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dickbill
professor emeritus


Reged: 09/30/08
Posts: 630
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: freestar8n]
      #2766004 - 11/23/08 11:20 AM

So true Frank. In the cgem thread, somebody asked me why a CG5 can't autoguidea C11 at F/10.
People don't realise that difficulties at these focal lenght makes it a all different world than imaging under 1000mm. Resolution squares when magnification doubles and
ff you have a cheap imager, chances are that you also get a cheap mount (like me). With a Meade DSI at prime focus of a C9.25 at F/10, M57 looks like a 200 or 250X magnification in the DSI field of view. Keeping an object perfectly immobile at 250X during long poses despite vibrations, wind, backlash, drift, mechanical imperfections in gears during tracking (Periodic or not periodic error), seeing turbulence, guide coorections, mirror shift, piggyback guide system shift, software errors, feet in the cables, defocus....did I forget something ?, this requires serious mounting.

For my new mount, I am hoping that the cgem is superior to the Atlas in this realm, but I know that I might still have to get a CGE to be realistic. No shorcut here and you get what you pay for.

It might also be true, as Frank said, that at short focal lenght imaging, a piggyback optical system autoguiding the mount has many advantages over an offaxis guider, but that at longer focal lenght these advantages disapear and OAG is the way to go.


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jrcrillyAdministrator
Refractor wienie no more


Reged: 04/30/03
Posts: 30716
Loc: NE Ohio
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: dickbill]
      #2766016 - 11/23/08 11:25 AM

Quote:

Keeping an object perfectly immobile at 250X during long poses despite vibrations, wind, backlash, drift, mechanical imperfections in gears during tracking (Periodic or not periodic error), seeing turbulence, guide coorections, mirror shift, piggyback guide system shift, software errors, feet in the cables, defocus....did I forget something ?, this requires serious mounting.




Yup. Even folks with high-end mounts generally use reflective or refractive correctors (AO-7, AO-8, AO-L) rather than relying on the mount at those focal lengths.

--------------------
John C

Battle Cry of Reno
http://www.wadsworthobservatory.com
My Cloudy Nights gallery

AT12RC
AT65EDQ
QSI683WSG-8
Roper Scientific Quantix 6303E "project" camera
mystery EQ mount on the way


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: jrcrilly]
      #2766114 - 11/23/08 12:26 PM

I am beginning to agree with the previous three posters. Maybe OAG is my next step to try out.

Still, I want to return my C-11 for a repair or replacement. The dent on my C-11 is not acceptable. I have a hard time collimating. Maybe the dent is enough to slightly tilt the lens corrector making it hard or impossible to collimate. The dent may have most likely happened at the factory after quality inspection (if they have one) and before packing/shipping.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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freestar8n
Carpal Tunnel


Reged: 10/12/07
Posts: 1781
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2766146 - 11/23/08 12:48 PM

Quote:

I am beginning to agree with the previous three posters. Maybe OAG is my ne




Hi Peter-

There is no question that OAG takes some effort - but when done systematically it is actually easy and the results are consistent. Many people have a bad impression of OAG from using crude OAG's with small mirrors and no adjustments - and then just hoping for a guidestar to appear rather than pre-selecting one. The preferred way is to pre-select the guidestar, and it is no different from what many people do with a dual-chip camera, in choosing a good, rather than random, guidestar.

A key thing is that you sound like you want good results at long focal length - and to me that suggests you would be a good match to OAG.

For a beginner or intermediate, there is no question that a guidescope and long guide exposures will make it easy to find guidestars and "autoguide." But if you are aiming for really tight stars at long focal length and long exposure, OAG may not just be preferred - it may be essential.

Note that refractors seem to do well with guidescopes - but I think that's a combination of not having heavy mirrors, and tending to image at shorter focal lengths.

Frank


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: freestar8n]
      #2766200 - 11/23/08 01:15 PM

I have good experience with OAG. About 30 years ago when I was a teenager I had an orange tube C-8 and I used OAG. Every object I imaged, I always find a guide star. This is with film (no CCD 30 years ago) and manual guiding with illuminated reticle eyepiece. So, I don't think I will have issues using OAG with C-11. It might be a little harder with C-11 than C-8 since C-11 has narrower field of view than C-8.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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AlexN
Pooh-Bah


Reged: 08/09/08
Posts: 1202
Loc: Brisbane - Australia
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2766286 - 11/23/08 02:11 PM

People have less issues with refractors + guide scopes for a few reasons, firstly, they usually use a refractor for guiding.. you're not going to get differential flexture when both scopes are refractors, (heavy in the front) Its alot more likely to get it when you've got an 11" mirror at the rear of one scope, and an 2x 80~100mm pieces of glass on the front of the other..

Now the question that everybody wants to have answered.

Whats the best off axis guider to use with a moderately large chip + C11?

--------------------
Custom Made 10" F/3.8 Newtonian Astrograph
EQ6-Pro
SBIG ST-8300M
FLI CFW 2-7
Astrodon 5nm NB Filters
Astrodon I series LRGB
OAG + QHY5


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: AlexN]
      #2766339 - 11/23/08 02:58 PM

According to Frank's web site, he used Mini-Tracker from Taurus Tech at www.taurus-tech.com/mini-tracker.htm . I am leaning towards that and the price is reasonable ($95). They have a high end one (Tracker III) which I think it's an over kill, expensive, little bigger and heavier ($320).

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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freestar8n
Carpal Tunnel


Reged: 10/12/07
Posts: 1781
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2766802 - 11/23/08 08:29 PM

I heard from someone that the mini-tracker has been discontinued, so it may not be available - but I'm not sure. I switched from the tracker III to the mini because it has a shorter light path and would work better with a reducer. There are several others on the market, but the main things I would look for are:

1) Cost of other adapters on the front and back end - if cost is a factor

2) Size of the mirror and how close it is to the guide camera. Closer is better, but the focus has to match the main camera.

3) Ease of rotation to the guide star angle.

I cut the guide camera focus side of my mini-tracker to allow the guide camera to be closer to the mirror, which lets it see more of the light path.

A nice thing about OAG is it should carry from one scope to another, so the investment isn't lost.

Frank


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: freestar8n]
      #2767537 - 11/24/08 10:43 AM

I e-mailed Taurus Tech and Frank is correct, they no longer make the Mini-Tracker OAG. So what's a good OAG besides the $300 one from Taurus?

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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yg1968
Carpal Tunnel


Reged: 01/26/04
Posts: 1859
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2767641 - 11/24/08 11:38 AM

Peter, nice M27 image.

Out of curiosity, how many counter weights, do you use? I deforked my CPC 1100 last week end in order to put it on my EQ-6 Pro and I was surprised how many counterweight were necessary (at least 47 pounds with the Orion 80ED on top used as a guide scope). I had not yet installed the imaging and guiding cameras. It would have been even more with them. How much weight can the Atlas handle?


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mclewis1
Thread Killer


Reged: 02/25/06
Posts: 8913
Loc: New Brunswick, Canada
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: yg1968]
      #2767710 - 11/24/08 12:16 PM

The Atlas/EQ-6 is generally rated at 40lbs of equipment load. Most imagers that I've talked to are running 20-30lbs with these mounts ... some a bit more.

The farther any extra weight is from the attachment point (like a piggyback scope) the worse the problem, which is why many folks have adopted side by side mounting to keep the overall weight closer to the rotational point of the mount.

Ever notice how the high end imagers setups rarely look overloaded? Sure it does take a lot of equipment to load down an AP1200 or a Paramount but even so most folks (well except Jerry Wise ) tend to stay around 50-75% of the mounts rated capacity. The mount is often the single largest investment imagers make.

--------------------
Mark

C11, C6, APM/TMB115, and AT80ED - Pier mounted CGE in a POD, and CG-5A, WO EZ-Touch and AT Voyager
25x100s and 8x56s, T-Mount Light, Mark 1 eyeballs - 350Da, DSI-P, SPC900, NexImage, Mallincam

Just because you can doesn't necessarily mean that you should


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freestar8n
Carpal Tunnel


Reged: 10/12/07
Posts: 1781
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2767721 - 11/24/08 12:21 PM


Quote:

So what's a good OAG besides the $300 one from Taurus?[\quote]

The moag is good but expensive. The Lumicon easy-guider may be ok, but I don't know first hand. And I recently learned of this one:

9mm OAG
Quote:






which looks interesting.

These are all metal and heavier - and harder to modify. The main thing is that the pickoff mirror be big and close to the guide camera so that you get less vignetting and see fainter stars. You may have a trade off between a large mirror and some vignetting of the main image - but much of that will go away with a flat.

There is a big added cost from the front and back adapters, so keep that in mind.

I have only used the taurus stuff and MOAG myself. Quite a spread of prices. Well - it's an investment.

Frank


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yg1968
Carpal Tunnel


Reged: 01/26/04
Posts: 1859
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: mclewis1]
      #2767730 - 11/24/08 12:30 PM

Mclewis1, thanks. I actually knew that already. But that is the equipement that I already have. I have the option of imaging with a C6 as well. But I already had the C11 and I like it more than any other scope that I have. So I am not going to sell it. Celestron says that the C11 is 27 pounds but I believe they do not factor in the Losmandy or ADM rail (2.5 pounds), the finder, visual back, etc. I was looking on the Orion site and they are using 3 x 11 pounds of counterweights. So it is unlikely that 27 pounds is the right weight (unless you take off everything from the scope including the visual back).

Peter, one thing about your problem is that drift alignement will be necessary regardless of whether you use a guide scope or OAG. The guiding does not compensate for field rotation. If your polar alignment is off, the guiding star will be round but all other stars will show the effects of field rotation.


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: yg1968]
      #2767817 - 11/24/08 01:12 PM

Quote:

Peter, nice M27 image.

Out of curiosity, how many counter weights, do you use? I deforked my CPC 1100 last week end in order to put it on my EQ-6 Pro and I was surprised how many counterweight were necessary (at least 47 pounds with the Orion 80ED on top used as a guide scope). I had not yet installed the imaging and guiding cameras. It would have been even more with them. How much weight can the Atlas handle?




With 80mm Short Tube (2.5lbs) piggyback via ADM mini-dovetail, huge Orion StarShoot CCD camera and SSAG, I use four 11 pounds counter weights. If I use OAG and get rid of 80mm ST, then I may reduce to three 11 pounds counter weights.

Your guide scope may be too heavy. I used to have Orion EON 80mm ED (6.5 lbs) as guide/imager on C-11 and total counter weights was 52 pounds!!!!!!!! Too heavy but this setup was used to image M27 and M57!!!!! M1 and NGC 891 image were imaged with 80mm ST guide scope.
Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: yg1968]
      #2767836 - 11/24/08 01:20 PM

Quote:

Peter, one thing about your problem is that drift alignement will be necessary regardless of whether you use a guide scope or OAG. The guiding does not compensate for field rotation. If your polar alignment is off, the guiding star will be round but all other stars will show the effects of field rotation.




You are correct that poor alignment will show field rotation regardless of guiding equipment. But I do not see much field rotation on my frames. I see stars shift in between frames. This looks more like flexure issue to me.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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yg1968
Carpal Tunnel


Reged: 01/26/04
Posts: 1859
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2767941 - 11/24/08 02:14 PM

Peter, I also have an Orion ST-80. I will probably use that instead of my Orion 80ED. It saves me about 3.5 pounds (6 pounds vs 2.5 pounds). Another option would be to get a Stellarvue F50 finder and use it to guide.

Quote:

But I do not see much field rotation on my frames. I see stars shift in between frames. This looks more like flexure issue to me.




Perhaps, you have both problems. But I doubt that you will be able to image longer than 10 minutes without doing a drift alignement. Anyways, your results are better than mine, so I am not sure that I should be giving you advice...


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AlexN
Pooh-Bah


Reged: 08/09/08
Posts: 1202
Loc: Brisbane - Australia
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: yg1968]
      #2768045 - 11/24/08 03:07 PM

My C11 takes 4 counter weights with the ST80, cameras etc for deep sky photography.. for visual or planetary imaging, its happy with only 3...

Im currently looking into a good finder scope that I can guide with, or an OAG to bring the weight of the system down...

--------------------
Custom Made 10" F/3.8 Newtonian Astrograph
EQ6-Pro
SBIG ST-8300M
FLI CFW 2-7
Astrodon 5nm NB Filters
Astrodon I series LRGB
OAG + QHY5


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: yg1968]
      #2768357 - 11/24/08 05:51 PM

Quote:

Perhaps, you have both problems. But I doubt that you will be able to image longer than 10 minutes without doing a drift alignement. Anyways, your results are better than mine, so I am not sure that I should be giving you advice...




Thanks to Deep Sky Stacker and Nebulosity for making my images look good but that's cheating!!!!

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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AlexDJ30
sage


Reged: 09/02/08
Posts: 405
Loc: Monterrey, Mexico
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2768369 - 11/24/08 05:56 PM

I think the problem relies on the C11 weight pklus all the accesories on it, the Atlas is a a very good and i have seen people take nic epictures with C11, but probably in paper i wouldnt try that even on an atlas, i would step down the aperture to something about C9.25 or a C8 so the system should have plenty of left over. I think with the C11 and accesories you are almost in the peak of their quality performance.

--------------------
Equipment:
- ETX 125 AT
- C6 ASGT
- WO 66mm SD
- 2.5X ED Barlow, 8-24mm Zoom Eyepice
- Canon EOS Rebel XSi
- Celestron Nextimagen
- Orion Starshoot CCD cam


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yg1968
Carpal Tunnel


Reged: 01/26/04
Posts: 1859
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding [Re: AlexDJ30]
      #2768473 - 11/24/08 06:57 PM

Personally I also have a C6 in addition to the C11. But the problem is that the time of exposure must be much longer with the C6 than the C11. The C6 is only 10 pounds but with a (somewhat heavy) dual saddle, it ends up being much heavier than that. Also the C6 with a larger camera or DSLR shows some vignetting which is not the case with the C11. The C11 is a light bucket and there is something to be said for that. My best images have been taken with the C11. So I am partial to keep it and using it. Although I also like my C6. It's nice to have options!

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