Jump to content


Photo

Celestron 11 inch OTA Pros and Cons ???

  • Please log in to reply
27 replies to this topic

#1 Dakota1

Dakota1

    Viking 1

  • *****
  • Posts: 693
  • Joined: 18 Oct 2010
  • Loc: West of the Mississippi

Posted 31 March 2013 - 10:09 AM

Looking at getting a Celestron 11in OTA with Starbright XLT mutlicoatings. In this area I do not know anyone with this scope to see how they rate the performance. I was thinking of the 9.25 edge to possibly do some DSLR photography maybe down the road not sure. I also know aperture rules. Would like to have any pros and cons on this 11 inch OTA on its all around performance. Thank you

#2 MikeBOKC

MikeBOKC

    Aurora

  • *****
  • Posts: 4646
  • Joined: 10 May 2010
  • Loc: Oklahoma City, OK

Posted 31 March 2013 - 12:48 PM

I own the CPC1100, which is the same OTA as you are considering for equatorial mounting. The pros:

-- Excellent aperture,a sweet spot in my opinion that opens up a lot of objects visualy that 8 inches and lower will struggle to get like the E & F stars in the trapezium, the M51 bridge, etc.

-- Holds collimation very well.

-- Kind to most eyepieces.

-- Excellent for binoviewing.

-- Big and weighty enough to resist wind and vibration.

The cons:

-- Hefty, not a struggle to transport and mount, but not for those with bad backs or other disabilities.

-- Because of its higher resolution, is also somewhat sensitive to poor seeing.

-- Cooldown time . . . not a grab and go by any means.

I would say if you are considering a lot of AP, the 9.25 Edge would be superior. If mostly visual, the 11.

#3 FXDX

FXDX

    Sputnik

  • -----
  • Posts: 45
  • Joined: 29 Mar 2013
  • Loc: Good old Europe

Posted 31 March 2013 - 01:29 PM

hello,

i had a nexstar 11 once (around 2005-2007) and a cpc9.25 now. what i notice is a better, sharper performance and more contrast. you have to consider that the 9.25 is not just an sc between the 8" and 11" aperture but has a longer focal length than those both. some users say the 9.25 comes close to a maksutov sc in performance.

just my two cents here...

:)

#4 Dakota1

Dakota1

    Viking 1

  • *****
  • Posts: 693
  • Joined: 18 Oct 2010
  • Loc: West of the Mississippi

Posted 31 March 2013 - 07:56 PM

FXDX--Looking at the focal lengths the 11 inch is 2800mm. the 9.25 is 2350. That's a big difference in aperture. I will probably go with the 11 inch for visual use. A friend of mine has an 8 inch and it get good views. the 11 inch has to be a lot better overall for visual use. Thanks for responding.

#5 Dakota1

Dakota1

    Viking 1

  • *****
  • Posts: 693
  • Joined: 18 Oct 2010
  • Loc: West of the Mississippi

Posted 31 March 2013 - 08:03 PM

MikeBOKC,-- Thanks for responding. I will most likely go with the 11 inch. I know I will end up with more visual that photography. I may sell my XX14i. It is taking up a lot of room everywhere I put it. I like it but some priorities change. I intend on using my Atlas mount is going to get more use for auto tracking something my Orion can not do making life better. Thanks again for responding.

#6 FXDX

FXDX

    Sputnik

  • -----
  • Posts: 45
  • Joined: 29 Mar 2013
  • Loc: Good old Europe

Posted 01 April 2013 - 02:45 AM

sorry B.,

wasn´t able to explain in english. i try again: the 9.25 tube has the same length as the 11" but less aperture (what is pretty obvious).
the size of the secondary mirror and the extension factor definitely differ from 8 and 11" SCs. seems, these features make it a very special cpc and the 9.25 is not just an "in between" scope though.

;)

#7 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15764
  • Joined: 06 Jul 2007

Posted 01 April 2013 - 09:18 AM

Looking at getting a Celestron 11in OTA with Starbright XLT mutlicoatings. In this area I do not know anyone with this scope to see how they rate the performance. I was thinking of the 9.25 edge to possibly do some DSLR photography maybe down the road not sure. I also know aperture rules. Would like to have any pros and cons on this 11 inch OTA on its all around performance. Thank you


What do you want to image? Unless it is small targets, stick with a C8. Less expensive, more field, less focal length. All the C11 buys you for imaging is more focal length and image scale.

The C11 is a fine scope for visual use with there being an obvious difference between it and the C9.25 visually. ;)

#8 Dakota1

Dakota1

    Viking 1

  • *****
  • Posts: 693
  • Joined: 18 Oct 2010
  • Loc: West of the Mississippi

Posted 01 April 2013 - 10:37 AM

rmollise Thanks for responding; I do love visual observing. The photo end is something that may never happen. I also know certain scopes are designed for specific things. I also thought about a refractor at one time, but realized they are limited especially for wide angle viewing as well as DSO in one scope. In a refractor in the 120-150mm range they are not good at wide angle viewing where I prefer a scope that will do both but yet have good light gathering capability. This is why I was thinking more to the Celestron 11 OTA or equiv. I need to downsize as far as space for storage and hauling equipment. I like the Orion 14 inch dob there are just to many pieces. It will be nice just to set up the mount and add the scope and go for it. Thank you

#9 gastargazer01

gastargazer01

    Vostok 1

  • -----
  • Posts: 146
  • Joined: 21 Dec 2012
  • Loc: Flowery Branch GA

Posted 08 April 2013 - 08:29 PM

This is the OTA that I have and I have been very happy. It does have a small FOV. I just started imagining and use a DSLR you can check out some of my beginner photos at my astrobin link. I did need to upgrade to the CGEM DX mount however most of the images were created with the CG-5 ASGT mount.

#10 dragonslayer1

dragonslayer1

    Apollo

  • -----
  • Posts: 1030
  • Joined: 25 Feb 2012
  • Loc: SLC, UT

Posted 08 April 2013 - 10:52 PM

Mike, good pictures, very good. And Saturn at 4.35 minutes shows the CG-5 to track very very well with the weight you have on it. I know the one Saturn says a CGEM but is the other one with a CG-5? Either way, very nice pictures. :bow:
Kasey

#11 gastargazer01

gastargazer01

    Vostok 1

  • -----
  • Posts: 146
  • Joined: 21 Dec 2012
  • Loc: Flowery Branch GA

Posted 09 April 2013 - 05:21 PM

Thanks, it's a start. I am not guiding at this point, just trying to dial in a good alignment with very little drift. The planetary and some of the moon shots were done using the video mode 5X in BackyardEOS. I have used the 6.3 focal reducer and field flattener and that you can see in the M42 M43 image and that is the full frame of the Canon T4i sensor. Right now I am getting a max exposure of 120 seconds, I have a lot of room for improvement. My goal is 600 second subs. Now all I have talked about has been imagining let me also say that for visual I was extremely happy with my mid range eyepieces. The scope I had prior was a Meade ETX-125 that had fine optics but the aperture difference is huge.
I do not consider myself an expert but this has been my experience.
Good luck

#12 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 10 April 2013 - 11:37 AM

I have an XLT version of the C11. It came as a Nexstar 11 GPS, but my main reason for buying it was to use it with hyperstar for imaging. In this mode, the performance is nothing short of incredible- it literally is possible to fully image 6-7 DSOs in one night.

However, the overall package was extremely heavy and clumsy to move around. So, I have now deforked the OTA and have it on a the Celestron version of a Losmandy dovetail. In this mode, it is surprisingly light and easy to move around, and easily goes on my Mach 1 GTO.

My least favorite modes have all be visual and native photography, since the coma is rather severe. I have gotten the Starizona SCT reducer/ flattener, but haven't had a chance to try it out- this has been a winter of very bad seeing, here abouts.

The hyperstar mode has some drawbacks, namely you have to replace the secondary after mount alignment. In my case, I have been getting an unusual internal flare sometimes on bright stars which produces a pure blue "pseudo nebula" artifact. I haven't been able to track down if anyone else has that. On that note, I see I have a post to make in the Cats and Casses forum.

The reason I'm not so hot on it for visual is I just never seem to be able to get one of the really good images from this scope. Maybe it's the desert always outrunning its cooldown, or what. I do better with my C8 consistently. At the moment, if it weren't for hyperstar I'd list it for sale immediately without a second thought.

-Rich

#13 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 10 April 2013 - 12:02 PM

For clarification, I have a C5, which seriously rewards good collimation, as does my C8. The C11 just never does better that mediocre images on planets or anything else. I have gone out when the house temperature is approximately the same as outdoors expecting better, I just haven't seen it. I've thought maybe I have one with bad glass, but it doesn't show any obvious signs from what I can check, though the hole isn't quite concentric on the corrector, which caused a problem getting good collimation with hyperstar. As far as I can make out, it's just vulnerable to seeing, though even using it from on top of a 9000 ft. peak hasn't fixed that. So, I won't argue with anyone's pet theory except to say I've tried every trick I've ever seen mentioned and a few others without ever getting a jaw-dropping visual image from a scope all the data says should produce them every day of the week. The C8 simply does better.

I remember better looking views from the C11 mounted in the dome at the PAS observing site.

My AP 130 EDFGT, a full 150mm smaller in aperture, doesn't take it to school; it's more like a gangland assassination.

-Rich

#14 gastargazer01

gastargazer01

    Vostok 1

  • -----
  • Posts: 146
  • Joined: 21 Dec 2012
  • Loc: Flowery Branch GA

Posted 10 April 2013 - 12:21 PM

Hey Rich I would love to see some of your images with the Hyperstar.

#15 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 10 April 2013 - 10:55 PM

Let's see.

#16 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 10 April 2013 - 11:11 PM

Let's see. This is the North America nebula with a Pentax K-7.

-Rich

Attached Files



#17 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 12:39 AM

Here is the hyperstar nebula in blue. This was shot with the more sensitive Pentax K-5.

-Rich

Attached Files



#18 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 12:43 AM

This time I took a crack at causing the blue nebula defect. No dice.

-Rich

Attached Files



#19 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 12:45 AM

These are all from 30 second exposures.

-Rich

#20 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 09:57 AM

This is M51. There are a bunch (at least 10) other galaxies in this image. Taken with the wonderful K-5, the best kept secret in astrophotography with its less aggressive IR cutoff filter, 14 bit images, iso 51200 max sensitivity, and on board interval timer.

-Rich

Attached Files



#21 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 10:01 AM

Here's a crop at 50% resolution so the little galaxies can be seen.

-Rich

Attached Files



#22 gastargazer01

gastargazer01

    Vostok 1

  • -----
  • Posts: 146
  • Joined: 21 Dec 2012
  • Loc: Flowery Branch GA

Posted 11 April 2013 - 11:32 AM

Nice, it just blows me away that 30 second give you that much light from M51. Thanks for the examples

#23 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 03:26 PM

Actually, this was only at ISO 12800. I'm still kicking myself for not going further.

-Rich

#24 Bill Barlow

Bill Barlow

    Vanguard

  • *****
  • Posts: 2432
  • Joined: 03 Dec 2007
  • Loc: Overland Park KS

Posted 11 April 2013 - 07:13 PM

Beautiful images, Rich. I saw your earlier post about your C11 not giving very sharp visual views. I have owned 3 C11's in the past and two behaved much like yours. No matter how good the collimation was or how long I sat out the scope to accilmate to the outside temperature, the visual views were never very sharp and contrasty..especially when viewing planets The one that put up very good visual views was one that I bought through Company 7. I now own a Meade 12' ACF that is excellent visually..much better than all of the C11's I owned.

Bill

#25 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5614
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 11 April 2013 - 07:51 PM

What's even more difficult to understand is how this is combined with extremely good focuser performance (very little focus shift in visual) and no focuser backlash. I've looked for obvious signs of something really being wrong... it's more like it's just never really great.

The older Meade 12' had a hyperstar version. The ACFs don't, so C11 or Edge HD 11 is basically the only game in town these days.

My understanding is the Edge HDs are a totally different critter- they're all ostensibly perfect. Of course, that doesn't make much difference for hyperstar, since it bypasses the internal flattener in the baffle tube.

I've sent in my picture of the hyperstar nebula to Dean at Starizona to see if he's seen it previously.

-Rich






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics