Why do really expensive scopes sell and what attracts us to them ?

[vlaiv]

15 minutes ago, jetstream said:

lol! Dragon flys among others sitting on an island across the bay, btw my eyes are 20/10 the doc says. Does the Dawes limit apply to flys?

Actually it does - if you have two flies side by side and you want to know if you'll be able to see them as two distinct things - they should be separated by that much arc seconds

Where confusion comes from in features that are smaller than Dawes limit and are seen - is about what it means to resolve something. To resolve means - to see as two distinct things - not to see at all.

We see stars, and star diameter is waaay smaller than Dawes limit of any one telescope we have ever used. Yet we see them no problem.

Similarly - we can see a feature that is rift or gap in ring system even if it's much narrower than Dawes limit. What we can't see is this - if we have two parallel lines and their distance is less than Dawes limit - we won't be able to tell that there are two lines, but we will still see the line.

And you are right - MTF is important bit in whole "can you see feature" game. At some point we won't be able to see the line anymore - and that has to do with contrast. If MTF lowers contrast enough - line will blend into background and we won't be able to see it.

This effect exists on stars as well - although maybe not directly recognized. Limiting magnitude depends on seeing. On night of poor seeing - we won't be able to go as deep as on night of good seeing. That is because MTF changes because of seeing and it affects contrast of that unresolved star against background.

Edited December 1, 2021 by vlaiv

[vlaiv]

2 minutes ago, Franklin said:

According to that my 53yr old eyes are 20/25. Best get down spec-savers!

Don't look at actual chart on screen - that will depend on what size your screen is and how far away you are looking at it

If you want to do that sort of test - you need printed chart of certain size and you need well lit room and you need to stand at such distance that 20/20 forms 5' squares.

Best done at eye doctor's office

 

[Franklin]

7 minutes ago, vlaiv said:

Best done at eye doctor's office

Yes, Spec-savers.😀

I have noticed one thing though. Having spent all my observing time at the telescope using my left eye only, my right eye is pants. But since I've been using binoviewers I am finding it easier using my right eye for cyclops viewing.

[vlaiv]

3 minutes ago, Franklin said:

Yes, Spec-savers.😀

I have noticed one thing though. Having spent all my observing time at the telescope using my left eye only, my right eye is pants. But since I've been using binoviewers I am finding it easier using my right eye for cyclops viewing.

I can't even use binoviewers. My right eye is completely messed up, I have severe astigmatism and see 3 images at once with it . Actually that is self diagnosed - I looked at the Moon and bright stars and I found out that my "PSF" for right eye is something like this:

I really see 3 moons superimposed with my right eye when I look at it.

That of course makes very blurry image.

I think my brain trained itself to ignore image from my right eye for the most part - I can tell that image is even perceived as less bright when using that eye - quick switching between eyes shows distinct less bright / more bright scene.

[Stu]

2 hours ago, vlaiv said:

To me, term snap to focus means following:

It's defocused - you turn focusing knob, turn, turn and then - suddenly it's in focus - snap to focus

I'd say effect has more to do with mechanics of focuser and seeing conditions than quality of optics.

First part is correct, but it’s not mechanics, it is the optics.

[vlaiv]

Here is interesting thought that I just had.

What if we change the question - just tiny bit?

Why do really expensive mounts sell and why are we drawn to them?

That question is not nearly as controversial as original one. To me, answer is rather simple and it consist of two things

1. Payload

2. Performance

There are few additional minor details - like if you want to guide or not (use of absolute encoders) - and that is it.

Not nearly as much mystique or price difference for "last few percent" as with scopes. Interesting isn't it? Maybe this is because performance of the mount is much more easily assessed?

[Stu]

2 minutes ago, vlaiv said:

Here is interesting thought that I just had.

What if we change the question - just tiny bit?

Why do really expensive mounts sell and why are we drawn to them?

That question is not nearly as controversial as original one. To me, answer is rather simple and it consist of two things

1. Payload

2. Performance

There are few additional minor details - like if you want to guide or not (use of absolute encoders) - and that is it.

Not nearly as much mystique or price difference for "last few percent" as with scopes. Interesting isn't it? Maybe this is because performance of the mount is much more easily assessed?

Hmmmm, I’m not so sure Vlad. I reckon there would be just as impassioned debates about best mounts as scopes! 🤣🤣🤪

I do wish this cloud would clear. Whilst I am enjoying this thread, I’m getting pretty exhausted by it so do fancy getting out to do some observing so I can post a report up! Ultimately, whilst all this stuff is interesting, it’s getting out under the stars which counts, whatever kit you use 👍

[Alien 13]

22 minutes ago, vlaiv said:

Here is interesting thought that I just had.

What if we change the question - just tiny bit?

Why do really expensive mounts sell and why are we drawn to them?

That question is not nearly as controversial as original one. To me, answer is rather simple and it consist of two things

1. Payload

2. Performance

There are few additional minor details - like if you want to guide or not (use of absolute encoders) - and that is it.

Not nearly as much mystique or price difference for "last few percent" as with scopes. Interesting isn't it? Maybe this is because performance of the mount is much more easily assessed?

I think you missed portability, I would argue that my Sirui camera tripod is the best on the planet...well it is for my needs.

Alan

[vlaiv]

1 minute ago, Alien 13 said:

I think you missed portability

Well spotted! That is indeed important factor in some cases.

[Deadlake]

16 minutes ago, vlaiv said:

Well spotted! That is indeed important factor in some cases.

Reliability?

Why do some mounts need after sale modifications…

[Stu]

Having pleaded exhaustion, I found the energy to dig this out which I always found interesting. It supports what Gerry says in terms of smoothness being very important; two 1/4 wave mirrors are not necessarily equal depending on their smoothness…

https://zambutomirrors.com/zambutoopticalcc.html

Image from the Zambuto website above.

[Franklin]

53 minutes ago, vlaiv said:

What if we change the question - just tiny bit?

That is quite a lot really.

But you cannot appreciate good optics without a suitable mount I suppose,

[John]

54 minutes ago, vlaiv said:

Here is interesting thought that I just had.

What if we change the question - just tiny bit?

Why do really expensive mounts sell and why are we drawn to them?

That question is not nearly as controversial as original one. To me, answer is rather simple and it consist of two things

1. Payload

2. Performance

There are few additional minor details - like if you want to guide or not (use of absolute encoders) - and that is it.

Not nearly as much mystique or price difference for "last few percent" as with scopes. Interesting isn't it? Maybe this is because performance of the mount is much more easily assessed?

I'm nowhere near as interested in mounts. Mostly I use low cost ones !

 

[John]

1 minute ago, Franklin said:

...But you cannot appreciate good optics without a suitable mount I suppose,

My Skytee II cost about £150 used and does a great job with my refractors up to and including 120mm in aperture. Enough to let me appreciate them I'm sure

I ended up spending more on a mount for the 130mm F/9.2 to get something that would hold it steady enough due to the long tube. 

[Franklin]

I think for visual a mount must be functional, but can be rustic. The higher end mounts are of more interest to the imaging guys/gals.

[F15Rules]

1 hour ago, Stu said:

Whilst I am enjoying this thread, I’m getting pretty exhausted by it

Me too, Stu. 

I've a heavy cold following two virus jabs in two weeks, and a session of the Norovirus a couple of days ago..wouldn't you know it, the sky is super clear here tonight, and I doubt I have the energy to lift my decloaked Axiom 31mm, never mind my FS128 and mount!

So I'm going to thank everyone for an interesting thread, and John for posting the original one...now, what was it about?? Ah, yes, "Why do really expensive scopes sell and what attracts us to them ?"..that was it!!🥴😁.

I'm off to bed!😂

Dave

[RobertI]

56 minutes ago, F15Rules said:

Me too, Stu. 

I've a heavy cold following two virus jabs in two weeks, and a session of the Norovirus a couple of days ago..wouldn't you know it, the sky is super clear here tonight, and I doubt I have the energy to lift my decloaked Axiom 31mm, never mind my FS128 and mount!

So I'm going to thank everyone for an interesting thread, and John for posting the original one...now, what was it about?? Ah, yes, "Why do really expensive scopes sell and what attracts us to them ?"..that was it!!🥴😁.

I'm off to bed!😂

Dave

And on that bombshell…..I’m off to bed too. 

[John]

Sleep tight Rob and Dave - hope you feel better soon Dave !

I think we have probably exhausted the original subject now. I'm grateful for so many contributions and opinions though and it's been a nice friendly chat with a few interesting diversions along the way

I'm actually observing tonight under a clear sky and with one of my least expensive scopes - my 12 inch dob

Edited December 1, 2021 by John

[F15Rules]

Thanks John, I slept pretty well, I felt, but Mrs Dave informed me that I was snoring a lot! - something I rarely do normally..🥴

It was VERY cold here last night, a hard frost, but lovely and clear. I do hope you and your Dob had a good session?😊👍

Dave

 

[dan_adi]

On 26/11/2021 at 22:35, John said:

This is a genuine question that I have been asking myself for the past 5 years or so but I'm still unsure what the answer is.

We have access to some excellent scopes these days for great prices and yet there seems to be unabated enthusiasm still for similar specified scopes from the really expensive marques.

My personal experience seems to indicate that the actual performance differences between moderately expensive scope and one of the really expensive versions amount to perhaps 5% or so (depends on how you quantify performance I suppose) but the price differential is often very much more than that - sometime 2x or 3x as expensive.

So what is it that motivates quite a number of us (including myself) to want to own these expensive instruments ?.

My best guess is that, once you have been in the hobby for some time, you develop a burning curiosity to see "what the fuss is all about" with these highly reputed brands. With widespread reporting, through forums such as SGL, I think expectations on what they deliver are, broadly well managed so there is no expectation that whole new target areas will become attainable but it is more about an enthusiasts desire to be using something that is, or is close to, as "good as it gets" within it's niche.

I'd be very interested in others views on this though, both those who have "taken the plunge" and those who have not

I've avoided the terms "premium" and "top end" deliberately because I'm not sure that they are helpful.

Though question. In my case I used the chineese made newts and SCTs for some years... visualy.. even a achromat here and there.

I was able to see the lack of performemce of these off the shelf scopes only when I tried imaging. I learned in about a year or two, that if you want peace of mind with astro imaging, it is important to have precision equipment. Otherwise most of my time will be wasted tinkering and troubleshooting sub par equipemnt with the hope that my effort will be rewarded in easier ,fuss free , imaging time. That never happend to me .... so I switched to using an 8 inch apo refractor, a quality mount, quality focuser, etc.

With the high quality stuff you don’t have to tinker every night, everything works as expected,... if the fwhm is not to your liking for the evening, the seeing is the culprit not the gear. How many of us are trully limited by seeing only? 

Overall, in my case, the difference between off the shelf stuff and premium stuff was important in imaging. If I knew back then what I know now .... 

Edited December 3, 2021 by dan_adi

[Sunshine]

On 01/12/2021 at 14:05, vlaiv said:

if you have two flies side by side

Get your swatter, quick! 😂

sorry, this is what I am able to contribute to this highly technical discussion.

Edited December 4, 2021 by Sunshine