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What do people see in Schmidt-Cassegrains?

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#101 Gil V

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Posted 05 October 2014 - 08:27 PM

Jon -

Yes, I built a 12-1/2" Dobsonian back in the day.

I prefer a GEM, but after a certain size, the mount just gets too heavy.

The Starfinder gets it's share of use. Those straps, though, they are NOT rotating rings, that's for sure.

I'm thinking about my next scope, I'd like a 14" Newtonian, probably mounted in a box.

If I had my dream scope, it would be a 12" F/5.5 on a GEM, with rotating rings of course.

My back hurts just thinking about the counterweight, though.

#102 BillP

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Posted 05 October 2014 - 10:20 PM

 

Something that I have wondered about for quite a while - why are Schmidt-Cassegrains so popular?

 

They are much more expensive than Newtonians of a given aperture - and never seem to perform quite as well.

Portability is commonly cited - but when factoring in a beefy mount and tripod, they will not be as portable as a dobsonian of equivalent aperture.

The goto and tracking popular on SCTs can be had on dobsonians - and often work extremely well with features such as dual encoders.

 

For a comparison, take the orion xt8g and the celestron cpc 800. The dobsonian performs slightly better, has an equally good goto system, costs half as much, and is more portable.

 

So what gives?

That's an easy one.  Put an 8" f/6 Newtonian on a CG5 EQ mount, and then think about your question.

 

SCTs are all about compromise; the balancing of virtues and vices.  While not quite as good as a scope with a smaller CO and a more thermally sensible design in image quality, they are compact and easily mountable on driven, tracking mounts, and are relatively cheap to boot.  Maybe not entry level Dob/Newt cheap, but close.

 

Also, a properly collimated and cooled C8 will give most mass-produced 8" Dob/Newts a run for the money.  The "properly collimated and cooled" part is the hard part, and 5 or 6 out of 10 times the reason an SCT under perform other designs.

 

- Jim

 

 

 

Actually...I like this answer the best.  But I don't think any of the answers quite hit the mark.  Let's face it...you want high sales figures and popularity?  Then the answer to "Why are Schmidt-Cassegrains so popular?" is really simple....offer any product that works and follow it with Superlative & Imagination Catching Marketing!  Celestron and Meade push it out all year every year relentlessly.


Edited by BillP, 05 October 2014 - 10:21 PM.


#103 Footbag

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Posted 05 October 2014 - 10:33 PM

I don't do much visual observing, but both a GEM or alt-az mounted SCT are much more comfortable to observe with then any other design. The closed cell is also a benefit in keeping the mirror clean. As well, the moving mirror is seperate from the rear port. That means you can put a lot of weight on it without worrying about a focuser slipping.

An SCT is a complex design with advantages and disadvantages. A Newt is a siple design with advantages and disadvantages. It all depends on what you want and how you want to use it. No ladders required with SCT's though.

#104 Sarkikos

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Posted 06 October 2014 - 06:02 AM

That's an easy one.  Put an 8" f/6 Newtonian on a CG5 EQ mount, and then think about your question.

 

Been there, done that.  Hell on two axes.  The Newt promptly went back on the Dob mount.

 

Mike


Edited by Sarkikos, 06 October 2014 - 06:03 AM.


#105 Sarkikos

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Posted 06 October 2014 - 06:05 AM

I don't do much visual observing, but both a GEM or alt-az mounted SCT are much more comfortable to observe with then any other design. The closed cell is also a benefit in keeping the mirror clean. As well, the moving mirror is seperate from the rear port. That means you can put a lot of weight on it without worrying about a focuser slipping.

I disagree.  IME a Dob mount is much more comfortable than a GEM.  

 

I've never had a fork mount, so I can't speak to that.  But I do have a single-arm NexStar SE 6/8 mount.  I like the goto/tracking, but I still think that Dobs are more comfortable to use.  I like being able to take that OTA and point it anywhere I want by hand.  Directional control from an HC doesn't quite cut it.

 

Mike


Edited by Sarkikos, 06 October 2014 - 06:08 AM.


#106 Sarkikos

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Posted 06 October 2014 - 06:11 AM

Yes, I built a 12-1/2" Dobsonian back in the day.

I prefer a GEM, but after a certain size, the mount just gets too heavy.

 

IME, the limit for easy portability on a GEM is about a 6" aperture.  And I'm not talking about a monster permanently mounted on a GEM sitting on casters in a garage, ready to be rolled out a few feet. I'm talking about a telescope you have to take out a door and down some steps.

 

Mike


Edited by Sarkikos, 06 October 2014 - 06:12 AM.


#107 Asbytec

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Posted 06 October 2014 - 06:37 AM

Actually...I like this answer the best.  But I don't think any of the answers quite hit the mark.  Let's face it...you want high sales figures and popularity?  Then the answer to "Why are Schmidt-Cassegrains so popular?" is really simple....offer any product that works and follow it with Superlative & Imagination Catching Marketing!  Celestron and Meade push it out all year every year relentlessly.

 

 

Yea, that's a good point, Bill. Sometimes I wonder if there is a herd mentality, too. Folks like to buy a popular design because they feel safe in doing so. So many others use them, there has to be a good reason. And there are several good reasons...



#108 Jon Isaacs

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Posted 06 October 2014 - 06:37 AM

Jon -

Yes, I built a 12-1/2" Dobsonian back in the day.

I prefer a GEM, but after a certain size, the mount just gets too heavy.

The Starfinder gets it's share of use. Those straps, though, they are NOT rotating rings, that's for sure.

I'm thinking about my next scope, I'd like a 14" Newtonian, probably mounted in a box.

If I had my dream scope, it would be a 12" F/5.5 on a GEM, with rotating rings of course.

My back hurts just thinking about the counterweight, though.

 

Gil:

 

I had the Meade 12.5 inch F/6 Research Grade, it had all the right stuff but it was just so massive that transporting it was out of the question.  And then the fact that it required a ladder, well that was an issue as well.  I figured out I am a Dob type.. I can setup my 25 inch by myself, the 12.5 inch inch RG, I did it once but realized I was lucky-lucky that I didn't drop the scope, that I didn't hurt myself.. 

 

We are all different. 

 

Jon



#109 GOLGO13

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Posted 06 October 2014 - 10:22 AM

I like SCTs, Refractors and Newts.

 

I think with these situations it's best to list the pluses and minuses of each design. Then it's usually a personal decision as to which scope is chosen.

 

GEM vs Alt/az is no problem as an SCT can be used on either. I personally like Alt/az over GEMs...mostly weight and setup related for me. In operation I like alt/az more also but having tracking is nice (availiable on some alt/az). Right now I am strictly a visual observer.

 

Cool down is my biggest problem with SCTs and newts. I don't usually have the time to observe a lot and don't usually want to leave a scope outside (or remember to get it out there). I also have to move around my yard a lot so I tend to like my smaller scopes at home. If I am able to travel to dark skies then cool down is OK. I just use my refractors until the bigger scopes have cooled. I don't plan on getting a refractor larger than my 103mm...so for DSOs I have to use something else.

 

If I had to choose between a 10 inch dob and a 9.25in SCT I'd probably choose the dob. But if it were an 8 inch SCT and 8 inch dob I may choose the SCT. Mounting of the scope maybe being my primary area of concern. I suppose if I got an FTX mount the 9.25 inch would be fine with me. Still I am not sure what I think about cool down with an SCT. I know there are some options for that.

 

In my opinion 9.25inch is as large an SCT as I would ever want (unless I had some sort of observatory), 4-5 inches for refractors (cost and size being factors), and 15 inches for a newt (though I may prefer just sticking with my 10 inch tube). I've got my small scopes figured out...so my next large scope is a tough situation...unless I just stick with the 10 inch dob.



#110 jrbarnett

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Posted 06 October 2014 - 01:27 PM

 

 

Something that I have wondered about for quite a while - why are Schmidt-Cassegrains so popular?

 

They are much more expensive than Newtonians of a given aperture - and never seem to perform quite as well.

Portability is commonly cited - but when factoring in a beefy mount and tripod, they will not be as portable as a dobsonian of equivalent aperture.

The goto and tracking popular on SCTs can be had on dobsonians - and often work extremely well with features such as dual encoders.

 

For a comparison, take the orion xt8g and the celestron cpc 800. The dobsonian performs slightly better, has an equally good goto system, costs half as much, and is more portable.

 

So what gives?

That's an easy one.  Put an 8" f/6 Newtonian on a CG5 EQ mount, and then think about your question.

 

SCTs are all about compromise; the balancing of virtues and vices.  While not quite as good as a scope with a smaller CO and a more thermally sensible design in image quality, they are compact and easily mountable on driven, tracking mounts, and are relatively cheap to boot.  Maybe not entry level Dob/Newt cheap, but close.

 

Also, a properly collimated and cooled C8 will give most mass-produced 8" Dob/Newts a run for the money.  The "properly collimated and cooled" part is the hard part, and 5 or 6 out of 10 times the reason an SCT under perform other designs.

 

- Jim

 

 

 

Actually...I like this answer the best.  But I don't think any of the answers quite hit the mark.  Let's face it...you want high sales figures and popularity?  Then the answer to "Why are Schmidt-Cassegrains so popular?" is really simple....offer any product that works and follow it with Superlative & Imagination Catching Marketing!  Celestron and Meade push it out all year every year relentlessly.

 

In our hobby I find marketing to be largely ineffective.  Case in point.  TEC does no advertising.  Televue advertises.  TEC 140s outsell NP101s.  Another case in point.  Marketing channels are dying.  Magazines, the traditional conduit for manufacturer marketing in this hobby, of on the ropes.  Subscribership is at all time lows.  Fewer people encounter the advertising that exists than in the past.  Instead I suggest that the reputation different equipment accrues in this hobby based on user experience and sharing, more so than manufacturer advertising.

 

In other words, CN forums sell far more telescopes than any amount of advertising does.  :grin:

 

- Jim


Edited by jrbarnett, 07 October 2014 - 10:55 AM.


#111 Glen A W

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Posted 06 October 2014 - 01:34 PM

It was a marketing free-for-all from about 1999 until around 2007.  Meade even managed to go public on the basis of a marketing success, the ETX.  Then the bottom fell out of it all.  Many people involved in this interest have been hit hard.  I don't feel astronomy itself has been hurt by this downturn, however.  I see more talk of the sky and less of gizmos, and that's fine with me.

 

On the alt-az vs. GEM debate, I am not so keen on an SCT on the alt-az.  They are short and this tends to bug me a little in moving the scope.

 

Glen



#112 BillP

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Posted 06 October 2014 - 03:07 PM

In our hobby I find marketing to be largely ineffective.  Case in point.  TEC does no advertising.  Televue advertises.  TEC 140s outsell NP101s.  

 

I don't consider the "marketing" that TV does relative to telescopes anything other than minor league.  Their marketing for eyepieces when they first came out was innovative and eye catching for the Naglers, and got the imagination sparked.  By comparison IMO their telescope marketing is lifeless and nil.  And compared to the massive telescope marketing that Meade and Celestron do, TV does not even register on tne radar IMO.  The quantities of SCTs that Meade and Celestron have sold is mind boggling.  TEC and TV (presuming they are selling about what TEC does) telescope sales more like rounding error compared to Celestron-Meade.

 

The real case in point is that TEC has sold on average 54 140s per year since they came out based on Yuri's latest post (about 650 made to date).  Celestron alone sells at least several hundreds of SCTs every year (based on serial number tracking by a CNer).  Add Meade sales to that and the TV - TEC crew is minor league sales. [EDIT - incorrectly said 35 scopes/year when should have been 54 on average based on 647 140's made in the past 12 years]

 

What I do wonder is how many Tak scopes are sold yearly?


Edited by BillP, 06 October 2014 - 09:07 PM.


#113 BillP

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Posted 06 October 2014 - 03:29 PM

I've got my small scopes figured out...so my next large scope is a tough situation...unless I just stick with the 10 inch dob.

 

I think about his often...and have experimented much with various designs of late.  IMO the SCT is just too limiting (for me) compared to other large aperture options like a Dob.  With an 8" or 10/11" SCT, 1.5 and 1 degree are going to be your TFOVs.  Similar sizes in Dobs are much larger (2 deg with my 10" Dob). 

 

A C11 Edge OTA is around $3,400.  Mounted on a GEM it's about $4,000 or more.  An XT10 Intelliscope with a new Paracorr is $1,200.  So with the $2,800 you will save, there is plenty for tracking platform and all kinds of accessories.  I think that planetary imaging is where one would consider the SCT over the Dob for larger apertures.  Anything else, and particularly visual, the Dob gets you more flexibility and capability in same aperture class.  What you lose is portability (although a C11 on a good mount is a back breaker) and of course imaging.



#114 MikeBOKC

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Posted 06 October 2014 - 03:57 PM

On the subject of advertising and marketing, it is not just within the hobby. I recall that Questar used to run ads regularly in magazines like National Geographic, Natural History, etc., and I would bet Celestron and Meade did too. SCTs are particularly well positioned to appeal to the more casual buyer who may not be an active hobbyist yet. I'd bet the major manufacturers have at least some ad budget that goes somewhere besides S&T and Astronomy.



#115 gene 4181

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Posted 06 October 2014 - 04:09 PM

sct's sell because of the compact design, available add ons and they can be mounted in a fork or eq. mount with go-to. the go-too factor is a major part of it. and while tele vue might advertise, there best advertisement is you guy's on cloudy nights,lol.



#116 Jon Isaacs

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Posted 06 October 2014 - 04:49 PM

 

The real case in point is that TEC has sold on average 35 140s per year since they came out based on Yuri's latest post (about 650 made to date).

 

 

In our hobby I find marketing to be largely ineffective.  Case in point.  TEC does no advertising.  Televue advertises.  TEC 140s outsell NP101s.

 

Bill and Jim:

 

What are the numbers for the TEC 140?  Based on serial numbers, TeleVue sells about 100 NP-101/year.  

 

Jon

 

 



#117 Sarkikos

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Posted 06 October 2014 - 05:17 PM

 

I've got my small scopes figured out...so my next large scope is a tough situation...unless I just stick with the 10 inch dob.

 

I think about his often...and have experimented much with various designs of late.  IMO the SCT is just too limiting (for me) compared to other large aperture options like a Dob.  With an 8" or 10/11" SCT, 1.5 and 1 degree are going to be your TFOVs.  Similar sizes in Dobs are much larger (2 deg with my 10" Dob). 

 

A C11 Edge OTA is around $3,400.  Mounted on a GEM it's about $4,000 or more.  An XT10 Intelliscope with a new Paracorr is $1,200.  So with the $2,800 you will save, there is plenty for tracking platform and all kinds of accessories.  I think that planetary imaging is where one would consider the SCT over the Dob for larger apertures.  Anything else, and particularly visual, the Dob gets you more flexibility and capability in same aperture class.  What you lose is portability (although a C11 on a good mount is a back breaker) and of course imaging.

 

 

I'm beginning to think that about an 8" is hitting the sweet spot for SCTs.  Much larger than that and a Dob makes more sense in terms of light grasp, resolving power, portability, ergonomics (if you keep the f number low and go light), cost per inch, versatility and adaptability.  A 14" SCT? Seriously? No sir, I would prefer not to.  But a well-thought-out 14" Dob is highly portable for dark site treking, gives great views of deep sky and planet/lunar, can implement goto and tracking, and still be used at every position of the OTA while remaining seated.

 

By the way, for similar reasons I think that the sweet spot for APO/ED refractors is about a 5".

 

If you go big, go Dob.

 

:grin:

Mike


Edited by Sarkikos, 06 October 2014 - 05:23 PM.


#118 Astrojensen

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Posted 06 October 2014 - 05:40 PM

 

 

I'm beginning to think that about an 8" is hitting the sweet spot for SCTs.  Much larger than that and a Dob makes more sense in terms of light grasp, resolving power, portability, ergonomics (if you keep the f number low and go light), cost per inch, versatility and adaptability.  A 14" SCT? Seriously? No sir, I would prefer not to.  But a well-thought-out 14" Dob is highly portable for dark site treking, gives great views of deep sky and planet/lunar, can implement goto and tracking, and still be used at every position of the OTA while remaining seated.

By the way, for similar reasons I think that the sweet spot for APO/ED refractors is about a 5".

If you go big, go Dob.

I agree with this.

 

 

Clear skies!
Thomas, Denmark



#119 Glen A W

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Posted 06 October 2014 - 06:03 PM

Many people, including myself, who have tried the C-14 have found it to be a real chore.  Everything about mine was beastly.  I don't recall ever getting really good views, due mostly to bad seeing.

 

Glen



#120 BillP

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Posted 06 October 2014 - 09:05 PM

Bill and Jim:

 

What are the numbers for the TEC 140?  Based on serial numbers, TeleVue sells about 100 NP-101/year.  

 

Jon

 

 

Yuri just made a post in the TEC Forums...

 

Wed Oct 1, 2014 11:32 am (PDT) . ...The first light this model [TEC140] had seen 12 years ago on Astrofest 2002. It is our best seller telescope, 647 telescopes has been sold up to today.

 

And obviously I can't do math as the average over the 12 years would be 54 scopes per year and not 35 :lol: 



#121 Jon Isaacs

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Posted 06 October 2014 - 09:39 PM

 

Bill and Jim:

 

What are the numbers for the TEC 140?  Based on serial numbers, TeleVue sells about 100 NP-101/year.  

 

Jon

 

 

Yuri just made a post in the TEC Forums...

 

Wed Oct 1, 2014 11:32 am (PDT) . ...The first light this model [TEC140] had seen 12 years ago on Astrofest 2002. It is our best seller telescope, 647 telescopes has been sold up to today.

 

And obviously I can't do math as the average over the 12 years would be 54 scopes per year and not 35 :lol: 

 

 

Bill:

 

Thanks for that information.  The NP-101 was introduced in August of 2001 and it took about 10 years to sell the first 1000... Cloudy Nights member Starhawk took delivery of the 1000th NP-101 in December of 2011.  

 

So, based on that information and the information you have provided, unlike what was previously suggested, the NP-101 not only outsells the TEC-140 but it outsells it by almost 2:1

 

Jon



#122 Sarkikos

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Posted 07 October 2014 - 09:47 AM

 

Cool!

 

I wanna see a photo through it!   ;)

 

I would too but honestly, I am not into A-P.. 

 

Jon

 

 

Don't you know that nothing is real unless you either take a photo of it or through it? I suppose that means nothing existed before the 1820's.  http://en.wikipedia...._of_photography

 

:grin:

Mike


Edited by Sarkikos, 07 October 2014 - 10:30 AM.


#123 Sarkikos

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Posted 07 October 2014 - 09:54 AM

 

Actually...I like this answer the best.  But I don't think any of the answers quite hit the mark.  Let's face it...you want high sales figures and popularity?  Then the answer to "Why are Schmidt-Cassegrains so popular?" is really simple....offer any product that works and follow it with Superlative & Imagination Catching Marketing!  Celestron and Meade push it out all year every year relentlessly.

 

 

Yea, that's a good point, Bill. Sometimes I wonder if there is a herd mentality, too. Folks like to buy a popular design because they feel safe in doing so. So many others use them, there has to be a good reason. And there are several good reasons...

 

 

There is also the fact that many newbies are scared away from Dobs by reports of how difficult they are to collimate, and how often you need to collimate them.  So they get a scope that - supposedly - you never have to collimate, that is, an SCT or refractor.   This is certainly my impression after talking to observers at my dark site, as well as reading threads here on CN.

 

Mike


Edited by Sarkikos, 07 October 2014 - 09:56 AM.


#124 LivingNDixie

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Posted 07 October 2014 - 10:35 AM

When that goto dies on the Orion GT dob, getting that repaired will be just about impossible, what does Orion charge for a new base... esp if your not the original owner. If a C8 with goto dies just put it on a ASGT and you are golden.

I have had two LX200s die on me in 15ish years, so yes they do kick it. However mounting on a GOTO mount is pretty straight forward, not so much with those large Orion dobs.

Personally I am done with goto for a long time. If that means it takes me years and years to develop star hopping skills and learn the Sky as well as the computer... I consider that time well spent... Heck it is cheaper then a shrink :lol:

#125 jrbarnett

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Posted 07 October 2014 - 10:48 AM

 

In our hobby I find marketing to be largely ineffective.  Case in point.  TEC does no advertising.  Televue advertises.  TEC 140s outsell NP101s.  

 

I don't consider the "marketing" that TV does relative to telescopes anything other than minor league.  Their marketing for eyepieces when they first came out was innovative and eye catching for the Naglers, and got the imagination sparked.  By comparison IMO their telescope marketing is lifeless and nil.  And compared to the massive telescope marketing that Meade and Celestron do, TV does not even register on tne radar IMO.  The quantities of SCTs that Meade and Celestron have sold is mind boggling.  TEC and TV (presuming they are selling about what TEC does) telescope sales more like rounding error compared to Celestron-Meade.

 

The real case in point is that TEC has sold on average 54 140s per year since they came out based on Yuri's latest post (about 650 made to date).  Celestron alone sells at least several hundreds of SCTs every year (based on serial number tracking by a CNer).  Add Meade sales to that and the TV - TEC crew is minor league sales. [EDIT - incorrectly said 35 scopes/year when should have been 54 on average based on 647 140's made in the past 12 years]

 

What I do wonder is how many Tak scopes are sold yearly?

 

I guess my point is this.  Meade and Celestron advertise where?  In magazines.  The vast majority of us neither subscribe to nor purchase those magazines.  Yet somehow we are still able to figure out what is available and how to get it.  I'd chalk Celestron's and Meade's sales volume up to being cheap, not to effective advertising.  More cheap scopes sell than expensive ones, whether or not the producer advertises effectively, simply because more prospective buyers can afford cheaper gear.

 

- Jim


Edited by jrbarnett, 07 October 2014 - 10:48 AM.



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