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Having a Hard time justifying getting a C-9.1/4

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#76 Jon Isaacs

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Posted 26 February 2020 - 04:46 AM

We did our best to keep the magnifications similar. I was using my ES 100 deg eyepeices and he was using some Naglers of similar magnifications.

 

 

In my mind, there are three ways to do comparisons;

 

- Same magnification

 

- Same exit pupil.  For extended objects like comets and galaxies, this means equal brightness.  Particularly for comets, this probably makes the most sense. 

 

- Best possible view in each scope. 

 

Jon



#77 luxo II

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Posted 26 February 2020 - 05:18 AM

Ralph I would concur.

While 8 vs 9.25” might not seem that different on paper, the real issue is that the distribution of deep sky objects vs mangitude is not a linear one.

Scopes smaller than 7” aperture are very limited when it comes to deep sky targets.

7” is where it gets interesting - with premium optics in a compact package you can get very nice planetary resolution, and in dark skies many interesting objects are within reach - notably galaxies.

But because of the nonlinear distribution of deep sky objects, every inch of aperture - 8, 9, 10 and 12” - brings a significant improvement.

The downside of course is the size. My 10” mak is a monster compared to a 7”.
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#78 Jon Isaacs

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Posted 26 February 2020 - 05:37 AM

While 8 vs 9.25” might not seem that different on paper, the real issue is that the distribution of deep sky objects vs mangitude is not a linear one.

 

 

But that doesn't make a difference when comparing two scopes on the same objects. 

 

The difference between these two scopes is 0.31 magnitudes.  That is significant but not earth shattering.  The difference between an 8 inch and an 11 inch is 0.7 magnitudes and it gets you into a different world.  An 8 inch to a 14 inch is 1.2 magntitudes and that's even more...

 

Jon



#79 aa6ww

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Posted 26 February 2020 - 11:44 AM

Anyone who routinely does observing with other friends and other astronomers, look through other scopes also. One person will have a slightly larger or smaller scope and we look at the same objects sometimes. When walking over to one scope vs our own, we notice these aperture differences.

By no means, did the 9.25 have "better" optics then my C8. Both were excellent, I mean really excellent. I was amazed at how crisp and how sharp all my views were. Even the dust lanes in M104 clearly stood out under the dark skies I was at. Even tiny M76 showed its pinched center. Even NGC-891, the needle galaxy had nice structure and shape in the C8.

This was the first time I've taken out my C8 Edge to dark skies with my GoTo AVX mount. I had a huge observing list ready to use, and only took out my tablet which had my observing list and Stellarium on it. The temps were in the high 40's so pretty comfortable, even for Californians. I was set up from before 6pm to 1am, so the scope had plenty of time to acclimate and produce extremely sharp performance. I had a Kendrix dew heater strap wrapped around the front of my C8 and another strap on my eyepiece, and a FarPoint flexible dew shield.

The C8 is a very solid performer anywhere you can use it. Under dark skies however, like all scopes, it really comes alive and in the case of the Edge HD C8, anyone should feel completely content with the performance of the C8 and happy to have this as your deep space scope.

When you are under dark skies and your mount is working very well for you, your eyepiece's are working well for you, and the conditions are comfortable and your scope is fully acclimated, the C8Edge no longer becomes the Jack of all trades, master of none. In my case, it was the Master of everything, for an 8" telescope. It did not have the wide field of view a smaller refractor, but it didn't have the smaller aperture also. The Leo triplets easily fit into the same field of view, so did the Draco triplets, so did a few of the other deep space galaxy systems. That was plenty wide for me. That's pretty impressive for a tiny little scope that can fit in a duffle bag and deliver deep space performance with extremely sharp optics.

...Ralph


Edited by aa6ww, Yesterday, 03:08 AM.

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#80 aa6ww

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Posted 26 February 2020 - 01:10 PM

8" vs 9.25" doesn't sound like much difference, but that's a 25% increase in aperture, not factoring in the central obstruction. 25% increase of almost everything is significant and noticeable.

...Ralph


Ralph I would concur.

While 8 vs 9.25” might not seem that different on paper, the real issue is that the distribution of deep sky objects vs mangitude is not a linear one.

Scopes smaller than 7” aperture are very limited when it comes to deep sky targets.

7” is where it gets interesting - with premium optics in a compact package you can get very nice planetary resolution, and in dark skies many interesting objects are within reach - notably galaxies.

But because of the nonlinear distribution of deep sky objects, every inch of aperture - 8, 9, 10 and 12” - brings a significant improvement.

The downside of course is the size. My 10” mak is a monster compared to a 7”.



#81 Astrojedi

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Posted 26 February 2020 - 04:48 PM

I violently agree with Ralph. He has put it very well. As I mentioned in my earlier post the difference in the 8" and 9.25" scopes is quite obvious. But it takes good skies for larger scopes to flex their muscle.

 

For example from my light polluted backyard my Tak 100DC puts up views that look very similar to my EdgeHD 8. In poor seeing the Tak is in fact better. Many immediately jump to the conclusion that this is due to Takahashi black magic / optical quality and that SCTs are useless. But in dark skies with good seeing the EdgeHD 8 blows away the 100DC on deep sky, lunar and planets.

 

Objectively, 30% is a noticeable difference. Of course it is not the same as a 1 mag difference but what that difference means to you is subjective and everyone will have their own opinion. For me it is significant enough that I have owned both sizes for many years.

 

The reason I still have a 8" is for portability. And I will add to what Ralph said. From a dark site I really enjoy the views (and portability + ergonomics) in my EdgeHD 8 and actually prefer it to my 10" Dob (am I allowed to say this on CN? wink.gif ). Although not as bright as the 10" the EdgeHD 8 has much better contrast and "sharpness" - not sure how else to describe it. A 10” with a very good / premium mirror may better it but most commercial 10” dobs will not match up to it.

 

Make no mistake the C8 is a lifetime scope. It is quite unmatched in its combination of portability, ergonomics and aperture. The EdgeHD optics brings the C8 SCT closer to the perfect scope in my view. Despite owning 16" and now a 14" Dobsonian with premium optics I enjoy the EdgeHD 8 just as much.


Edited by Astrojedi, 26 February 2020 - 04:55 PM.

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#82 Bill Barlow

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Posted Yesterday, 10:19 AM

A difference of 34% light grasp between the C8 and C9.25 should be noticeable at the eyepiece, especially for galaxies/nebula and globular clusters.  All scopes seem to come alive under darker skies, even my 3” Tak FC76 DCU.

 

Bill


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#83 AhBok

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Posted Yesterday, 05:27 PM

I just bought my 3rd C9.25 in the last 20 years. I sold the last two after reading threads about how un-special C9.25’s are. I now know better. C9.25s are magical, or at least mine is.

“Any sufficiently advanced SCT, such as the C9.25, is indistinguishable from magic.” It is not to be explained, but only enjoyed.

- Apologies to Arthur C. Clarke
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#84 Cpk133

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Posted Yesterday, 11:54 PM

I just bought my 3rd C9.25 in the last 20 years. I sold the last two after reading threads about how un-special C9.25’s are. I now know better. C9.25s are magical, or at least mine is.

“Any sufficiently advanced SCT, such as the C9.25, is indistinguishable from magic.” It is not to be explained, but only enjoyed.

- Apologies to Arthur C. Clarke

Shhhhhh!  



#85 Axunator

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Posted Today, 12:22 AM

I just bought my 3rd C9.25 in the last 20 years. I sold the last two after reading threads about how un-special C9.25’s are. I now know better. C9.25s are magical, or at least mine is.

“Any sufficiently advanced SCT, such as the C9.25, is indistinguishable from magic.” It is not to be explained, but only enjoyed.

- Apologies to Arthur C. Clarke

Yeah, the amount of disdain C9.25 gets here is pretty amazing.

 

I guess we can thank Ed Ting’s (in)famous review also for that, as some people seem to feel a compulsory need to try and prove repeatedly how wrong he was lol.gif


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#86 Jon Isaacs

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Posted Today, 08:01 AM

8" vs 9.25" doesn't sound like much difference, but that's a 25% increase in aperture, not factoring in the central obstruction. 25% increase of almost everything is significant and noticeable.

...Ralph

 

It's 16% increase in aperture, a 34% increase in light gathering... 

 

It's the same as going from an 80mm refractor to a 92mm refractor.  More, but more than same than different. 

 

Jon



#87 AhBok

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Posted Today, 09:31 AM

I agree, but it’s more than light gathering. It’s more light gathering, more contrast and more resolution. The difference is easily seen :>)
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#88 John O'Grady

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Posted Today, 10:32 AM

It's 16% increase in aperture, a 34% increase in light gathering... 

 

It's the same as going from an 80mm refractor to a 92mm refractor.  More, but more than same than different. 

 

Jon

While that may be an accurate comparison in terms of increase in light gathering... (I'm too lazy to check your math) the comparison is not equivelant given that an 8" SCT has considerable more light gathering than an 80mm to begin with.  So that 34% is going work out to be significantly better than what one would experience going from an 80mm to a 92mm refactor.  I'm not saying that was your point at all.  Just that it may be interpreted wrong by a beginner reading this thread.  So thought I would point out.   Otherwise, I thought it was an interesting example.


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#89 John O'Grady

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Posted Today, 11:17 AM

Hi,

 

I'll share my experience with a C9.25.  I've owned one C8, two C9 and two C11 over the years.  I currently own a C9 Edge and C11 standard.  

I keep going back to the C9, I just like the size, fit and capability of the scope.  I tend to ignore the hype about its design being special as that's not important to me.

In terms of C8 vs C9 here's my observation: 

 

  • C8 seems tiny by comparison to a C9, it is a really nice form factor for portability, I would consider it grab and go ready with my alt-az EzTouch mount (not everyone would)
  • C8 performs well on DSO objects and does a nice job on planetary as well.  Imaging or visual.
  • My experience has been the C9 does show more on DSO and planetary objects but I never performed a side by side comparison of the two scopes
    • The cigar galaxy always seemed to look great in the C9

    • It performs really well on jupiter and other planets

    • Globulars look noticeably better

  • C9 starts to push mount load capacity, particularly for imaging.  While you can get it to work well on CGEM/EQ6 level mounts for imaging (visual works fine) don't bother if its a windy night, not without having some wind block/shelter, then imaging with it is going to be a challenge.  Imaging with the C9 on my AP1100GTO on the other hand - it doesn't blink even on a night with strong of wind gusts 

Basically, a C9 performs better than a C8 to a level that's immediately noticeable but not jaw drawing.  Its a level of improvement one would expect.

If you have a C9, don't look at planets and DSO through a C11 or you'll want to upgrade.  That jump is jaw dropping in my opinon.  Saturn imparticular is really breathtaking in a C11 and you can spot quite a few of its moons.  As others regularly report here, this step up to a C11 is much more noticeable and I agree. With a binoviewer, I find it's a real treat view planetary nebula and the FOV plus light gathering helps reveal a much more detail and contrast in those small planetary nebula.   Its quite noticeable the improvement over a C9.  But that's just been my experience.  Also, I would add that in terms of size of a C11 vs C9 it seems to me to be less of a big a step up in size, whereas C8 to C9 seems more noticeable.

 

As I do more imaging these days than visual the C9 gets more use than the C11 as a result.  

But that's only because its focal length with reducer provides the scale that I prefer to image DSO's at.

And I can only use the mount for one purpose at a time - imaging or visual.

If I had a second mount that would handle the C11, while the C9 is out imaging, the C11 would get a lot more use.

But dealing with another setup would complicate things and require investing more money than I care to at this time (priorities right).

 

I hope someone finds my experience with a C9 helpful.

 

Thanks - John


Edited by John O'Grady, Today, 11:43 AM.

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