work which equals or exceeds the pics Palomar used to send to the textbooks. But if you compare everything pixel by pixel the high end equipment is sure sweet when it is in the hands of people who know how to use it.

Greg N


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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Servo vs Stepper new [Re: gnowellsct]
      #5404153 - 09/04/12 11:48 PM

Greg N - actually, I had a great Ferrari mechanic and bought the 328GTS new, so except for tune-ups/oil changes, I never had a minute's trouble for almost 8 years (never should have gotten rid of it). But I couldn't put groceries or anything in it, hence the Toyota. Now a Lotus!!! That thar's trouble!

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photodady
journeyman


Reged: 09/03/12

Re: Servo vs Stepper new [Re: EFT]
      #5404175 - 09/05/12 12:04 AM

The CGEM mount is what it is, no more, no less.

Interesting that the link you provided shows that most of the photos, that had the info provided, were captured using a AP 1200 mount. I do understand that the machining tolerances are important but being machined with equal tolerances the larger diameter gear WILL ALWAYS be more precise.

A single ten minute exposure will exceed, by far, ten one-minute stacked exposures. With AP mounts this IS easily doable without guiding.

I can easily produce a Horse-head nebula photo that rivals one shot from the Hubble derived solely from a dark frame exposure given enough time and effort post-processing and an example to work from. That is the difference between multi-short exposure composites and true long exposure photos that still retain intact data that might be scientifically useful. Most amateur astrophotography, that you see on the web, is merely an artistic rendering subjectively highly manipulated, aligned, and warped on several levels in order to achieve the final result.

The SOLE reason I posted my reviews in my blog is that there is a lack of TRUTHFUL REALISTIC reviews on the web that would possibly have prevented me from wasting my money on a CGEM. By the way if you are interested mine is for sale while I put my name on the AP waiting list.

In the mean time I will be activating my SkyX TPoint trial and will be posting extensive data on numerous tolerances (or lack thereof) in many aspects of the CGEM mount, watch my blog for updates probably sometime later this month or possibly early next month.

http://www.photodady.com/blog

The latest development from AP with precision encoders on the AP 3600:
"The measured tracking error was well below 1/2 arc second for a 20 minute time period" (only in the wildest dreams of a a CGEM user)
http://www.astro-physics.com/index.htm?products/mounts/3600gto/3600gto

Good luck and clear seeing.


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Falcon-
Post Laureate
*****

Reged: 09/11/09

Loc: Gambier Island, BC, Canada
Re: Servo vs Stepper new [Re: photodady]
      #5404206 - 09/05/12 12:42 AM

Quote:

Most amateur astrophotography, that you see on the web, is merely an artistic rendering subjectively highly manipulated, aligned, and warped on several levels in order to achieve the final result.




Yes, true.

And so are most of the pretty pictures released for PR use from NASA, ESO, etc, and by those using mounts such as the AP3200 that may grace a magazine cover.

Astrophotography *IS* about the end result image, not scientific data gathering after all...

Quote:

The SOLE reason I posted my reviews in my blog is that there is a lack of TRUTHFUL REALISTIC reviews on the web that would possibly have prevented me from wasting my money on a CGEM.




I get the strong impression that what is considered realistic in this case is very much a mater of perspective. Nearly the entirety of my imaging has been done on a CG-5 mount! For me a CGEM's failings would be a wonderful blessing! From my perspective I *expect* auto-guiding to be required to achieve 10-minute exposures. I would consider the CGEM well worth praise if it does allow guided 10 minute exposures at relatively long focal lengths.

I can understand being disappointed if you come from the perspective that no guiding should be necessary, but to my mind that is not a realistic expectation at this price point.


(BTW - While I do not consider myself the equal of the top-end astrophotographers, I still do have a lot to learn with processing especially, but I think I am also justified in using myself as an example that good AP can be done with "poor" mounts.)

Anyway, just to be clear I am not trying to be confrontational, just trying to point out the disparity of perspectives.


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jrcrillyAdministrator
Refractor wienie no more
*****

Reged: 04/30/03

Loc: NE Ohio
Re: Servo vs Stepper new [Re: photodady]
      #5404218 - 09/05/12 12:57 AM

Quote:

I do understand that the machining tolerances are important but being machined with equal tolerances the larger diameter gear WILL ALWAYS be more precise.




A larger worm wheel diameter will provide greater torque but doesn't affect precision. For a given worm accuracy, it's the tooth count on the worm wheel that determines drive precision. The more teeth per 360 degree rotation, the less erroneous axis motion results from a given worm error.

Quote:

A single ten minute exposure will exceed, by far, ten one-minute stacked exposures.




It'll certainly exceed the stack in terms of random noise - a real image killer. Otherwise the result is pretty similar so the noise is by far the most significant difference. Stacking is an essential part of CCD imaging because of its ability to cancel random noise.


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austin.grant
professor emeritus
*****

Reged: 10/18/10

Loc: Shreveport, LA
Re: Servo vs Stepper new [Re: photodady]
      #5404230 - 09/05/12 01:11 AM

Quote:



The SOLE reason I posted my reviews in my blog is that there is a lack of TRUTHFUL REALISTIC reviews on the web that would possibly have prevented me from wasting my money on a CGEM. By the way if you are interested mine is for sale while I put my name on the AP waiting list.






Speaking of REALISTIC, I don't think anyone here would agree that you had REALISTIC expectations. You didn't get burned by Celestron or the CGEM, you got burned by your own desire to be cheap. You wanted lab-grade results from a consumer-grade product.... That's silly.


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jrcrillyAdministrator
Refractor wienie no more
*****

Reged: 04/30/03

Loc: NE Ohio
Re: Servo vs Stepper new [Re: Falcon-]
      #5404234 - 09/05/12 01:17 AM

Quote:

I would consider the CGEM well worth praise if it does allow guided 10 minute exposures at relatively long focal lengths.




One of my observing buddies is doing some VERY nice work at 2000mm on a CGEM. Another uses an Atlas for narrowband work at quite long exposures. Both mounts can be capable imaging platforms. It just requires more work and greater effort (and more savvy) to use them than using a premium mount.

That said, my usual recommendation for a bargain imaging mount is a used CGE. Higher build quality, greater precision, more load capacity, and they can be found for $2000 or less. That's not all that much more than a new CGEM.

Edited by jrcrilly (09/05/12 01:17 AM)


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Servo vs Stepper new [Re: photodady]
      #5404253 - 09/05/12 01:48 AM

Quote:

Interesting that the link you provided shows that most of the photos, that had the info provided, were captured using a AP 1200 mount. I do understand that the machining tolerances are important but being machined with equal tolerances the larger diameter gear WILL ALWAYS be more precise.




Actually, what is interesting is that I'm sure you had to look at each image to determine which ones were taken with a CGEM and which were taken with the vastly more expensive AP1200. The point is that, in the hands of someone who is good at AP imaging and post processing, both mounts can produce stunning images.

As noted by others, the "larger diameter gear WILL ALWAYS be more precise" statement is clearly incorrect.

It all comes down to expectations. If you had actually read a lot of the threads discussing the CGEM I doubt you would have bought it since there many threads where people have compained about the CGEM incessantly. Most of use who appreciate the CGEM mounts have problem of "truthful realistic" reviews of the CGEM to be just the opposite of you. So unless the only reviews you looked at were the ones in the big magazines, I'm not sure what you are talking about. I'm actually happy to see the number of people defending these and other similar mounts in this case.

Good luck with your further testing of the CGEM, but I doubt it will every live up to your expectations. But if you want any chance at that, then you had best consider tuning it up some to make it perform at its best.


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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: Servo vs Stepper new [Re: jrcrilly]
      #5404256 - 09/05/12 01:52 AM

The blog post does reveal the CGEM in ways noone else has. I think the data he collected about the CGEM is pretty representative. While the expectations may be unrealistic the shortcomings are documented. usually one only gets subjective "feelings". The CGEM can do good work but many times the extra time and effort working with less mount is not revealed, just the "pretty" picture. I get the feeling he wants a mount that doesn't have to be fussed with and babied to work well. If that is the case the CGEM is out.

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orlyandico
Post Laureate
*****

Reged: 08/10/09

Loc: Singapore
Re: Servo vs Stepper new [Re: Stew57]
      #5404317 - 09/05/12 04:15 AM

I think what truly premium buys you is less hassle.

My old AP600 guides very well but very jerkily when west heavy.

I'm putting an Aero quest worm on my CGEM and expect much lower PE. But it will still be balance sensitive and have declination guiding problems. Can these be worked around and good images taken? I suspect yes.

But the premium mounts would not be so persnickety...


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Servo vs Stepper new [Re: photodady]
      #5404345 - 09/05/12 05:53 AM

Quote:

The latest development from AP with precision encoders on the AP 3600: "The measured tracking error was well below 1/2 arc second for a 20 minute time period" (only in the wildest dreams of a a CGEM user) http://www.astro-physics.com/index.htm?products/mounts/3600gto/3600gto.




I think no one here is surprised that the $27,000 3600GTOPE outperforms the $1500 CGEM in most every way by a wide margin. I myself am surprised anyone would even mention the AP mount when discussing a mount like the CGEM.

In terms of astrophotography it is well known, that the mount is the most important factor. In fact that is the reason A-P went into the mount business, no sense in building the best telescopes if there is nothing to mount them on. Roland Christen is a perfectionist.

As others have pointed out, to get the professional level photographs requires professional equipment. One can take satisfying photos with a mount like the CGEM if one has reasonable expectations. In the photo world, a good mount/tripod is imperative but the job of the mount is simple so one does not expect to pay more for the mount than for the camera and lenses...

Jon Isaacs


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brianb11213
Postmaster
*****

Reged: 02/25/09

Loc: 55.215N 6.554W
Re: Servo vs Stepper new [Re: Jon Isaacs]
      #5404370 - 09/05/12 06:28 AM

Quote:

In the photo world, a good mount/tripod is imperative but the job of the mount is simple so one does not expect to pay more for the mount than for the camera and lenses...



Well, supporting a camera and short tele lens weighing a couple of pounds for exposures under a second is a great deal less of a challenge from the support point of view than supporting a longish focus scope and camera weighing scores of pounds and expecting it to follow an apparently moving target accurately for tens of minutes.

Actually, with current highly sensitive digital cameras and stabilised lenses, for many types of "normal" photo work a tripod is more of an encumbrance than a help. My Manfrotto 028B spends far more time supporting a pair of binoculars for night time astronomy than it does holding up a camera.


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ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: Servo vs Stepper new [Re: orlyandico]
      #5404383 - 09/05/12 06:49 AM

Quote:

...Steppers suffer from a lack of dynamic range (if you want precision, you can't get fast slews). My GoTo conversion is limited to 160X sidereal, which is pretty slow but surprisingly can be lived with.
...



You must have used a very old stepper+high gear-down combo.
Modern microstepping GOTO controller design (see EQ6 GOTO, say Orion Atlas) can go as high as 800x and in tracking speed fine adjustment in +-1% step.


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ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: Servo vs Microstepping Stepper new [Re: orlyandico]
      #5404394 - 09/05/12 07:00 AM

Quote:

I don't really see why there is this story floating around that precision microstepping is "hard" - you can do this with an Arduino and an A4988 driver, which is a single $10 chip.



This is what microcontroller or what development platform is more suitable type of hardware debate. I'd also recognize that "microstepping" as a software module has existed for a long, long time. But I'd say this: a properly designed microstepping GOTO controller for astro application (or high grade, professional quality) is not so easy. I had a list of requirements previously in CN's ATM forum (and in another forum outside the CN). For some hobby-DIY self-developed attempts, I'd say they only meet some of them (and leave the rest of tasks for future work ) So you decide.

Clear Skies!

ccs_hello


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: Servo vs Microstepping Stepper new [Re: ccs_hello]
      #5404540 - 09/05/12 09:34 AM

@photodady

You can't judge CGEM's AP performance using 9.25” EdgeHD on DSO targets and better yet, unguided!? It' hilarious really.
Blogs like yours are reason why I don't read blogs.

Knez


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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: Servo vs Microstepping Stepper new [Re: orion69]
      #5404608 - 09/05/12 10:22 AM

Look his expectations may have been a bit unrealistic but he did get to the bottom of some of the behavior issues with the CGEM. A lot more in depth tahn a lot I have seen even here. Like he said the CGEM is what it is and now we know more of what it is.

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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: Servo vs Stepper new [Re: photodady]
      #5404616 - 09/05/12 10:25 AM

I would like to see give the same treatment to the Atlas and IEQ45. I think that would be interesting read.

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Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Servo vs Stepper [Re: psandelle]
      #5404638 - 09/05/12 10:39 AM

Ok,

If this is where you're coming from, visit this web site:

www.astro-physics.com

Call them and tell them you want a Mach 1 GTO mount. Trust me- this is what you are looking for. Spend some time on the site and choose your accessories carefully.

-Rich

Quote:

Greg N - actually, I had a great Ferrari mechanic and bought the 328GTS new, so except for tune-ups/oil changes, I never had a minute's trouble for almost 8 years (never should have gotten rid of it). But I couldn't put groceries or anything in it, hence the Toyota. Now a Lotus!!! That thar's trouble!




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Ray Gralak
Vendor (PEMPro)


Reged: 04/19/08

Re: Servo vs Stepper [Re: Jon Isaacs]
      #5404719 - 09/05/12 11:38 AM

Quote:

Quote:

The latest development from AP with precision encoders on the AP 3600: "The measured tracking error was well below 1/2 arc second for a 20 minute time period" (only in the wildest dreams of a a CGEM user) http://www.astro-physics.com/index.htm?products/mounts/3600gto/3600gto.




I think no one here is surprised that the $27,000 3600GTOPE outperforms the $1500 CGEM in most every way by a wide margin. I myself am surprised anyone would even mention the AP mount when discussing a mount like the CGEM.
Jon Isaacs




I think the reason he mentioned AP mounts is that someone gave him a link to pictures that were supposedly done with a CGEM, but most were actually done with an AP1200. That said those pictures, although colorful, had a little too much noise reduction for my taste. The excessive noise reduction caused some stars to be misshaped (visible in some of the full sized images) and areas to be featureless hazes. In my humble opinion, although they are not bad, they are definitely not up to the best deep sky images of these areas that I've seen, mostly because of the excessive noise reduction.

-Ray


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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: Servo vs Stepper [Re: psandelle]
      #5404804 - 09/05/12 12:30 PM

I like the Lotus analogy as my brother in law had one (Elise). When it was on it was great but it wasn't always on shall we say. When you make something that light something has to go so it was rather uncomfortable and noisy. When you develop that much power out of a little toyota 1.8, the engine is stressed and tuned to the max. Same moter detuned is quite reliable.

When engineers want to carry a heavier payload with a inexpensive mount that is not exceptionaly heavy, well something has to give. The compromises made for affordabilty will lead to less performance and lower longevity.

The blog posts reveals some of the compromise. I for one would like to see the compromises made in the case of the Atlas and IEQ45 also.


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