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Equipment Discussions >> Cats & Casses

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Jarrod
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Reged: 01/20/13

Loc: SE USA
Is an SCT a good all-rounder for visual + imaging?
      #5677276 - 02/13/13 09:20 AM

Thinking of getting a Celestron C6 or C8 or ?? on their new VX mount. This will be my first "serious" scope and I want it to be something that:

a) Provides good visuals
b) Is reasonably good for imaging DSOs, the moon, and planets (priority in that order).
c) No more than $2k for scope + goto mount.

I considered a mounted newt, but realized that all the added weight would require a much sturdier and $$ mount, making the whole thing much less convenient to move and store than a SCT. Someday I may add a 10-12" dob as a dedicated visual scope. In the meantime I need an all-rounder.

What about the size? My concern is aperture vs. field of view. Obviously the bigger mirror can collect more light. But the C6 and C8 are both f/10 or f/6 with a reducer. How much does the difference in FOV at prime focus impact astrophotography? Can you put a widefield in and use the projection method with reasonable results on these scopes? Basically looking to understand what are the tradeoffs.

Sorry - I know these are very basic questions, but I'm trying to get up to speed so I can make an informed decision.


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Eddgie
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Reged: 02/01/06

Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Jarrod]
      #5677379 - 02/13/13 10:34 AM

As you have already surmized, but scopes are natively f/10 without a reducer and f/6.3 with a reducer.

For extended targets, brightness has nothing to do with aperture. It is totally a function of focal ratio and focal ratio alone, and this is true for both visual and imageing use.

For imaging an extented target, if you use the same camera at the same exposure in both scopes at f/10, you get the exact same brightness in each image. Same at f/6.3. For a given expousre time, the image will be just as bright in each scope.


For visual observing of extended objects (nebula, galaxies, and planets), if you have two f/10 telescopes and you use the same eyepeice in each, you get the same brightness as well. So, brigthness for extended targets is simply a function of focal ratio.

In the case of the C6, for whatever reason that only Celetron knows, they used a very small baffle, so this means thatwhen imageing you will get about the same size true field from it as you will get form a C8 before vignetting starts.

So, the C6 will give just as bright an image, but at a smaller image scale. No wider field though because of the vignetting imposed by the small primary baffle.

For visual use, you get more contrast and more angular resolving power, and better limiting magnitude (fainter stars visible in Globulars).

The C6 will on the other hand be lighter and easier to use for long exposures becasue it will make less demand on the mount.

My own recommendation would be for the C8 because in most things to do with telescope performance when used visually, a bigger aperture is generally a better aperture.

The C8 can give a field that is almost as wide and much better illuminated than a C6 when used visually. The C6 gains a lot of focal lenght when used with 2" diagonals, and will loose a lot of illumination at the edge of the field when used this way. The C8 can be used with eyepeices like a 35mm Panoptic and remain very well illuminated at the edge of the field makeing it (to me) a better wide field telescope.

And for planets and deep sky observing, the extra aperture allows for higher magnifications at the same brightness, which helps greatly in observing.

But a C8 weighs more, and there will be many people that say that the scope you use the most is the best scope (I personlly think bigger is just about always better, but that is me).

So, for exposure times, both will give about the same brightness and about the same well illuminated true field size, but the C8 will give a bigger image scale.

For visual, the C8 has the advantage of better resolving power, better contrast transfer, and a field that is more fully illuminated when using very low power wide field eyepeices. It will be better for just about all observing.

But it weighs more.

In my opinion, everyone should have a C8. The penalty in size and weight over a C6 is simply to small to me to be meaningful, though it is a factor when it comes to mount capacity for imageing.

People will think I am bashing the C6 though. I am not. For people with bigger scopes, the C6 can make a fine smaller scope.

But if I could only have one scope (and I do have a C5, a C8, a 6" APO, and a C14), it would be the C8..

LOL. Only kidding.. Dude.. It would be the C14. By my C8 would be my second choice.

But seriously, if you can only have one or the other, my own suggestion for all of the requirments you have put forward would be a C8. It will be better at imageing and at visual use for the requirements you specified.

Again, I am not C6 bashing, but the C8 does everything as well or better than the C6 in a package that is only a bit bigger and a bit heavier. The C6 might make a great second scope, but for a primary scope, the C8 to me is about 72% better.


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RichD
Carpal Tunnel


Reged: 11/08/07

Loc: Derbyshire, UK
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Eddgie]
      #5677415 - 02/13/13 10:50 AM

Yes.

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REC
Post Laureate
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Reged: 10/20/10

Loc: NC
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: RichD]
      #5677436 - 02/13/13 10:57 AM

An 8" SCT is a great all around scope. Get yourself 3-4 EP's and a 2" dielectric diagonal, a dew shield, a chair and you good to go! Fork mount is ok for viewing a short exposures and easy to point and use. GEM is bigger, but better for AP.

Have fun and welcome to CN:)

Bob


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Julio
sage
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Reged: 01/18/07

Loc: Pembroke Pines ,FL
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: RichD]
      #5677468 - 02/13/13 11:14 AM

C8..trust me, thay are fantastic if you get a good one. Celestron's quality control has improved quite a bit.

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t.r.
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Reged: 02/14/08

Loc: Upstate NY
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Julio]
      #5677702 - 02/13/13 01:33 PM

There is good reason that the 8" SCT has garnered the reputation it has...BEST ALL AROUND, JACK OF ALL TRADES, BANG FOR THE BUCK! As an only scope...in a heart beat!

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Crow Haven
Pooh-Bah


Reged: 01/09/09

Loc: Oregon USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: t.r.]
      #5677791 - 02/13/13 02:35 PM

+1
I've enjoyed both a C-5 and C-8 since the 1980's. So much so, in fact, that I recently ordered a new C-8 SE XLT orange OTA (should have it by the 19th) to replace my old C-8 that was bare-bones with only the "special coatings". I already have a f/6.3 reducer/corrector, and a 35mm Panoptic for wider fov use when needed. The C-8 is my ultra-portable med-large scope vs my 10" dob, which although is portable is certainly a bit less so.
---Maya


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WarmWeatherGuy
Carpal Tunnel
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Reged: 08/27/11

Loc: Orlando, FL 28 N, 81 W
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Jarrod]
      #5677951 - 02/13/13 04:20 PM

You should watch this video about how important it is to determine your field of view before you buy your telescope and camera.

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jgraham
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Reged: 12/02/04

Loc: Miami Valley Astronomical Soci...
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: WarmWeatherGuy]
      #5678117 - 02/13/13 06:17 PM

I consider my 8" SCT to be the most versatile visual/imaging scope that I own.

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GeneT
Ely Kid
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Reged: 11/07/08

Loc: South Texas
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: t.r.]
      #5678144 - 02/13/13 06:33 PM

Quote:

There is good reason that the 8" SCT has garnered the reputation it has...BEST ALL AROUND, JACK OF ALL TRADES, BANG FOR THE BUCK! As an only scope...in a heart beat!




agree


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Jarrod
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Reged: 01/20/13

Loc: SE USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: GeneT]
      #5678646 - 02/14/13 12:22 AM

Thanks for the feedback, especially Eddgie for taking the time to explain the differences between the C6 and C8 in such detail.

The C8 seems like a winner, until I go read the answers to basically the same question asked in the imaging forum. Apparently imaging is not possible unless you have a refractor

Jokes aside, it seems there is no easy answer.


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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Jarrod]
      #5678685 - 02/14/13 01:13 AM

I prefer newts and real cassegrains, but an 8" SCT is hard to beat for an all-rounder, as others have said.

-Tim.


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kansas skies
sage


Reged: 12/02/12

Loc: Kansas, USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: tim53]
      #5678929 - 02/14/13 08:10 AM

A 6" SCT and an 8" SCT will take about the same amount of time to reach thermal equilibrium, so that shouldn't be much of an issue in making a decision. The 8" will take up more space and be somewhat heavier, making it a little less portable. Only you can decide if that's an issue. As already stated, given the same eyepiece, the 6" will offer a smaller image within a wider field of view at the same level of brightness. By selecting different eyepieces of appropriate focal lengths, it's possible to achieve the same field of view in both, in which case the 8" will present a brighter image. In addition, the 8" offers better resolution and will show fainter stars. That being said, either should work well for visual use and for photography. The mount required for the imaging might then be more of a factor.

Bill


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Illinois
Carpal Tunnel


Reged: 12/18/06

Loc: near Dixon, Illinois USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: kansas skies]
      #5678949 - 02/14/13 08:32 AM

forget 6 inch! Use 8 inch for lifetime! If you have 6 inch then you will think about that should get 8 inch!

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Jarrod
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Reged: 01/20/13

Loc: SE USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Illinois]
      #5679038 - 02/14/13 09:43 AM

Quote:

In addition, the 8" offers better resolution and will show fainter stars. That being said, either should work well for visual use and for photography. The mount required for the imaging might then be more of a factor.




Can we talk about that for a minute? I'm pretty set on getting the new Celestron Advance VX mount. Really can't see spending much more than that on a mount to start with, until/unless I'm *certain* that astrophotography is something I'm going to pursue longer-term.

So, I'm thinking really hard about the C8/VX package for around $1600.


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drbyyz
sage
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Reged: 11/04/12

Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Jarrod]
      #5679196 - 02/14/13 11:08 AM

I would push you towards the 8" as well. It is a very noticeable improvement over a 6" and most people have no issue with handling it...they aren't huge.

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bilgebay
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Reged: 11/06/08

Loc: Türkiye - Istanbul and Marmar...
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: drbyyz]
      #5679245 - 02/14/13 11:29 AM

Just go the extra mile and buy the Edge 8". You will not regret it.

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Escher
Pooh-Bah
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Reged: 08/30/07

Loc: Fenton, MI
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: bilgebay]
      #5679251 - 02/14/13 11:32 AM

Quote:

Just go the extra mile and buy the Edge 8". You will not regret it.




Yes!!

Get the 8" Edge and a CG5-ASGT and done... Its enough to get you going and you can do *some* AP with it... you will be able to resell the mount and upgrade to a heavier mount down the road.


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Jarrod
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Reged: 01/20/13

Loc: SE USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Escher]
      #5679557 - 02/14/13 01:58 PM

So you are saying this one (I'd get it with the new AVX mount) is well worth the extra $400? What is this "Fastar" thing? f/2.8??!!

Do these things ever go on sale? $2k is at the upper limit of my budget and I'd need to still get some AP accessories (reducer, t-ring, filters, etc, etc.).


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Ed Wiley
scholastic sledgehammer


Reged: 05/18/05

Loc: Kansas, USA
Re: Is an SCT a good all-rounder for visual + imaging? new [Re: Jarrod]
      #5679786 - 02/14/13 03:53 PM

I vote for an Edge. Mine is on a Losmandy G-11--excellent mount. I have not experience with Vixen mounts but if you are contemplating astrophotography I would recommend doing some research as the mount is perhaps the most important component of any astrophoto system. This is not so important with solar system objects and webcams, but it is critical for DSOs. The usual formula is to keep the OTA+accessories about 1/2 the stated capacity of the mount. Many units are sold "undermounted" to the frustration of the budding astrophotographer. Investigate carefully.

Ed


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