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Why do people even buy SCTs???

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#1 Eddgie

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Posted 29 November 2013 - 10:55 AM

Nothing is right about them.

None of the manufacturers flock the inside of the baffles, and gee, if the manufacturers only did this, it would improve the contrast by 50%.

And the obstruction is huge. If they left off the secondary baffle, they could reduce the obstruction by 4%.

And they don't come in a Truss design.

And the corrector is not in the right spot. By making the tube 30% longer and moving the corrector, they could make it better.

And seeing makes them useless for planetary observing. You can't even get the moon into focus it affects SCTs so bad.

Oh, and cooling. You can't even see stars I guess unless you put in cryogenic refrigeration plumbing. I mean why bother using them at over 75x when you can use a refractor at 75X and see the same size true field. Sure, nebula and extended targets will be brighter, but they are wiggling around so much and they are sooo blurry that what it the point????

I just don't get it. How can so many people be so happy with what is more of a kit car than a telescope it would appear. The thing is practicallly unusable out of the box. You have to take it apart and competely rebuild it to make it work as well as a 100mm APO.

I will never buy another one. I just don't have the time to rebuild it in order to get it to be even marginally useful.

Just kidding of course. I get the "ATM" spirit.

But all of these "Mod" posts really make me wonder sometimes if the commercial SCT is worth the time and effort if so many mods need to be made to get it to perform well?


I have just been so thrilled with my SCTs in the past. Most of them were really able telescopes that presented me with hundereds of hours of wonderful observing. And none of the mods I tried seemed to make any meaningful difference for my own observing needs that I stopped chasing the "Mod of the day" a long time ago. And the bigger I went, the more I enjoyed them. The more I could see. More deep sky, more planetary detail, more stars in clusters. No mods or anything. I just went bigger and bigger and saw more and more.


The SCT is not the scope people love to hate, it is the scope people hate to love.... It seems like so few people "Believe" in their SCTs.

These forums make it hard for me to continue recommending SCTs to people though. I used to make the C8 my "Standard" recommendation for people wanting their first telscopes. Enough apeture to do great all around observing. Inexpensive, easy to store and transport, comfortable to use, and just a great telecope.

But these days, I am more inclined to recommend a small refractor. Nothing to do. Just plug and play.

That is the world we live in.

I am starting to get the refractor forum's superiority complex.

Modders, please do not take offense. This is not directed at any individual. Rather it is just a rant about how so many people perceive so much wrong with a design that I have loved dearly over the decades, but now feel as if may be damaged by the perception that there is so much wrong with them.. So sad. Great telescopes.

At least one person loves them just the way they are...
 

#2 orion61

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Posted 29 November 2013 - 11:17 AM

I love my SCT's, especially my C6! I have a large refractor
but hardly use it because of the pain in my back it gives me!
Newtonian, have that too, quite sharp, but I live in IOWA the windiest part of the Nation,dont believe me? just ask the 20,000 Migrating birds that run into all the Wind turbine
generators each year!
So I'll keep my stubby, Ugly, Blurry Worthless sct
 

#3 Martin Lyons

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Posted 29 November 2013 - 11:20 AM

Yep, SCTs suck........
 

#4 PowellAstro

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Posted 29 November 2013 - 11:21 AM

They are great scopes. But, what's wrong with someone doing a lot of work. If they want to and the scope can be made even better...
 

#5 drago

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Posted 29 November 2013 - 11:23 AM

very good question.
all these may be formed to one: why people do dumb things?
What you think, why?
i think, in general, because most of people is that, about what Einstein says "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
 

#6 Roy McCoy

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Posted 29 November 2013 - 11:33 AM

You had me up until the word "thrilled".
:smirk:
 

#7 Footbag

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Posted 29 November 2013 - 12:17 PM

SCT's have one fatal flaw. They cannot hold their own against telescopes 10x their price. ;)
 

#8 herrointment

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Posted 29 November 2013 - 12:20 PM

What the dog said.
 

#9 drago

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Posted 29 November 2013 - 12:20 PM

SCT's have one fatal flaw. They cannot hold their own against telescopes 10x their price. ;)


they cannot hold even against cheaper newtonians. newtonians have smaller central obstruction, less light loss and scatter taht catadioptrics. imho only cat's pluss in general is their compact size. all another compared to newtonians and refractors, is minuses...
 

#10 Joe Aguiar

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Posted 29 November 2013 - 12:23 PM

eddie your funny

i love scts they are called the best all round general telescope, not the best in a specific field, but i think it does give decent views on most stuff.

Its the size that makes it one of the best selling kinda scopes.

I cant imagine using a 12" F/10 refelctor ( i dont even think they make one)normally in this size its an F/4.8 to 5.

At about 2ft long no other scope in its size class can match the portabililty, and iam sticking to this LOL
 

#11 rmollise

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Posted 29 November 2013 - 12:41 PM


they cannot hold even against cheaper newtonians. newtonians have smaller central obstruction, less light loss and scatter taht catadioptrics. imho only cat's pluss in general is their compact size. all another compared to newtonians and refractors, is minuses...


Newtonians are fine if you just want to look. If you decide you want to do more than that, the SCT is far more versatile and adaptable. ;)
 

#12 DesertRat

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Posted 29 November 2013 - 12:55 PM

Maybe some have too many cloudy nights? Some just like to do ATM like stuff. Amateur astronomy has all kinds of people, and lets hope that's always the case.

Some just like to come to Cat&Casses and leave newt (or other) bombs. Clearly too much time or too many cloudy nights or maybe they just got lost?

By the way, my first serious scope was a 8" newt. Very nice and great memories.

Love is not a word I associate with a telescope. I am strongly attached to my Edge14. The best scope in its class I've ever used. I like my refractors and Mak, but that SCT is special.

One thing though, in my climate the TEMP-est fan system has clearly improved cooldown. At least for me. If I lived somewhere were temps did not fall like they do here I would not even need that.

The C8 is an ideal starter scope. Celestron's sales record for them is a clear indication that many have had plenty of enjoyment from them.

Can we all just get along and enjoy the heavens and avoid :slapping: or :beat: ?

Glenn
 

#13 Footbag

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Posted 29 November 2013 - 01:07 PM

SCT's have one fatal flaw. They cannot hold their own against telescopes 10x their price. ;)


they cannot hold even against cheaper newtonians. newtonians have smaller central obstruction, less light loss and scatter taht catadioptrics. imho only cat's pluss in general is their compact size. all another compared to newtonians and refractors, is minuses...


That does kind of go back to my point about their price. With an SCT, you get a build quality that you don't get in the cheaper newts. I would say the build quality of SCT's is well beyond the starting price newts. And after the starting price points, Newts jump. Personally, I think AT needs to boost the build quality and introduce premium imaging newts.

It's also nice to not need a coma corrector.

But, most people seem to be comparing Edge to refractors. An Edge vs a Newt would be an interesting shootout.
 

#14 Steve Darden

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Posted 29 November 2013 - 01:17 PM

I hate my C8 so much that it may be the last telescope I buy. :)

Just kidding of course. I had a 10 inch dob and while it showed more than the C8, it wasn't comfortable for me to use. I also didn't like that the optics were open and got dirty quickly.

Both designs have their benefits and while I may buy a bigger dob some time in the future, the C8 is the scope I use when I have more than an hour to view.
 

#15 David Pavlich

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Posted 29 November 2013 - 01:26 PM

I've been an SC owner since I attended my first outreach. Our club president at the time had a C11 on a G11 set up next to me with my C6R on an Atlas. After looking at Jupiter for a while through my scope, I wandered over to Ron's C11 and at that point, I was hooked. It was a well turned C11 that was acclimated and collimated. Jupiter looked great! The only scope on the field that bettered it was a 16" NightSky dob.

It's a very versatile design that gives a lot of options for visual and imagers alike. You just have to know how to treat them to get the best out of them.

David
 

#16 BKBrown

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Posted 29 November 2013 - 01:56 PM

Portability of aperture, price point, versatility...all things I associate with SCTs. I am fortunate to have an excellent C9.25 XLT and an even better C11 Edge HD; how that happened I can't imagine since "the mass market quality control" on these scopes is clearly so bad :smirk: Fact is, I haven't personally owned a real dog of an SCT so I don't understand what the complaints are about. And being a lunar and planetary imager, I am content to settle for the scope of choice used by many of the top amateur LP imagers in the field today...

Clear Skies,
Brian
 

#17 rcdk

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Posted 29 November 2013 - 02:11 PM

Good post.

I used to hate them. Then I bought one. The only mod I made was Bob's knobs, but it is rarely necessary to touch them.

Which is odd considering the main reason I never liked them before is because I had literally never looked through one that was properly collimated. Finally a friend (who knows how to properly collimate a scope) bought a used Dynamax and I was blown away by the sharpness of the image.
 

#18 coinboy1

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Posted 29 November 2013 - 02:15 PM

I love my C11. Its the older carbon fiber Nexstar 11 GPS but it has excellent optics. I make optics as a hobby and have made a 9.25" 1/13 wave parabolic mirror and I can say that my C11 image quality is very good. Its compact size is amazing. I can haul my C11 around much easier than my 9.25" newtonian. My C11 also has the ability to accept Hyperstar. You know, for imaging at F/2. What other telescope can be at a Native F/2 and a Native F/10. I can use my SCT for high focal length planetary imaging (no diffraction spikes to deal with) or SUPER wide FLAT field and SUPER FAST F/2 imaging.

I believe the SCT has an excellent bang for the buck. The SCT has some of the larger after market accessories available to them. I am an amateur telescope maker and have made several newtonians but I still much prefer my SCT for viewing and imaging for these reasons.

Also collimation in an SCT is easier than a RC telescope. I have a 6" AT6RC and collimation is a HUGE pain the but. My C11 SCT holds collimation very well and produces excellent images. Plus my SCT central obstruction is considerably smaller than the Ritchey Chretien.

I dont understand the point of this thread. The SCT is an excellent scope for viewing and imaging. And if you dont like the heavy curvature of field for your SCT for imaging, get a good field flattener/focal reducer. There are plenty of them out there made JUST for them. Other telescopes dont have as many options IMHO.
 

#19 MikeML

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Posted 29 November 2013 - 02:18 PM

Because I only have space for so many telescopes.
 

#20 jimbo728

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Posted 29 November 2013 - 02:40 PM

There is nothing wrong with an SCT that a bigger SCT wont cure.
Jim
 

#21 JohnH

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Posted 29 November 2013 - 02:51 PM

SCT's are for the most part, the equivalent of a Ford Focus or some other car costing around $10K-15K.

They fill the need of people needing to get around to work, shopping kids from school and the occasional road trip. Good all around. Inexpensive, able to do most things well but not outstandingly.

SCTs are the telescopic version. A good scope to learn on and is all most people will ever need. Does imaging and visual; is easy to maintain and keep clean; and is useable most of the time.

Newtonians have the edge for imaging faint objects visually but are heavier and need more adjusting; Maksutovs also stay cleaner and well adjusted and are heavier and more expensive; corrected D/K's and R/C's are suited for demanding imaging with higher costs and less utility for visual use
 

#22 kkokkolis

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Posted 29 November 2013 - 02:59 PM

SCTs (and all Cats) are in fact heavily moded Newtonians. Take a fast Newtonian, replace the secondary with a f/5 mirror, add a Schmidt lens to seal the tube, voilĂ . Then open the tube because sealing brings problems, add fans, then dew heaters, then dew shields (that make them long again) and ofcourse focal reducers to make fast again what you made slow. Fast again but with added glass! Then add a refractor/ finder for widened views and a diagonal to replace the removed diagonal/ secondary. You still see a reversed image! Have an Amici somewhere close for terrestrial. Find a capable mount. Now add Ethos corrected to f/4 although your SCT isn't f/4 at all. Or remove the secondary to make it fast again for astrophotography. Oh! I forgot the coatings! Add coatings. And the glass should be good. Beware not to brake it.
Now you have your SCT.
And you start moding it. Bob's knobs is just for start.
Somewhere in the moding process, one might make it a Newtonian again!
 

#23 drago

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Posted 29 November 2013 - 03:03 PM

built quality?
be more real. look at interferometer test on mr. Rohr or on VAGO - these objectively show us most SCT "quality" - strehl ratio even without central obstruction be about 0.5 !
http://fidgor.narod....t/test_104.html
http://fidgor.narod....st/test_22.html
http://fidgor.narod....st/test_30.html

yes, there are some exemplars who show strehl about 0.85 and up, even 0.96 or so - but when we count central obstruction, who in general is larger than on newtonians, big problem with thermal equilibrium, a rough corrector plate plishing and so on - SCT have no chances to good newtonian, imho.
 

#24 WesC

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Posted 29 November 2013 - 03:08 PM

I don't agree with that. SCTs and Newtonians are very different designs. They work differently, run differently and have different pros and cons. The only similarities are that they are folder optics and need to be collimated. But even those similarities are different.

Nope. Apples to pomegranates. ;)
 

#25 Footbag

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Posted 29 November 2013 - 03:08 PM

built quality?

SCT have no chances to good newtonian, imho.


So... What is a good Newtonian?

Strehl doesn't matter if your focuser cannot hold your CCD camera.
 






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