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Equipment Discussions >> Mounts

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RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
EQ6/Atlas PE graph--should I upgrade new
      #5757550 - 03/26/13 06:43 AM Attachment (37 downloads)

Hi all, for the last little while, I've been contemplating an upgrade from my EQ6 to something with less PE. I knew it had quite an error, but I never bothered measuring it. I wasn't looking at more payload, just better tracking. I've always needed to autoguide, even with focal lengths as short as 200mm.

Last night, under the full Moon, I decided to finally measure what error was there. I'm going to post my findings, and tap into the extensive knowledge of the group for suggestions. How bad is it? As was suggested by one member previously, maybe an Aeroquest worm would fix it? Ring gear? Scrap it, and get a CGE/G11 that could be just as bad?

At this time, a Mach 1 or EM200 isn't in the budget, so no need in suggesting one. Thanks...


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RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757551 - 03/26/13 06:44 AM Attachment (22 downloads)

This is another one of the graphs, which I have no clue on how to interpret.

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RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757553 - 03/26/13 06:45 AM Attachment (22 downloads)

I think this one says what I could expect if I ran PEC.

I ran one of my logs that were picked up when autoguiding, and they read +/- 3-ish arc seconds. Is this good?


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757572 - 03/26/13 07:07 AM

Hi Roger,

Your graph is VERY smooth, so it should respond well to PEC.

Your total PE is 40" peak-to-peak of which over 2/3 is the fundamental. SO the fundamental PE is about (100 / 128) * 40" = 31". Reasonable.

If you get the $100 Aeroquest worm, you can cut down the fundamental from 31" to 15". So your total PE will go down from 40" to 25". Not too great, but heck it's $100.

And yes, the +/- 4" is the residual after PEC. So I suggest, get that PEC working. It's the cheapest solution. If the results aren't great then look at the $100 worm.

And only after that, then you can look at other solutions.


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RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: EQ6/Atlas PE graph--should I upgrade new [Re: orlyandico]
      #5757587 - 03/26/13 07:16 AM

I figured the curve was nice and regular, but with a large error. My guiding results showed that, in that I've always needed to autoguide, but it's always been relatively painless...

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RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757591 - 03/26/13 07:18 AM

I think that the proposed curve after PEC is still higher than what I'd get with autoguiding, no? Can I autoguide in addition to PEC, or is that going to introduce more gremlins?

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orlyandico
Postmaster
*****

Reged: 08/10/09

Loc: Singapore
Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757628 - 03/26/13 07:43 AM

Yes you can autoguide on top of PEC. Contrary to popular belief, it actually works well.

On the AP600 (which I've been giving a lot of attention lately, hmm hmm..) I got the PE down to about 3" with PEC. It can do 10 minutes unguided, but not 20 minutes.

So I guide with it. Guiding corrections only happen once every 5-10 seconds, so I can use long guide exposures (3.5 - 4 seconds).

Heck I even guide with the Mach1 which has 0.5" PE after PEC. Because you can't get a perfect polar alignment, and the king rate changes across the sky. So if you want long exposures, you will still need to guide.

The advantage of low PE is you can lengthen your guide exposures. Very useful if your guide chip is sitting behind an NB filter.


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rmollise
Postmaster
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Reged: 07/06/07

Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757683 - 03/26/13 08:33 AM

Quote:

Hi all, for the last little while, I've been contemplating an upgrade from my EQ6 to something with less PE. I knew it had quite an error, but I never bothered measuring it. I wasn't looking at more payload, just better tracking. I've always needed to autoguide, even with focal lengths as short as 200mm.

Last night, under the full Moon, I decided to finally measure what error was there. I'm going to post my findings, and tap into the extensive knowledge of the group for suggestions. How bad is it? As was suggested by one member previously, maybe an Aeroquest worm would fix it? Ring gear? Scrap it, and get a CGE/G11 that could be just as bad?

At this time, a Mach 1 or EM200 isn't in the budget, so no need in suggesting one. Thanks...




That's easy to answer. Is this causing problems for guiding during imaging? This is not an unusual degree of PE for the mount, more than some, but it looks smooth and manageable.

As far as upgrading, forget doing much unguided imaging unless you are willing to upgrade to the the Mach 1 level and above.

All the mounts in this price range, and even those at the next level up (G11) will be more like your Atlas than different.


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RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: EQ6/Atlas PE graph--should I upgrade new [Re: rmollise]
      #5757701 - 03/26/13 08:44 AM

Quote:



All the mounts in this price range, and even those at the next level up (G11) will be more like your Atlas than different.




That's what I figured. It would seem a used Atlas at or around $1000 is a pretty danged good deal then...


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: EQ6/Atlas PE graph--should I upgrade new [Re: RogerRZ]
      #5757758 - 03/26/13 09:30 AM

You nailed it Roger.

The Atlas (and to a lesser extent the CGEM) are the best bargains in mounts. The rash of complaints about them are from folks who don't know how much you need to pay to get perfection.


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WadeH237
Pooh-Bah


Reged: 02/24/07

Loc: Snohomish, WA
Re: EQ6/Atlas PE graph--should I upgrade new [Re: orlyandico]
      #5757965 - 03/26/13 11:09 AM

Your PE graph looks pretty good. I agree with others that the smoothness is more important than the absolute PE. You've also confirmed that the mount guides well.

The question of whether to upgrade depends on your goals and expectations. If you expect that an upgrade would allow you to shoot unguided, I would suggest that it would not. For deep sky exposures to work well unguided, you either need to shoot at a short focal length, or you need to have some kind of pointing model that accounts for errors not related to mechanical PE (like atmospheric refraction, etc.)

I've been imaging with a CGE for 10 years. Depending on vintage, CGEs have periodic error between 20 and 40 arc seconds peak to peak. The thing is that the guide well, and got lots of successful results.

I just upgraded to an Astro-Physics mount, not because of problems with the CGE, but because I want to shoot at much longer focal length and more weight. Once I get all of my automation workflow adjusted and get comfortable with the mount at 2300mm focal length, I am planning to image with my C14 at 3900mm. The CGE just won't do that well.

So I guess that my answer to your question about upgrading, is that I would not upgrade unless you need more weight or a much longer focal length than you are current using.


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galaxy_jason
Vendor


Reged: 05/22/07

Loc: Texas
Re: EQ6/Atlas PE graph--should I upgrade new [Re: WadeH237]
      #5758410 - 03/26/13 03:05 PM

Quote:

Your PE graph looks pretty good. I agree with others that the smoothness is more important than the absolute PE.




Exactly!! That and correctability, that is, can very fine corrections be sent to the mount? I run all my Meade's at 20% correction rates. Much older Meade's only allowed 1x corrections, too aggressive for CCD work.


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tjugo
scholastic sledgehammer


Reged: 11/06/07

Re: EQ6/Atlas PE graph--should I upgrade new [Re: galaxy_jason]
      #5758438 - 03/26/13 03:20 PM

Hi,

A more interesting figure is the residual error after guiding. I own an Atlas and EM200. The transition from the Atlas to the EM200 was not painless.

My Atlas have a similar PE as yours, the EM200's PE is 10 arcsec p-p. At a image scale of 1.6 arcsec/pixel the images produced by the Atlas are hardly indistinguishable from the images produced by the EM200.

The EM200 doesn't care much about autoguide parameters, on the other hand the you need to find the right autoguiding settings for the Atlas. The EM200 is very forgiving about poor balance while the Atlas is picky.

So my advise is that you keep your mount unless it is giving you issues. I am sure you'll be more happy with an image with round stars that with a low PE plot.

Cheers,

Jose


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neilson
professor emeritus


Reged: 08/22/10

Re: EQ6/Atlas PE graph--should I upgrade new [Re: tjugo]
      #5759505 - 03/27/13 01:56 AM

Hi,
Recently I have been going through a few mounts looking for low PE thinking I could do unguided imaging of DSO's. I upgraded to the CGEM DX that was pretty good, then I switched to the G11 gemini2 and it had even more PE so after changing the worm and doing other tricks I got the PE down low, but I didn't like the Gemini2 controller. It might be better than what the G11 use to have but I feel the Nexstar is better. I couldn't afford anything more expensive so I decided to go back to the CGEM DX. I mentioned it in a Cloudy Nights thread and they recomended I buy a used CGE to handle my 34lb. payload with 2350 fl. and accept that I'll have to guide.
The CGE quickly became the best mount I ever owned.

I bought the used CGE and got one that had only been used a few times. I got lucky, this one only has 3 arc.seconds peak to peak of PE with PEC off. So I decided to try unguided imaging. You definately have to do a really good drift Polar alignment. I tried about 30 images from 2 minutes to 5 minutes using a T1i DSLR. I got some that had nice round stars. But many were not as good. Atmospheric conditions is one thing that having good PE cant overcome. But guiding can.

I have finally accepted that I must guide. But having nice low smooth PE makes it easier. Your PE is smooth so its guidable. But since it's kind of high you might want to upgrade your worm. If your stars are nice and round then theres no need to do anything unless you decide to increase your payload and focal length.

neilson


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RogerRZ
Whatta you lookin' at?
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Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: EQ6/Atlas PE graph--should I upgrade [Re: neilson]
      #5759611 - 03/27/13 05:57 AM

Given the poopy seeing we have under the jestream here, I'll likely just leave well enough alone. I can't see myself going longer than the 1200mm reduced C8 I'm using now, nor heavier than the 900mm MN65 that, complete with mini guidescope and camera weighs in at just over 25lbs. I guess I just had the slightly unrealistic goal of better, while not sacrificing the cheaper... I'm still following the "cheap encoder solution" thread though--_$500-ish for that kind of performance? Where do I sign?

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