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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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Madratter
Postmaster


Reged: 01/14/13

New Telescope
      #6115845 - 10/03/13 06:41 PM Attachment (25 downloads)

I have been wanting a new Telescope to replace my C8 for Astrophotography for some time. After much thinking (probably too much), I ended up getting an Astro-tech AT8RC Ritchey-Chretien. I also purchased a Astrophysics CCDT67 reducer. Together they can turn it from f/8 into a f/5.36. However, I'll need an additional spacer for that. Currently it turns it into a f/6.4, which is very similar to my C8 with the Celestron f/6.3 focal reducer.

Reasons for wanting the new scope:

1) Better stars in the corners.
2) No mirror flop (this would especially bite me with focus after meridian flips).
3) Hopefully better overall FWHM.
4) Easier (and hopefully more stable) focusing
5) Faster focal ratio, somewhat better FOV, and better matched sampling with my camera once I get the spacers I need.
6) Less problems with dew.

We shall see how that all pans out. However, I have looked at a lot of pictures produced by this combination of telescope and reducer and I like what I see.

Initial impressions are the mechanicals are really nice compared to the Celestron Powerstar III. I do plan to replace the focuser with either a motorized Feather Touch or Moonlight but that will have to wait for now. My impression is the stock focuser is going to be serviceable until then.

I checked collimation with a Cheshire and I did need to adjust the secondary. The primary looked at least ballpark good.

Forecast is partially cloudy tonight. Hmm...

Here is a photo of the new setup:

Edited by Madratter (10/03/13 09:25 PM)


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rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: New Telescope new [Re: Madratter]
      #6115860 - 10/03/13 06:49 PM

Excellent!! I think you are really going to enjoy it. I'm liking my Levenhuk Ra 8RCCF more and more since getting the AP CCDT67. Looking forward to seeing what you can do with it and the 8300M!

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terry59
Post Laureate
*****

Reged: 07/18/11

Loc: Colorado, USA
Re: New Telescope new [Re: Madratter]
      #6115876 - 10/03/13 06:55 PM

That looks good. I hope collimation treats you well. I know some have issues with it

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rigel123
Postmaster
*****

Reged: 06/29/09

Loc: SW Ohio
Re: New Telescope new [Re: Madratter]
      #6116044 - 10/03/13 08:52 PM

Congrats! I love my 6" and I'm sure you will enjoy the 8!

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proteus5
Pooh-Bah
*****

Reged: 06/24/10

Loc: Southern New Jersey
Re: New Telescope new [Re: rigel123]
      #6116096 - 10/03/13 09:19 PM

Congrats!!!! can't wait to see first light.

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CounterWeight
Postmaster
*****

Reged: 10/05/08

Loc: Palo alto, CA.
Re: New Telescope new [Re: proteus5]
      #6116184 - 10/03/13 10:05 PM

Nice image congrat's on the new gear. Hope you get clear skies soon to get it dialed in and photon hoovering.

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Ranger Tim
scholastic sledgehammer
*****

Reged: 03/25/08

Loc: SE Idaho, USA
Re: New Telescope new [Re: CounterWeight]
      #6116256 - 10/03/13 10:48 PM

You may find that you need the additional focuser collimation ring. Did you get one? My AT6RC has issues with the focuser alignment and this adapter ring should fix it. Waiting patiently for the package, along with waiting for the AT65EDQ....

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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Ranger Tim]
      #6116330 - 10/03/13 11:29 PM Attachment (10 downloads)

Thanks for the encouragement and well wishes!

As for the collimation ring, my understanding is that one comes with the moonlight so I'll probably wait until I get that.

Here is first light. It isn't much but it is what I have since the clouds rolled in. Given the forecast and the weather satellite, I was fortunate to get this.

It is a 1 second exposure used for focusing and is binned 2x2. I actually ran it through PixInsight, and it says that my FWHM on this frame as a whole was 2.38. Given the weather, I'll definitely take that. It looks like stars are pretty good across the frame.

I was able to calculate my image scale. It is .938 seconds of an arc/pixel. That gives me an effective focal length of roughly 1190mm and an f/ratio of 5.85. So it is already faster than my C8 even without any additional extension between the CCDT67 and the camera.


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Wouter D'hoye
Carpal Tunnel
*****

Reged: 06/27/03

Loc: Belgium
Re: New Telescope new [Re: Madratter]
      #6116465 - 10/04/13 01:24 AM

Looks like some great gear. Have fun!

Wouter.


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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Wouter D'hoye]
      #6116902 - 10/04/13 10:10 AM Attachment (17 downloads)

Thanks Wouter.

I woke up around 3 in the morning and was having a hard time going back to sleep. Although I wasn't expecting good news given the weather report and what things looked like when I went to bed, I checked outside. It was clear!

I set things up to take the Horse Head. This morning the data was waiting for me. I love automation.

I'll be processing that data later. In the meantime, here is what CCDInspector is showing. I'm pretty happy with this result, given it says my collimation is off by 6" and that this data was binned 2x2 which reduces my FWHM when undersampled (which this data was). Most importantly, note how relatively flat the field is when using the Astrophysics CCDT67. That is quite believable as stars look good in the corners, something that was never true with the Celestron C8.

I should mention this was just the first frame from the series and was not the best.

Edited by Madratter (10/04/13 10:51 AM)


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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Madratter]
      #6116932 - 10/04/13 10:28 AM Attachment (11 downloads)

By way of contrast here is my best sub with the Powerstar III C8 from the NGC 7771 image I posted yesterday. This was binned 1x1 and was shot at f/10 which is where I get my best FWHM values with that scope.

The curvature is horrible. It isn't any wonder the corners look so bad.

Edited by Madratter (10/04/13 10:28 AM)


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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Madratter]
      #6116946 - 10/04/13 10:35 AM Attachment (9 downloads)

Here is the best frame with the C8 from that NGC 7771 shoot binned 2x2.

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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Madratter]
      #6116978 - 10/04/13 10:47 AM Attachment (8 downloads)

Here is about as directly comparable shot with the C8 as I can manage. This is the best Ha sub from the Dragon, Sharpless 2-132. This was taken at f/6.3 with the Celestron focal reducer/flatterer and binned 2x2.

Again curvature is horrible, and the corners are real real bad.

Edited by Madratter (10/04/13 10:48 AM)


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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Madratter]
      #6117012 - 10/04/13 11:01 AM Attachment (8 downloads)

Now that all the data is transferred, here is the best frame from the Horse Head shoot with the new AT8RC. Again, this is HA binned 2x2 with the Astrophysics CCDT67. FWHM would be even better binned 1x1 since this is under sampled. CCDInspector is inconsistent with itself, but reports FWHM for the frame as a whole as 2.66 arc-seconds.

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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: Madratter]
      #6117024 - 10/04/13 11:10 AM Attachment (7 downloads)

An independent view of this best frame from the AT8RC. This is a map of the FWHM using the PSF Estimator Script in PixInsight. It produced a very similar reading to CCD Inspector. The PSF Estimator value for the entire frame is 2.64 arc-seconds.

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Phil Hosey
Carpal Tunnel
*****

Reged: 10/29/08

Loc: LaGrange, GA
Re: New Telescope new [Re: Madratter]
      #6117447 - 10/04/13 03:07 PM

Nice scope, I just ordered the OPT branded version while they had them on sale for under $800, mine should be here Monday.

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TimN
Pooh-Bah


Reged: 04/20/08

Loc: Ontario, Canada
Re: New Telescope new [Re: Phil Hosey]
      #6117468 - 10/04/13 03:21 PM

Congratulations! I was looking at the same scope. I figured it would get me a bit deeper and I also liked some of the images that I've seen with it. However, I decided to wait awhile and put some more money into my observatory instead. Will be interested in watching your images.

Edited by TimN (10/04/13 03:22 PM)


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Madratter
Postmaster


Reged: 01/14/13

Re: New Telescope new [Re: TimN]
      #6117486 - 10/04/13 03:31 PM

Phil, if I recall, you had one in the past. Enjoy it!

Tim, not sure what you are doing with you observatory, but I consider mine my most important piece of equipment, so that certainly makes sense.


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Phil Hosey
Carpal Tunnel
*****

Reged: 10/29/08

Loc: LaGrange, GA
Re: New Telescope new [Re: Madratter]
      #6118106 - 10/04/13 10:29 PM

Quote:

Phil, if I recall, you had one in the past. Enjoy it!





Yup, I used to have the CF version, in fact I bought it from Joel (Buckeyestargazer). I was a nice scope and I regret selling it (which is why I'm getting another one).


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rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: New Telescope new [Re: Phil Hosey]
      #6118206 - 10/04/13 11:48 PM Attachment (7 downloads)

Madratter, I just downloaded CCDInspector and I'm a noob at this. Can you explain what this stuff means? Good? Bad?
This is from a single sub from my RC.

EDIT: Weird because its all over the map depending on what sub I input into it. I tried one from my apo and it shows worse collimation and curvature than my RC. I know that the apo is spot on. I just dont know what I'm doing with this program I guess.

Edited by rflinn68 (10/05/13 12:25 AM)


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