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Migelo
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Reged: 10/03/12

Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Peter in Reno]
      #5550652 - 12/02/12 04:44 PM

We're not going to use any focal reducer, because it would cause huge vignetting, so backfocus won't be a problem.

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Peter in Reno
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Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Migelo]
      #5550666 - 12/02/12 04:54 PM

Maybe go in baby steps. Start autoguiding only with OAG and go from there. Make sure the OAG will work well with AO in the future so you won't have to buy a different OAG just to work with AO. If you are satisfied with this results then you are set. Otherwise AO may be the next step.

I also suggest to get the highest sensitivity autoguider camera if you choose to use OAG. Lodestar may be the best. SBIG also has a pretty high sensitivity autoguider camera called STi but it uses a noisier Kodak CCD and you may see more hot pixels than Lodestar but hot pixels may be removed with dark subtraction.

Peter


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Migelo
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Reged: 10/03/12

Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Peter in Reno]
      #5550675 - 12/02/12 05:02 PM

That's a nice idea.

So I'll take that OAG-6 OAG and this lodestar camera for guiding: http://www.teleskop-express.de/shop/product_info.php/info/p2915_Starlight-Xpr...

and see how it goes. If needed, I may purchase an additional AO unit.

Does that moving prism in the OAG-6 do bad stuff if used with AO?


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Peter in Reno
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Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Migelo]
      #5550688 - 12/02/12 05:10 PM

I am not sure what you mean by moving OAG's prism doing bad stuff to AO. I am not familiar with AO, I only mentioned SX AO from reading reports. Once you moved the prism to the desired spot, you can lock it and it will never move. Just don't let the prism go too far down that could obstruct part of the CCD camera. The lower the prism the better so that it's closer to on-axis and the stars would be rounder. Stars at off axis tend to be elongated.

Peter


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Migelo
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Reged: 10/03/12

Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Peter in Reno]
      #5550714 - 12/02/12 05:25 PM

I was just wondering if in the case that the prism is not parallel with the AO moving parts, it could lead to some errors, just wanted to cover all the bases. xD

And noted the prism-not-obstructing-CCD-camera part.


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Peter in Reno
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Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Migelo]
      #5550726 - 12/02/12 05:32 PM

From what I have read, Maxim should take care of the mechanical imperfections (parts not parallel with each other) by running a calibration. SX software for AO does not have calibration so the autoguider must be squared with AO. I don't think you have to worry about this with Maxim. I would consult with Maxim and SX about this.

Peter


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Rick J
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Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Peter in Reno]
      #5550802 - 12/02/12 06:29 PM

The guide camera in that thread is not very sensitive. Works with a separate guide scope but can be a big hassle otherwise. With a decent guide camera, like the LodeStar and 12" aperture you won't have an issue for guiding. Finding one for correcting seeing which takes =<0.1" is often a problem however. This is where The Sky I think you mentioned as having will help as it can show you the ring your guider can reach around your chip. This makes it very easy, especially if you have a rotator.

While I don't guide very often the guide chip in my camera is even smaller than a LodeStar into that prism and I've never had an issue finding a guide star even working behind the filters and you are working ahead of the filters.

The SBIG AO unit is for much smaller chips. At 60mm the other one is marginal. Contact them to be sure it will work. Your chip is 52mm corner to corner and while its clear aperture is 60mm you need considerably more to give room for guiding. How far you can go before bumping the mount with it I don't know. Likely not very far. Since you are permanent you can get very good polar alignment so if it can handle the periodic error that should be sufficient.

Rick


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Migelo
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Reged: 10/03/12

Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Rick J]
      #5551774 - 12/03/12 10:16 AM

As it seems, I'll be going with the StarlightXpress AO unit, because it's about the same price as MonsterOAG and OAG-6, here in Europe.

It's an OAG with AO, so I'll be getting 2 for the price of 1.

What is your opinion?

@Rick: What do you mean by "The Sky I mentioned"


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Peter in Reno
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Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Migelo]
      #5551806 - 12/03/12 10:46 AM

I think you should double check whether OAG comes with SX-AO. I believe SX-AO and OAG are sold separatly.

Peter


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Migelo
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Reged: 10/03/12

Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Peter in Reno]
      #5551814 - 12/03/12 10:52 AM

It does come, it says so on the site and I've just used Skype credit to call StarlightXpress and they also confirmed it.


http://www.teleskop-express.de/shop/product_info.php/info/p2922_Starlight-Xpr...

It says, right to the picture: Off Axis Guider included

StarlightXpress said that the prism will cause some obstruction if streched all the way, because the AO unit was intended to be used with the 11000 chip.


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Peter in Reno
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Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Migelo]
      #5551837 - 12/03/12 11:03 AM

That's good to know. The picture showed a thicker OAG. SX also has Ultraslim OAG to allow to include filter wheel. Adding filter wheel to the thicker OAG may cause parfocal issue between main and guider camera. See picture of SX-AO with Ultraslim OAG and filter wheel at:

http://www.sxccd.com/sxv-ao-lf

I wonder which OAG comes with SX-AO. You might want to contact the vendor and ask if it can come with Ultraslim OAG.

Peter


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Migelo
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Reged: 10/03/12

Re: Guiding Schmidt–Cassegrain 300/3000 new [Re: Peter in Reno]
      #5551861 - 12/03/12 11:17 AM

Did just that and they said the slim version of their OAG is to be used with their filter wheel.

The AO unit comes with their standard "thick" OAG.


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