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Equipment Discussions >> Mounts

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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Orion Atlas EQ-G new [Re: jrbarnett]
      #5438702 - 09/24/12 08:08 PM

Jim,

What is the significant issue? The most common issues that I see with the CGEM are exactly the same as with the Atlas, inbility to balance and poor error for AP work related mostly to fit and finish and final assembly issues. While I have seen few of either, I have seen 1 or 2 more bad Atlas motor boards than CGEM motor boards.

I don't know about 10 times as many complaint threads but I do know about 10 times as many people who love to bash on Celestron every chance they get.

The CGEM is not perfect but neither is the Atlas. In fact, the Atlas has some major design flaws that were addressed with the CGEM like the counterwieght bar, latitude adjustment, clutch placement and saddle. In all these years, the only thing addressed on the Atlas has been the saddle.

The mounts that I receive for HyperTuning are not necessarily deficient in any respect, that's why I get a fair number sent right from the dealer or from a used seller. The average CGEM or Atlas is a good visual performer and a mediocre AP performer. The majority of mounts that come to me (including Celestron, Orion and Losmandy) are sent so that they can be good AP performers. If you talk to the mount designers, they will tell you that the mounts are designed and built within set cost constraints like any business. Anything above that cost has to be left to the aftermarket servicers and upgraders to take care of for those people who desire or need that additional bit of performance. I work on many mounts that "just work." They get sent to me so that they work even better. The ratio of Atlas to CGEM HyperTunes or kits has always been and remains about the same.

Ed.


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artcarter
member


Reged: 08/22/12

Loc: Olympia, WA
Re: Orion Atlas EQ-G new [Re: Pat at home]
      #5438997 - 09/24/12 11:47 PM

How does the iEQ45 from IOptron compare to the CGEM or the EQ-G?

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orlyandico
Post Laureate
*****

Reged: 08/10/09

Loc: Singapore
Re: Orion Atlas EQ-G new [Re: artcarter]
      #5439047 - 09/25/12 12:44 AM

The CGEM has a very well known 8/3 periodic error (182-second period) that cannot be corrected with PEC. This error varies widely in magnitude, on my CGEM it is 22" which is larger than the fundamental.

Another poster here (Luke) reports a 5" magnitude fast periodic error with a 6.2-second period on his iEQ45, this cannot be corrected by autoguiding or PEC because it's too fast (almost 1" per second).

Both of these cases, the error is in the motor gearbox.

The Atlas / EQ6 has a dead-simple one-stage gearbox with a 12-tooth gear on the motor, and a 47-tooth gear on the worm (with an idler in between). I have no proof for this, but I believe the simpler gearbox means there is less chance of gearbox-induced periodic errors.

That is just my theory though.

From a mechanical perspective I think they are all more-or-less equivalent. The fundamental periodic error (of the worm gear) will be similar in magnitude - and in general is not a problem since it is so slow (480-second period) so can be guided out.

It is the gearbox errors which are hard (or impossible) to guide out - but if they are small, they will not be a problem either. The 5" fast periodic error in the iEQ45 can probably be lived with - bouncing of the guide star due to seeing will be at the 2" to 3" level anyway.

The CGEM's huge 8/3 cannot be ignored - but it's slow, so can be guided out. What this means though is - for my CGEM at least with its huge 22" 8/3 error - is that autoguiding is required. My CGEM cannot be used for unguided imaging at all except at very short focal lengths and for exposures much less than 182 seconds.

But then almost everyone with this class of mount auto-guides. So probably still not an issue anyway.


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Orion Atlas EQ-G new [Re: jrbarnett]
      #5439513 - 09/25/12 10:51 AM

If you want to see what I consider to be a significant issue with this mount, just look at this thread:

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5428887/page/1/view/collapsed/sb/5/o/all/fpart/1.


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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Orion Atlas EQ-G new [Re: EFT]
      #5441774 - 09/26/12 02:22 PM Attachment (48 downloads)

A few days ago, I was doing some tracking experiments with my Atlas mount to help out a friend who is having problems getting his tracking working. The two attached pictures are each composites of the same four 10 minute exposures of the area around Gamma Triangulum, which was close to the zenith when imaged. The first one is a merge of the calibrated images, the second a merge after alignment of the individual images. Guiding was done using a webcam (not my usual guide camera) on an 80ST with PhD, where the guide star had a S/N ratio of around 12, possibly a bit less. This is a portable astro imaging setup and also doesn't have perfect polar alignment. Images were taken using an unmodified Canon T3i camera at prime focus of an 8" f/4.9 Newtonian reflector. A Baader MPCC was used to help control coma at the edges of the FOV.

Note: I'll need to send the pictures as two separate posts.

Phil


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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Orion Atlas EQ-G [Re: Phil Sherman]
      #5441777 - 09/26/12 02:23 PM Attachment (43 downloads)

Here's the aligned version.

Phil


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