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AT 125 EDL doublet

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#26 BillP

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Posted 30 July 2020 - 03:43 PM

I have to wonder about that.  Any touch up would require recoating the lens(es) which is not a minor task.  Particularly for a lens that is already coated.  

 

Jon

Define "touch up".  Could mean anything, even like putting a 1mm mask around it to eliminate a bad edge.


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#27 daquad

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Posted 30 July 2020 - 06:34 PM

That lens in a Moonraker tube would be cool.

Yeah, but in a Moonraker you are paying more for the superb artistry rather than superb optics.  Whatever floats your boat.

 

Dom Q.



#28 areyoukiddingme

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Posted 30 July 2020 - 09:57 PM

Maybe someone can quote their claims on what they were doing with the lenses at Stellarview.

 

But my collection was that they were at least giving the impression that there was figuring going on. I'm also skeptical, that's the case, but took what I believe was their word on that.

 

But I'm going on recollection, and if they claimed no such thing, I don't want to be putting words in their mouth.

 

I think they sold a few of them towards the end of the run, so maybe some owners can chime in.



#29 peleuba

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Posted 31 July 2020 - 08:39 AM

Define "touch up".  Could mean anything, even like putting a 1mm mask around it to eliminate a bad edge.

 

?

 

Umm, No.   That's not a touch-up, rather you are describing a mechanical/structural aperture stop.  When speaking of optics, a touch-up refers to just that - some alteration to an actual optical surface (including the coating), or the spacing and rotation of the lens elements.   

 

Only in the absolute most liberal terms would any aperture stop be described as a touch-up.  Even then its a B-I-G stretch.



#30 starryhtx

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Posted 01 August 2020 - 08:01 AM

Anyone know when they are supposed to come in stock?



#31 CHASLX200

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Posted 01 August 2020 - 08:36 AM

No, Thank you.  

F/16 would be even better for my taste.


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#32 BillP

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Posted 01 August 2020 - 03:03 PM

?

 

Umm, No.   That's not a touch-up, rather you are describing a mechanical/structural aperture stop.  When speaking of optics, a touch-up refers to just that - some alteration to an actual optical surface (including the coating), or the spacing and rotation of the lens elements.   

 

Only in the absolute most liberal terms would any aperture stop be described as a touch-up.  Even then its a B-I-G stretch.

Umm, Yes...there is no standard for how one used a phrase when technical terms are not specifically used.  Touch up is touch up and it means anything they want it to.  Without further definition it is a meaningless term like "all natural" in foods (the FDA has not developed a definition for use of the term natural or its derivatives).  If someone, anyone of an stature in the industry, told me the "touched up" the lens, I would immediately follow up with a question asking them to specifically detail what they did, otherwise I would be just another stupid consumer.  If any vendor chooses to use this kind of casual lingo to describe what is supposed to be a professional technical process, well I would never hire them that's for sure.  I can just hear it now, the developer came to me and reported that they touched up the subroutine ... or the crew chief of the aircraft I was about ready to pilot told me they just finished "touching up" the hydraulics lol.gif  Yea...try again!


Edited by BillP, 01 August 2020 - 03:12 PM.

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#33 Passerine

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Posted 01 August 2020 - 03:52 PM

Bill,

I don't think there is any dispute about the fact that "touch up" is a vague term.  People were simply speculating on exactly what that term might mean, specifically on the Stellarvue "touched up" doublets, which I think they only offered for a very short time.  I think Jon and Paul were simply saying that the "touching up" of the doublets most likely did not involve fine tuning the lens surface/figure and then multicoating, and I tend to agree with them on that.  I think Paul was just pushing back on the idea that part of how an objective is "touched up" might include "putting a 1mm mask around it to eliminate a bad edge."  And on that specific point, I have to side with him.  I can't believe any vendor would use a slightly different retaining ring resulting in less clear aperture on only some of the samples of a given model.  On the other hand, if they do it on all of the scopes, then I wouldn't call that a "touch up" but rather a standard design feature of every scope. shrug.gif ...?

 

Dave

 

PS.

There has been discussion in other threads about the practice of testing less than 100% of the full objective, masking off a turned edge or essentially "cheating" to attain a higher measured Strehl.  I see that as a separate matter, not part of touching up or fine tuning.


Edited by Passerine, 01 August 2020 - 04:13 PM.

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#34 starryhtx

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Posted 01 August 2020 - 04:25 PM

Umm, Yes...there is no standard for how one used a phrase when technical terms are not specifically used.  Touch up is touch up and it means anything they want it to.  Without further definition it is a meaningless term like "all natural" in foods (the FDA has not developed a definition for use of the term natural or its derivatives).  If someone, anyone of an stature in the industry, told me the "touched up" the lens, I would immediately follow up with a question asking them to specifically detail what they did, otherwise I would be just another stupid consumer.  If any vendor chooses to use this kind of casual lingo to describe what is supposed to be a professional technical process, well I would never hire them that's for sure.  I can just hear it now, the developer came to me and reported that they touched up the subroutine ... or the crew chief of the aircraft I was about ready to pilot told me they just finished "touching up" the hydraulics lol.gif  Yea...try again!

That's the thing about English, I find we never have enough words to describe things. In Arabic, for example, there are over 100 different words for Camel. 


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#35 HubSky

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Posted 01 August 2020 - 06:11 PM

I corresponded with Vic and Alex several times when I purchased my SV125.  From what I could tell, they were removing the lenses and testing them and they had an issue with some of them not passing.  What happened with the ones that didn't pass muster I don't know. 

When I purchased mine, they had three available that past their tests ranging from Strehl 0.958 to 0.971.  I took the 0.971 and couldn't be happier with the scope. 

They were great to work with. I think the issues of receiving acceptable lenses by their standards and with the price point they were shooting for made the SV line and especially the SV 125 unsustainable.


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#36 Tropobob

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Posted 01 August 2020 - 10:50 PM

F/16 would be even better for my taste.

And F/20 would be even better or will nothing less than F/50 do?  lol.gif



#37 StarAlert

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Posted 01 August 2020 - 11:28 PM

I’m curious as to why the manufacturers/vendors who market with Strehl ratios haven’t introduce variable pricing.  
 

You want the Strehl of 0.97? That’ll cost $xxx more than the 0.95. We have a 0.94 over there. You can buy it for $xxx less.

 

I’m sure there are a bunch of people who would be willing to pony up a premium for the 0.97, but I can’t believe I’d be able to tell the difference between a Strehl of 0.93 and 0.97 and would be okay with a 0.93 if it was discounted. 

I corresponded with Vic and Alex several times when I purchased my SV125.  From what I could tell, they were removing the lenses and testing them and they had an issue with some of them not passing.  What happened with the ones that didn't pass muster I don't know. 

When I purchased mine, they had three available that past their tests ranging from Strehl 0.958 to 0.971.  I took the 0.971 and couldn't be happier with the scope. 

They were great to work with. I think the issues of receiving acceptable lenses by their standards and with the price point they were shooting for made the SV line and especially the SV 125 unsustainable.


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#38 areyoukiddingme

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Posted 02 August 2020 - 01:41 AM

Because they make money by selling telescopes to people, and there is a large enough number that will only want the highest strehl.

 

Then they are stuck with a pile of scopes they can't sell.

 

There's a common measurement technique in psychophysiology called the just noticeable difference. It's the minimal physical change in a stimulus that can be distinguished 50% of the time (i.e., the threshold of chance).

 

It's useful for experiments where you either want to understand the nature of human perception of physical quantities like light and sound, but it's also useful for characterizing stimuli for new experiments--I do experiments with voice pitch, and it would be daft to present stimuli inside the JND if you want to see how people react to different pitches, for example.

 

I doubt anyone has ever attempted to express a JND in terms of Strehl in a quantifiable manner. The closest I have heard is some crude comparisons to see if people in the filed can distinguish 1/4 from 1/10 wave (or something like that) mirrors. I think the answer is that most people cannot.

 

In any case, this experiment could be done, and we could find out the JND of Strehl for the average amateur astronomer, and characterize 'high' and 'low' in that fashion.

 

I somehow doubt it would catch on, but it would be interesting to find out what the number is. It would also be interesting to find out how variable individuals are in the JND--age eyesight, experience all being relevant moderators. 


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#39 StarAlert

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Posted 02 August 2020 - 02:06 AM

Because they make money by selling telescopes to people, and there is a large enough number that will only want the highest strehl.

 

Then they are stuck with a pile of scopes they can't sell.

 

There's a common measurement technique in psychophysiology called the just noticeable difference. It's the minimal physical change in a stimulus that can be distinguished 50% of the time (i.e., the threshold of chance).

 

It's useful for experiments where you either want to understand the nature of human perception of physical quantities like light and sound, but it's also useful for characterizing stimuli for new experiments--I do experiments with voice pitch, and it would be daft to present stimuli inside the JND if you want to see how people react to different pitches, for example.

 

I doubt anyone has ever attempted to express a JND in terms of Strehl in a quantifiable manner. The closest I have heard is some crude comparisons to see if people in the filed can distinguish 1/4 from 1/10 wave (or something like that) mirrors. I think the answer is that most people cannot.

 

In any case, this experiment could be done, and we could find out the JND of Strehl for the average amateur astronomer, and characterize 'high' and 'low' in that fashion.

 

I somehow doubt it would catch on, but it would be interesting to find out what the number is. It would also be interesting to find out how variable individuals are in the JND--age eyesight, experience all being relevant moderators. 

I agree. It would be very interesting. Could potentially change a lot of behavior.

 

By guaranteeing a minimum Strehl, aren’t they already trashing lens cells that don’t meet the threshold, but are still very good optics? If Astronomics is guaranteeing a 0.95 strehl, who is paying for the cost of the lens cells that are only 0.94? Those who are buying the 0.95 and higher. Why not just package the 0.94 and sell it at a discount?

 

Maybe Astronomics never even sees the “duds”. I have no idea how the nuts and bolts work in this industry.  
 

Anyway, you see variable pricing in a lot of other markets. Night vision in one.. The best tubes cost the most money. The lesser tubes are still being sold, however, but to different consumers. 
 

That’s all I’m going to say about this topic in this thread. I don’t want to hijack it. 


Edited by StarAlert, 02 August 2020 - 02:08 AM.

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#40 CHASLX200

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Posted 02 August 2020 - 07:14 AM

And F/20 would be even better or will nothing less than F/50 do?  lol.gif

I guess even a F/9 or 10 would be nice. I just like longer scopes as there seems to be a million brands all the same FL these days.


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#41 Jon Isaacs

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Posted 02 August 2020 - 07:48 AM

By guaranteeing a minimum Strehl, aren’t they already trashing lens cells that don’t meet the threshold, but are still very good optics? If Astronomics is guaranteeing a 0.95 strehl, who is paying for the cost of the lens cells that are only 0.94? Those who are buying the 0.95 and higher. Why not just package the 0.94 and sell it at a discount?

 

My understanding is that the supplier is guaranteeing a Strehl of 0.95 or greater.

 

Regarding what to do with the lesser lenses.. 

 

One thing might be to only test the inner 95% of the objective.   

 

Jon


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#42 Galicapernistein

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Posted 02 August 2020 - 08:17 AM

I guess even a F/9 or 10 would be nice. I just like longer scopes as there seems to be a million brands all the same FL these days.

I had a Skywatcher 100 F/9, now I have a TS 102 F/11, and it performs noticeably better at high power. Every step up in F ratio improves performance and reduces optical distortions. It’s too bad there aren’t more options for people who like to push their optics to the limit. An F/16 ED refractor would be a stunning performer.


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#43 russell23

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Posted 02 August 2020 - 08:26 AM

I think the 125mm f/7.8 is about as long a refractor OTA (~1000mm FL or 36" OTA) as most people want to deal with setting up.   Any longer and a more permanent mount setting starts to make sense - and of course there are exceptions.   So from a business point of view you have to consider the demand.  A 125mm f/12 APO would be an incredible scope.  I would love to throw a 48mm Brandon in one.  But there probably is not enough demand to justify the manufacture of such a scope. 

 

Perhaps one way a scope like that could be produced would be a pre-sale with 50% down kind of ordering.  So if you can get X# of people to commit to purchase with a 50% down payment then you place the order.


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#44 BillP

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Posted 02 August 2020 - 11:26 AM

My understanding is that the supplier is guaranteeing a Strehl of 0.95 or greater.

Is anyone guaranteeing .95 strehl at a specific wavelength?  Or are they just finding the one wavelength in the visual range that happens to reach 0.95? lol.gif


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#45 25585

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Posted 02 August 2020 - 11:36 AM

I think the 125mm f/7.8 is about as long a refractor OTA (~1000mm FL or 36" OTA) as most people want to deal with setting up.   Any longer and a more permanent mount setting starts to make sense - and of course there are exceptions.   So from a business point of view you have to consider the demand.  A 125mm f/12 APO would be an incredible scope.  I would love to throw a 48mm Brandon in one.  But there probably is not enough demand to justify the manufacture of such a scope. 

 

Perhaps one way a scope like that could be produced would be a pre-sale with 50% down kind of ordering.  So if you can get X# of people to commit to purchase with a 50% down payment then you place the order.

My answer is a Q1.6x extender on my 900mm F9 FC100DL. That gives me F14.4, 1440mm FL with the Q. And its invisible with no optical detriment I have noticed.

 

Lower budget, an Antares 1.6x 2" Barlow will give the same F# & FL on a S-W 100mm ED F9 (or any other make with those specs).


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#46 Jeff B

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Posted 02 August 2020 - 12:23 PM

I guess even a F/9 or 10 would be nice. I just like longer scopes as there seems to be a million brands all the same FL these days.

I agree!  An F10 would be really attractive to me for visual use, especially with a bino-friendly OTA.

 

Jeff



#47 PETER DREW

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Posted 02 August 2020 - 12:33 PM

I think the value of an F16 lies in it being the native focal ratio of the objective.  Converting a F8 achromat to an effective F16 by inserting a 2x Barlow does not transform it into a great telescope.


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#48 Tropobob

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Posted 02 August 2020 - 04:57 PM

I had a Skywatcher 100 F/9, now I have a TS 102 F/11, and it performs noticeably better at high power. Every step up in F ratio improves performance and reduces optical distortions. It’s too bad there aren’t more options for people who like to push their optics to the limit. An F/16 ED refractor would be a stunning performer.

I have the same TS 102 F/11 and love it. I think that we are very fortunate that this scope is available and at such an affordable price.  A slower scope may be interesting for a 102mm, but becomes problematic in larger sizes, if not permanently mounted.  

 

I owned a Meade 127mm ED F/9, which performed well, but I did not use it very often because of its size.  I have also previously owned a Uniton 76mm F/16, which was surprisingly light, but I then felt restricted into a high magnification mode.  


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#49 peleuba

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Posted 02 August 2020 - 07:09 PM

Umm, Yes...there is no standard for how one used a phrase when technical terms are not specifically used.  Touch up is touch up and it means anything they want it to.  Without further definition it is a meaningless term like "all natural" in foods (the FDA has not developed a definition for use of the term natural or its derivatives).  If someone, anyone of an stature in the industry, told me the "touched up" the lens, I would immediately follow up with a question asking them to specifically detail what they did, otherwise I would be just another stupid consumer.  If any vendor chooses to use this kind of casual lingo to describe what is supposed to be a professional technical process, well I would never hire them that's for sure.  I can just hear it now, the developer came to me and reported that they touched up the subroutine ... or the crew chief of the aircraft I was about ready to pilot told me they just finished "touching up" the hydraulics lol.gif  Yea...try again!

 

 

No.  But whatever.   I don't think you know enough about how optics are made, tested and certified to come across as an authority on the term "touched-up".  Your aircraft metaphor falls a little short of the runway so-to-speak. 

 

When designing my test area I spoke at length to folks who make custom optics vocationally and professionally serving the amateur and government/aerospace markets.  And, while "touched-up"  is not a technical term, its used in the daily vernacular to describe the "act of altering the glass to improve upon it".  And nothing to do with the opto-mechanical assembly (OTA/cell etc.)  Don't take my word for it - go to the ATM forum here, lots of smarter people then I will tell you the same thing.  

 

I think I read somewhere that you made a mirror or two previously, so am not sure why you want to argue the definition.

 

Pan-Pan (pilot lingo) Bill, it is what it is and I am sorry that I cannot make you see it so.  Lately, at least, it seems we are on opposite sides of things and for my part, it's not personal, but when I see things that I know to be in error, I am not shy about it.  

 

Wheelz-Up.


Edited by peleuba, 02 August 2020 - 07:35 PM.

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#50 Bomber Bob

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Posted 02 August 2020 - 07:37 PM

I agree. It would be very interesting. Could potentially change a lot of behavior.

 

By guaranteeing a minimum Strehl, aren’t they already trashing lens cells that don’t meet the threshold, but are still very good optics? If Astronomics is guaranteeing a 0.95 strehl, who is paying for the cost of the lens cells that are only 0.94? Those who are buying the 0.95 and higher. Why not just package the 0.94 and sell it at a discount?

 

Maybe Astronomics never even sees the “duds”. I have no idea how the nuts and bolts work in this industry.  
 

Anyway, you see variable pricing in a lot of other markets. Night vision in one.. The best tubes cost the most money. The lesser tubes are still being sold, however, but to different consumers. 
 

That’s all I’m going to say about this topic in this thread. I don’t want to hijack it. 

I don't know what happens to these "seconds" but... those off-brand EDs on eBay have to have lenses made somewhere by some company...


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