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Equipment Discussions >> Cats & Casses

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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: Why do people even buy SCTs??? new [Re: Dwight J]
      #6235736 - 12/05/13 04:27 PM

I'm Not sure I'd be able to show my face in the Astro community again sporting a gifted AP 175.... Or, come to that, sporting the C14, with everyone knowing I'd turned down an AP175.

I'll stick with the C8, and assorted 4"-5"ers and keep my friends on CN


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NHRob
Post Laureate
*****

Reged: 08/27/04

Loc: New Hampshire
Re: Why do people even buy SCTs??? new [Re: Dwight J]
      #6235738 - 12/05/13 04:29 PM

I don't like the long focal length of the C14.
As a general purpose instrument I like a shorter FL for wider field views.


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roadi
Pooh-Bah
*****

Reged: 08/18/07

Loc: Great Grey Spot "Denmark"
Re: Why do people even buy SCTs??? new [Re: t.r.]
      #6235784 - 12/05/13 04:59 PM

Quote:

I did my best to stay out of this...but I finally caved . Here is the litmus test...

Two scopes side by side.

One a new C14.

The other a new AP 175 EDF refractor.

You can have one for FREE...BUT cannot sell it and must keep it forever as your only scope.

You have NO health or mounting/use issues.


Logic, MTF and Physics would dictate that you must pick the C14...right?

You MUST choose the C14.

How many of you can say that you would?

My




I wouldn't know before looking through each of them
Relating to reality, me.. I'd chose the C14.


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: Why do people even buy SCTs??? new [Re: roadi]
      #6235790 - 12/05/13 05:02 PM

The 14! I use two F/6.3 reducers on mine to yield F/4 and it works pretty good. I have gotten some great images in just minutes this way.

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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: t.r.]
      #6235796 - 12/05/13 05:06 PM

Quote:

I did my best to stay out of this...but I finally caved . Here is the litmus test...

Two scopes side by side.

One a new C14.

The other a new AP 175 EDF refractor.

You can have one for FREE...BUT cannot sell it and must keep it forever as your only scope.

You have NO health or mounting/use issues.


Logic, MTF and Physics would dictate that you must pick the C14...right?

You MUST choose the C14.

How many of you can say that you would?

My





That's a tough call. I have the AP 175 f/8 (plus the both field flatteners, one is also the f/6.1 focal reducer), and it's a highly versatile scope for photo-visual apps (the Moon, Jupiter & Saturn look great in it, as do the brighter DSOs). I guess I'd have to look through a C-14 for a while to really make the call (to evaluate its thermal characteristics, optics smoothness, etc.).

The C14 could allow you to go deeper (depending on the image scale you choose), but it's sort of a 'tweener scope: compact, very good DSO performance (but not as good as relatively larger Newt-Dobs), and the image scale and aperture to potentially provide great planetary views.

Mind you, I'm not suggesting the AP 175 would outperform the C-14 in resolution and limiting magnitude (and if that was the case, I'd fix the C-14). It's just that, after using the AP175, it'd be hard to think of not having that instrument. It's difficult to not get attached to well-designed and manufactured telescopes.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: drago]
      #6235798 - 12/05/13 05:06 PM

Quote:

Quote:

"Why do people even buy SCTs???"


Nothing wrong with SCT, only some manufactures QC but this might have changed.




about a 38 percent central obstruction cannot be named as "nothing wrong", especially for visual instrument...




Then why do you have issues with the Tak Mewlon 300's CO?


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David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Why do people even buy SCTs??? new [Re: Dwight J]
      #6235813 - 12/05/13 05:16 PM

Quote:

Geez, I dunno. With that giant secondary obstruction, thermal equilibrium issue, hours of set-up time, focus shift, dew on corrector plate - I'd take the.....C14 any day of the week. My ego does not require a fancy refractor.




What Dwight said.

David


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Mark Costello
Post Laureate
*****

Reged: 03/08/05

Loc: Matthews, NC, USA
Re: Why do people even buy SCTs??? new [Re: t.r.]
      #6235815 - 12/05/13 05:17 PM

Quote:

I did my best to stay out of this...but I finally caved . Here is the litmus test...

Two scopes side by side.

One a new C14.

The other a new AP 175 EDF refractor.

You can have one for FREE...BUT cannot sell it and must keep it forever as your only scope.

You have NO health or mounting/use issues.


Logic, MTF and Physics would dictate that you must pick the C14...right?

You MUST choose the C14.

How many of you can say that you would?

My





Hello, Tim. I couldn't quite do that, even if the 'frac was my ES AR 127. It's pretty darn good - at least for me - and I couldn't manage a C14. But here's the litmus test that I war game as I occasionally window shop.

Occasionally, I window shop for a complement to my 5" F6.5 achro. It's going to work with mirrors since I couldn't either afford or manage a large refractor. So will it be a Newtonian (a dob since I'll never again have a Newt on a GEM) or will it be an SCT?

Here're the things in favor of the Newt - from where I sit.

1) Assuming the same construction quality, the Newt will have the superior optics due to the size of its secondary mirror assembly (central obstruction or CO).

2) A Dob is going to be less expensive than a SCT rig. Or put in a way of more interest to me is this: The money that I might spend on a 9.25"-10" SCT (or 8" Edge) rig gets me in the ballpark of what it would take to buy a premium Dob like one from Teeter. Doing that presumably eliminates concerns over build quality.

3) The Newt should cool faster than a SCT with its open tube.

Even assuming all of that, if I did buy a complement to my achro, it'd probably be an SCT.

1) Saying that the optics of a Newt are superior to those of an SCT does not mean - at least to me - that the SCT optics are as a rule bad. Not by a long shot. I've looked through a couple of SCTs, one an 8" Meade looking at the moon at 400X, the other a C9.25 aimed at Saturn at about 150X. Both views were impressive, particularly the view of Saturn in the C9.25. It was to die for, it looked like a cut out from a photograph that you'd see in National Geographic - except in scale. So my assumption is that the SCT is capable of providing nice images.

2) To me, a SCT and a faster achro like my AR127 make good complements. One would provide the big picture view, the other gets down into the details.

3) Along that line, a SCT and my 'frac could ride side by side on one Alt-az mount. The achro would do the driving, finding things and getting that big picture view. The SCT would ride shotgun to get all the details.

4) At least at this time, I'm buying the argument I've read here that the SCTs holds collimation very well (read indefinitely), while the Newt needs fiddling every so often.

There is one more comparison - SCT versus MCT. But I spend little time these days on that comparison. MCTs at least here are getting hard to buy and with the Edge and ACF and (presumably) improved and more consistent quality of build, the SCTs appear to be closing the optical superiority gap to the MCTs.

Best Regards,


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Starman27Moderator
Post Laureate
*****

Reged: 01/29/06

Loc: Illinois, Iowa
Re: Why do people even buy SCTs??? new [Re: Mark Costello]
      #6235909 - 12/05/13 06:03 PM

I guess I would choose the 14 inch SCT because I have one. Of course it is not my only scope.

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jgraham
Postmaster
*****

Reged: 12/02/04

Loc: Miami Valley Astronomical Soci...
Re: Why do people even buy SCTs??? new [Re: Starman27]
      #6235949 - 12/05/13 06:22 PM

C14, 'cause I'd just love to have one. I also own a fair sized refractor (152mm f/8) but I'd have to go for that big beautiful cat.

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WadeH237
Pooh-Bah


Reged: 02/24/07

Loc: Snohomish, WA
Re: Why do people even buy SCTs??? new [Re: jgraham]
      #6236007 - 12/05/13 06:58 PM

I have a C14 and I love it.

...But if there is anyone out there who wants to trade straight up for their AP175, I'll do it. I'll even promise to never sell or trade it away and make sure that it gets used as often as is practical.


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DwainM
member


Reged: 07/30/12

Loc: NW AR
Re: Why do people even buy SCTs??? new [Re: Mark Costello]
      #6236011 - 12/05/13 07:01 PM

Quote:


Hi Doug, loosely translated, it means "reduce to an absurdity." Actually, it's a technique used to prove a lot of mathematical theorems. The technique involves assuming the opposite of the statement of the theorem, then making logical deductions until you've reached a contradiction to a previously established statemetn (e.g., definition, theorem.). An example is the theorem "The Null Set is a subset of every set." You assume that there is a set of which the Null Set is not a subset and the deductions from there lead you to a position contradicting the definition of the Null Set.

Back to your regularly scheduled programming.




Ummm +1.
I think...


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Roy McCoy
Pooh-Bah
*****

Reged: 10/13/05

Loc: Glendale, AZ
Re: Why do people even buy SCTs??? new [Re: t.r.]
      #6236018 - 12/05/13 07:07 PM

Quote:

I did my best to stay out of this...but I finally caved . Here is the litmus test...

Two scopes side by side.

One a new C14.

The other a new AP 175 EDF refractor.

You can have one for FREE...BUT cannot sell it and must keep it forever as your only scope.

You have NO health or mounting/use issues.


Logic, MTF and Physics would dictate that you must pick the C14...right?

You MUST choose the C14.

How many of you can say that you would?

My





This is similar to the current Ford commercial where this choice is: more? or better?

Unlike the commercial there is no “and”.

I can see more in my friends 8HD than I do in my 4" APO refractor, but I just never linger at the 8 inch.

I can see more in my friends 11HD than I do in my 6" APO.
I never linger at the 11 inch.

I always go back to the APO.

I would take the AP175 for the quality and presentation of view without a second thought.


Regards.


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maknewtnut
Member
*****

Reged: 10/08/06

Re: Why do people even buy SCTs??? new [Re: jgraham]
      #6236026 - 12/05/13 07:09 PM

The 175. I've owned 2 C14's (and 1 C11, 4 C8's, 2 C5, 2 C90's). Preference based on personal experience has nothing to do with ego.

If I could find a C8, C9, or C11 with a wavefront error ~1.5x better than the refractor, I might just take that instead.


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WesC
Carpal Tunnel
*****

Reged: 02/06/13

Loc: La Crescenta, CA
Re: Why do people even buy SCTs??? new [Re: maknewtnut]
      #6236034 - 12/05/13 07:16 PM

I would mug you and take BOTH!

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A6Q6
professor emeritus


Reged: 05/31/11

Loc: Stroudsburg,Pa,U.S.A
Re: Why do people even buy SCTs??? new [Re: t.r.]
      #6236074 - 12/05/13 07:39 PM

Questar 12....Oh, wrong thread

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Namlak
member


Reged: 06/14/12

Loc: Northridge, CA
Re: Why do people even buy SCTs??? new [Re: A6Q6]
      #6236160 - 12/05/13 08:35 PM

Why would you want to use an SCT with a 38% central obstruction when you can use a refractor and look through the little hole in the center of the 62% outer obstruction?



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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: Why do people even buy SCTs??? new [Re: Namlak]
      #6236177 - 12/05/13 08:48 PM

Quote:

Why would you want to use an SCT with a 38% central obstruction when you can use a refractor and look through the little hole in the center of the 62% outer obstruction?








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kansas skies
sage


Reged: 12/02/12

Loc: Kansas, USA
Re: Why do people even buy SCTs??? new [Re: Namlak]
      #6236276 - 12/05/13 09:42 PM

Quote:

Why would you want to use an SCT with a 38% central obstruction when you can use a refractor and look through the little hole in the center of the 62% outer obstruction?






Wow - That sure sounds like "checkmate" to me...

Bill


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KeithC
super member


Reged: 08/23/06

Loc: Atlanta GA
Re: Why do people even buy SCTs??? new [Re: Ed Holland]
      #6236302 - 12/05/13 09:56 PM

Quote:

Quote:

Why would you want to use an SCT with a 38% central obstruction when you can use a refractor and look through the little hole in the center of the 62% outer obstruction?

















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