686 replies to this topic

[Rasfahan]

Thank you so much for doing this test. It shows exactly what I expected. I would still judge it very good value for money, just not the game changer some hoped for. Its price is comparable to achromats of this size and it should beat them handily. It’s probably more suited to long-exposure imaging in average seeing conditions or DSO visual than any kind of planetary or high-resolution work, though.

Edited by Rasfahan, 30 January 2024 - 09:22 PM.

[Joe G]

Well, this is a big refractor.  So I will say I was a little disappointed in the Ronchis.  But there are compromises.

 

Here is a grid that compares the Askar 185 F7 to:  TMB/LZOS 175 F8 (from Jeff B), CFF 185 F6.8 (Jeff B), and the TMB 180 F6 Achro (Scott in NC).

 

These images came from the DPAC repository.

 

Clearly with the white light images the TMB 180 F6 achro seems to show the most color.

 

In green the CFF wins, might be a slight edge issue.  The TMB achro looks good.  The TMB 175 is okay,maybe an edge issue.  The Askar has some curve to it.

 

In red, CFF seems the best.  The Askar looks okay.  Maybe an edge issue for the TMB 175.  The TMB achro is by far the worst.

 

Blue in all scopes is off, likely by design.

 

What is visible at the eyepiece?  I will wait to judge it in better seeing.  But it is important to note TMB/LZOS, CFF have very solid reputations.  And they cost a whole lot more for a 180mm =/- refractor.

 

Maybe the Askar isn't so bad.  No scope is perfect.

 

So the Askar is far from perfect.  It is hard to get perfect at the aperture. 

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[Cbaxter]

Well, this is a big refractor. So I will say I was a little disappointed in the Ronchis. But there are compromises.

Here is a grid that compares the Askar 185 F7 to: TMB/LZOS 175 F8 (from Jeff B), CFF 185 F6.8 (Jeff B), and the TMB 180 F6 Achro (Scott in NC).

These images came from the DPAC repository.

Clearly with the white light images the TMB 180 F6 achro seems to show the most color.

In green the CFF wins, might be a slight edge issue. The TMB achro looks good. The TMB 175 is okay,maybe an edge issue. The Askar has some curve to it.

In red, CFF seems the best. The Askar looks okay. Maybe an edge issue for the TMB 175. The TMB achro is by far the worst.

Blue in all scopes is off, likely by design.

What is visible at the eyepiece? I will wait to judge it in better seeing. But it is important to note TMB/LZOS, CFF have very solid reputations. And they cost a whole lot more for a 180mm =/- refractor.

Maybe the Askar isn't so bad. No scope is perfect.

So the Askar is far from perfect. It is hard to get perfect at the aperture.

Looking at those side-by-side the Askar 185 doesn't look as bad.

[Joe G]

Yep, I gave it some thought and went to the DPAC repository and compared the Askar to some of the larger aperture scopes.  Left off a few.  I think Jeff B had a non-ED AP scope that seemed worse.

 

I think if the green lines in the Askar were just a little straighter it would not be as much of a deal.  But it seems there must be some kind of a hill or something in the middle of the lens.  I can't read these things.  Hopefully the DPAC experts will chime in.

 

But I wonder what that TMB achro cost new?  My guess is more than the Askar at the time not adjusting for inflation.

[Joe G]

The DPAC tests of this Askar scope led me to re-read the thread on the Stellar Vue SVX-180T which was figured in red.  Such a long discussion.  But what strikes me the most is the statement by Rick Runcie, the owner of the scope.  When you read what he says it sounds like it is a somewhat amazing scope with some flaws.  No scopes are perfect.

 

He saw some flaws.  But he also says it put up some incredible views.  I am not going to debate his opinion or opine about the merits of that scope.  Likely if you paid four times the price of the Askar 185 you want perfection. 

 

I didn't expect perfection at one quarter the price.  I hoped the scope would provide "refractor" like views of stuff.  Meaning good on Jupiter, Saturn and the Moon.  And because of the larger aperture, nice refractor-like views of open star clusters, globs, etc.

 

My first report last night was with "good" but not "great" seeing.  Likely it was "great" by most of the country on average nights.  The views were nice.  I was more concerned that this scope, with the lesser non-disclosed glass, would have a lot of purple fringing.  But it seemed closer to an APO than a achromat.

 

It did seem to offer a deeper view of nebulosity and faint stars.  Aperture does matter.

 

Time will tell.  I need to see how it performs in great seeing.  My guess is it will be fine.

 

But it is a large refractor.  These are very expensive.  This breaks a lot of price points in a part of the telescope market that does not have a lot of competition.

 

For sure, I have owned 8" reflectors.  They give a good bang for the buck.  I have a couple of really nice Dobs with premium mirrors.  Under good conditions they perform wonderfully.

 

But this is about large refractors at a reasonable price.

 

Hope to get a night on the moon with stable seeing.

 

This scope isn't cheap.  It is made well.  But it isn't $18,000 plus dollars. 

 

Here is Rick's description of his SV 180.  Siouxsie loves her Stellar Vue 180.  Not sure how the 180s, post the "thread," would DPAC.  Likely we will never know.

 

https://www.cloudyni...0#entry12564112

 

 

[fate187]

Well, this is a big refractor.  So I will say I was a little disappointed in the Ronchis.  But there are compromises.

 

Here is a grid that compares the Askar 185 F7 to:  TMB/LZOS 175 F8 (from Jeff B), CFF 185 F6.8 (Jeff B), and the TMB 180 F6 Achro (Scott in NC).

 

These images came from the DPAC repository.

 

Clearly with the white light images the TMB 180 F6 achro seems to show the most color.

 

In green the CFF wins, might be a slight edge issue.  The TMB achro looks good.  The TMB 175 is okay,maybe an edge issue.  The Askar has some curve to it.

 

In red, CFF seems the best.  The Askar looks okay.  Maybe an edge issue for the TMB 175.  The TMB achro is by far the worst.

 

Blue in all scopes is off, likely by design.

 

What is visible at the eyepiece?  I will wait to judge it in better seeing.  But it is important to note TMB/LZOS, CFF have very solid reputations.  And they cost a whole lot more for a 180mm =/- refractor.

 

Maybe the Askar isn't so bad.  No scope is perfect.

 

So the Askar is far from perfect.  It is hard to get perfect at the aperture. 

Joe, thank you for the extensive comparison. An important question Joe to better compare these pictures: Whats the line density of the ronchi grating used? A large LPI will show errors of optics quite more easily (e.g. stronger line bending) compared to lets say 66lpi. Nowadays I try to use 133lpi (forum standard ) for in- and outside of focus, while 66lpi is good for "null" analysis at focus. It gives you a nice and sharp picture without interference from adjacent line pairs.

 

Additionally, I would like chime in on you very nice comparison! I also owned an CFF185 f6.8 tuned for AP during the time of manufacture. The results posted by Jeff B are similar to mine back then:

https://www.cloudyni...ent/?p=10625552 . Test was done with 200lpi grating, so a severe test for any lens.

 

Seeing your DPAC results I would assume, that this 185 will still make a nice telescope for visual, and with a flattener or reducer will produce good results in AP, we have seen sample images already. Visually, especially Mars should look nice. The spherochromatism (bending of lines) could be difficult for Jupiter (contrast/sharpness lowered) and should be visible in a star test when properly performed. You will probably also notice the center dip in- or outside of focus. 

On the positive side this scope has a nice edge and the surface (or wavefront) in general looks quite smooth, which is important for contrast.

[Joe G]

I used a glass etched 100 LPI screen.  I have other plastic screens that go to 133 LPI but are not as clear.  I can't remember where I got the glass etched screen though.

[Joe G]

Joe, thank you for the extensive comparison. An important question Joe to better compare these pictures: Whats the line density of the ronchi grating used? A large LPI will show errors of optics quite more easily (e.g. stronger line bending) compared to lets say 66lpi. Nowadays I try to use 133lpi (forum standard ) for in- and outside of focus, while 66lpi is good for "null" analysis at focus. It gives you a nice and sharp picture without interference from adjacent line pairs.

 

Additionally, I would like chime in on you very nice comparison! I also owned an CFF185 f6.8 tuned for AP during the time of manufacture. The results posted by Jeff B are similar to mine back then:

https://www.cloudyni...ent/?p=10625552 . Test was done with 200lpi grating, so a severe test for any lens.

 

Seeing your DPAC results I would assume, that this 185 will still make a nice telescope for visual, and with a flattener or reducer will produce good results in AP, we have seen sample images already. Visually, especially Mars should look nice. The spherochromatism (bending of lines) could be difficult for Jupiter (contrast/sharpness lowered) and should be visible in a star test when properly performed. You will probably also notice the center dip in- or outside of focus. 

On the positive side this scope has a nice edge and the surface (or wavefront) in general looks quite smooth, which is important for contrast.

Michael, I looked at your DPAC images.  I just took Jeff's example because it was easier to bring into Photoshop.  Certainly great scopes. 

 

I don't have a problem with the price of premium scopes.  If you have the money and it means something, then great.  I bought a second-hand Mike Lockwood 16" by 1" thick quartz mirror and replaced it in my Dob.  Really awesome.  Personally I would not spend close to $20,000 (USD) on a 7" refractor. 

 

But Askar priced this thing at $4800.  Different story.

 

I love that the telescope/imaging market has seen so much new stuff over the last few years.  Kind of crazy!

[banatop]

Michael, I looked at your DPAC images.  I just took Jeff's example because it was easier to bring into Photoshop.  Certainly great scopes. 

 

I don't have a problem with the price of premium scopes.  If you have the money and it means something, then great.  I bought a second-hand Mike Lockwood 16" by 1" thick quartz mirror and replaced it in my Dob.  Really awesome.  Personally I would not spend close to $20,000 (USD) on a 7" refractor. 

 

But Askar priced this thing at $4800.  Different story.

 

I love that the telescope/imaging market has seen so much new stuff over the last few years.  Kind of crazy!

Hi Joe, Thanks for the interesting report. I also think that the Askar compares well with the other scopes in your dpac  diagram and, taking cost into account, is closer in quality than you'd expect.
  I have the Meade 178ed and I've used it for thousands of hours over the years. One thing to remember is that for a seven inch to perform really well the seeing needs to be MUCH better than average. My seeing is good and I can often use 180 - 220x which works well on the Planets with quite satisfying views. However for the hubble like views that we all crave, where powers of 50x plus per inch can be used, the seeing needs to be near perfect. This only happens a few times a year for me although there are great micro moments during most viewing sessions. As far as I'm concerned the secret ingredient is patience. The Askar is probably figured well enough to do everything you'd expect of a seven inch Apo refractor and the fact that it compares well to your Esprit 150 is very good news!! And although I understand the usefulness of the dpac test, the most important test of all is what you see at the eyepiece, which seems very good so far. 

Edited by banatop, 31 January 2024 - 03:01 AM.

[fate187]

I used a glass etched 100 LPI screen.  I have other plastic screens that go to 133 LPI but are not as clear.  I can't remember where I got the glass etched screen though.

I got mine years ago from Ronchiscreens.com website I think. They are nice and were cheap and I still use them to this day. They came in 66/133/200 lpi flavor  .

 

Considering you used 100lpi one has to remember, that the line bending and with the spherochromatism during DPAC would show more strongly with 133 or even 200lpi screens. Thus carefully take that into account.

 

As for the discussion for what you get for a price tag and comparison to "premium" manufacturerers: They certainly use different (more expensive glass), also polishing/surface finish to reduce spherochromatism is what drives the price. From communication with CFF I know, that the finishing touches are done by hand. Obviously with a rotating polishing machine. Its the process of trial and error to put the lens together and see for the final result. On one occasion one glass member was the culprit during the manufacture of one lens, but was only seen after multiple attempts to make a good lens. Suchs things happen and they have to be considered when giving the scopes a price tag.There is a margin on top to that.

 

If the chinese manufacturer found a cheaper approach with different material and faster processing routes they will quickly penetrate the market, granted the level of quality is what the buyers expects.

 

Ultimately, this pricing discussion is similar to the discussion of fracs vs mirrors. Why buy a 100mm frac when you can get 12" inces of mirror - just different arguments. Buy what you want and want to afford. And don't forget to properly mount it  .

 

Best,

Michael

[CHASLX200]

Yep, I gave it some thought and went to the DPAC repository and compared the Askar to some of the larger aperture scopes.  Left off a few.  I think Jeff B had a non-ED AP scope that seemed worse.

 

I think if the green lines in the Askar were just a little straighter it would not be as much of a deal.  But it seems there must be some kind of a hill or something in the middle of the lens.  I can't read these things.  Hopefully the DPAC experts will chime in.

 

But I wonder what that TMB achro cost new?  My guess is more than the Askar at the time not adjusting for inflation.

Not sure on new price for the TMB but now around 15k or more used for a APO and achro not sure.

Edited by CHASLX200, 31 January 2024 - 06:55 AM.

[Yu Gu]

I wonder if using a prism diagonal would help correct some of these spherical aberration, or would it make it worse? 

[CHASLX200]

The DPAC tests of this Askar scope led me to re-read the thread on the Stellar Vue SVX-180T which was figured in red.  Such a long discussion.  But what strikes me the most is the statement by Rick Runcie, the owner of the scope.  When you read what he says it sounds like it is a somewhat amazing scope with some flaws.  No scopes are perfect.

 

He saw some flaws.  But he also says it put up some incredible views.  I am not going to debate his opinion or opine about the merits of that scope.  Likely if you paid four times the price of the Askar 185 you want perfection. 

 

I didn't expect perfection at one quarter the price.  I hoped the scope would provide "refractor" like views of stuff.  Meaning good on Jupiter, Saturn and the Moon.  And because of the larger aperture, nice refractor-like views of open star clusters, globs, etc.

 

My first report last night was with "good" but not "great" seeing.  Likely it was "great" by most of the country on average nights.  The views were nice.  I was more concerned that this scope, with the lesser non-disclosed glass, would have a lot of purple fringing.  But it seemed closer to an APO than a achromat.

 

It did seem to offer a deeper view of nebulosity and faint stars.  Aperture does matter.

 

Time will tell.  I need to see how it performs in great seeing.  My guess is it will be fine.

 

But it is a large refractor.  These are very expensive.  This breaks a lot of price points in a part of the telescope market that does not have a lot of competition.

 

For sure, I have owned 8" reflectors.  They give a good bang for the buck.  I have a couple of really nice Dobs with premium mirrors.  Under good conditions they perform wonderfully.

 

But this is about large refractors at a reasonable price.

 

Hope to get a night on the moon with stable seeing.

 

This scope isn't cheap.  It is made well.  But it isn't $18,000 plus dollars. 

 

Here is Rick's description of his SV 180.  Siouxsie loves her Stellar Vue 180.  Not sure how the 180s, post the "thread," would DPAC.  Likely we will never know.

 

https://www.cloudyni...0#entry12564112

Love to side by side it with my freaky sharp 826.

[CHASLX200]

Hi Joe, Thanks for the interesting report. I also think that the Askar compares well with the other scopes in your dpac  diagram and, taking cost into account, is closer in quality than you'd expect.
  I have the Meade 178ed and I've used it for thousands of hours over the years. One thing to remember is that for a seven inch to perform really well the seeing needs to be MUCH better than average. My seeing is good and I can often use 180 - 220x which works well on the Planets with quite satisfying views. However for the hubble like views that we all crave, where powers of 50x plus per inch can be used, the seeing needs to be near perfect. This only happens a few times a year for me although there are great micro moments during most viewing sessions. As far as I'm concerned the secret ingredient is patience. The Askar is probably figured well enough to do everything you'd expect of a seven inch Apo refractor and the fact that it compares well to your Esprit 150 is very good news!! And although I understand the usefulness of the dpac test, the most important test of all is what you see at the eyepiece, which seems very good so far. 

Anyone ever DPAC  a Meade 7" ED?  Mine had a good lens after i got rid of it for a hour before it lost center after someone fooled around with it.  I sure wished it worked when i had it but it went back to Meade 3 times and was always the same when i got it.

[Astrojensen]

I wonder if using a prism diagonal would help correct some of these spherical aberration, or would it make it worse? 

If it's undercorrected, a prism can help. 

 

 

Clear skies!

Thomas, Denmark

[peleuba]

I am betting a poor attempt at aspherizing.  Yeah, I know, I'm only betting one dollar US.  But it sure does look similar to a good start to a figure on a mirror's parabolic surface and an initial Foucault...there may be something really cool going on here.  More than just a zone.  Or it is really bad, per your allusion to an infamous Leuba test. 

 

<<<perk>>>   Did someone ring?  Infamous?  I am flattered!

 

I will respectfully disagree - there is no aspherization of this lens.  There is absolutely no money in this build for an optician to aspherize this lens.   Hard to say exactly what happened with the hill in the center.   It looks like a valley in DPAC, but in real life its a hill.      

 

This lens looks very much like the SVX180 I tested 10 months ago and published here on CN.  If you recall, during in my comments on the SVX180, I mentioned that these ~180mm class lenses, all of similar design, were the rage in imaging circles in Asia in early 2023.  This scope has same type of correction, but when paired with the sub aperture corrector/reducer, the null is shifted to a more neutral position and becomes a nice imaging scope.   This is just a variation on that VERY same theme.

 

Anyway, this lens is nulled in red.   As with the SVX180, when you null a ~180mm air spaced ED triplet in red, green will be ~¼ wave out and blue about a ~½ wave out.  And, it becomes impossible for blue and red (spherochromatism) to balance one another.  To my eye, this lens looks to be worse then ¼ wave in green and worse then ½ wave in blue.   In red its about ⅙ wave.  An interferometer might give slightly better or slightly worse results.  But my estimates are in the ball park.

Edited by peleuba, 31 January 2024 - 11:10 AM.

[peleuba]

I took the liberty of taking Joe's excellent DPAC images of this Askar 185 and comparing them with the StellarVue SVX180 I tested in March of 2023.  

 

The bottom line is that the Askar 185 is quite similar to the SVX180.  Notice the very similar central zone and the spherical correction looks nearly identical.

 

Click on the image to see full size.

 

 

Green

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Edited by peleuba, 31 January 2024 - 10:46 AM.

[peleuba]

Red

 

No real difference in spherical correction.  The Askar looks worse because the central zone is worse then what is seen in the SVX180.  In red, the SVX180 is a high Strehl scope.

 

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Edited by peleuba, 31 January 2024 - 10:59 AM.

[peleuba]

Blue

 

Very similar correction.  Both scopes are way out in blue.

 

 

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Edited by peleuba, 31 January 2024 - 10:34 AM.

[peleuba]

White

 

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[peleuba]

So...   On the bench where the observer's brand bias is neutralized these scopes look remarkably similar with the Askar being slightly worse overall.  Color correction appears to be very close between the two.  This is not surprising as both are similar apertures, focal lengths and designs.  The main difference is the price.  The SVX180 is nearly $20k.   The Askar 185 is less then $5k. 

Edited by peleuba, 31 January 2024 - 10:46 AM.

[SandyHouTex]

Not sure on new price for the TMB but now around 15k or more used for a APO and achro not sure.

So I did some checking on prices and here's what I found:

 

TMB LZOS 175 - $12,000 USD (lens only).   http://scopeviews.co.uk/TMB175.htm

CFF 180 (the 185 is sold out) - $17, 650 USD.  https://www.cffteles...ctor-180-185-mm

TMB 180 (not available ) APM 180 - $17,000 USD.  https://www.astrosho...scopes/10/m,APM

TEC 180 - $19,000 USD.  https://www.telescop...e/apo180fl-f-7/

 

So anything this size looks to be around $17,500 USD.  I don't think you can beat an Askar 185 at $4,900.

Edited by SandyHouTex, 31 January 2024 - 11:52 AM.

[Astrowl]

Well there are few questions behind this DPAC results. First is to know the constant quality of the Askar 185. Can you get good and not as good models. Is this one a good or bad model ?

 

And after all will this defect deteriorate significantly the image (visual and photo) ?

 

As there are also several aperture with the same optical design and glasses (Askar 140, 120, ...),

Do this smaller scopes have similar issue or are they better because smaller apertures are better managed ? 

[bobhen]

So...   On the bench where the observer's brand bias is neutralized these scopes look remarkably similar with the Askar being slightly worse overall.  Color correction appears to be very close between the two.  This is not surprising as both are similar apertures, focal lengths and designs.  The main difference is the price.  The SVX180 is nearly $20k.   The Askar 185 is less then $5k. 

Agree with all of Paul's posts (41 to 46) and comments.

 

Also consider that the price of $4,799 includes a profit for the manufacturer and a profit for the retailer. That means that these telescopes are probably being produced for much less money than the retail price of $4,799 indicates.

 

The test similarities also allude to the origin of the SV lens.

 

Bob

[Joe G]

So...   On the bench where the observer's brand bias is neutralized these scopes look remarkably similar with the Askar being slightly worse overall.  Color correction appears to be very close between the two.  This is not surprising as both are similar apertures, focal lengths and designs.  The main difference is the price.  The SVX180 is nearly $20k.   The Askar 185 is less then $5k. 

Paul,

 

The first thing I thought about after running these tests was your test of the infamous SVX 180.  Amazing how close they look with the Askar looking worse.

 

But I remember Rick's description in that thread that I linked to above.  Fortunately the Askar is far less expensive because I doubt Askar is going to change how they test scopes as apparently Stellarvue did after your test results.

 

Given the Askar is not made with FPL53/55 or equivalent glass my expectations were such that it should not be as good as the much more expensive premium scopes.