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Criterion RV-8 Dynascope: rough, but rockin'

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#26 terrapin

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Posted 16 February 2021 - 07:30 PM

Thank you, David. That's very interesting info. I've never done Focault testing, but I think I'm reaching the point where I should start. I'll have to dig in to how to build a tester -- it actually seems a little bit intimidating at first glance.

 

That said, I strongly suspect I'd be able to differentiate the views and photos between a spherical 8-inch f/8 and 1/4 wave. I have/had scopes that definitely look sharp and are fine, but not like what appears to be *near* perfect sharpness on a good night with my RV-6. Differentiating between 1/4 wave and better, though, I don't know. I consider all of the telescopes I use on regular basis to put up "good," relatively sharp views, but I definitely notice differences in optical quality among them and often do direct comparisons. It's tough to be objective, but I think it's definitely possible given enough time and usage with multiple scopes to notice very small differences in optical quality without testing.

 

I'll be very interested to see how my RV-8 primary compares to my RV-6 (which I'll likely see before I have a chance to build a tester). Obviously not a direct comparison, but I think it will be clear if the RV-8 is not as well figured.



#27 CHASLX200

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Posted 16 February 2021 - 07:46 PM

 TEST the mirror. I have tested around 12 of them and they all have been spheres. You will get an image that comes to focus and it will not be a fuzzy mess. So it will easily fool most.  Just when you crank up the power, you will never see the detail that a correctly figured 8" f/8 will produce. The owners swore up and down they had great optics and it gave super sharp images but a simple  30 second Foucault test told a different story.

 

                - Dave 

That RV8 I had was a killer. Mount was way too small.  The guy who bought it from me had posted images of Jupiter on here and it was crazy good.  I have had many slow 8" Newts and it was up there with the best.


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#28 DAVIDG

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Posted 16 February 2021 - 09:32 PM

That RV8 I had was a killer. Mount was way too small.  The guy who bought it from me had posted images of Jupiter on here and it was crazy good.  I have had many slow 8" Newts and it was up there with the best.

  It certainly may have had a great mirror but  I have heard this many times  that optics were great  when actually tested were not and seen images taken then post processed with optics that were 1/4 wave or worse. The optical bench tells the true story not images.  As I has said I have tested around 12 of them that have been spheres and we just had another one independently tested that was also a sphere.  

 

                  - Dave 


Edited by DAVIDG, 17 February 2021 - 12:17 PM.


#29 DAVIDG

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Posted 16 February 2021 - 09:39 PM

Thank you, David. That's very interesting info. I've never done Focault testing, but I think I'm reaching the point where I should start. I'll have to dig in to how to build a tester -- it actually seems a little bit intimidating at first glance.

 

That said, I strongly suspect I'd be able to differentiate the views and photos between a spherical 8-inch f/8 and 1/4 wave. I have/had scopes that definitely look sharp and are fine, but not like what appears to be *near* perfect sharpness on a good night with my RV-6. Differentiating between 1/4 wave and better, though, I don't know. I consider all of the telescopes I use on regular basis to put up "good," relatively sharp views, but I definitely notice differences in optical quality among them and often do direct comparisons. It's tough to be objective, but I think it's definitely possible given enough time and usage with multiple scopes to notice very small differences in optical quality without testing.

 

I'll be very interested to see how my RV-8 primary compares to my RV-6 (which I'll likely see before I have a chance to build a tester). Obviously not a direct comparison, but I think it will be clear if the RV-8 is not as well figured.

 A simple Foucault test is easy to make. All it is a light source on a simple stand with a knife edge which is usually just  a razor blade. You don't need to measure zones  since typical errors are easy to see visually and the difference from a sphere and parabola are very apparent visually. I wouldn't say it is a  difference between night and day but almost that much difference. So it only takes minutes to see if mirror has a problem or not.

 

          - Dave 


Edited by DAVIDG, 16 February 2021 - 09:48 PM.

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#30 DAVIDG

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Posted 17 February 2021 - 12:29 PM

 Here is a  link  from a thread that was posted here that shows the design for a simple Foucault tester from one of the best books on mirror making and testing, Sam Browns "All About Telescopes" . With this simple tester and the pictures in the book you can easily tell  within minutes if your mirror is spherical or some other shape. The book has great drawing of  what all the typical defects look like so again within minutes you'll know if you are even in the "ball park". 

  What I found many many times is that you not trying to tell if  the mirror is between 1/8 and 1/10 wave but one look shows it has major defects and can't be anywhere near that good. 

 

https://www.cloudyni...ercial-mirrors/

 

 I'm not trying the discourage  anyone from restoring and using classic telescope, just that one should pay as much attention to the quality of the optics has one does to the matching of the paint color and polishing the metal parts.  

 

                    - Dave 


Edited by DAVIDG, 17 February 2021 - 03:46 PM.

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#31 Jason H.

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Posted 19 February 2021 - 09:26 PM

That RV8 I had was a killer. Mount was way too small.  The guy who bought it from me had posted images of Jupiter on here and it was crazy good.  I have had many slow 8" Newts and it was up there with the best.

This is one example from the RV-8 he mentioned, in November 2012, using a Canon Powershot A540 (a point-n-shoot camera) in video mode, frames stacked in Registax, first frame of the animation that follows (it was registered and rotated for alignment with other frames before converting/degrading it to 256/8 bit color GIF animation;.) 

 

MVI_1204r.png


Edited by Jason H., 19 February 2021 - 10:08 PM.

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#32 Jason H.

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Posted 19 February 2021 - 09:28 PM

That RV8 I had was a killer. Mount was way too small.  The guy who bought it from me had posted images of Jupiter on here and it was crazy good.  I have had many slow 8" Newts and it was up there with the best.

This is the animation I made from that night's videos using THAT RV-8

 

JupiterbyJason.gif


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#33 Jason H.

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Posted 19 February 2021 - 09:33 PM

That RV8 I had was a killer. Mount was way too small.  The guy who bought it from me had posted images of Jupiter on here and it was crazy good.  I have had many slow 8" Newts and it was up there with the best.

This was Saturn with the white storm of 2011 using THAT RV-8, and Mars in 2010.  One can see my other somewhat primitive point-n-shoot images (some better than these even) from my Criterion RV-6, RV-8 and Dynascope 12 at this link https://floridaastro...stro-jason.html I don't recommend using point-n-shoots for planet imaging, there are cheaper ways of doing this that are better methods, but back then I was determined to take those P&S cameras as far as they could go.  I even did a Saturn with a P &S last year through the Dynascope 12 just to see how it would go, but one can get a beginner's planet camera for $59 these days that can do better (if you use the methods of a good planet imager that is; I might some day :^) 

 

SaturnatOppositionApr42011.jpg

 

Saturnretry-1.gif

 

Mars2010.gif


Edited by Jason H., 19 February 2021 - 09:54 PM.

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#34 DAVIDG

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Posted 19 February 2021 - 10:15 PM

 Very nice images BUT they are stacked, sharpened and contrast enhanced. made from hundreds of frames.  I helped with Richard Berry's CCD Camera CookBook and built my own CCD camera from scratch and wrote my own image processing software when CCD first started in amateur astronomy.  I know the subject very well and what software can do to enhance detail. Optics that are 1/2 to 1/4 wave  can produce images of quality in your processed image. True 1/8 wave or better optics will show the detail a single frame  that multiple stacked fames and  processed images will show  or visually when the seeing snaps.

   Test your optics and see what you really have.  Your mirror might be great but again I have tested around  12 RV-8 and we just had another tested independently and they all were spheres. There is  a pattern here. If these optics were critically tested by Criterion or who ever made them for Criterion , then how can spherical mirrors make it out of the optical shop when parabolic mirrors are required?   The difference is Very easy to see on the test stand  and requires the simplest of equipment.  

 

                 - Dave 



#35 Jason H.

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Posted 19 February 2021 - 11:11 PM

 Very nice images BUT they are stacked, sharpened and contrast enhanced. made from hundreds of frames.  I helped with Richard Berry's CCD Camera CookBook and built my own CCD camera from scratch and wrote my own image processing software when CCD first started in amateur astronomy.  I know the subject very well and what software can do to enhance detail. Optics that are 1/2 to 1/4 wave  can produce images of quality in your processed image. True 1/8 wave or better optics will show the detail a single frame  that multiple stacked fames and  processed images will show  or visually when the seeing snaps.

   Test your optics and see what you really have.  Your mirror might be great but again I have tested around  12 RV-8 and we just had another tested independently and they all were spheres. There is  a pattern here. If these optics were critically tested by Criterion or who ever made them for Criterion , then how can spherical mirrors make it out of the optical shop when parabolic mirrors are required?   The difference is Very easy to see on the test stand  and requires the simplest of equipment.  

 

                 - Dave 

Hi Dave, I was only responding to CHASLX200, since I was the one who bought his scope.  I do not know the figure of this RV-8's mirror.  Perhaps I might get it tested when it gets re-coated some day, but I haven't been concerned about it since it's almost as good as my RV-6 :^)  Regarding your converting numerous RV-6 and RV-8 mirrors from their original forms, I imagine over time people will eventually think Criterion mirrors are good if you convert them all to 1/10 wave :^)  I take it at your word that there are some serious issues at play here, and my sympathies go to those who may also consider Criterion mirror figures to be a problem.  On the other hand, consider these next two images I post that are from a SINGLE EXPOSURE 1/30th of a second image, no sharpening, via a point-n-shoot camera through the RV-6. Click on the image, which is much bigger than the default one served in the forum, check out those crater terraces!  I'm not saying the mirror is factory original, I don't know since I'm not the original owner.  I don't even know if CHAS's RV-8 is the original figure (I'm just replying to CHAS's post with some images from it).  The Criterion's are working, that's good enough for me at the moment; I might test them someday, but probably not soon.  Here's the first RV-6 image (reduced to half it's original size and greatly compressed to fit in this forum.)

Attached Thumbnails

  • e_moon-50pct-100_6436sm.jpg

Edited by Jason H., 20 February 2021 - 12:05 AM.

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#36 Jason H.

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Posted 19 February 2021 - 11:17 PM

And Dave here is the last one I'm posting on this subject, another SINGLE 1/30th of a second image, no sharpening, using a point-n-shoot camera at the RV-6.  Go ahead, click on it and look at the center of it! Single exposure, no sharpening. Maybe even the moon imager guys might appreciate this one being only one exposure.  I really don't know if it this is an original mirror, I got it from Tim Middendorf (at least that's the name I recall) more than 10 years ago and for all I know somebody (even you) could have fixed this mirror decades ago, replaced it, whatever.  I just know it's in my RV-6 and it works for me, wherever it's from.  If its figure is bad, I'm OK with this kind of bad and would be afraid to make it worse (especially since it is optically better than all of my 30+ cheap discard telescopes.)

 

3_moon-50pct-100_6444sm.jpg

 

 Very nice images BUT they are stacked, sharpened and contrast enhanced. made from hundreds of frames.  I helped with Richard Berry's CCD Camera CookBook and built my own CCD camera from scratch and wrote my own image processing software when CCD first started in amateur astronomy.  I know the subject very well and what software can do to enhance detail. Optics that are 1/2 to 1/4 wave  can produce images of quality in your processed image. True 1/8 wave or better optics will show the detail a single frame  that multiple stacked fames and  processed images will show  or visually when the seeing snaps.

   Test your optics and see what you really have.  Your mirror might be great but again I have tested around  12 RV-8 and we just had another tested independently and they all were spheres. There is  a pattern here. If these optics were critically tested by Criterion or who ever made them for Criterion , then how can spherical mirrors make it out of the optical shop when parabolic mirrors are required?   The difference is Very easy to see on the test stand  and requires the simplest of equipment.  

 

                 - Dave 


Edited by Jason H., 19 February 2021 - 11:57 PM.

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#37 Gil V

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Posted 20 February 2021 - 07:37 AM

He’ll never stop. He’s like a T-1000.

#38 CHASLX200

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Posted 20 February 2021 - 08:06 AM

This was Saturn with the white storm of 2011 using THAT RV-8, and Mars in 2010.  One can see my other somewhat primitive point-n-shoot images (some better than these even) from my Criterion RV-6, RV-8 and Dynascope 12 at this link https://floridaastro...stro-jason.html I don't recommend using point-n-shoots for planet imaging, there are cheaper ways of doing this that are better methods, but back then I was determined to take those P&S cameras as far as they could go.  I even did a Saturn with a P &S last year through the Dynascope 12 just to see how it would go, but one can get a beginner's planet camera for $59 these days that can do better (if you use the methods of a good planet imager that is; I might some day :^) 

 

attachicon.gifSaturnatOppositionApr42011.jpg

 

attachicon.gifSaturnretry-1.gif

 

attachicon.gifMars2010.gif

That RV8 you bought from me really was a killer.  Love to have that mirror tested.  But we know it is super good just with my eyes and your pics. Never had a bad  slow 8" Newt. Now compare them to SCT's and it is not even close. I never had anything done to the mirror and don't know if it had ever been reworked.  


Edited by CHASLX200, 20 February 2021 - 08:12 AM.

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#39 DAVIDG

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Posted 20 February 2021 - 10:37 AM

 Very nice moon shots but again these are low power images so not at  a magnification to be diffraction limited. That is just math behind the  imaging so they are not a critical test of optical quality. 

   Look at the wonderful images Schmidt camera produce but these are low power wide angle views. The optical error only have to be smaller then the grains on film or the pixel size not to be visible. So these optics are not operating at diffraction limits. It is same with many day modern day optics. Binoculars are  another typical example. The objectives are usually F/3 achromats so they have  about 1/2 wave  or worse of chromatic aberration but since they have fixed low power magnification the chromatic aberration isn't magnified enough to become objectionable.

 

                 - Dave  



#40 DAVIDG

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Posted 20 February 2021 - 11:00 AM

He’ll never stop. He’s like a T-1000.

 That is right Gil I won't stop because I'm trying to educate amateur that the optics in their telescope may be far worse then what they believe and they may have paid good money for something they didn't get. It is shame that see amateurs  use equipment for years only to discover what they have been missing because of poor optics they thought were great. Worse is when somebody gives up the hobby because they look at Jupiter and say " Is that all you can see".  Just is bad is when manufacture state they have made the optics to "1/8 wave " or is case of the RV--8 ads state " Exquisite Fully Corrected Optical System". A 8" f/7 sphere is 1/3 wave and no where near "fully corrected"  

   Also now that more people are testing optics and posting the results here, they see what I have been saying. There are some good ones but there are a fair amount of bad ones. So if manufactures are really testing all their optics how come  these dogs keep showing up  ? It is not just one manufacture or one type of telescope. It is refractors, SCT, Maks , and Newtonians. 

   As I said it doesn't take much to build a simple Foucault tester from a block of wood, razor blade and LED to test a mirror. One can see in minutes if their mirror has a chance of being parabolic or is spherical or has zone errors. So if you going to spend hours restoring a telescope why not spend a little time critically evaluating the optics and just assuming they are diffraction limited ? 

 

                 - Dave  



#41 terrapin

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Posted 20 February 2021 - 06:05 PM

I think both sides of this debate have a piece of the truth. I can understand David's advocacy of meticulous objective evaluation of optical quality, but also think there's value in others (including myself) making subjective judgments that a mirror is excellent without insisting that it's perfectly corrected.

 

I don't have to test my RV-6 mirror to know that it consistently blows me away visually and photographically on nights with good seeing. Am I curious to know if it's spherical or 1/4 or wave or better? Somewhat. But I don't think it will change my assessment. But it might be interesting to find out if even better views might await me someday from an even better mirror.

 

There is also much more to using a telescope than the objective quality of the optics. The entire gestalt of the experience using a particular classic telescope may ultimately be more significant, imo, than if the optics are 1/4 wave or 1/8 wave. Again that difference is not irrelevant, but I'm not going to feel that I wasted my time or money on my RV-8 if the views look good to me.


Edited by terrapin, 20 February 2021 - 06:06 PM.

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#42 KBHornblower

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Posted 20 February 2021 - 08:52 PM

A guest speaker at the Almost Heaven Star Party a few years ago reported that Edmund Scientific and Criterion got their mirrors from the same optical shop during the heyday of their Newtonians, and that the mirrors were usually excellent.  For most customers a mirror within 1/4 wave at the best focus wavefront was considered excellent, provided it was a smooth figure.  It could be 1/8 or 1/10 and give lousy results if it had bad zones or "dog biscuit" roughness.  At 6" f/8, a perfect sphere is slightly over 1/4 wave from a perfect paraboloid, and at 8" f/8 it is about 1/3 wave.  An ellipsoid that is much closer to the sphere than to the paraboloid can get the error under 1/4 wave in each case.  I can imagine an experienced technician, with a properly set up machine and good control of the hardness of the pitch, consistently turning out such mirrors.  I once got a perfect Foucault null on a 6" f8, polishing by hand, and like a fool I sold it to a friend instead of going on to get it sort of parabolic but still smooth.  I think I outsmarted myself on the technicalities of figuring, along with youthful impatience.

 

Skilled observers in excellent seeing can indeed see the improvement in going from 1/4 wave to 1/8 or better, but the difference is reportedly subtle and not easily recognized by most of us.  For those of us who can see the difference we can work on fine figuring as a labor of love (often tough love) or turn to someone like Carl Zambuto.


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#43 CHASLX200

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Posted 21 February 2021 - 07:05 AM

A guest speaker at the Almost Heaven Star Party a few years ago reported that Edmund Scientific and Criterion got their mirrors from the same optical shop during the heyday of their Newtonians, and that the mirrors were usually excellent.  For most customers a mirror within 1/4 wave at the best focus wavefront was considered excellent, provided it was a smooth figure.  It could be 1/8 or 1/10 and give lousy results if it had bad zones or "dog biscuit" roughness.  At 6" f/8, a perfect sphere is slightly over 1/4 wave from a perfect paraboloid, and at 8" f/8 it is about 1/3 wave.  An ellipsoid that is much closer to the sphere than to the paraboloid can get the error under 1/4 wave in each case.  I can imagine an experienced technician, with a properly set up machine and good control of the hardness of the pitch, consistently turning out such mirrors.  I once got a perfect Foucault null on a 6" f8, polishing by hand, and like a fool I sold it to a friend instead of going on to get it sort of parabolic but still smooth.  I think I outsmarted myself on the technicalities of figuring, along with youthful impatience.

 

Skilled observers in excellent seeing can indeed see the improvement in going from 1/4 wave to 1/8 or better, but the difference is reportedly subtle and not easily recognized by most of us.  For those of us who can see the difference we can work on fine figuring as a labor of love (often tough love) or turn to someone like Carl Zambuto.

1/4 wave done right with a super smooth surface should be fine.  I gotta wonder what is always wrong with SCT's with super mushy views.  Optics that are so bad?  Or is something not right with how the 2 ndary is placed, or something else?  It is not collimation as i am a freak about it.


Edited by CHASLX200, 21 February 2021 - 07:05 AM.


#44 starman876

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Posted 21 February 2021 - 09:08 AM

How many times do we have to see this back and forth on how to determine the quality of optics.  Dave is 100% correct in his statements.  Bench testing will show one the truth about the optics.  Takes all the gusswork and heresay out of the disscussion.   The moon is an easy subject to take pictures of.   I had a scope that had lousy optics, but you put a video camera on that scope and put the image on a large monitor you swear you were flying a low altitude over the moon.  Come to think of it the moon was the only thing  that scope was good for crazy.gif.    The only ones I have ever seen argue with Dave about how to evaluate optics are the ones that have never made a bench test set up.  



#45 Jason H.

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Posted 21 February 2021 - 01:38 PM

David, I like people fixing their mirror figures, especially when they have concerns about them.  I haven't made any claims about my telescopes being "diffraction limited" or even being 1/4 wave (let alone 1/10th or higher.)  They could have good figures or not, I really don't know.  Criterion marketing materials may have made that 1/10th wave claim in their ads for some of their scopes, but I also think that it's very clear in retrospect that the RV line were not generally 1/10 wave, and I defer to experts, including you, to determine their actual condition.

 

OTOH, addressing your concern about my particular RV-6 lunar images "Very nice moon shots but again these are low power images...",  I'm just showing what they look like, not making any claims that the mirrors are perfect parabolas (or even spheres).  Since you seem concerned about "low power" you might be interested in looking at this HIGH MAGNIFICATION VIDEO FROM MY CRITERION RV-8 OF THE MOON THAT I SHOT yon many years ago.  https://youtu.be/FUr7CPgS0z8

 

This is a thumbnail image of that video (i.e. it's not a clickable link image, see link above), which I believe I shot before 2012, but uploaded there in 2012.

MoonThumb.JPG  

 

Keep in mind if you do watch it that it was shot in 720 in a BestBuy Insignia camera (with no magnification in the camera itself) that I bought on closeout for $20, so watching it on a 4K monitor I'd recommend keeping it in YouTube's default play size to keep it closer to 1:1 (to prevent artificial over-scaling to 4K width to mess up the view.)  Please note the crater terracing in the clear 'seeing' moments.  You wanted high magnification, here it is.  I'm not saying this is diffraction limited, I'm not saying this is 1/10th-1/4th or anything about the mirror figure, I'm just showing how it performs AS-IS.  I guess the quality may not be good to some people, but I'm OK with the apparent sub-arc second resolution (in the planet images features obviously smaller than the jovian moon and the Cassini division), even if it might not be getting all the way to the 0.57 arc second theoretical limit of an 8" (and ignoring atmospheric turbulence/diffraction being a wrench in the works of getting there); I'm somewhat disinclined to check the mirror figure(s) soon (but maybe someday when it's re-coated?)

 

Jason H.       

 

 

 Very nice moon shots but again these are low power images so not at  a magnification to be diffraction limited. That is just math behind the  imaging so they are not a critical test of optical quality. 

   Look at the wonderful images Schmidt camera produce but these are low power wide angle views. The optical error only have to be smaller then the grains on film or the pixel size not to be visible. So these optics are not operating at diffraction limits. It is same with many day modern day optics. Binoculars are  another typical example. The objectives are usually F/3 achromats so they have  about 1/2 wave  or worse of chromatic aberration but since they have fixed low power magnification the chromatic aberration isn't magnified enough to become objectionable.

 

                 - Dave  


Edited by Jason H., 21 February 2021 - 03:39 PM.

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#46 CHASLX200

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Posted 21 February 2021 - 03:25 PM

David, I like people fixing their mirror figures, especially when they have concerns about them.  I haven't made any claims about my telescopes being "diffraction limited" or even being 1/4 wave (let alone 1/10th or higher.)  They could have good figures or not, I really don't know.  Criterion marketing materials may have made that 1/10th wave claim in their ads for some of their scopes, but I also think that it's very clear in retrospect that the RV line were not generally 1/10 wave, and I defer to experts, including you, to determine their actual condition.

 

OTOH, addressing your concern about my particular RV-6 lunar images "Very nice moon shots but again these are low power images...",  I'm just showing what they look like, not making any claims that the mirrors are perfect parabolas (or even spheres).  Since you seem concerned about "low power" you might be interested in looking at this HIGH MAGNIFICATION VIDEO FROM MY CRITERION RV-8 OF THE MOON THAT I SHOT yon many years ago.  https://youtu.be/FUr7CPgS0z8

 

This is a thumbnail image of that video (i.e. it's not a clickable link image, see link above), which I believe I shot before 2012, but uploaded there in 2012.

attachicon.gifMoonThumb.JPG

 

Keep in mind if you do watch it that it was shot in 720 in a BestBuy Insignia camera (with no magnification in the camera itself) that I bought on closeout for $20, so watching it on a 4K monitor I'd recommend keeping it in YouTube's default play size to keep it closer to 1:1 (to prevent artificial over-scaling to 4K width to mess up the view.)  Please note the crater terracing in the clear 'seeing' moments.  You wanted high magnification, here it is.  I'm not saying this is diffraction limited, I'm not saying this is 1/10th-1/4th or anything about the mirror figure, I'm just showing how it performs AS-IS.  It may suck to somebody, but I'm OK with it, so I'm not inclined to check the mirror figure soon (but maybe someday when it's re-coated.)

 

Jason H.       

I say the mirror is more than good and if i could i would prove it by having it tested if it was still mine.


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#47 starman876

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Posted 21 February 2021 - 08:53 PM

David, I like people fixing their mirror figures, especially when they have concerns about them.  I haven't made any claims about my telescopes being "diffraction limited" or even being 1/4 wave (let alone 1/10th or higher.)  They could have good figures or not, I really don't know.  Criterion marketing materials may have made that 1/10th wave claim in their ads for some of their scopes, but I also think that it's very clear in retrospect that the RV line were not generally 1/10 wave, and I defer to experts, including you, to determine their actual condition.

 

OTOH, addressing your concern about my particular RV-6 lunar images "Very nice moon shots but again these are low power images...",  I'm just showing what they look like, not making any claims that the mirrors are perfect parabolas (or even spheres).  Since you seem concerned about "low power" you might be interested in looking at this HIGH MAGNIFICATION VIDEO FROM MY CRITERION RV-8 OF THE MOON THAT I SHOT yon many years ago.  https://youtu.be/FUr7CPgS0z8

 

This is a thumbnail image of that video (i.e. it's not a clickable link image, see link above), which I believe I shot before 2012, but uploaded there in 2012.

attachicon.gifMoonThumb.JPG

 

Keep in mind if you do watch it that it was shot in 720 in a BestBuy Insignia camera (with no magnification in the camera itself) that I bought on closeout for $20, so watching it on a 4K monitor I'd recommend keeping it in YouTube's default play size to keep it closer to 1:1 (to prevent artificial over-scaling to 4K width to mess up the view.)  Please note the crater terracing in the clear 'seeing' moments.  You wanted high magnification, here it is.  I'm not saying this is diffraction limited, I'm not saying this is 1/10th-1/4th or anything about the mirror figure, I'm just showing how it performs AS-IS.  I guess the quality may not be good to some people, but I'm OK with the apparent sub-arc second resolution (in the planet images features obviously smaller than the jovian moon and the Cassini division), even if it might not be getting all the way to the 0.57 arc second theoretical limit of an 8" (and ignoring atmospheric turbulence/diffraction being a wrench in the works of getting there); I'm somewhat disinclined to check the mirror figure(s) soon (but maybe someday when it's re-coated?)

 

Jason H.       

That is what the image lookes like through one of my 60mm looks like .  The moon is such a large scale and so bright that just about any scope will show a lot of detail.  Come on now, have any of you ever seen a bad view through your scope of the moon???



#48 Jason H.

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Posted 22 February 2021 - 01:17 PM

That is what the image lookes like through one of my 60mm looks like .  The moon is such a large scale and so bright that just about any scope will show a lot of detail.  Come on now, have any of you ever seen a bad view through your scope of the moon???

Do show us.  Post a link to a video of the Moon with your 60 mm that is the same scale and resolution as mine.  Or post an image of the Moon, Jupiter or Saturn with your 60 millimeter that are the same or better than any of the above I've posted, or any of the following of MY BEST EVER CRITERION RV-8 PLANET IMAGES with point-n-shoot cameras (which I also posted in Solar System imaging forum here on CN years ago when I did them.)  The Moon images are not stacks, but single frames, I left them noisy and didn't do noise removal on purpose to preserve details.     

 

MVI_0147redover.jpg  SaturnApril17CanonA590.png

 

MOONIMG_0668TWO.JPG

 

MOONIMG_0755POUND.jpg


Edited by Jason H., 22 February 2021 - 01:32 PM.


#49 CHASLX200

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Posted 22 February 2021 - 01:22 PM

The last C8 i had made in 2004 was bad on any object moon inlcuded. Total mush and no collimating would take away the mush.  There are plenty of scopes with bad images as i have had a few.  I would bet anyone that RV8 i had would test out well.



#50 starman876

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Posted 22 February 2021 - 02:54 PM

Do show us.  Post a link to a video of the Moon with your 60 mm that is the same scale and resolution as mine.  Or post an image of the Moon, Jupiter or Saturn with your 60 millimeter that are the same or better than any of the above I've posted, or any of the following of MY BEST EVER CRITERION RV-8 PLANET IMAGES with point-n-shoot cameras (which I also posted in Solar System imaging forum here on CN years ago when I did them.)  The Moon images are not stacks, but single frames, I left them noisy and didn't do noise removal on purpose to preserve details.     

 

attachicon.gifMVI_0147redover.jpg attachicon.gifSaturnApril17CanonA590.png

 

attachicon.gifMOONIMG_0668TWO.JPG

 

attachicon.gifMOONIMG_0755POUND.jpg

I did say the moon and nothing else. Has been a long time since I took any pictures through a 60mm.  However, I do remember seeing images like that.   




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