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How much strehl difference is actually detectable?

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240 replies to this topic

#226 teashea

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Posted 07 May 2021 - 09:12 PM

Do you think that a person with a high quality telescope means that just by owning such an telescope means they do not work at observing?

 

Do you think that a person with a high quality telescope might, through years of experience and observing and owning lesser telescopes, have learned that high quality optics deliver more?

 

Do you think a person who owns high quality telescope means that they are not skilled?

 

Do you think that a person after years of observing and working his or her way up to owning a high quality telescope has nothing to teach a newcomer?

 

Would all TEC, CFF, Takahashi, Astro-Physics, Questar, LZOS, Tele Vue and other high end brand owners all be, as you define them, common loud, braggarts?

 

Can you post specific examples where people who own a high quality telescopes are bragging about owning such telescopes and are putting down the owners of lesser telescopes?

 

Bob

Well stated Bob.


 

#227 teashea

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Posted 07 May 2021 - 09:14 PM

Owning the finest quality telescopes does not preclude one from being a good observer.  


 

#228 teashea

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Posted 07 May 2021 - 09:23 PM

Incidentally it is for that reason that a 6 inch is considered a minimum aperture for best planetary resolution...the limitation being the eye below that mark 300x giving a .5mm exit pupil.
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Considered by whom?  For what specific purpose?  All but one of my Takahashi telescopes are less than 6 inches.  


 

#229 teashea

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Posted 07 May 2021 - 09:28 PM

If at all and then maybe on only the best of nites, for brief periods ? The cost per those types of views can sky rocket up into outer space pretty fast ! Leaving just a number that means ........ ?

To some, owning the finest is worth the cost even though the incremental difference is small.  


 

#230 RLK1

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Posted 07 May 2021 - 09:35 PM

I'm just speculating that many of these fine instruments are being utilized primarily for imaging and a lot less for observing. At least that's been my experience in the field. So, I'm not sure what that does for one's observing skills and I'm not sure whether or not a 0.94 versus a 0.98 strehl really matters in imaging, particularly since I'm a visual observer. 


 

#231 teashea

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Posted 07 May 2021 - 09:36 PM

Perhaps this deviates from the topic a little but some things start to cost too much to enjoy them, I experienced that a little when I owned a questar….  actually  scared you will damage it, you hear stories of people buying cheap scopes to travel with because they are worried their Astro physics might get scratched etc…. The winning scope certainly is not the absent one. And a 60mm refractor really out performs the 5” takahashi that seemed just too much trouble to set up that night. Or even leaving your nice scope at home because your public outreach event has lots of children waiting to wrestle your scope. Anyway you get my point, it’s a tool…. If it’s a little beat up that can be a good thing

I disagree.  Some people enjoy owning the finest.  If you do not, that is your choice.  To me "a little beat up" is not a good thing.  I enjoy excellence.  


 

#232 Joe1950

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Posted 07 May 2021 - 09:37 PM

Owning the finest quality telescopes does not preclude one from being a good observer.  

 

No one said it did. That was an erroneous interpretation by Mr. hen.

The original post, with a totally different meaning, was deleted.

So why don’t we just drop it?


 

#233 LDW47

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Posted 07 May 2021 - 09:39 PM

To some, owning the finest is worth the cost even though the incremental difference is small.  

Nothing wrong with just wanting to own something, I do it with rare coins, sonar gear and at one time Antiques ! As long as you know your expectations. 


 

#234 Asbytec

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Posted 07 May 2021 - 09:54 PM

Owning the finest quality telescopes does not preclude one from being a good observer.

The same is true with a larger aperture as it is with a premium optic. In all scopes, detail is still visible at the limits of our acuity. By definition, I guess, a good observer knows how to detect that detail, recognizes it when we see it, and trusts what we see. In my view, when we talk about increasingly smaller differences in Strehl, this is what we mean. The important thing to seeing such detail is our observing conditions (seeing and transparency), scope preparation (collimation and thermal stability), and our experience. I'd prefer an excellent scope in lab-like observing conditions over the same excellent scope in average seeing, but a modest scope in favorable observing conditions is fine, too. Either with a skilled observer at the helm. We like what we see, that's what we need to know because we know what we like to see.

This is where high Strehl shines, to see slightly darker blacks, more definite boundaries between the slightest shades of grey, and splitting close unequal doubles. All great stuff, but not easy to see in any scope. If seeing get's in the way, forget it. In my experience, anyway. I have seen detail in the Martian polar cap, craters smaller than the Dawes limit, and albedo features on Ganymede to name a few through a modest refractor-size aperture of unknown Strehl. No matter how good the scope, none of that would have been visible if the seeing was not diffraction limited or better. A premium refractor can present the same detail as being a little cleaner to a good observer who get's lucky enough to see what their scope can do. Unfortunately, though, not under the jet stream even though seeing favors smaller apertures.

Edit: I guess my response to the OP is, sure, one can tell a difference. However, and like most things, so many variables make it difficult to say when and how much. Get a scope that pleases you, first off, and a better scope when you know what to look for, when your ready for it, and able and want to pay for it. And, by all means, pray for good seeing. Improving your skill will make every scope better until you reach the limits of the scope and your own acuity. Then get a bigger scope. :lol:

Edited by Asbytec, 07 May 2021 - 11:00 PM.

 

#235 Kevin Barker

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Posted 07 May 2021 - 10:24 PM

Some astronomers like optics and the science of how they work as much as the views. Nothing wrong with this.
I have always liked the challenge of splitting close doubles and seeing faint planetaries/ globulars etc with modest aperture. I was delighted when I finally saw trapezium in M42 E and F stars in 80 mm refractor and 90 mm Mak
One observation I often notice if using telescopes of similar design and supposed similar quality is on the average night seeing and cool down does seem to favour the smaller aperture.
I have two Intes scopes of the same design IM603 and IM703. For years I convinced myself the 703 was inferior till a night when it really delivered. I might explore the insulation method to settle the 703. The 603 is used more as it fits small mounts and cools a little better.
Why I say this I often read reports of perfect optics with smallish apertures say under 5 inches.
I very much doubt I could tell the difference between a 0.94 strehl and a 0.98 strehl at the eyepiece if two identical scopes were side by side.
 

#236 LDW47

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Posted 07 May 2021 - 10:53 PM

The same is true with a larger aperture as it is with a premium optic. In all scopes, detail is still visible at the limits of our acuity. By definition, I guess, a good observer knows how to detect that detail, recognizes it when we see it, and trusts what we see. In my view, when we talk about increasingly smaller differences in Strehl, this is what we mean. The important thing to seeing such detail is our observing conditions (seeing and transparency), scope preparation (collimation and thermal stability), and our experience. I'd prefer an excellent scope in lab-like observing conditions over the same excellent scope in average seeing, but a modest scope in favorable observing conditions is fine, too. Either with a skilled observer at the helm. We like what we see, that's what we need to know because we know what we like to see. 

 

This is where high Strehl shines, to see slightly darker blacks, more definite boundaries between the slightest shades of grey, and splitting close unequal doubles. All great stuff, but not easy to see in any scope. If seeing get's in the way, forget it. In my experience, anyway. I have seen detail in the Martian polar cap, craters smaller than the Dawes limit, and albedo features on Ganymede to name a few through a modest refractor-size aperture of unknown Strehl. No matter how good the scope, none of that would have been visible if the seeing was not diffraction limited or better. A premium refractor can present the same detail as being a little cleaner to a good observer who get's lucky enough to see what their scope can do. Unfortunately, though, not under the jet stream even though seeing favors smaller apertures. 

You speak well but you forget the original intent of this thread, is there a noticeable difference between a strehl of 0.94 and 0.98 in the views ? How and where does your write apply to that original enquiry ? Did I, did we miss it ? 


Edited by LDW47, 07 May 2021 - 10:55 PM.

 

#237 Asbytec

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Posted 07 May 2021 - 11:01 PM

You speak well but you forget the original intent of this thread, is there a noticeable difference between a strehl of 0.94 and 0.98 in the views ? How and where does your write apply to that original enquiry ? Did I, did we miss it ?


I implied it. :lol:
 

#238 LDW47

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Posted 07 May 2021 - 11:06 PM

I implied it. lol.gif

Implied it or applied it ?


 

#239 Asbytec

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Posted 07 May 2021 - 11:15 PM

Implied it or applied it ?


I'm not even sure we're still answering the OP, we're just talking amongst ourselves. Which is fine. Social Media, you know. :)
 

#240 LDW47

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Posted 07 May 2021 - 11:22 PM

I'm not even sure we're still answering the OP, we're just talking amongst ourselves. Which is fine. Social Media, you know. smile.gif

The OP is probably out observing with their 0.96 strehl scope or long gone to bed, one or the other, lol ?


 

#241 noisejammer

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Posted 08 May 2021 - 12:03 AM

Ok folks, the signal-to-noise has dropped well below 0.1 ...

The story is over.crazy.gif

 

quickety-quick it's clickety-click lock.gif


 


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