SVX127D tests superbly

[jetstream]

Over on the other forum another SVX127D tested very well, the first one excellent the second one unbelievably good! Not sure why I'm starting this thread really- I'm puzzled by the lack of attention and reaction to these tests actually- I know I'm pretty excited though! To see any doublet of any brand test this well is a testament to the makers ability, triplet level correction in a doublet lens- and at near 130mm aperture... not that easy.

If anyone has one of these and gets it under great seeing, please post the results. I feel the SVX127D would at least equal my TSA120 and keep up to my sometimes extreme temp swings at certain times of the year.  The fit and finish of the new SVX line is said to be fantastic.

I know this- I want one of these telescopes....

Any banter on anything related to the DPAC testing, SV scopes or others welcome.

Gerry

[jetstream]

Hmmm... no response to a scope testing at the top of the heap. It must be an internet thing or something that feeds momentum in certain preferred directions.

From my thinking this 127D might be a big hit for people, maybe one of their best sellers.If it works out down the road I'll buy one and compare to my Tak 120. With regards to sample to sample optical test result variations a buddy in the business told me an optic is worked until it meets a minimum spec or worked to the highest spec possible and then stopping when the numbers start to go backwards a tiny bit.

It is therefore normal for this variation.

IMHO any refractor that tests over .90 Strehl in all colours and is nicely smooth will provide fantastic views. In reality any refractor that goes over .80 Strehl, is reasonably smooth and with good colour correction will give good views. I feel my SW120ED falls in between these 2 boundaries and the views are now very good.

From the reports I believe the TSA120 tests typically in the mid 90's Strehl, is very smooth and has a balanced colour correction. It is amazing that the SVX127D has some tests in the same league and maybe better in some.

I love comparing test results for refractors and have done so for years- amazing that some well known, preferred scope brands give great views can have a spec or two "off" a bit by todays sky high standards.

Gerry

 

[Captain Scarlet]

Well of course I have a 3-month-old SVX140T, which whoever has read my most recent obs report, performs to my eyes as a _superb_ scope. Its star tests also seem to match exactly Suiter’s “perfect” columns. I can also attest to its manufacturing quality, the fit and finish are flawless, and the native focuser is just like the several Diamond Steeltracks that I have on other scopes. I would have chosen an FT had it been available, but I wouldn’t be confident of ever getting one.

Being as I am, far from any testing facilities and not prepared to risk taking it to the UK across a customs border, I’m unlikely to be able to have it tested any time soon.

Cheers, Magnus

[Highburymark]

We don’t get these scopes in the UK Gerry unfortunately. Or at least I’m not aware of an official dealer. Shame because this would be a real contender for anyone wanting to upgrade from a 4”. Would be interested to hear your impressions if you press the green button, though whether you’d see any benefits over the TSA is another matter. I’d also like to know how manoeuvrable/mountable it is.

[Captain Scarlet]

Gerry @jetstream already has a great (SV) 90mm, and of course the TSA120. No, he needs to fill the gaping void between his TSA120 and the 15”. Namely an SVX152T 😈 

Edited May 19, 2023 by Captain Scarlet

[Jim L]

 

Gerry, I’ve got the SVX102D, the smaller brother of the SVX127D.  The optics, fit and finish, and mechanics are all extraordinary. It is in every way the equal of my Taks and my Astro Physics 92 Stowaway, and is in some ways their superior. I would expect no less from the SVX127D, and with 55% more light gathering objective area views through it should be brilliant.

StellarVue doesn’t sell through dealers, and when you purchase one of their scopes you will be working with one of their people. No middleman , no dealer markup, always a StellarVue employee. Whomever you work with at StellarVue, and it can easily be the owner, Vic Maris, customer service is exemplary.

If you can swing it, order your SVX127D with the Feather Touch focuser.  It’s a bit more, but the focuser is a work of art and should you ever need it serviced the people at Starlight Instruments will take excellent care of you.

All in all, I can see nothing but years and years joy coming from owning this instrument. It’s not inexpensive, but one look through it and I doubt you’ll think of the cost again unless it’s to reflect on what a terrific bargain it is.  That’s how I feel about my own StellarVue scope.  Good luck!

 

[jetstream]

18 hours ago, Highburymark said:

though whether you’d see any benefits over the TSA is another matter

I agree- best case scenario would be no difference to my TSA120- the Tak is a superb telescope. I am curious about the SVX127D's performance in comparison to the Tak..

I just have a weakness for good glass lol

[jetstream]

16 hours ago, Jim L said:

 The optics, fit and finish, and mechanics are all extraordinary. It is in every way the equal of my Taks and my Astro Physics 92 Stowaway, and is in some ways their superior. I would expect no less from the SVX127D, and with 55% more light gathering objective area views through it should be brilliant.

Excellent and congratulations for owning a fine telescope Jim. I think in the end the optical quality of the SV refractors will have some critics not saying much.... All the testing is a good thing IMHO- the price we are paying for these telescopes should mean we all get what we are paying for.

My hats off to SV for weathering the storm.

The old SVR90CF still puts up a great view after years of harsh dark site trips and was the first to show me IC434 when I was burrowed up on a logging road north of here in -30c.  I would try the SVX150 but if its a wide spaced air triplet keeping up to my temp drops here will be an issue, even the TSA120 will struggle at times.

How much mag will your SVX102 take on the moon and not breakdown? My 90mm SV supports 262x easily with a Vixen 2.4HR and more with the VIP barlow.

Gerry

[jetstream]

17 hours ago, Captain Scarlet said:

Gerry @jetstream already has a great (SV) 90mm, and of course the TSA120. No, he needs to fill the gaping void between his TSA120 and the 15”. Namely an SVX152T 😈 

I would love one Magnus...

[badhex]

Would be great if Stellarvue were more easily available in the UK, I can't say I've heard much bad said about them. Would love to look through the SVX127D! 

[Jim L]

7 hours ago, jetstream said:

…..

How much mag will your SVX102 take on the moon and not breakdown? My 90mm SV supports 262x easily with a Vixen 2.4HR and more with the VIP barlow.

Gerry

Great question, Gerry, and I’m afraid I don’t know.  My shortest eyepiece is a 3.5mm Nagler which provides a magnification of 204X with an exit pupil of 0.5mm. The scope is capable of much much more, but I’m not and so I haven’t explored its limits.

A smaller than 0.5mm exit pupil means I’m learning more about the junk floating around within my eyeballs than the surface of the moon, but you’ve now got me curious and the next time the notoriously abysmal seeing in my area improves beyond the typical Pickering 3 or 4 to at least 5 or 6, I’ll throw on a Barlow and see what happens.

I can say that the SVX102D resolves stars in M13 and shows detail in the disk of Andromeda even in mediocre seeing, but that’s probably not unusual for a 4” scope. I can also say that I don’t see any reportable distinction between the views through my StellarVue doublet or my Astro Physics 92 Stowaway triplet; they’re both excellent scopes and easily better than my skies, eyes, or skill as an observer. My apologies, Gerry, I wish I could be more helpful.

[jetstream]

14 hours ago, Jim L said:

I wish I could be more helpful.

This is great info Jim- a 4" class refractor punches through challenging seeing better than any other scope IMHO. I'm fortunate to observe under Pickering 8-9 frequently and 7 most of the time. Im up here in NW Ontario.

I can observe at low exit pupils but my sweet spot is around .8mm exit pupil, which my 15" provides at a very useable 300x mag.

Eagerly waiting observing reports Jim!

Gerry

[900SL]

On 18/05/2023 at 18:32, jetstream said:

Over on the other forum another SVX127D tested very well, the first one excellent the second one unbelievably good! Not sure why I'm starting this thread really- I'm puzzled by the lack of attention and reaction to these tests actually- I know I'm pretty excited though! To see any doublet of any brand test this well is a testament to the makers ability, triplet level correction in a doublet lens- and at near 130mm aperture... not that easy.

If anyone has one of these and gets it under great seeing, please post the results. I feel the SVX127D would at least equal my TSA120 and keep up to my sometimes extreme temp swings at certain times of the year.  The fit and finish of the new SVX line is said to be fantastic.

I know this- I want one of these telescopes....

Any banter on anything related to the DPAC testing, SV scopes or others welcome.

Gerry

My issue with the rash of DPAC testing 'over there' is that the tests are single examples and appear to be carried out by amateurs in the main, who typically are not qualified and are 'dabblers' or 'smatterers'

Then there's the clear bias shown by a number of contributors against SV. I don't own an SV, I have no bias either way, but seriously, some of those pompous blowhards are beyond belief.  There's like a busload of them bowl into most every thread waving their pitchforks. The site seems to tolerate them, maybe because it's sponsored by a competitor. 

 

[Maciek_Cz]

52 minutes ago, 900SL said:

My issue with the rash of DPAC testing 'over there' is that the tests are single examples and appear to be carried out by amateurs in the main, who typically are not qualified and are 'dabblers' or 'smatterers'

Then there's the clear bias shown by a number of contributors against SV. I don't own an SV, I have no bias either way, but seriously, some of those pompous blowhards are beyond belief.  There's like a busload of them bowl into most every thread waving their pitchforks. The site seems to tolerate them, maybe because it's sponsored by a competitor. 

 

I think your assessment is very unfair. Many of the ATM specialists have experience in the field of optics and quality analysis with the help of interferometry, the Foucault/Ronchi test and others comparable or maybe even the same as SV employees.

The "DPAC" is such a simple test that you don't really need any knowledge to perform it correctly. It seems to me that it is the opposite of what you wrote, that people who complain about these tests have no clue how they are carried out and how they work.

[900SL]

2 hours ago, Maciek_Cz said:

I think your assessment is very unfair. Many of the ATM specialists have experience in the field of optics and quality analysis with the help of interferometry, the Foucault/Ronchi test and others comparable or maybe even the same as SV employees.

The "DPAC" is such a simple test that you don't really need any knowledge to perform it correctly. It seems to me that it is the opposite of what you wrote, that people who complain about these tests have no clue how they are carried out and how they work.

You could be 100% correct, as I am myself a novice.  However I still find them a truckload of insufferables. 

 

[Jim L]

Maciek and 900SL, I believe you are both correct in that the optical tests are reliable and valuable, and that there is an overtly anti-SV cohort which aggressively seeks to poison every discussion involving StellarVue.
 

As to the former, testing improves the breed for all of us and should be encouraged. Many telescopes of various makers have undergone testing, some revealing themselves to be better than expected and others, including some of the most revered makes, coming up short. Not all Televue, Astro Physics, and APM scopes test well either, and the test results are there for anyone who’s interested. What’s important are the actions the maker takes to protect their customers and to improve the quality of their scopes.
 

Concerning the anti-SV group, it’s difficult to understand the motivations of a group that seeks to harm one of the very few telescope makers left in the free world and that makes available excellent telescopes in the quantities that have a tangible positive impact on amateur astronomy. It’s a tough nut to crack. After some thought the only reason that makes sense for me is that they harbor a misguided fear that ascension of StellarVue as a premier telescope maker threatens the status of their own favored brand. Status worship and insecurity is at the root of many social ills, some trivial and some very dangerous, and while I’m surprised to see it applied to telescopes I probably shouldn’t be. I’m grateful for all of my StellarVue, Astro Physics, and TeleVue gear, and I see no need for or value in elevating one brand over another.

[Maciek_Cz]

Hi Jim,

I won't say anything about anti-SV group because I don't know anything about it. However, I can comment on the tested few SV telescopes.
As for the model in the title of this thread, I analyzed both DPAC tests with the AOS program of my authorship.
It is precisely about estimating the correction of spherical aberration.
The recently tested copy is indeed perfect, this is beyond dispute. However, the one tested earlier is simply good.
I wonder what the differences are. And indeed the only thing that comes to my mind is the lack of quality control for wavelengths other than the one used in the ZYGO interferometer used by SV.
We have two telescopes, the same models, from the same manufacturer with very similar certificates provided by the manufacturer.
However, the DPAC tests show that they differ significantly, one has an SA correction of 1/10 lambda or better over a wide range of the light spectrum,
the other has such a good correction only for red light, green is at the level of 1/6-1 /7 lambda, and blue 1/4 lambda.
Clearly, the manufacturer may not have had any idea about the situation for green and blue. With the help of control on ZYGO,
he minimized astigmatism, coma, zones and edge. However, spherochromatism cannot be predicted by testing only one of the wavelengths.
There is a risk that not all of these telescopes are as finely corrected as the last one studied.
However, there is nothing to complain about, this earlier copy is good. It all depends on what the buyer expects.
I suspect most amateur astronomers wouldn't be able to tell the difference between the two telescopes when observing the sky.

[jetstream]

23 minutes ago, Maciek_Cz said:

the other has such a good correction only for red light, green is at the level of 1/6-1 /7 lambda, and blue 1/4 lambda.

These are still vg numbers, not as good as the other sample but vg IMHO. I have no bias just a weakness for good optics. Out of curiosity regarding the TEC 160ED tested Mar16/2019 what would your program assign for numbers? Would it be similar to the first, lesser spec SV or better?

One thing that interests me is the possibility of distortion in the camera taking the pictures of the fringes, for any test not just the ones of the mentioned scopes.

Heres the blue outside focus for the mentioned TEC 160ED.

 

[Maciek_Cz]

18 minutes ago, jetstream said:

These are still vg numbers, not as good as the other sample but vg IMHO. I have no bias just a weakness for good optics. Out of curiosity regarding the TEC 160ED tested Mar16/2019 what would your program assign for numbers? Would it be similar to the first, lesser spec SV or better?

One thing that interests me is the possibility of distortion in the camera taking the pictures of the fringes, for any test not just the ones of the mentioned scopes.

Heres the blue outside focus for the mentioned TEC 160ED.

 

 

Ok, I can do the analysis. Just give me the parameters of the Ronchi screen (lines per mm) and the focal length of the lens.

[kasprowy]

I lurk around mostly elsewhere, but also here now and then (haven't posted much here, if at all). The SV127 is the scope I would like to purchase in the coming years. There is a nice review of it in the March 2023 issue of Sky & Telescope, and 127mm is still a manageable size. For myself, scopes are inversely proportional to age. When you can move them, you can't afford them, and when you can afford them, you can't move them. 

If you look hard enough at anything, you WILL find something to be worried about. Amateur astronomy is definitely not for the perfectionist. 

Cheers, from Chicago

Edited May 23, 2023 by kasprowy

[Maciek_Cz]

@jetstream ready:-)

This photo was taken by Jeff. Its grid is 5,236 lines per mm. The lens is f/7. Below is the result.

[Maciek_Cz]

I will only add that this analysis takes into account only spherical aberration.
Please tell me if the focal ratio is correct because I found information about the TEC 160 f/7 but also f/8.
The given focal length significantly influences the result. If it's f/8 then we're dealing with an even better result around ~0.89.

[Sunshine]

I wouldn't hesitate on a SVX127, I have read nothing but stellar reports as I was seriously interested a couple of years ago until I got a ridiculous shipping quote, I was ready to pull the trigger. No doubt the 127D would replace the TSA120 and cool faster, and those 7mm extra aperture won't be a big deal but it won't hurt. As for the tests, don't become the guy who spends more time testing and looking at out of focus stars than in focus ones. 🤣

[jetstream]

1 hour ago, Maciek_Cz said:

I will only add that this analysis takes into account only spherical aberration.
Please tell me if the focal ratio is correct because I found information about the TEC 160 f/7 but also f/8.
The given focal length significantly influences the result. If it's f/8 then we're dealing with an even better result around ~0.89.

Excellent.

Looking at the bands I was guessing .80ish strehl but I basically know nothing about all this. I hope to test in the future and want all my ducks in a row. The camera lens distortion deal vs distance to focal plane needs to be sorted out in my mind first so I dont add or subtract error in the images.

So I guess we can say this TEC 160 "only"  has .80ish strehl in blue- not too good really as was insinuated for the SV127D at the same level.

2 hours ago, Maciek_Cz said:

Clearly, the manufacturer may not have had any idea about the situation for green and blue

This ^^ in reference to SV- I wonder if this idea applies to this particular TEC160?

[Jim L]

9 hours ago, Maciek_Cz said:

Hi Jim,

I won't say anything about anti-SV group because I don't know anything about it. However, I can comment on the tested few SV telescopes.
As for the model in the title of this thread, I analyzed both DPAC tests with the AOS program of my authorship.
It is precisely about estimating the correction of spherical aberration.
The recently tested copy is indeed perfect, this is beyond dispute. However, the one tested earlier is simply good.
I wonder what the differences are. And indeed the only thing that comes to my mind is the lack of quality control for wavelengths other than the one used in the ZYGO interferometer used by SV.
We have two telescopes, the same models, from the same manufacturer with very similar certificates provided by the manufacturer.
However, the DPAC tests show that they differ significantly, one has an SA correction of 1/10 lambda or better over a wide range of the light spectrum,
the other has such a good correction only for red light, green is at the level of 1/6-1 /7 lambda, and blue 1/4 lambda.
Clearly, the manufacturer may not have had any idea about the situation for green and blue. With the help of control on ZYGO,
he minimized astigmatism, coma, zones and edge. However, spherochromatism cannot be predicted by testing only one of the wavelengths.
There is a risk that not all of these telescopes are as finely corrected as the last one studied.
However, there is nothing to complain about, this earlier copy is good. It all depends on what the buyer expects.
I suspect most amateur astronomers wouldn't be able to tell the difference between the two telescopes when observing the sky.

Hi Maciek,

I’m by no measure an optical expert, but given that StellarVue uses their Zygo interferometer primarily as a tool to produce consistently repeatable results while figuring a multitude of optical elements, I’d expect that them meeting their internal standards would be the the norm, rather than the exception.

So why the difference between the two scopes you’ve mentioned? We can expect small differences between scopes due to manufacturing tolerances, but significant differences may have other causes. I place a high value on testing, but variability in testing methodology can have a profound impact on the results, and especially so when testing for minusculey small differences. I’ve tested a variety of materials under ASTM (American Society for Testing and Materials) standards and by far the most important part of reliable testing is controlling variables. There are no sensitive tests insensitive to external variables and it’s the job of the tester to understand those variables and to minimize them to the degree possible.

Here’s two examples of obvious variables: StellarVue tests their optical elements oriented vertically to more closely mimic how we normally use our scopes. Most other testers orient their test subjects horizontally, because it’s usually more convenient. Next, after they’ve been worked, StellarVue let’s their optical elements reach ambient temperature overnight in a carefully temperature controlled room before testing. How were the two scopes mentioned tested by their respective testers? We don’t know, but unless their methodologies were identical, and identical to StellarVue’s, I would not expect three identical results. I recall a photograph of one optical test showing a large computer beneath the test bench. It’s probable the heat rising from the computer didn’t do the test results any favors, and that same scope tested in a cool basement or garage might appear to be a different instrument entirely.

We think of optical glass as dimensionally stable, but anyone who’s watched the view through their large reflector change in realtime as the mirror cooled could be convinced otherwise. Even with my own modest refractors I can easily discern the optical difference between a scope I just took outside and that same scope after its cooled for half an hour. Most of us viewing in average seeing can’t tell the difference between a diffraction limited scope and a sensibly perfect one if the image is in focus. Perhaps the significantly smaller test result differences between some scopes can be at least partially attributed to variables related to methodology?

Edited May 24, 2023 by Jim L
Clarity