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Equipment Discussions >> Cats & Casses

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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: azure1961p]
      #6239693 - 12/07/13 06:56 PM

Quote:

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




Ganymede is challenging. On nights with excellent seeing (not common here), I've easily seen albedo features with my AP 254 mm Mak-Cass. I drew them at the EP and later compared them to those made by Italian observers centuries ago (they were nearly identical). One night, two of my Astro friends were able to see one of the albedo features, but not as completely as I did (to my eyes, it looked like the Greek letter tau).

I've seen similar albedo features on Ganymede with an AP 180 f/9 EDT (regrettably, I sold that stunning scope). I don't recall them looking as impressive as they did with the 10" MCT, but then again, the comparison is meaningless unless both scopes are used at the same time, more or less.

Edited by JJK (12/08/13 08:39 AM)


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azure1961p
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Reged: 01/17/09

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Re: Why do people even buy SCTs??? new [Re: JJK]
      #6240031 - 12/07/13 11:19 PM

Yes I noticed the italics added and the effort is appreciated . Thanks.

Pete


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drago
sage


Reged: 01/11/08

Loc: Latvia
Re: Why do people even buy SCTs??? new [Re: azure1961p]
      #6240217 - 12/08/13 03:38 AM

Quote:



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




we there not discuss about a 4" apo without CO is better contrast than 14" SCT
there, in big appertures, are always good alternative to SCT - a newtonian.
and there, when you compare 14" SCT with CO, say, 38% ( not know, what exactly CO is in 14" SCT, but near, i suppose), and 14" newtonian with, say, 23% obstruction - there is a reasonably difference, i sure.
and contrast differences, when we look at already low contrast objects, cannot be overrated.


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Daniel Mounsey
Vendor (Woodland Hills)
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Reged: 06/12/02

Re: Why do people even buy SCTs??? new [Re: Eddgie]
      #6240249 - 12/08/13 04:42 AM

Ed,
In my opinion, the SCT design is generally soft, but good enough for the average consumer. Most observers do not have the observational experience or seeing conditions conducive enough to appreciating the difference between SCT's and world class Newtonians, apos and Maks. I'm sure if more observers spent some time viewing with some really world class optics in the right seeing locations, they'd have an awakening. That is not to say there hasn't been a few really good SCT's out there.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6240269 - 12/08/13 05:08 AM

Quote:

None of those images has received significant post-processing, the original data was excellent; that is why I chose them for that comparison.




So, they were a single image rather than a stacked and processed summation of a number of images a la webcam?

Jon


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Why do people even buy SCTs??? new [Re: JJK]
      #6240280 - 12/08/13 05:19 AM

Quote:

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.






That is about the long and short of it.

It's not a NP-101 or a C-14 it's an NP-101 and a C-14... The things an 4 inch apo does well are not possible with a 14 inch SCT and versa vice.. two scopes greatly increase the range of possible objects, possible views...

It really is about the right tool for the job.

Jon


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crow
sage
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Reged: 07/09/12

Loc: BC, Canada
Re: Why do people even buy SCTs??? new [Re: Daniel Mounsey]
      #6240387 - 12/08/13 08:38 AM

'The average consumer', I feel suitably humbled.

Doesn't NASA have one on the ISS? I don't particularly care, its your tax money they spent getting it up there.


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herrointment
Post Laureate
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Reged: 03/12/11

Loc: North of Hwy. 64
Re: Why do people even buy SCTs??? new [Re: Jon Isaacs]
      #6240389 - 12/08/13 08:39 AM

Yup, good enough for the likes of me and easy to disassemble!

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BKBrown
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Reged: 08/23/09

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Re: Why do people even buy SCTs??? new [Re: Jon Isaacs]
      #6240444 - 12/08/13 09:37 AM

Quote:

Quote:

None of those images has received significant post-processing, the original data was excellent; that is why I chose them for that comparison.




So, they were a single image rather than a stacked and processed summation of a number of images a la webcam?

Jon




No Jon, there is a difference between processing and post-processing. The stacking process is fundamental to modern planetary imaging for the generation of the base image or "stack". What I am talking about is all the steps that can be taken to alter/enhance the image data. Those images received a de-noising pass, adjustment of brightness "Levels", and a touch of "Unsharp Mask". Really good data often does not require significant enhancement. A very large percentage of experienced planetary imagers use SCTs because of the benefits I outlined earlier when I addressed the OP's question about "Why do people even buy SCTs???" What is your point?

Clear Skies,
Brian


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6240481 - 12/08/13 10:09 AM

Quote:

Quote:

Quote:

None of those images has received significant post-processing, the original data was excellent; that is why I chose them for that comparison.




So, they were a single image rather than a stacked and processed summation of a number of images a la webcam?

Jon




No Jon, there is a difference between processing and post-processing. The stacking process is fundamental to modern planetary imaging for the generation of the base image or "stack". What I am talking about is all the steps that can be taken to alter/enhance the image data. Those images received a de-noising pass, adjustment of brightness "Levels", and a touch of "Unsharp Mask". Really good data often does not require significant enhancement. A very large percentage of experienced planetary imagers use SCTs because of the benefits I outlined earlier when I addressed the OP's question about "Why do people even buy SCTs???" What is your point?

Clear Skies,
Brian




My point is make it clear that images like these are representative of what can be done with modern planetary imaging and processing techniques and not necessarily representative of the differences one would see at the eyepiece if comparing the scopes.

When someone posts that they can see the differences between the images, the story might have been quite different had they been looking through the eyepiece.

Jon


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maknewtnut
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Reged: 10/08/06

Re: Why do people even buy SCTs??? new [Re: Jon Isaacs]
      #6240518 - 12/08/13 10:33 AM

Daniel and Jon provide excellent commentary on this page. Any person that might find themselves shaking their head in disagreement would be well served by reading their posts again with an open mind. That's not simply because I concur with their opinions, but that their statements are based in fact.

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BKBrown
Post Laureate
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Reged: 08/23/09

Loc: Northern Virginia, USA
Re: Why do people even buy SCTs??? new [Re: Jon Isaacs]
      #6240560 - 12/08/13 11:09 AM

Quote:

Quote:

Quote:

Quote:

None of those images has received significant post-processing, the original data was excellent; that is why I chose them for that comparison.




So, they were a single image rather than a stacked and processed summation of a number of images a la webcam?

Jon




No Jon, there is a difference between processing and post-processing. The stacking process is fundamental to modern planetary imaging for the generation of the base image or "stack". What I am talking about is all the steps that can be taken to alter/enhance the image data. Those images received a de-noising pass, adjustment of brightness "Levels", and a touch of "Unsharp Mask". Really good data often does not require significant enhancement. A very large percentage of experienced planetary imagers use SCTs because of the benefits I outlined earlier when I addressed the OP's question about "Why do people even buy SCTs???" What is your point?

Clear Skies,
Brian




My point is make it clear that images like these are representative of what can be done with modern planetary imaging and processing techniques and not necessarily representative of the differences one would see at the eyepiece if comparing the scopes.

When someone posts that they can see the differences between the images, the story might have been quite different had they been looking through the eyepiece.

Jon




Fair enough, and thanks for the clarification...your previous post did not really convey that well. The visual experience and the imaging experience are two very different animals, folks should be careful in making comparisons. What I would like to see in discussions like this is a tacit understanding that we are not all in this game for the same reason and that our equipment expectations do not always overlap...there are very few absolutes when it comes to telescopes and what they can do.
I am both an imager and a visual observer, so when the OP asked his question I tried to look at both sides of the coin. Bottom line for me is that given reasonable/average conditions, for what I do my excellent C11 Edge SCT will always outperform my other scopes, including my superb TEC 140, due to its greater light gathering power and resolution. The only thing it gives up is FOV for broad targets. I will caveat this by saying that it is permanently mounted in an observatory and is always acclimated, I maintain rigorous collimation standards, and constantly monitor the factors that impact my scope during imaging/observing sessions. That said, I still consider my C11 to be my primary imaging tool while my TEC 140 is my primary observing tool...because I just love the views
One final thing I would like to hit on is the notion that some folks here at CN, and I don't mean you Jon, seem to believe that stacked planetary images are constructs that are somehow not "legitimate" or representative of reality. When it comes to the work of most serious imagers this is pure, unmitigated nonsense. There is no magic involved in producing these images, it is a mechanical process that produces consistent, repeatable results in the form of interpretable data. That is why professional astronomers engaged in planetary research desire, and solicit, amateur data to help them in their work. It is not an anecdotal visual observation report, subject to fallible human memory or biases, it is data with a capital "D". Check out the new January 2014 issue of Sky & Telescope (p.30, "Jupiter Since Galileo") to see how amateur imagers are contributing to real planetary science. I guess many of us are just content to plod along in the footsteps of Damian Peach and Christopher Go, trying to make do with our sub-standard, barely useable SCTs

Clear Skies,
Brian


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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Re: Why do people even buy SCTs??? new [Re: David Pavlich]
      #6240565 - 12/08/13 11:11 AM

Quote:

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

David




To be fair, Hyperstar images are not C14 images. There are corrective lenses involved and the secondary mirror is not used. To show the imaging capabilities of a C14 one would be compelled to show images actually shot through an intact C14, I would think.

Dave


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: BKBrown]
      #6240572 - 12/08/13 11:15 AM

Quote:

Quote:

Quote:

None of those images has received significant post-processing, the original data was excellent; that is why I chose them for that comparison.




So, they were a single image rather than a stacked and processed summation of a number of images a la webcam?

Jon




No Jon, there is a difference between processing and post-processing. The stacking process is fundamental to modern planetary imaging for the generation of the base image or "stack". What I am talking about is all the steps that can be taken to alter/enhance the image data. Those images received a de-noising pass, adjustment of brightness "Levels", and a touch of "Unsharp Mask". Really good data often does not require significant enhancement. A very large percentage of experienced planetary imagers use SCTs because of the benefits I outlined earlier when I addressed the OP's question about "Why do people even buy SCTs???" What is your point?

Clear Skies,
Brian




Larger SCTs are useful for imaging planets because they provide a good baseline image scale (i.e., long focal length) that is difficult to achieve with wide field refractors, they have the potential for high resolution (assuming the scope is well made, collimated, and in equilibrium with the ambient temperature), and they are relatively cheap (as in low-cost). I wouldn't say that they are optimally designed for planetary imaging, but they're very good at it.


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EFT
Vendor - Deep Space Products
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Reged: 05/07/07

Loc: Phoenix, AZ
Re: Why do people even buy SCTs??? new [Re: Cotts]
      #6240636 - 12/08/13 11:48 AM

Quote:

Quote:

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

David




To be fair, Hyperstar images are not C14 images. There are corrective lenses involved and the secondary mirror is not used. To show the imaging capabilities of a C14 one would be compelled to show images actually shot through an intact C14, I would think.

Dave




That would imply that images taken with a reducer, flattener, barlow, etc. are not "images" representative of the quality of the scope used. I think that it is necessary to consider every configuration that a scope is designed to be used in as a measure of its overall usefulness and quality if there is going to be any kind of comparison done. Versatility, or lack thereof, is another important attribute to consider when deciding on going with a particular design.


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EFT
Vendor - Deep Space Products
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Reged: 05/07/07

Loc: Phoenix, AZ
Re: Why do people even buy SCTs??? new [Re: drago]
      #6240690 - 12/08/13 12:17 PM

Quote:

Quote:



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




we there not discuss about a 4" apo without CO is better contrast than 14" SCT
there, in big appertures, are always good alternative to SCT - a newtonian.
and there, when you compare 14" SCT with CO, say, 38% ( not know, what exactly CO is in 14" SCT, but near, i suppose), and 14" newtonian with, say, 23% obstruction - there is a reasonably difference, i sure.
and contrast differences, when we look at already low contrast objects, cannot be overrated.




You can lead a horse to water, but continuing to beat this dead one is still not going to make it drink. The poster's bias against SCTs is so strong there is obviously nothing that can be said to sway his opinion, so why keep trying. Even if he were to look though a perfect SCT that the majority of people would say outshined the other scopes it was being compared to, he would still not see it because his bias will cloud his vision. Showing him beautiful images will only result in the argument that they could be better if a better instrument were used. If he is happy spending far more per inch of aperture on something else, then the dealer will have a good day when he comes in (it would certainly make my day). For the rest of us, we should continue to enjoy our reasonably priced, large aperture scopes for what they are and not worry about trying to convert someone to our point of view who is beyond conversion.


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crow
sage
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Reged: 07/09/12

Loc: BC, Canada
Re: Why do people even buy SCTs??? new [Re: EFT]
      #6240691 - 12/08/13 12:17 PM

I love the circular logic by people in this thread, I think the OP's point has been proven, the sct can't get a break.

If its good down the eyepiece, its because you got a 'good one', if it produces jaw dropping images, well its probably not too good down the eyepiece, if its via hyperstar its not really a C14 image, only 'average consumers' use them, but nasa launched one into space (ignore that) and so on.....

Well in Eddgie, you hit the nail on the head.


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BKBrown
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Reged: 08/23/09

Loc: Northern Virginia, USA
Re: Why do people even buy SCTs??? new [Re: EFT]
      #6240716 - 12/08/13 12:27 PM

Quote:

Quote:

Quote:



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




we there not discuss about a 4" apo without CO is better contrast than 14" SCT
there, in big appertures, are always good alternative to SCT - a newtonian.
and there, when you compare 14" SCT with CO, say, 38% ( not know, what exactly CO is in 14" SCT, but near, i suppose), and 14" newtonian with, say, 23% obstruction - there is a reasonably difference, i sure.
and contrast differences, when we look at already low contrast objects, cannot be overrated.




You can lead a horse to water, but continuing to beat this dead one is still not going to make it drink. The poster's bias against SCTs is so strong there is obviously nothing that can be said to sway his opinion, so why keep trying. Even if he were to look though a perfect SCT that the majority of people would say outshined the other scopes it was being compared to, he would still not see it because his bias will cloud his vision. Showing him beautiful images will only result in the argument that they could be better if a better instrument were used. If he is happy spending far more per inch of aperture on something else, then the dealer will have a good day when he comes in (it would certainly make my day). For the rest of us, we should continue to enjoy our reasonably priced, large aperture scopes for what they are and not worry about trying to convert someone to our point of view who is beyond conversion.




Dead on target Ed...you made your point Eddgie

Clear Skies,
Brian

Edited by BKBrown (12/08/13 03:37 PM)


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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: crow]
      #6240724 - 12/08/13 12:30 PM

Just like I said early in this thread, everyone's favorite whipping boy. Except for those that own and love them for what they are. The problem is what telescope is the favorite whipping boy of SCT owners?

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BKBrown
Post Laureate
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Reged: 08/23/09

Loc: Northern Virginia, USA
Re: Why do people even buy SCTs??? new [Re: crow]
      #6240771 - 12/08/13 12:59 PM

Nobody here but us "average consumers"...
http://www.damianpeach.com/barbados10.htm

Clear Skies,
Brian


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