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Why do people even buy SCTs???

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#101 ErikB

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Posted 30 November 2013 - 03:30 PM

An SCT can be just as good for imaging DSOs than any other design, and usually better. A Newtonian is harder to balance and mount, and a refractor lacks aperture, which is also important unless all you want is wide field. ;)


While it is true that an sct is easier than a newt for the mount to handle, all to often the beginner might fall into the trap of thinking the mount portion of a forked sct is of suitable quality for imaging faint objects. (Ask me how I know.) In fact I believe that for the smaller sct sizes, likely to be someone's first scope, the amount of money sunk into the design by the manufacturer for the mount portion of a forked sct is less than would be appropriate for imaging of faint objects requiring multiminute exposures at the focal length of the sct. That is of course a generalization that isn't going to be true for every case, but with a majority of new users being visual, how could it, in general, be any different? So, yes for given scope spec's, an sct is easier on the mount with respect to stability, but that means little if the beginner planning dso imaging finds that the fork drive is of insufficient quality for successful guiding. And, yes, if high magnification is desired, an sct variety may be the ticket, but the beginner may all too easily make the mistake of thinking an 8" sct will guide well with its standard fork or with a cheap GEM. Besides those issues, I believe the average standard sct (I only have experience with two 8"s and one 9.25") creates more bloated star images than good newts or refractors, even at the center, for the same aperture and magnification. This of course is another aspect of how contrast varies with the scale of object detail, but it definitely has a negative impact on both imaging and visual use.
 

#102 drago

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Posted 30 November 2013 - 03:33 PM

But what really got me about the C5 was the sharpness of the image. I had never seen that in a SCT,and the portability is unbelievable. I hate to say It, but I would take that little C5 over the RV6 that I once had and that scope you could set next to anything. So for me that's why "people even buy SCTs???" even if its an optical gamble.


as i understand, people buy SCT for that, SCT sometimes got a sharp image. not a near as sharp, as in normal APO, but a bit more sharp than a absolute messy image...? :D
 

#103 rmollise

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Posted 30 November 2013 - 03:37 PM

i hear, Anatoliy Sankovich, a word famous Santel MCT maksutov scopes maker once says: "who understand, choose newtonian..." :)


All things being equal, perhaps...but no matter what Antoiliy says, all things are rarely equal. :lol:
 

#104 rmollise

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Posted 30 November 2013 - 03:39 PM


While it is true that an sct is easier than a newt for the mount to handle, all to often the beginner might fall into the trap of thinking the mount portion of a forked sct


Perhaps, though countless good pictures have been done with forks. AND you can put your C8 on a dadgum AP1600 if the spirit moves you. :lol:
 

#105 orion61

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Posted 30 November 2013 - 03:46 PM

Rod, Mark twain once said...
"Never get into an argument with an idiot, He will bring you down to his level and beat you with experience"?
To each their own.. You cant prove Memories, or opinions.
This one is going South.. I'm happy with my Schmidt, I wonder why people try so hard to convince me, my opinion of my equipment is wrong, when I have had all the different types of scopes, and I'm so happy with what I have, and the results I have achieved from it????
 

#106 David Pavlich

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Posted 30 November 2013 - 04:05 PM

[quote
All that said, I don't expect a far lower cost SCT to perform at the same level of a much more expensive scope. However, I would like it to perform better than the ones I tested long ago. I'm in the market for one (or two). [/quote]

I'm all for giving props when deserved. So many times, we have off the shelf SCs compared to what are essentially hand made refractors or high end Newts that cost much more than the SC. John has stated above what few ever do when making this type comparison. Thanks, John!

David
 

#107 PowellAstro

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Posted 30 November 2013 - 04:14 PM

I have an 8 inch SCT that the only reason I would trade it even for a top of the line 6 inch APO, would be so I could sell it and get another 8 inch SCT and pocket the rest!
 

#108 Geo31

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Posted 30 November 2013 - 05:40 PM

I love watching people.. :bangbangbang:
We are just.. :beat:


Boy howdy (obscure southern expression that essentially means: I couldn't agree more) :grin:
 

#109 JJK

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Posted 30 November 2013 - 06:05 PM

To each their own.. You cant prove Memories, or opinions.
This one is going South.. I'm happy with my Schmidt, I wonder why people try so hard to convince me, my opinion of my equipment is wrong, when I have had all the different types of scopes, and I'm so happy with what I have, and the results I have achieved from it????


I don't recall anyone here suggesting you have, or anyone else has, the wrong equipment. I'm not even sure what that statement would mean.

From your signature line, and what I'd like to do in the future, you seem to have good stuff. I have enough scopes and mounts for my own personal use, but I'm thinking about setting up an observatory for public use in a mountain community. A C-14 could be a good compromise, in the sense that while it can't provide as deep a view at the EP that a 32" Dob-Newt can, it can certainly show very nice views of a lot of DSOs, and striking images of fainter ones if a CCD camera is used as an electronic eyepiece (and th C-14 is pretty compact).
 

#110 kkokkolis

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Posted 30 November 2013 - 06:56 PM

Hey people, this is the Cats and Casses field. Whoever loves mostly Newtonians and Refractors can visit their specialized subforums! It seems simple to me. :grin:
 

#111 jgraham

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Posted 30 November 2013 - 10:10 PM

As far as imaging goes... as with visual, my experience has been that an SCT makes a fine general purpose platform, particularly when paired with a modern DSLR or large format (APS-C) CCD. I usually leave mine at its native f/10 for deepsky imaging, though I'll occassionally pull it in to f/6.3. For planetary I'll stretch it out to f/30. The long focal length made imaging with small chip CCDs a challenge, but that's not the problem that it once was with the advent of affordable DSLRs and their modern CCD cousins.
 

#112 EFT

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Posted 30 November 2013 - 10:27 PM

An SCT can be just as good for imaging DSOs than any other design, and usually better. A Newtonian is harder to balance and mount, and a refractor lacks aperture, which is also important unless all you want is wide field. ;)


While it is true that an sct is easier than a newt for the mount to handle, all to often the beginner might fall into the trap of thinking the mount portion of a forked sct is of suitable quality for imaging faint objects. (Ask me how I know.) In fact I believe that for the smaller sct sizes, likely to be someone's first scope, the amount of money sunk into the design by the manufacturer for the mount portion of a forked sct is less than would be appropriate for imaging of faint objects requiring multiminute exposures at the focal length of the sct. That is of course a generalization that isn't going to be true for every case, but with a majority of new users being visual, how could it, in general, be any different? So, yes for given scope spec's, an sct is easier on the mount with respect to stability, but that means little if the beginner planning dso imaging finds that the fork drive is of insufficient quality for successful guiding. And, yes, if high magnification is desired, an sct variety may be the ticket, but the beginner may all too easily make the mistake of thinking an 8" sct will guide well with its standard fork or with a cheap GEM. Besides those issues, I believe the average standard sct (I only have experience with two 8"s and one 9.25") creates more bloated star images than good newts or refractors, even at the center, for the same aperture and magnification. This of course is another aspect of how contrast varies with the scale of object detail, but it definitely has a negative impact on both imaging and visual use.


Some people seem to confuse the term "SCT" with "fork mount." We are not talking about mounts here at all. Mounts are a whole other issue. We are only talking about optical tube assemblies without regard to what kind of mount you want to have it on, GEM, fork or other. A fork mount is not the "standard" mount for all SCTs, particularly for astrophotography, and there are only a couple of "fork" mounts that are designed to really handle SCTs for astrophotography but still allow the SCT to be removed and used on other mounts.

Not speaking to anyone in particular, but when it comes down to it, some people will always think that their favorite scope type is better than one of the other scope types and some even feel the need to put down the other types. The rest of us understand that every scope type is a compromise of one sort or another and each type has their value without being somehow degraded by comparison to another type of scope. I love CATs, I love refractors and can even love Newts (although I have little interest in owning another one at this time). In addition, there are variants of those three types like the MakNewt, DK, etc. that are wonderful scopes as well for certain purposes. Those that choose to strongly put down one or another type if scope are often over invested (monetarily or mentally) in the particular type of scope they own and may never be able to admit the value of one of the other types even if everyone else could see it provide better results.
 

#113 A6Q6

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Posted 01 December 2013 - 02:27 AM

drago said: "but a bit more sharp than a absolute messy image...?" Sharp is Sharp, not a little bit or almost. If you haven't experienced what a good SCT can do you don't know what your missing. I would not keep my C5 if it wasn't capable of producing a really sharp image.
 

#114 drago

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Posted 01 December 2013 - 02:58 AM

drago said: "but a bit more sharp than a absolute messy image...?" Sharp is Sharp, not a little bit or almost. If you haven't experienced what a good SCT can do you don't know what your missing. I would not keep my C5 if it wasn't capable of producing a really sharp image.


maybe i wrong, in that case please say, but:
image sharpness in large degree is affected by central obstruction? bigger is CO, softer image.
Also resolution is affected by CO.
the larger is CO, the worster is image.as i understand, most SCT have obstruction larger than 30 percent?
CO is a really evil, and that become undetectable only if it less than 16 percent by diameter. and that is only about CO there. we do not speak about machine-polished rough corrector plate, who also do not add benefits, and maybe about 3rd spherical aberration - dont know, it is a SCT satellite, or not? in MCT it is impossible to avoid SA, as i hear.
 

#115 A6Q6

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Posted 01 December 2013 - 10:23 AM

drago said:"dont know, it is a SCT satellite, or not? in MCT it is impossible to avoid SA, as i hear" Seeing is believing, so you have to go to a star party on a night of good seeing and actually look through good examples of these two optical designs. It really really will make a believer out of you. ;)
 

#116 Cotts

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Posted 01 December 2013 - 10:35 AM

The CO's typical in an SCT are not so large that it has any affect at all at prime focus where the entire diffraction pattern is only a pixel or two wide.

Even for high resolution imaging the CO of an SCT does not reduce contrast to any ruinous degree or else images like these would not be possible.

CO's of 25-35% by diameter do have an effect on high magnification visual viewing of planets and the moon in scopes up to 8" in size when compared to same-sized (or slightly smaller) unobstructed scopes.

Once you get into 9" and larger scopes the central obstruction is a given in virtually every scope owned by amateurs - unless you know of some people with 9" or larger refractors in their backyards. From about 9" and up aperture and lens/mirror quality are pretty much the only variables worth considering.

I sometimes grow weary of the "CO is a disaster" way of thinking. As in so many debates here on CN, the truth is "it depends."

Dave
 

#117 Vondragonnoggin

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Posted 01 December 2013 - 10:38 AM

Was their a point to this whole thread? Every design has a compromise built in. Know your scopes, buy what you deem to be the best compromise to you for the application you'll use it in.

Move on and don't worry when someone spends time modding their scope. You can do it too if you want. If you never saw a difference after mods and someone else does, so what. No need to bake your noodle over it.

Enjoy your compromised scope whether its a big or small SCT, MCT, Apo, Dob, RC, Achro, or (name anything else because it all applies).

:p
 

#118 PowellAstro

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Posted 01 December 2013 - 10:40 AM

+1
 

#119 drago

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Posted 01 December 2013 - 10:41 AM

i'd read a professional optical system designers things about MCT design. they said, in that design cannot be avoid of higher orders SA.
I personally never have an SCT or MCT. One time i thinking about get in my paws a 127 Synta's MCT for megaportable lunar instrument, and also be a test cats with my own experience, but i go reading, concearning, and got to a conclusion, on a planets i not win anything in comparing to 100ed, and on DSO it also be a questionable. i add this to very long thermostabilization times ( in winter there may be a delta with room temperature, to outdoors as 40 or bit more, degrees of kelvin), and stay at me 100ed, with next goal to a larger newtonian dob, who i realised in last months :)

P.S. about a CA: in a start of my telescopes owning i have a two scopes: a bresser 60 \ 800 achro and a "bresser pluto" - 114 / 500 scope, whose real aperture be around of 85 - 90 mm, and central obstruction is close to 40 or so, percents.
i be compare these two on moon and jupiter, and the difference on jupiter was a very terribly. on moon these newtonian looks better than achro, this is a very contrasty objects. but on jupiter is be very hard to see a cloud strips on planet discs. on a smaller achro it is impossible to miss that strips. that's my experience about CA importancy in visual observations.
 

#120 kansas skies

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Posted 01 December 2013 - 10:54 AM

Was their a point to this whole thread?


Sure, it was a perfect opportunity for a few friends to get together over the Thanksgiving weekend (at least in the USA) and enjoy a lively discussion involving something very dear to their hearts...

Cheers, Bill
 

#121 drago

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Posted 01 December 2013 - 11:04 AM

Was their a point to this whole thread? Every design has a compromise built in.


cannot imagine, what compromise is in an apo? :-O
 

#122 Footbag

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Posted 01 December 2013 - 11:06 AM

Was their a point to this whole thread? Every design has a compromise built in.


cannot imagine, what compromise is in an apo? :-O


Price!
 

#123 Vondragonnoggin

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Posted 01 December 2013 - 11:08 AM

Was their a point to this whole thread? Every design has a compromise built in.


cannot imagine, what compromise is in an apo? :-O


Size constraints. Mounting requirements, portability when using larger sizes. Cost prohibitive for a good majority. Doesn't have to be an optical compromise to be a compromise.
 

#124 rmollise

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Posted 01 December 2013 - 11:16 AM

Was their a point to this whole thread? Every design has a compromise built in.


cannot imagine, what compromise is in an apo? :-O



Start with small aperture. ;)
 

#125 drago

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Posted 01 December 2013 - 11:17 AM

on that view all is compromise. i want an 2 metres of aperture with 1 kilogramm weight, and with compactness no larger than a 10x50 binoculars. :D
it is like to a demagogy. price also not a optical system compromise. i think, refractors is most perfect optical scheme. second will be newtonians, especially in designs without CO....
but ok, be a happy what your have. some folks were beware of looks in another optical systems, because all is relative, and can be perceived in comparison - if you never see and sit in ferrary, you can think, a vw passat VR6 is "very good,fast and sporty car"...:D
 






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