14 replies to this topic

[Showtime]

I am getting ready to order a Celestron SCT and I have boiled it down to 2 choices: the Celestron C11-A-XLT or Celestron 9.25" EdgeHD.  The 11 inch is 27.5 pounds and the 9.25 is 21 pounds.  Which would be best for both viewing and AP if weight is not a big issue?

Thanks!

[pyrasanth]

The 9.25" Edge is going to have a very flat field which is important to get nice stars to the edge of the sensor- not so important for centralised planetary photography but still nice to have. Back focus is more critical on the edge systems and the Celestron reducer is quite expensive. However it is a very capable and light weight system and the 9.25 has a reputation for great optics- probably the best in the SCT series due to its slightly longer focal length mirror.

 

The 11" will have more light grasp and potential resolution however larger sensors will show a slight field curvature due to the field not being corrected as in the Edge. If deep sky AP is your desire this would be a good option as a compromise for price vs light grasp. The Edge 9.25 will give you a nicer field whilst the 11"- accepting the slight compromise- will give you a bit more resolution and a brighter image.

 

The field curvature on the 11" for visual would probably not be noiticeable in other than the widest field eyepieces- it's AP where the difference between the 9.25 Edge and the 11 would be noticed especially with larger camera sensors.

Edited by pyrasanth, 08 April 2021 - 11:03 AM.

[Spikey131]

Visual and solar system AP - C11 because of aperture, and you are mainly concerned about the center of the FOV.

 

Deep sky AP - C9.25 HD because aperture is less critical and you will need the edge correction.

Many will disagree because this is CN and that is what we do 

[pyrasanth]

Visual and solar system AP - C11 because of aperture, and you are mainly concerned about the center of the FOV.

 

Deep sky AP - C9.25 HD because aperture is less critical and you will need the edge correction.

Many will disagree because this is CN and that is what we do 

Wash your keyboard out- I've never seen anybody on this forum disagree

[Robindonne]

Wash your keyboard out- I've never seen anybody on this forum disagree

I don’t think that’s correct. I read many posts without different opinions, so....

[jpengstrom]

[Snip]

Many will disagree because this is CN and that is what we do 

Truer words were never spoken! 

[pyrasanth]

I don’t think that’s correct. I read many posts without different opinions, so....

So.....I lied........just a bit

[COViewer]

I'd even say go an Edge 8.  For AP aperture is less important.  For suburban skies aperture is less important.  Then get a light bucket for visual.

[pyrasanth]

I'd even say go an Edge 8.  For AP aperture is less important.  For suburban skies aperture is less important.  Then get a light bucket for visual.

I don't agree- aperture is king for AP- if that were so we would all be imaging with a 60 mm finder scope.

[COViewer]

@pyra, well to a degree. But consider three scenarios:

1. C8 Edge for AP, 12" Dob for visual
2. C9.25 Edge for both
3. C11 for both

I'd go 1.

[pyrasanth]

@pyra, well to a degree. But consider three scenarios:

1. C8 Edge for AP, 12" Dob for visual
2. C9.25 Edge for both
3. C11 for both

I'd go 1.

Again it will mostly be target dependent. The larger aperture will give you image scale and light grasp which can be important to resolve fine detail. I've also found that larger apertures at long focal lengths are not so affected by light pollution gradients- of course SNR will suffer under poor sky conditions however the calibration appears for me to be easier. I know there is no clear answer however I always prefer larger aperture for DSO work.

 

I have a Nexstar 9.25 and the difference between that and the C14 is night and day- on image scale and detail.

Edited by pyrasanth, 08 April 2021 - 04:01 PM.

[Epox75]

That depends on what you are looking for and on your mount. Assuming that your mount can handle them both, for planetary imaging and for imaging small objects like planetary nebulae, I would say the C11 but for deep sky imaging of larger objects like many galaxies, reflection and emission nebulae I would say the C9.25 EdgeHD for its flat field. The C9.25 EdgeHD has also the mirror lock and ventilation for a faster cooldown.  

 

Anyway the steadiness of tracking/guiding is more important than aperture in my opinion, so if your mount hits its astrophotography payload limit with the C11, I would definitely suggest to go lighter and get the C9.25 EdgeHD. 

Edited by Epox75, 08 April 2021 - 04:07 PM.

[Showtime]

Thanks everyone!  I have the following equipment so far:  Skywatcher EQ6 Pro mount (44 lb capacity), ZWO-ASI533MC-P primary camera, ZWO-ASI178MM guide camera, Orion 50mm guide scope, Celestron Focus Motor, ZWO ASIAIR PRO WI-FI CAMERA CONTROLLER, filter drawer (I think that is all).  I am pretty sure I could handle the 27.5 lb 11 inch but I am leaning toward the Edge for the the flat field.  The targets I intend to capture are primarily the larger deep sky objects.  I love hearing everyone's opinion.  Seems like there is no wrong way to go because either scope can be modified to F2.  

Edited by Showtime, 08 April 2021 - 10:34 PM.

[ERHAD]

I currently image with a ZWO533 as well. I am using a NON-Edge C9.25 with very pleasing results (with and without reducer). The small sensor on the 533 poses no challenge to the scope, and I get very good stars right to the edge of the image (no need to have the EDGE HD for this sensor in my opinion). I image with an EQ6-R Pro as well, fully loaded (  Eagle 3 computer riding on top of tube, Off axis guider, filter drawer, electronic focuser, camera, etc..), I get very, very good guiding. My main interest is in the smaller stuff, planetary nebula and galaxy mainly, so the narrow field of view is not a problem for me. My skies also seem to tolerate the high image scale as well (0,55" per pixel), and I am extremely pleased with my setup. If you want to image wider stuff, and/or you plan to get a camera with a bigger sensor down the road, going for the EDGE may be a better "future-proof" option. I've thought about the C11, but frankly, the results I am getting are so good I don't see how it would make much difference, the 9.25 already provides more than enough resolution and focal length.

 

Be aware, though, that as far as I know you won't be able to control Celestron´s motor focus (which I also have) with the ASIAir unit, so that might pose a problem. Hope that helps...

 

Erik

Edited by ERHAD, 09 April 2021 - 06:32 AM.

[ewave]

With your mount, get the C9.25 Edge.  It is a lighter OTA than the C11 and is wonderful visually and photographically.

Your mount and your back will thank you for it.  Also, the reducer for the C9.25 edge is reasonably priced for that series.

I think the C11's weight may be a little too taxing on the EQ6R for deep space long-exposure photography.