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10" DK vs SCT

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#51 alrosm

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Posted 23 April 2014 - 03:01 PM

The problem is, if I buy something of better quality to replace my C14, it's gonna be a Plainwave CDK 14, $15.000, yep can be done but a consumer need to know where to stop.

There is an average between what you want, the price and the quality.

What Dan is trying to do is to convince us that for the same price we should choose and buy smaller and more expensive designs and that the loss of aperture is ok.

The problem for Dan who is an expert buy also a salesman is that for many of us, the loss of quality of the SCT is not bad enough to justify buying another design of better quality and smaller aperture for the same price.

#52 BillP

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Posted 23 April 2014 - 03:35 PM

Thomas nailed it! :waytogo:
Any visual only observer, that attempts to report something that doesn't match the physics of the situation, is beat like a baby seal, until they retract and toe the party line!


Well...I would alter what you said a little, as when folks think the "physics of the situation" wasn't a match, it's largely because they are mis-applying the physics and trying to extrapolate the behavior of some single variable they know the physics of to a system of variables. That just doesn't work :shrug:

#53 azure1961p

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Posted 23 April 2014 - 03:43 PM

I think the core issue of what irks me about this thread is its got nothing to do with astronomy. Nothing. Its one mechanical optical device compared to another compared to another to the point it precludes observing and merely feeds itself in some OCD circle. Its not astronomy. Its a compulsion that precedes the endeavor .



Pete

#54 alrosm

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Posted 23 April 2014 - 03:56 PM

Ok I need to add something, at the beginning I was a visual only observer.

The problem I got with your point of view and the point of view of few others is that I was very close to give up after 6 months because of the lack of aperture of my first scope. Now I'm fine, and I got a hobby for life...

My feeling is that if I reacted this way, I'm not probably the only one.

#55 Brent Campbell

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Posted 23 April 2014 - 04:05 PM

This opinion is based strictly on our personal experience comparing these telescopes last night and others. My observing buddy Herberth Zelaya and I decided to compare what is considered by most observers to be a high quality SCT of similar aperture to a high quality 10" DK. My friend and I actively acclimated both telescopes about two hours prior to the observation so that by sundown, Jupiter would be in an optimal position with decent background lighting, good for planetary observation. Both had high quality diagonals and eyepieces which I've used for years.

At 300x both of us easily agreed that the DK revealed crisp, hard outlines with sharp surface structure and color contrast, while the SCT at just 260x revealed soft outlines and soft surface detail that was harder to discern by comparison. It was easy to see the difference. There was also some image shift in the SCT and later on some dewing up since I observe near the ocean where onshore air is present. I do not use heat straps because they produce thermals, which degrade the image. If you think humans are a bad source of heat, dew straps are worse.

About an hour after sundown, the seeing went sour as expected on this particular evening and this is why I wanted to catch Jupiter before it got too dark. Later, another observing buddy of mine Luigi arrived but as the seeing declined he said the differences between the two scopes were pretty close and in very brief moments of steady seeing could easily tell that the DK was superior in optical performance to the SCT. This just comes to show how much seeing can affect two telescopes being compared even when one is unquestionably superior to the other.

I have tested numerous SCT's over the years and have expressed this opinion for years. Below is a review written in 2003 where I briefly explained that other optical designs would be more suitable for critical planetary observation for observers who are more serious. The purpose of my post is to help clarify some comments that others have made in the forums so they have a better idea where I stand on the subject. If they have a special SCT they would like me to compare, I'll be happy to honor their request and announce whatever my findings are constructively.

http://www.cloudynig...ryeyepieces.pdf

As I've stated before, SCT's are perfectly fine telescopes for consumers to enjoy astronomy and image with. We should still try to enjoy the night sky with whatever we have. I would not expect the average SCT owner to go to the lengths we do to produce an extremely nice looking visual image. But when you are comparing them in seeing conditions which are conducive to revealing their true performance characteristics, it becomes obvious which telescope is which. Observers may often see surface detail on planets in their SCT's and see what they consider to be a great looking image, but observations are relative. Unless you compare telescopes that are in locations where the seeing is really good, you may not even know what it is you don't know and it also means that you and I just have a different understanding about what a world class image is expected to look like.

People can debate all they wish regarding optical theory, but at the end of the day, the scope needs to perform and it's as simple as that. It's not about numbers, it's about looking at planets in the eyepiece and seeing something beautiful that nature has to offer in all its splendor. I have an observing buddy who has what I know for a fact to be a world class 8" apochromatic refractor. After he brought it to Pinos a couple of times, he stopped bothering because people kept wanting to look at planets through it and after they did, they kept saying the image looked like their SCT's and observers would simply conclude that SCT's are just as good as a $30,000 apochromatic refractor. I can assure you that's not the case.

Seeing conditions at Pinos are pathetic and frustrating to say the least for observers who love double stars and planets. I've been viewing there since 1992 and Pinos isn't even close to what world class seeing is all about. All Pinos is, is a decent dark sky site for "deep sky observing" on the far inland west coast with excellent transparency at about 8200 ft. Other than that the seeing rarely ever breaks the sub arc barrier and it's too dark for planets. Pinos is not a good planetary observation site or at least is not consistent. As an observer who's been doing these comparisons on the west coast for many years, I whole heartedly understand my friends frustration and would just prefer to observe with a few friends who have an understanding of this hobby and what it entails. Sometimes it is frustrating dealing with observers expectations when all you are trying to do is just enjoy a night of observing.

Ask any professional golfer, and you will get an array of answers about how the undulation of the greens affect their putting performance. Seeing conditions are no different and can fool even the best observers. For example you could stand and look at the night sky to see how the stars twinkle. If they're twinkling a lot, it most likely means the seeing conditions are not very good. If the stars don't twinkle at all, it may also still mean your seeing conditions are not good. Why is that? It's because the seeing is so bad, the stars blend into one wooly ball that your eyes and brain perceive as a perfect point of light standing dead still. When the seeing is really good, the stars will most likely make just a short pulse or small twitch from time to time. That's how good seeing normally behaves.

I believe the lack of good seeing conditions (not collimation as so many observers advocate) among most parts of the country is most likely the real reason why so many SCT owners are convinced planets are just as good as telescopes that cost several times as much, no different than my friends experiences with SCT users at Pinos. I can assure you unless you have something really unique, that's not going to be the case from where I'm looking. If you want world class optics, then you'll just have to pay for them. If more observers were given the opportunity to see what I've seen while making these comparisons, they would have a better understanding of what I'm trying to explain.

We live in a time where people are really hard up for money and many of them try to convince themselves that even as little as they've spent, they've got something special and believe it or not, once in a great while they may really have something special, but far more often, that's not the case. One of my friends has a couple of hand picked SCT's he swears are incredibly good. I personally have not tested them but he's quite experienced and I believe him. But he's had to go through many SCT's to find something he considers extra superb. Does this mean you have a bad SCT? Of course not! As a consumer, you need to be realistic about how you expect an optic to perform like and if SCT's were really that bad, why are so many SCT owners happy with them. I myself have tested a couple of SCT's that I thought were quite superb but we also had the proper location and seeing conditions to test them.

A telescopes optical performance is only going to be as good as its weakest link. I'll tell you a brief story about a friend I originally met at Pinos about 10 years ago who owned a high quality 10" Mak cass. A couple of my buddies and I walked over to ask him some questions about what appeared to be a pretty new scope and we had never seen him before. We then asked him how he liked it and he said he really hadn't been able to test the optics yet. Our first thought was why would anyone try to test a telescope like this here. A large, simple light bucket or a rich field refractor is fine for Pinos, but a scope like this is really all about high magnification image quality at F20.

By the end of the night, we could tell he was pretty frustrated and we weren't surprised at all. Pinos has a very rapid temperature descent and this is really bad news for a 55lb. Mak with a hefty meniscus. We could tell he was a nice person, so we invited him to let us test it at Charlton Flats with him and he gladly obliged. Charlton is unique for a few reasons. 1.) It resides at 5,500 ft. above sea level which aids in transparency, 2.) It has a slow temperature descent, 3.) It's positioned where onshore ocean flow moves, and 4.) It's light polluted and the combination of these advantages make it vastly superior to Pinos on a more consistent basis. A nice quality optical system at a place like Pinos is like a wild stallion trapped in a cage with no where to spread its legs. His first evening at Charlton changed his whole perspective on observation and within a year he moved into even greater telescopes and appreciated what the guys shared with him. So, the moral of the story is location, location, location.

There may be many SCT owners who vehemently disagree with what I've just said and that's okay. People will always disagree, that's nothing new. But before you do, ask yourself how many comparisons you've actually contributed to the CN forums and then ask yourself where those comparisons were conducted. If the best answer is some optical certificates and formulas, then I'll let you know I don't observe at a desk.

steady skies :smirk:


This post sounds allot like advertising to me! Shame. EPIC FAIL! And the condescending part at the end that says "I'll let you know I don't observe at a desk." Using snobbery to put your point across- that works. I'll let you know, these posts don't make me want to go out and spend my hard earned money on a new telescope. Besides for what your getting for a 10" DK on your web site, I can purchase an heck of a Zambuto DOB (larger than 10") that will "wipe the floor" with your 10" DK.

#56 azure1961p

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Posted 23 April 2014 - 05:46 PM

I would add to that last paragraph of his that more than likely the nights he was doing comparisons everyone else was observing - they didn't give a hot **** if their scope was better, worse or okay because they were too busy being astronomers.

Pete

#57 WesC

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Posted 23 April 2014 - 05:51 PM


The elitist tone and demeaning commentary on SCT users as "not serious," "consumers," that "we all think we have something special," or that our evaluation of our own equipment is flawed because we haven't his level of superior experience or superior equipment to show us how bad our SCTs really are... plus the implication that only inexperienced persons would choose an SCT is insulting. None of that was remotely necessary in order to compare these two scopes.

And yes, I read it. Fully. More than once. And I thought about it, and kept coming away with the same conclusion. I was being shamed for buying and using an SCT. Maybe when I grew up I could have a real scope. :foreheadslap:

Reading it a couple of times, you've come to realize its the truth, now next step is to accept it ;)



LOL! If I had all the money in the world, very likely one of the LAST telescopes I would buy would be a Mewlon.

But, I will happily accept the use of your credit card to buy a TEC140 and an AP1100! ;)

Oh, and I am keeping my Edge 11!

#58 William Mc

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Posted 23 April 2014 - 09:08 PM

I guess what got me was that the OP's huge post had 3 paragraphs of the actual comparison, and 10 additional paragraphs talking about the peasants that use them. You know, the non serious, and deluded ones. Thank goodness other vendors are more accommodating to "consumers".

#59 svdwal

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Posted 24 April 2014 - 01:47 AM

That you can trade off telescope quality and telescope size in a certain range is in itself good news. Smaller telescopes are generally easier to house, lighter and easier to move. So, if for your purpose a smaller telescope works as well, or even better than a bigger telescope, excellent.

Personally, my biggest gripe is that there is no reasonable way to compare the quality of telescopes of different kinds to each other by examining their specifications. I want to be able to compare different scopes with different sizes and different qualities in an objective way.

But what you get are proxies like scope diameter, the size of an obstruction, and the stuff the tube appears to be made from.

What I would like to know is how much bigger an off-the-shelf SCT with Strehl of 0.85 and 30% optical obstruction must be to give an image of equal quality compared to a DK with 25% central obstruction and a Strehl of 0.92.

#60 roadi

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Posted 24 April 2014 - 07:40 AM

Reading it a couple of times, you've come to realize its the truth, now next step is to accept it ;)



LOL! If I had all the money in the world, very likely one of the LAST telescopes I would buy would be a Mewlon.


WesC,
A wise decision! ;) You wouldn't know what you'll be missing, a good thing to a peaceful mind :grin:

But, I will happily accept the use of your credit card to buy a TEC140 and an AP1100! ;)


Great choices in equipment.. but not so by using my credit card! :lol:

#61 WesC

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Posted 24 April 2014 - 12:21 PM

Reading it a couple of times, you've come to realize its the truth, now next step is to accept it ;)



LOL! If I had all the money in the world, very likely one of the LAST telescopes I would buy would be a Mewlon.


WesC,
A wise decision! ;) You wouldn't know what you'll be missing, a good thing to a peaceful mind :grin:

But, I will happily accept the use of your credit card to buy a TEC140 and an AP1100! ;)


Great choices in equipment.. but not so by using my credit card! :lol:



Rrrrrrrats! :bawling:

#62 elwaine

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Posted 24 April 2014 - 01:33 PM

Might I dare ask Daniel a question, and perhaps sooth the angst brought about by such dastardly terms as "consumer" (I can't think of a single term in the English language more demeaning than "consumer")? :lol:

Daniel, please tell us if there were diffraction spikes visible when viewing those sharp planetary details through the DK. Some find those annoying: others, not.

#63 Asbytec

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Posted 24 April 2014 - 11:13 PM

Since we don't know anything specific about either of the scopes mentioned other than the optical design, the comparison given is somewhat meaningless. That aside, is it any surprise a scope probably costing 3 times as much as the other ends up being better? :smirk: But we don't know that either because information about what scopes were actually being tested was left out of the report.

What we are left with is 'trust me, me and my buddies are expert observers in world class observing conditions and everyone else is just a consumer...and sorry about your luck that you don't live in a world class observing area because you will never get to really observe fully." :(

I am so thankful that I have the opportunity of sharing my love of the night sky with others whether I'm using a refractor, newt, SCT or whatever design. I hate elitism and false humility in all it's forms. There are many fine amateur astronomers who are doing real work in research, outreach, and education who are inspiring the next generation of observers, scientists, and lovers of the night sky. They are not just consumers, rather they are the true face of amateur astronomy.

Patrick


Well said, Patrick (and Bill Barlow following your comment.) I do have the luxury of living in a region where seeing is excellent quite often. And I have a cheapo scope that puts up some excellent images that I'd gladly match to a high quality scope of same (or nearly the same) aperture and design, including an expensive DK or APO.

While it makes sense optical performance is very important, seeing and - get this - experience are equally important. You have to know what you're looking for and at. I'd bet two observers of varying experience looking through the same high quality scope will see the same object differently. I know this to be the case because of my own experience learning to observe planets (and doubles) improved over time. Critical observing benefits from optical and physical design, but only if you know how to use it (cooled, collimated, maybe even cleaned, and in good seeing.)

The cost of a good scope is found in the cost to produce it. Hand figured optics, solid materials, custom work all cost money. But any optic that can reach a Strehl of high 90's, a peak intensity above 80% or better, and has excellent stray light control is about as good as any optic can be at any price. The real difference is care, location, and experience. Observing takes work, patients, and training, even in excellent seeing.

I am a believer in science because care, location, and experience have allowed me to observe the true diffraction limit in the final image. It's quite beautiful, even in a truly diffraction limited cheapo. "Trust me." Craters resolved in crater form and doubles resolved with a dark space - both below the Dawes limit. Surface albedo on Ganymede or the "apparent" elongation if Io in a 150mm (at about 0.04 RMS.) How is that possible? Answer, care, seeing, and experience and at least descent optics and stray light control (I can forgive a little image shift.)

So, my question is, has the OP observed these things or more in his much better scope? If he had, he might be more of a proponent of the science behind it. So, it begs the question, what is he seeing in such a fine scope that leads him to believe science (and the numbers) are not a good approximation of what can be observed? To me, such a comment becomes suspect. I'd be adverse to paying that much for a scope that could not deliver the theoretical diffraction limit (unless it exceeds it in some way. Is that possible?)

Jupiter simply explodes with detail. The vast majority of that is, again, care, location, and experience. I wonder if the additional $29,000(?) is worth the view even to the most experienced observer other than possibly slightly better stray light control and mechanical engineering.

If your scope drops your jaw, enjoy it. I left my jaw on the front lawn so often I'm surprised a cat hasn't dragged it off, already. As a result, there is little incentive to spend thousands more. And aperture fever goes away, too.

#64 DesertRat

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Posted 24 April 2014 - 11:21 PM

Great comments Norme!

I'm happy with my Toyota. Daniel probably has a BM. :lol:

For the record 2 Tak Mewlons I observed with in the field had about a half wave of coma. The owners were happy with it. :p
They begged me off to offer collimation help. :foreheadslap:

Glenn

#65 areyoukiddingme

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Posted 24 April 2014 - 11:40 PM

I notice in many of these threads that a lot of credence is given to the importance of experience in observing. I have to agree that knowing what you are looking for/at helps. As does basic ability to use equipment (e.g, fine collimation; picking optimal magnifications and so on). However . . . I would love to see some empirical evidence for the 'experience effect'.

My guess is that the major determinants of ability to resolve details are: 1. eyesight; 2. aperture; 3. seeing/transparency; 4. optical quality; and a distant 5th: experience.

Seems to me that an awful lot of hubbub is associated with 4 and 5.

#66 Asbytec

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Posted 25 April 2014 - 12:20 AM

Glenn, where's the "like" button when you need one? Your comments deserve it, even if it is a popularity contest. :)

RUkidding, empirical evidence? Dunno. My eyesight is okay: astigmatism, floaters, and possibly a small cataract. It used to be much better. At small exit pupils, astigmatism is not so bad, but floaters get bothersome. I suspect a cataract because of some occasional blurring. So, as for empirical evidence, that's the best I can offer you.

As for experience being a distant 5th, who's to say where it fits in the greater scheme of things? It's just important, probably higher up the ladder than a distant 5th. As for empirical evidence, I can only speak to experience.

Ganymede is a perfect example. I never thought Ganymede, being about the same diameter as the Airy disc, could ever show some albedo. However, high power observation showed something weird like maybe a brighter spot dancing around, even in 8/10 Pickering, near one limb. Not sure what it was or if it was imagination or seeing effects. I was not sure if it was Osiris, didn't even know where Osiris was or what it would look like. But, research showed Osiris was, indeed, exactly where that rather difficult bright spot was seen...on multiple occasions. And no bright spot was observed when Osiris was not visible. So, it clicks, okay, that's Osiris and that's what it looks like. Darker features are much more challenging, but they can be discerned once you know what they look like apart from seeing effects.

Actually, Jupiter is also a great example. Observing Jove, you could be absolutely astonished (if you don't know already) how much learning to observe color makes all the difference. Jupiter is not like a coloring book with it's differently colored features defined by a black outline. One color simply contrasts to another often very softly.

For example, the EZ basically looks pretty much white when you look at it (especially at low magnification.) However, on closer inspection there are white features within it. So, if those features are white, then the EZ cannot be white. It must be a different hue. Learning to discriminate white on Jove set all other hues apart. Everything daisy chains from there. Grey is not white and tan is not grey and so on all the way to reddish hues and black. And, indeed, festoons are not grey, because grey can be seen somewhere else. They indeed have a bluish hue to them...separate from the grey features one can observe.

When you recognize the not white hue, you begin to notice it elsewhere...features that initially look white are not. They might be grey or tawny and only faintly so. Ever see a blue grey in the SEB? Once you see it, then you realize the rest of the SEB is also a different hue. At this point, resolution of Jove's details begin to explode.

Jupiter is no longer white with two grey belts, it comes alive with color. And observing these very weak contrasting hues takes time, training, and experience. Once you've understood what you're seeing, Jove is never boring (unless seeing washing it out.) Most folks won't see all this color during a brief glance, it does take time to learn to see it.

Someone mentioned optimal magnification above. That's up there in importance, too. A lot of people love the 30x per inch on Jove. I actually prefer 40x per inch, but no more, because image scale I suspect helps a bit with very low contrasts. (In much the same way higher magnification helps with low contrast planetary nebula.) So, yea, optimal magnification seems important with soft contrast as well as resolution. Too low and irradiation might obliterate the very soft contrasts.I nearly blew out an eyeball trying to observe BA at 30x per inch. It was surprisingly easy, set within a modestly contrasting cloud structure, at 40x per inch.

Point of all of that is, you just gotta learn to see what you're looking at in order to observe such things. Io's apparent elongation is much more tricky. For that, you need a reference to what round looks like. Europa works nicely. Try it next time seeing permits. It can be done in a modest diffraction limited aperture - once you learn to recognize it. That so many planetary observer pass over this observation is telling of either seeing conditions or experience, and that my own cheapo scope can do it speaks to the diffraction limit most scopes, including SCTs, should be able to attain. In fact, I'd wonder if a fine 150mm APO could observe the /apparent/ elongation of Io due to it's slightly larger Airy disc or observe a crater below the Dawes limit.

#67 areyoukiddingme

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Posted 25 April 2014 - 12:40 AM

Interesting points Norme. . . but I'm still having a nagging feeling that the experience variable is explaining a rather small part of the variance.

Jupiter is a nice example. I have definitely learned to see more over time, but I have also found that other observers are limited to particular colors b/c of their vision. I see the equatorial bands as a dark, rusty color. Others can only make out contrasts of white and gray.

Still others--including the originator of this thread if I'm not mistaken--have some really interesting descriptions of blue festoons. Despite a good number of hours on my edgehd in binoviewers under some occassional very good conditions, I'm afraid blue festoons escape me (in fact, even in images the parts that I would take for blue are gray to me). I have had very nice high resolution views where low-level contrasts where very apparent, but I could not differentiate shades of white from any blues (I suspect that my eyes are not particularly sensitive to this region of the spectrum).

Though I would welcome being corrected by a superior view in a boutique DK! :)

#68 Asbytec

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Posted 25 April 2014 - 01:03 AM

Kiddingme, okay, what you say makes sense, as well. Eyesight is important when seeing hues, as well as resolution one might suppose. And maybe no amount of experience, nor probably optical quality, can overcome it entirely.

It did for me in a descent good scope, so I throw that out there based on experience with it. It's the best empirical evidence I am aware of.

One memorable night, Jove's colors just exploded upon differentiating white and not white. It was a learning experience and Jove was never the same afterward.

My eyes are not what they used to be, but we work with what we have. :) If your eyes are sharp, give Io a close look (compared to Europa.)

Yea, that would be interesting, if a boutique DK will show you soft blue hues when an SCT won't. That would be amazing, really. I like my crow served up cold, if I must eat my words on that one. :lol:

#69 Starhawk

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Posted 25 April 2014 - 09:05 AM

And if you still feel like disagreeing, ask yourself how many of the items compared YOU are offering for sale! ;)

http://telescopes.ne...ham&order=re...

Seriously, this reads very differently than it would if the thread hadn't come from a vendor. It used to be there was a rule about vendors only starting threads in the Vendor forum. No matter- this serves as a perfect illustration of why.

-Rich

I have tested numerous SCT's over the years and have expressed this opinion for years. Below is a review written in 2003 where I briefly explained that other optical designs would be more suitable for critical planetary observation for observers who are more serious. The purpose of my post is to help clarify some comments that others have made in the forums so they have a better idea where I stand on the subject. If they have a special SCT they would like me to compare, I'll be happy to honor their request and announce whatever my findings are constructively.

http://www.cloudynig...ryeyepieces.pdf

As I've stated before, SCT's are perfectly fine telescopes for consumers to enjoy astronomy and image with. We should still try to enjoy the night sky with whatever we have. I would not expect the average SCT owner to go to the lengths we do to produce an extremely nice looking visual image. But when you are comparing them in seeing conditions which are conducive to revealing their true performance characteristics, it becomes obvious which telescope is which. Observers may often see surface detail on planets in their SCT's and see what they consider to be a great looking image, but observations are relative. Unless you compare telescopes that are in locations where the seeing is really good, you may not even know what it is you don't know and it also means that you and I just have a different understanding about what a world class image is expected to look like.

People can debate all they wish regarding optical theory, but at the end of the day, the scope needs to perform and it's as simple as that. It's not about numbers, it's about looking at planets in the eyepiece and seeing something beautiful that nature has to offer in all its splendor. I have an observing buddy who has what I know for a fact to be a world class 8" apochromatic refractor. After he brought it to Pinos a couple of times, he stopped bothering because people kept wanting to look at planets through it and after they did, they kept saying the image looked like their SCT's and observers would simply conclude that SCT's are just as good as a $30,000 apochromatic refractor. I can assure you that's not the case.

Seeing conditions at Pinos are pathetic and frustrating to say the least for observers who love double stars and planets. I've been viewing there since 1992 and Pinos isn't even close to what world class seeing is all about. All Pinos is, is a decent dark sky site for "deep sky observing" on the far inland west coast with excellent transparency at about 8200 ft. Other than that the seeing rarely ever breaks the sub arc barrier and it's too dark for planets. Pinos is not a good planetary observation site or at least is not consistent. As an observer who's been doing these comparisons on the west coast for many years, I whole heartedly understand my friends frustration and would just prefer to observe with a few friends who have an understanding of this hobby and what it entails. Sometimes it is frustrating dealing with observers expectations when all you are trying to do is just enjoy a night of observing.

Ask any professional golfer, and you will get an array of answers about how the undulation of the greens affect their putting performance. Seeing conditions are no different and can fool even the best observers. For example you could stand and look at the night sky to see how the stars twinkle. If they're twinkling a lot, it most likely means the seeing conditions are not very good. If the stars don't twinkle at all, it may also still mean your seeing conditions are not good. Why is that? It's because the seeing is so bad, the stars blend into one wooly ball that your eyes and brain perceive as a perfect point of light standing dead still. When the seeing is really good, the stars will most likely make just a short pulse or small twitch from time to time. That's how good seeing normally behaves.

I believe the lack of good seeing conditions (not collimation as so many observers advocate) among most parts of the country is most likely the real reason why so many SCT owners are convinced planets are just as good as telescopes that cost several times as much, no different than my friends experiences with SCT users at Pinos. I can assure you unless you have something really unique, that's not going to be the case from where I'm looking. If you want world class optics, then you'll just have to pay for them. If more observers were given the opportunity to see what I've seen while making these comparisons, they would have a better understanding of what I'm trying to explain.

We live in a time where people are really hard up for money and many of them try to convince themselves that even as little as they've spent, they've got something special and believe it or not, once in a great while they may really have something special, but far more often, that's not the case. One of my friends has a couple of hand picked SCT's he swears are incredibly good. I personally have not tested them but he's quite experienced and I believe him. But he's had to go through many SCT's to find something he considers extra superb. Does this mean you have a bad SCT? Of course not! As a consumer, you need to be realistic about how you expect an optic to perform like and if SCT's were really that bad, why are so many SCT owners happy with them. I myself have tested a couple of SCT's that I thought were quite superb but we also had the proper location and seeing conditions to test them.

A telescopes optical performance is only going to be as good as its weakest link. I'll tell you a brief story about a friend I originally met at Pinos about 10 years ago who owned a high quality 10" Mak cass. A couple of my buddies and I walked over to ask him some questions about what appeared to be a pretty new scope and we had never seen him before. We then asked him how he liked it and he said he really hadn't been able to test the optics yet. Our first thought was why would anyone try to test a telescope like this here. A large, simple light bucket or a rich field refractor is fine for Pinos, but a scope like this is really all about high magnification image quality at F20.

By the end of the night, we could tell he was pretty frustrated and we weren't surprised at all. Pinos has a very rapid temperature descent and this is really bad news for a 55lb. Mak with a hefty meniscus. We could tell he was a nice person, so we invited him to let us test it at Charlton Flats with him and he gladly obliged. Charlton is unique for a few reasons. 1.) It resides at 5,500 ft. above sea level which aids in transparency, 2.) It has a slow temperature descent, 3.) It's positioned where onshore ocean flow moves, and 4.) It's light polluted and the combination of these advantages make it vastly superior to Pinos on a more consistent basis. A nice quality optical system at a place like Pinos is like a wild stallion trapped in a cage with no where to spread its legs. His first evening at Charlton changed his whole perspective on observation and within a year he moved into even greater telescopes and appreciated what the guys shared with him. So, the moral of the story is location, location, location.

There may be many SCT owners who vehemently disagree with what I've just said and that's okay. People will always disagree, that's nothing new. But before you do, ask yourself how many comparisons you've actually contributed to the CN forums and then ask yourself where those comparisons were conducted. If the best answer is some optical certificates and formulas, then I'll let you know I don't observe at a desk.

steady skies :smirk:



#70 roadi

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Posted 25 April 2014 - 09:37 AM

And if you still feel like disagreeing, ask yourself how many of the items compared YOU are offering for sale! ;)

http://telescopes.ne...ham&order=re...

Seriously, this reads very differently than it would if the thread hadn't come from a vendor. It used to be there was a rule about vendors only starting threads in the Vendor forum. No matter- this serves as a perfect illustration of why.

-Rich

I have tested numerous SCT's over the years and have expressed this opinion for years. Below is a review written in 2003 where I briefly explained that other optical designs would be more suitable for critical planetary observation for observers who are more serious. The purpose of my post is to help clarify some comments that others have made in the forums so they have a better idea where I stand on the subject. If they have a special SCT they would like me to compare, I'll be happy to honor their request and announce whatever my findings are constructively.

http://www.cloudynig...ryeyepieces.pdf

As I've stated before, SCT's are perfectly fine telescopes for consumers to enjoy astronomy and image with. We should still try to enjoy the night sky with whatever we have. I would not expect the average SCT owner to go to the lengths we do to produce an extremely nice looking visual image. But when you are comparing them in seeing conditions which are conducive to revealing their true performance characteristics, it becomes obvious which telescope is which. Observers may often see surface detail on planets in their SCT's and see what they consider to be a great looking image, but observations are relative. Unless you compare telescopes that are in locations where the seeing is really good, you may not even know what it is you don't know and it also means that you and I just have a different understanding about what a world class image is expected to look like.

People can debate all they wish regarding optical theory, but at the end of the day, the scope needs to perform and it's as simple as that. It's not about numbers, it's about looking at planets in the eyepiece and seeing something beautiful that nature has to offer in all its splendor. I have an observing buddy who has what I know for a fact to be a world class 8" apochromatic refractor. After he brought it to Pinos a couple of times, he stopped bothering because people kept wanting to look at planets through it and after they did, they kept saying the image looked like their SCT's and observers would simply conclude that SCT's are just as good as a $30,000 apochromatic refractor. I can assure you that's not the case.

Seeing conditions at Pinos are pathetic and frustrating to say the least for observers who love double stars and planets. I've been viewing there since 1992 and Pinos isn't even close to what world class seeing is all about. All Pinos is, is a decent dark sky site for "deep sky observing" on the far inland west coast with excellent transparency at about 8200 ft. Other than that the seeing rarely ever breaks the sub arc barrier and it's too dark for planets. Pinos is not a good planetary observation site or at least is not consistent. As an observer who's been doing these comparisons on the west coast for many years, I whole heartedly understand my friends frustration and would just prefer to observe with a few friends who have an understanding of this hobby and what it entails. Sometimes it is frustrating dealing with observers expectations when all you are trying to do is just enjoy a night of observing.

Ask any professional golfer, and you will get an array of answers about how the undulation of the greens affect their putting performance. Seeing conditions are no different and can fool even the best observers. For example you could stand and look at the night sky to see how the stars twinkle. If they're twinkling a lot, it most likely means the seeing conditions are not very good. If the stars don't twinkle at all, it may also still mean your seeing conditions are not good. Why is that? It's because the seeing is so bad, the stars blend into one wooly ball that your eyes and brain perceive as a perfect point of light standing dead still. When the seeing is really good, the stars will most likely make just a short pulse or small twitch from time to time. That's how good seeing normally behaves.

I believe the lack of good seeing conditions (not collimation as so many observers advocate) among most parts of the country is most likely the real reason why so many SCT owners are convinced planets are just as good as telescopes that cost several times as much, no different than my friends experiences with SCT users at Pinos. I can assure you unless you have something really unique, that's not going to be the case from where I'm looking. If you want world class optics, then you'll just have to pay for them. If more observers were given the opportunity to see what I've seen while making these comparisons, they would have a better understanding of what I'm trying to explain.

We live in a time where people are really hard up for money and many of them try to convince themselves that even as little as they've spent, they've got something special and believe it or not, once in a great while they may really have something special, but far more often, that's not the case. One of my friends has a couple of hand picked SCT's he swears are incredibly good. I personally have not tested them but he's quite experienced and I believe him. But he's had to go through many SCT's to find something he considers extra superb. Does this mean you have a bad SCT? Of course not! As a consumer, you need to be realistic about how you expect an optic to perform like and if SCT's were really that bad, why are so many SCT owners happy with them. I myself have tested a couple of SCT's that I thought were quite superb but we also had the proper location and seeing conditions to test them.

A telescopes optical performance is only going to be as good as its weakest link. I'll tell you a brief story about a friend I originally met at Pinos about 10 years ago who owned a high quality 10" Mak cass. A couple of my buddies and I walked over to ask him some questions about what appeared to be a pretty new scope and we had never seen him before. We then asked him how he liked it and he said he really hadn't been able to test the optics yet. Our first thought was why would anyone try to test a telescope like this here. A large, simple light bucket or a rich field refractor is fine for Pinos, but a scope like this is really all about high magnification image quality at F20.

By the end of the night, we could tell he was pretty frustrated and we weren't surprised at all. Pinos has a very rapid temperature descent and this is really bad news for a 55lb. Mak with a hefty meniscus. We could tell he was a nice person, so we invited him to let us test it at Charlton Flats with him and he gladly obliged. Charlton is unique for a few reasons. 1.) It resides at 5,500 ft. above sea level which aids in transparency, 2.) It has a slow temperature descent, 3.) It's positioned where onshore ocean flow moves, and 4.) It's light polluted and the combination of these advantages make it vastly superior to Pinos on a more consistent basis. A nice quality optical system at a place like Pinos is like a wild stallion trapped in a cage with no where to spread its legs. His first evening at Charlton changed his whole perspective on observation and within a year he moved into even greater telescopes and appreciated what the guys shared with him. So, the moral of the story is location, location, location.

There may be many SCT owners who vehemently disagree with what I've just said and that's okay. People will always disagree, that's nothing new. But before you do, ask yourself how many comparisons you've actually contributed to the CN forums and then ask yourself where those comparisons were conducted. If the best answer is some optical certificates and formulas, then I'll let you know I don't observe at a desk.

steady skies :smirk:


Hahaa.. Come on!! Is it so hard to swallow?? shall we all just clap in our hands, nodding and say.. "I Agree.." or "Thats Great.." no matter what one thinks? :lol:

#71 Mark Costello

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Posted 25 April 2014 - 12:36 PM

http://telescopes.ne...telescopes.html

Regards,

#72 azure1961p

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Posted 25 April 2014 - 01:24 PM

I notice in many of these threads that a lot of credence is given to the importance of experience in observing. I have to agree that knowing what you are looking for/at helps. As does basic ability to use equipment (e.g, fine collimation; picking optimal magnifications and so on). However . . . I would love to see some empirical evidence for the 'experience effect'.

My guess is that the major determinants of ability to resolve details are: 1. eyesight; 2. aperture; 3. seeing/transparency; 4. optical quality; and a distant 5th: experience.

Seems to me that an awful lot of hubbub is associated with 4 and 5.


I'm not so sure "experience " is being defined thoroughly here. Yes there's the experience and acumen gained over the seasons and decades but there's another "experience" that seems to make scant profile on these boards - "learning to see".

Its not a lesson or or test or classroom matter. Its all about quickening the eye brain response while observing so the observer records fiber and fiber details and over time much faster.

Then it goes away.

The planet season passed the scope is stored and the training of the eye brain relaxes eventually to its original speed and sensitivety settings.

Its like a muscle toned and then relaxed only to be trained and developed at another date.

Terrence Dickerson claims he's done the eye brain training to the point it now only requires a session or two to get his speed and sensitivety back up to pitch.

Alas the muscle analogy is relevant here as training of the muscle groups often leaves them with "memory" that allows the strength and exertion to be reached even after a long lay off much quicker than had it but received such training in the first place.

Experience in terms of quickening of the eye brain response will leave the veteran observer trouncing the DK observer despite the optical mechanical edge simply because the eye brain has been trained to work more effectively at quicker intervals on low contrast targets.

And its THAT which dwarfs this daft comparison between and $11,000 OTA to a $1500.

The best experienced observer with his eye brain at pitch will see more with the DK. But that's not in question here - there's no uncovered secret here that if you triple or quadruple your budget you get a better scope. Of course you do. I didn't think it needed testing much less preaching in admonishing tones .

The fact is the individual can maximize their own visual advantage that trumps these empty comparisons.


Pete

#73 areyoukiddingme

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Posted 25 April 2014 - 02:26 PM

Pete, I agree that we need to be clear about what we mean by "experience". Then an empirical question is tractable. Is it really true that we can train eye sight in the same way that we can train muscles?

It must be true that the ability to pick up fine details improves with practice (that seems to be a truism about biological systems), but it would be interesting to find out how much of this is a subjective sense vs. veridical, and how big this factor is relative to others.

My guess is that this is not something that has ever been tested experimentally, but it wouldn't be difficult to do.

For example, if we take two groups of astronomers (say those with 2 years experience or less, and those 20 years or more), and we then compare them in their ability to discern fine detail at the limits of vision. We could come up with an experimental stimulus that either does or does not contain a target object.

If it really is true that experienced astronomers have this ability, then we need to show it first.

If there is evidence for such an effect, then we could quantify it relative to other inputs. Size and brightness of an image to simulate aperture, for example. We could even test your proposal. Experienced astronomers before vs. after planet season!

Anyway . . .

#74 azure1961p

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Posted 25 April 2014 - 03:12 PM

Where this eye/brain training is actually done with regularity is speed reading. Here through exercises the mind learns to process quicker with less hang time. I'm very sure there is documented testing on this . I did the exercises as a kid in jr high and high school (1970s). The results are surprisingly impressive. I would venture to say that investigating speed reading technique would yield far more emperical information than lunar/planetary observational pursuits.

It must be kept up with exercise (again like a muscle) . Practiced observers who will observe mars every clear night are way on top of their game while that pause that we take that can last for months turns our well earned speed to something more relaxed and slow paced.

I'm going to buzz about looking under speed reading - I'm very confident there in lies your answers on empirical values and such.

Pete

#75 issdaol

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Posted 25 April 2014 - 09:14 PM

This is a very interesting comparison.

I have owned Multiple SCT's (both Meade and Celestron) and refractors (Vixen and Takahashi) and have used and compared quite a few others.

Based on this, I can see some of the points that Daniel is trying to get across. While my SCT's were great examples I did not realise how much better the Mewlon was (both optically and mechanically) until I used one side by side with my SCT.

However apart from this particular point the rest of the comparison is very poorly thought out and articulated. To the point of sounding degrading/insulting to other peoples choices, experience, budgets.

First there is no definition as to what particular manufacturers scopes were being used.

Just in the DK options alone there are now a considerable number of differences between manufacturers.

Then the rest of comparison mainly waffles on about supposed expert site selection and observation without any more detail comparison on the OTA's or targets observed.

Seems mainly like a self justifying post to either garner sales interests in DK's or stir up the form.

PS: I also note that since the original post that Daniel has not bothered to address any of the other forum members valid questions


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