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Equipment Discussions >> Cats & Casses

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Jan Owen
Pooh-Bah
*****

Reged: 02/12/06

Loc: Sun City West, Arizona
Re: Why do people even buy SCTs??? new [Re: Jon Isaacs]
      #6238814 - 12/07/13 11:09 AM



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nicklane1
sage
*****

Reged: 03/04/08

Re: Why do people even buy SCTs??? new [Re: Jon Isaacs]
      #6238862 - 12/07/13 11:32 AM

Quote:

Quote:

Would you rather watch the big game on a 100" standard definition TV or 60" high definition TV?




Since resolution is directly proportional to aperture and Newtonian optics can more carefully figured, I would choose the 100" Retina display..



Jon




Not trying to diss SCTs here. I would consider buying one in the future. Sharpness is not a strength of SCTs but rather one of the trade offs with all that extra glass in the lightpath and generally large COs.

And yes I have seen nice images in a C11...


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: David Pavlich]
      #6238879 - 12/07/13 11:43 AM

Quote:

Quote:

Quote:


Given that the Hyperstar system doesn't accommodate a color filter wheel, (it has an optional single filter drawer), it doesn't seem amenable to remote imaging. For most of us, that likely isn't a severe issue.






With the size of the C14, you do have the option of the QSI583ws with its compact size and internal filter wheel. S&T did a test with just this setup. And because of the short focal length of the HS equipped C14, the 8300 chip would be terrific.

David




Thanks DavId. When I first saw the Hyperstar system at the Starizona's booth in ASAE (Tucson) last month, I thought about putting a tiny camera body (e.g., an SX offering) on the system. But, because the camera is reasonably far from the corrector, a somewhat larger body camera could still work.

If anyone has a C-14 with Hyperstar, I'd appreciate seeing their images.


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David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Why do people even buy SCTs??? new [Re: JJK]
      #6238960 - 12/07/13 12:27 PM

Here's some C14 images from the Starizona site: C14.

David


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: Wmacky]
      #6238964 - 12/07/13 12:30 PM

Quote:

Soooooo-

Edggie Creates the thread out of his frustration about the constant SCT bashing that goes on. (In case you didn't know why?)

And then several take the opportunity to do just that?

What a group!

I really don't see what the mystery is? I, as many on the site, have built a small observatory with a centrally located EQ mount for both imaging , and visual duty. I can easily swap out refractors for imaging, and SCTs for visual.

What the hell would I do with a DOB? Balance it on top of my GEM? Put it on the roof? I don't care how good the views are, a Dob is worthless in my observatory. Refractors work nicely, and I do use them to image, but they are too small for many many DSOs. If your are a retired Doctor, or lawyer with a giant AP refractor, then good for you, but I would think most people will never own a giant premium refractor. Beside they would not fit into the average size home observatory.

I just don't see the mystery?

For me - A SCT offers decent aperture for DSO's, but can still be quickly mounted on a GEM - Can be used for imaging DSOs at long focal lengths for close ups. - Is a preferred planetary imaging platform. - Can be easily swaped out on the GEM with a refractor for widefeild imaging, and views- Finally they don't cost much.

?????????????




Eddgie's obvious tongue-in-cheek OP aside, I don't recall anyone meaningfully suggesting there is a mystery about why anyone would buy an SCT. The compact design has proven remarkably versatile (especially now with Hyperstar's introduction), and has offered a huge bang for the buck for over 4 decades.

As to the "constant SCT bashing" you mentioned, I don't see it. If someone here describes issues he or she has had with an SCT, or why those issues prevented them from buying such a scope, that's their valid perspective. Now, if their reasoning is faulty, the group could provide evidence to the contrary.

Over a decade ago, I was looking for an 11"(plus or minus)-class telescope, and looked critically through many C-11s. I wasn't impressed with any I tested and bought a more expensive 10" Mak-Cass. That doesn't mean I thought all C-11s or SCTs were unacceptable. It simply means I didn't want to spend the time cherry picking through a lot of scopes and then fix their obvious thermal and focuser issues (some folks here like to tinker with that sort of stuff, but I spend a lot of time doing that sort of thing, and don't want to do it at home). If I truly thought SCTs were terrible, why would I read anything in a forum dedicated to them? I'm still interested in getting one (now, a C-14 class instrument) for a different purpose than I had a years ago, but I'll need to check them out firsthand and get others' opinions.

Someone here referred to refractors as "spyglasses". Given that I have had 10 premium apos (regrettably, not all at once, and I'm not an MD or a retired lawyer), should I take exception to that term? I assumed that poster either said it in jest, or hates the scopes, which is his prerogative. If he doesn't want to look through or image with a high quality apo, that's his loss. I am continually stunned by how good the Moon, Jupiter and Mars look in a relatively small Zeiss 130 mm f/7.7 APQ (they look absolutely etched), but that didn't stop me from training larger aperture telescopes on the same objects.

If you have no need for a particular design scope (e.g., a Newt-Dob), or can't afford a premium apo, that's your business, and no one here would suggest you made a terrible mistake (which, BTW, you did ).

Finally, if everyone remained quiet about the shortcomings of a particular SCT implementation's shortcomings or other issues, e.g., mirror flop, focuser shift, thermal issues, tendency for the corrector to easily dew over, relatively poor optical quality (I'm not saying all SCTs have poor optics), etc., then there'd be no pressure for the manufacturer to improve the product, or for others here to share their fixes.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: David Pavlich]
      #6238970 - 12/07/13 12:32 PM

Quote:

Here's some C14 images from the Starizona site: C14.

David




Thanks David. I saw those images and more at Starizona's booth, which whetted my appetite. I'd like to see more taken by many others with a range of cameras. I'd like to get the right combination the first time.


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BKBrown
Post Laureate
*****

Reged: 08/23/09

Loc: Northern Virginia, USA
Re: Why do people even buy SCTs??? new [Re: drago]
      #6239013 - 12/07/13 12:47 PM Attachment (10 downloads)

Quote:

Quote:


What are you basing your opinion on? Have you actually ever critically looked through an AP 10" f/14.6 Mak-Cass (CO ~ 23 %) or a Tak Mewlon 300 CDK? Their aperture and optical quality make their COs irrelevant.




i based it from my small knowledge in optics, my readings about a topic from amateur astronomers, who at the same time is professional optics ( most known there is Valeriy Deryuzin, i think), as so as another amateur publiced tests result in astroforums, who's compare various instruments and test one instrument with various central obstruction ( create a different masks, and test), and also my own small experience, when i have a newtonian with about 40+ percent CO and small achro at the same time.
and also from theoretical material, like as from link, who i publiced there.
also, theoretically, anyone can test central obstruction involved effects - there is need a good telescope ( apo, say), or off-axis clear aperture mask on newtonian, or SCT. any can look throught its clear aperture without CO, and then induce in that central aperture various circles to emulate a various CO. and compare it all between and without obstruction at all. its not a difficult, but a bit tiresome work, with very demonstratable results. sure, test object must be not very contrast, like moon, but object with small contrasts, where a small contrast loose give a big diff in view. say - jupiter....

also, if aperture make irrevelant CO, than their make irrevelant also instrunment optical quality, be consistent.




This thread appears to be stumbling forward with no end in sight: often amusing, occasionally thought provoking, increasingly absurd. I want to ask just one question now based on a side-by-side imaging comparison I did last year of three different scopes shooting in very good seeing conditions with the same camera: Which shows the best color saturation and resolution? Look at them all, note that one is a mass produced SCT, one is a superb premium Apo, and one is an excellent ED doublet...which one is "best"? Inquiring minds want to know

Clear Skies,
Brian


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Vondragonnoggin
Post Laureate
*****

Reged: 02/21/10

Loc: Southern CA, USA
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6239038 - 12/07/13 12:58 PM

I don't know saturation levels, but I do know that C11 pic and view beats the pants off the 100ED (although a very nice pic for a 100ED).

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kansas skies
sage


Reged: 12/02/12

Loc: Kansas, USA
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6239061 - 12/07/13 01:08 PM



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RobVG
scholastic sledgehammer
*****

Reged: 01/09/06

Loc: Seattle Washington
Re: Why do people even buy SCTs??? new [Re: kansas skies]
      #6239138 - 12/07/13 01:48 PM

Was searching for the words "focal reducer". Supposedly somewhere in this thread they're hiding.

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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6239182 - 12/07/13 02:10 PM

Quote:

Quote:

Quote:


What are you basing your opinion on? Have you actually ever critically looked through an AP 10" f/14.6 Mak-Cass (CO ~ 23 %) or a Tak Mewlon 300 CDK? Their aperture and optical quality make their COs irrelevant.




i based it from my small knowledge in optics, my readings about a topic from amateur astronomers, who at the same time is professional optics ( most known there is Valeriy Deryuzin, i think), as so as another amateur publiced tests result in astroforums, who's compare various instruments and test one instrument with various central obstruction ( create a different masks, and test), and also my own small experience, when i have a newtonian with about 40+ percent CO and small achro at the same time.
and also from theoretical material, like as from link, who i publiced there.
also, theoretically, anyone can test central obstruction involved effects - there is need a good telescope ( apo, say), or off-axis clear aperture mask on newtonian, or SCT. any can look throught its clear aperture without CO, and then induce in that central aperture various circles to emulate a various CO. and compare it all between and without obstruction at all. its not a difficult, but a bit tiresome work, with very demonstratable results. sure, test object must be not very contrast, like moon, but object with small contrasts, where a small contrast loose give a big diff in view. say - jupiter....

also, if aperture make irrevelant CO, than their make irrevelant also instrunment optical quality, be consistent.




This thread appears to be stumbling forward with no end in sight: often amusing, occasionally thought provoking, increasingly absurd. I want to ask just one question now based on a side-by-side imaging comparison I did last year of three different scopes shooting in very good seeing conditions with the same camera: Which shows the best color saturation and resolution? Look at them all, note that one is a mass produced SCT, one is a superb premium Apo, and one is an excellent ED doublet...which one is "best"? Inquiring minds want to know

Clear Skies,
Brian




There's no doubt that SCTs have proven their worthiness in planetary imaging, and the extra aperture can be helpful because it makes it easier to get the proper image scale (long focal length) and provides the potential high resolution (limited by the particular scope's quality, whether the scope is thermal equilibrated with the ambient temperature, and the seeing).

The latter is obviously crucial. I tried to use "lucky" imaging of Jupiter (take lots of frames and only keep the best) one or two Winters ago with two different top-notch mid-aperture scopes (254 mm and 300 mm aperture). The Jet Stream was unusually bad every single clear night. The seeing that season reduced all my large scopes to a 4" refractor's resolving power. . I guess on the bright side, I could have saved myself the hassle of setting up heavier scopes.


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drago
sage


Reged: 01/11/08

Loc: Latvia
Re: Why do people even buy SCTs??? new [Re: JJK]
      #6239257 - 12/07/13 02:46 PM

Quote:


Why don't you ask Valery Deryuzhin, who collaborated on the AP Mak-Cass project with Roland Christen, about that scope's performance? I've found it to provide large refractor-like views (high contrast views of Saturn, Jupiter, Ganymede; tiny pinprick stars; delicate network nebulosity in M42; central star in M57; etc.), that no 11" SCT I've critically looked through up to a decade ago ever did (not even close).




he's already write that. if i remember correctly, he said, a cat can be better than apo in large diameters - if it is a very high optical quality MCT with minimized central obstruction - don't remember, it state that must be less than 21 or 19 percent.


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drago
sage


Reged: 01/11/08

Loc: Latvia
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6239264 - 12/07/13 02:52 PM

there is many aspects in comparision, and if we do comparission without take it into, we get a mess in result.
for example, you can get an 50mm f4 scope, and 40mm f12 scope, and get throught both of it a m42 pics at,say, 40 secs. as so, on 50 mm you get far better exposed image, and can be stated, a big telescopes do bad on DSO and \ or large F number is bad for DSO viewing visually.
the both stats be wrong, sure. i think, we cannot also compare contrasts on planets throught pictures comparission. especially, if there is a lot postprocessing.


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Dwight J
scholastic sledgehammer
*****

Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: Why do people even buy SCTs??? new [Re: JJK]
      #6239271 - 12/07/13 02:57 PM

Quote:

Quote:

Soooooo-

Edggie Creates the thread out of his frustration about the constant SCT bashing that goes on. (In case you didn't know why?)

And then several take the opportunity to do just that?

What a group!

I really don't see what the mystery is? I, as many on the site, have built a small observatory with a centrally located EQ mount for both imaging , and visual duty. I can easily swap out refractors for imaging, and SCTs for visual.

What the hell would I do with a DOB? Balance it on top of my GEM? Put it on the roof? I don't care how good the views are, a Dob is worthless in my observatory. Refractors work nicely, and I do use them to image, but they are too small for many many DSOs. If your are a retired Doctor, or lawyer with a giant AP refractor, then good for you, but I would think most people will never own a giant premium refractor. Beside they would not fit into the average size home observatory.

I just don't see the mystery?

For me - A SCT offers decent aperture for DSO's, but can still be quickly mounted on a GEM - Can be used for imaging DSOs at long focal lengths for close ups. - Is a preferred planetary imaging platform. - Can be easily swaped out on the GEM with a refractor for widefeild imaging, and views- Finally they don't cost much.

?????????????




Eddgie's obvious tongue-in-cheek OP aside, I don't recall anyone meaningfully suggesting there is a mystery about why anyone would buy an SCT. The compact design has proven remarkably versatile (especially now with Hyperstar's introduction), and has offered a huge bang for the buck for over 4 decades.

As to the "constant SCT bashing" you mentioned, I don't see it. If someone here describes issues he or she has had with an SCT, or why those issues prevented them from buying such a scope, that's their valid perspective. Now, if their reasoning is faulty, the group could provide evidence to the contrary.

Over a decade ago, I was looking for an 11"(plus or minus)-class telescope, and looked critically through many C-11s. I wasn't impressed with any I tested and bought a more expensive 10" Mak-Cass. That doesn't mean I thought all C-11s or SCTs were unacceptable. It simply means I didn't want to spend the time cherry picking through a lot of scopes and then fix their obvious thermal and focuser issues (some folks here like to tinker with that sort of stuff, but I spend a lot of time doing that sort of thing, and don't want to do it at home). If I truly thought SCTs were terrible, why would I read anything in a forum dedicated to them? I'm still interested in getting one (now, a C-14 class instrument) for a different purpose than I had a years ago, but I'll need to check them out firsthand and get others' opinions.

Someone here referred to refractors as "spyglasses". Given that I have had 10 premium apos (regrettably, not all at once, and I'm not an MD or a retired lawyer), should I take exception to that term? I assumed that poster either said it in jest, or hates the scopes, which is his prerogative. If he doesn't want to look through or image with a high quality apo, that's his loss. I am continually stunned by how good the Moon, Jupiter and Mars look in a relatively small Zeiss 130 mm f/7.7 APQ (they look absolutely etched), but that didn't stop me from training larger aperture telescopes on the same objects.

If you have no need for a particular design scope (e.g., a Newt-Dob), or can't afford a premium apo, that's your business, and no one here would suggest you made a terrible mistake (which, BTW, you did ).

Finally, if everyone remained quiet about the shortcomings of a particular SCT implementation's shortcomings or other issues, e.g., mirror flop, focuser shift, thermal issues, tendency for the corrector to easily dew over, relatively poor optical quality (I'm not saying all SCTs have poor optics), etc., then there'd be no pressure for the manufacturer to improve the product, or for others here to share their fixes.




I am that "someone" and it was partially in jest and partially serious. A comparison between a refractor and a C14 would require a 12" apo refractor to level the field. To put spyglass in perspective, our club uses a 4" Genesis as a finder on the C14. My overall point is that any design has issues but SCT's seem to be singled out as particularity bad by mostly refractor aficionados. Often price is equated to quality and refractors smugly refer to how much they have paid per inch over the lowly SCT. I had the opportunity a few years ago to compare a "cheap" Orion 80mm apo to a Televue 85mm. The Orion spanked it on color correction.
In terms of using or imaging thru an apo, I have used the club Genesis to take a few piggyback images but overall I have no need for a refractor except as a finderscope. My 8" Cerevolo MakNewt will scare the pants off 7" apo refractors.


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bob gunnerson
journeyman


Reged: 11/13/08

Re: Why do people even buy SCTs??? new [Re: David Pavlich]
      #6239381 - 12/07/13 04:13 PM

I find myself going through various phases or cycles of enjoying one particular type of telescope for a while and then moving to another type. I am fortunate have many scopes to use and compare the views. For example I have had many fine views of Jupiter with a C-14 under steady skies, with more fine detail than with any of my other scopes. I also have my 1974 old orange C-8 that sits ready to go by the door for the quick two minute "look-sees" to see if it is worth observing, or say for quick look at M-42. This C-8 takes 30 seconds max to be up and ready for observing. These scopes get used a lot and are thus some of my favorites.

Then there are the good seeing nights where I use my AP 155 and see the very tiny perfect airy disks of the stars in an open cluster, or use it to cleanly split a very close double star. When this happens, then for a while, this scope may become my favorite.

The large reflector telescope (port-a-ball) also get used, but usually only when I have more time to observe. Then, depending on what I was able to see, how long the mirror has had to cool off, the quality of the seeing, how dark the sky is, etc, then it may become my favorite telescope for a while, in part, due to its ease of use and no awkward observing positions .

Then along comes another good night with a good view through the C-14, it becomes my favorite, and the process starts all over again.

I think the SCT, Refractors, and Reflectors all have their place depending upon your interests and that is why people buy them, even the all around SCT. This variety is what makes the hobby fun.


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BKBrown
Post Laureate
*****

Reged: 08/23/09

Loc: Northern Virginia, USA
Re: Why do people even buy SCTs??? new [Re: drago]
      #6239409 - 12/07/13 04:26 PM

Quote:

there is many aspects in comparision, and if we do comparission without take it into, we get a mess in result.
for example, you can get an 50mm f4 scope, and 40mm f12 scope, and get throught both of it a m42 pics at,say, 40 secs. as so, on 50 mm you get far better exposed image, and can be stated, a big telescopes do bad on DSO and \ or large F number is bad for DSO viewing visually.
the both stats be wrong, sure. i think, we cannot also compare contrasts on planets throught pictures comparission. especially, if there is a lot postprocessing.




The OP's question was why do people buy SCTs. Short answer: portability, versatility , and decent quality for a reasonable price. An 11 to 14 inch average quality SCT has significantly more light gathering power than many smaller and more expensive scopes...and that gives the user better color and compensates for CO contrast issues (which are HIGHLY over-rated). None of those images has received significant post-processing, the original data was excellent; that is why I chose them for that comparison. You are talking theory, I am demonstrating capability in a practical application. Professional astronomers use tons of amateur acquired data for real world, every day planetary scientific research (see the new January 2014 S&T) and a major portion of it is acquired with SCTs. There must be some value in those nasty old SCT images...just ask Damian Peach and Christopher Go

Clear Skies,
Brian


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6239436 - 12/07/13 04:37 PM

Quote:

This thread appears to be stumbling forward with no end in sight: often amusing, occasionally thought provoking, increasingly absurd. I want to ask just one question now based on a side-by-side imaging comparison I did last year of three different scopes shooting in very good seeing conditions with the same camera: Which shows the best color saturation and resolution? Look at them all, note that one is a mass produced SCT, one is a superb premium Apo, and one is an excellent ED doublet...which one is "best"? Inquiring minds want to know

Clear Skies,
Brian




I would have to give the win to the C14. The TEC might be slightly sharper, but the C14 shows more detail overall. Not a particularly surprising result since this is where the C14 really shines. For planetary imaging it is usually going to be the winner and cost less.


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crow
sage
*****

Reged: 07/09/12

Loc: BC, Canada
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6239458 - 12/07/13 04:48 PM

Ahh, the mighty, mighty....mighty C11 Edge.

Did I say mighty?.....


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Why do people even buy SCTs??? new [Re: crow]
      #6239652 - 12/07/13 06:36 PM

I say to anyone with a small to medium sized apo challenging an 8" or larger SCT:

Observe Ganymede.

Forget the similar whole planet views of Jupiter with similar contrast. The grand scale of the test can mask truths about the finer edge the larger sct has over the smaller apo. Here it'll be clear - either you have enough light and angular seperation to breakdown the light of a 1.7" orb into discrete features or you don't. Leave behind the 150x-200x Jupiter views and look at Ganymede on a great night at 400x.

I would bet this test would be far more revealing of a greater apertures advantage. Here's where small aperture would "hit the wall" before the CO effects do.

Pete


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: Dwight J]
      #6239673 - 12/07/13 06:48 PM

Quote:

Quote:

Quote:

Soooooo-

Edggie Creates the thread out of his frustration about the constant SCT bashing that goes on. (In case you didn't know why?)

And then several take the opportunity to do just that?

What a group!

I really don't see what the mystery is? I, as many on the site, have built a small observatory with a centrally located EQ mount for both imaging , and visual duty. I can easily swap out refractors for imaging, and SCTs for visual.

What the hell would I do with a DOB? Balance it on top of my GEM? Put it on the roof? I don't care how good the views are, a Dob is worthless in my observatory. Refractors work nicely, and I do use them to image, but they are too small for many many DSOs. If your are a retired Doctor, or lawyer with a giant AP refractor, then good for you, but I would think most people will never own a giant premium refractor. Beside they would not fit into the average size home observatory.

I just don't see the mystery?

For me - A SCT offers decent aperture for DSO's, but can still be quickly mounted on a GEM - Can be used for imaging DSOs at long focal lengths for close ups. - Is a preferred planetary imaging platform. - Can be easily swaped out on the GEM with a refractor for widefeild imaging, and views- Finally they don't cost much.

?????????????




Eddgie's obvious tongue-in-cheek OP aside, I don't recall anyone meaningfully suggesting there is a mystery about why anyone would buy an SCT. The compact design has proven remarkably versatile (especially now with Hyperstar's introduction), and has offered a huge bang for the buck for over 4 decades.

As to the "constant SCT bashing" you mentioned, I don't see it. If someone here describes issues he or she has had with an SCT, or why those issues prevented them from buying such a scope, that's their valid perspective. Now, if their reasoning is faulty, the group could provide evidence to the contrary.

Over a decade ago, I was looking for an 11"(plus or minus)-class telescope, and looked critically through many C-11s. I wasn't impressed with any I tested and bought a more expensive 10" Mak-Cass. That doesn't mean I thought all C-11s or SCTs were unacceptable. It simply means I didn't want to spend the time cherry picking through a lot of scopes and then fix their obvious thermal and focuser issues (some folks here like to tinker with that sort of stuff, but I spend a lot of time doing that sort of thing, and don't want to do it at home). If I truly thought SCTs were terrible, why would I read anything in a forum dedicated to them? I'm still interested in getting one (now, a C-14 class instrument) for a different purpose than I had a years ago, but I'll need to check them out firsthand and get others' opinions.

Someone here referred to refractors as "spyglasses". Given that I have had 10 premium apos (regrettably, not all at once, and I'm not an MD or a retired lawyer), should I take exception to that term? I assumed that poster either said it in jest, or hates the scopes, which is his prerogative. If he doesn't want to look through or image with a high quality apo, that's his loss. I am continually stunned by how good the Moon, Jupiter and Mars look in a relatively small Zeiss 130 mm f/7.7 APQ (they look absolutely etched), but that didn't stop me from training larger aperture telescopes on the same objects.

If you have no need for a particular design scope (e.g., a Newt-Dob), or can't afford a premium apo, that's your business, and no one here would suggest you made a terrible mistake (which, BTW, you did ).

Finally, if everyone remained quiet about the shortcomings of a particular SCT implementation's shortcomings or other issues, e.g., mirror flop, focuser shift, thermal issues, tendency for the corrector to easily dew over, relatively poor optical quality (I'm not saying all SCTs have poor optics), etc., then there'd be no pressure for the manufacturer to improve the product, or for others here to share their fixes.




I am that "someone" and it was partially in jest and partially serious. A comparison between a refractor and a C14 would require a 12" apo refractor to level the field. To put spyglass in perspective, our club uses a 4" Genesis as a finder on the C14. My overall point is that any design has issues but SCT's seem to be singled out as particularity bad by mostly refractor aficionados. Often price is equated to quality and refractors smugly refer to how much they have paid per inch over the lowly SCT. I had the opportunity a few years ago to compare a "cheap" Orion 80mm apo to a Televue 85mm. The Orion spanked it on color correction.
In terms of using or imaging thru an apo, I have used the club Genesis to take a few piggyback images but overall I have no need for a refractor except as a finderscope. My 8" Cerevolo MakNewt will scare the pants off 7" apo refractors.




The Astro folks who I hang with aren't biased against any scope design in particular. Like me, they want the right tool for a given job. I don't worry about the cost at first, but if I can get by with a lower-cost scope, that'd be great. If not, I either go without or sell something else.

I haven't used a TeleVue 85, but I recently sold a William Optics 80 mm f/6 with a LOMO triplet that was an impressive little scope. In a critical comparison between it, a Questar 3.5, an AP 92 mm f/4.9 StowAway and AP 105 mm f/5.9 Traveler, the performance of it and the other three scopes fell precisely into line with their apertures. That said, the WO 80 wasn't much less in image quality than the AP StowAway, certainly not in proportion to the cost ratio!

I haven't had the pleasure of critically looking through one of Peter Ceravolo's 8" Mak-Newts (I was, however, fortunate to find one of his 300 mm astrographs). It might outperform a 7" apo, but given its CO, it it has less than 8" of aperture, so I'm not sure it would do quite as well as you suggested. I'd certainly like to compare it to my AP 175 f/8 EDF. Even if the Ceravolo performed on par with the AP, it'd be impressive.

I've looked through a very nice C-14, and want one, but I'm not sure it'd outperform a 12" apochromatic refractor, especially in modest seeing conditions. While actually enjoying the views through my scopes and others, I've spent a fair bit of time critically comparing the views through a 175 mm f/8 apo and a Tak Mewlon 300. Both scopes provide pinpoint stars and nice contrasty views, but on many nights, the 175 isn't left behind in the dust.

The apos I've used are excellent visual instruments and serve double duty with imaging (which I only recently became interested in). But, as I've always thought, they aren't the only game in town, and SCTs are highly versatile.

Edit note: I added a single word above ("much"), which is italicized.

Edited by JJK (12/08/13 12:24 AM)


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