686 replies to this topic

[BWAZ]

To be fair if it were my scope I'd be more than just happy, let alone at this price point.

 

Thanks OP for the DPAC test!

Edited by BWAZ, 31 January 2024 - 05:09 PM.

[Maciek_Cz]

Hello, very interesting research.
I will also post my analysis.
Overall, the results are close to the curve shown by Paul (Strehl as a function of wavelength).
In red Strehl oscillates between 0.89-0.93 (p-v ~1/5 or better),
for green it is about 0.5 (p-v ~ 0.4), and for blue 0.2-0.3 (p-v ~ 1/2).
The p-v results are already divided by 2, i.e. those that can be compared to certificates from interferometric tests.
Additionally, these are the best focus results for each line. The situation will look slightly different when we set best focus to red. Then the blue one rather flies into space...

 

red:

 

 

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[Maciek_Cz]

green:

 

 

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[Maciek_Cz]

blue:

 

 

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[SandyHouTex]

That is unfortunate, as a prism (or a binoviewer) will then only make the situation worse. 

 

On the other hand, you could most likely improve the situation by respacing the objective, and respacing for overcorrection is easier than for undercorrection, because you need to increase the distance between the lenses, and there's no risk of running out of space between the lenses. 

 

 

Clear skies!

Thomas, Denmark

That's an excellent thought.

[CHASLX200]

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.

Well it better come close to my freaky sharp 826 for the price. This is what keeps me from big pricey fracts when a cheap Newt can kill them everytime in my seeing.

[CHASLX200]

As an "imaging" refractor, with today's post processing, digital capabilities, it will do okay. If Paul's estimates are close (and they will be), as a visual refractor with 1/4 wave in the green, I do not think this scope is worth the money, even at $4,799.

 

The reason to buy a "visual" refractor is for a refractor's high contrast, low scatter, high definition, suburb sharpness and the ability to take high magnification and retain those qualities. For visual, one would be better off with an 8" Newtonian of mid FL with a high-quality mirror. The Newtonian would also cost a few thousand dollars less than even this low cost refractor. 

 

Bob

More like $120 for my freaky sharp 826. No 7" APO can come close for the money and weight. I can carry the whole thing and the mount needed for a 7" APO is gonna be 10 times more heavy.

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[RichA]

While the transparency was good the seeing according to Meteoblue was supposed to be about 1.5 arc secs.  I'd say the seeing was about average from my location a couple blocks from the ocean.

Those charts are interesting, but in urban areas, I've seen seeing change from moving 20ft in a backyard.

[John Huntley]

 

....This is exactly the type of scope I would expect at this price point.  My sense is they'll sell a gazillion of them - especially to all of the YouTube "influencers"  .....

"Dammed with faint praise" as the saying goes 

[RichA]

I see some bending of the jail bars. I need this thing on my dead still nites.  If it is as good as my SW150ED i guess i would be happy with it. But 5k is still a lot of money and then buying a monster mount to hold it is gonna cost many K. I don't see it working on my CI-700.  I gotta ask myself.  Is this scope gonna give a view better than my freaky sharp Meade 826 that cost $120????????????????????.

The price increases above 150mm are substantial.  You have to ask if the extra percentage of light gathering is worth it. 

Addition:  Also, it seems like scopes over 6 inches are prone to having zones, even some costly ones, strehl ratings notwithstanding.

Edited by RichA, 01 February 2024 - 09:29 PM.

[Joe G]

Well, this an interesting issue.  My carbon fiber Esprit tests very well in DPAC.  I have posted the results.  It puts up great visual images.  I have used it for photography.  I think visual is the best test.

 

I have owned a lot of various scopes over the years.  Most seemed okay.  One stood out which it seemed that it was obviously not great.  That was a Meade Lightbridge 16" Dob.  I had it side by side next to an Orion XT12i Intelliscope.  It was clearly inferior. I had that BK7 mirror refigured and it was an obvious improvement.

 

I then had my 12" Orion Intelliscope refigured by John Hall of Pegasus optics.  I couldn't tell the difference.

 

I now have a 16" Mike Lockwood 1" thick quartz mirror in a Dob.  It is really nice and in my environment cools quickly. 

 

I have really nice seeing at times.  Has to be some of the best in the country otherwise I would not be between Mt Wilson and Mt Palomar geographically. 

 

My point is that obsessing about perfection may not be the best way to evaluate telescope optics.  I will say that I was hopeful that the DPAC was better.  It seemed very close to the SV 180 that Paul evaluated. 

 

I don't know whether Askar intentionally figured this lens in Red, as StellarVue did for their scope.  I do wonder whether Stellarvue just let the scopes they sold, where no one complained, just sit out there.  It seems improbable they would have sent a notice out saying, "Doh, we used a red laser interferometer to figure your lens.  If you want us to look at the DPAC results in green, please send it back."

 

But who knows?

 

I knew this purchase would be a risk.  And my expectations were that it would be okay on Jupiter and show more on deeper stuff.  One night is not going to determine this.  I need to look thru it for a few more nights.

 

But it seems there are not a lot of options in a 7" plus refractor and the price seemed good.  So is it going to be a dud like my Meade Lightbridge 16?  I doubt it.

 

Yeah, of course, there are various other telescope designs in this range.

 

I don't know whether Askar intentionally designed this to be used with their reducer/flatteners to give good astrophotography results at the expense of visual.  It seemed that StellarVue didn't.  They just optimized in red because that is what their Zyogo IF did.

 

I have owned a ES AR152 achromat and compared it to my 150mm Esprit.  I did not like that scope.  Too much color.

 

I thought that the Askar would be closer to an APO than a Achro.  Another 1" of aperture.

 

So far that seems to be the case.  Time will tell.

 

All scopes have price/performance compromises.

 

 

 

 

[betacygni]

The price increases above 150mm are substantial. You have to ask if the extra percentage of light gathering is worth it.

Yes, I’ll be curious to see how it compares further to his 150mm. I’ve been very curious about the relative merits of more aperture with a lesser optic, vs lesser aperture with better optics. I’m sure there is a point the two equal out at.

[Joe G]

Yes, I’ll be curious to see how it compares further to his 150mm. I’ve been very curious about the relative merits of more aperture with a lesser optic, vs lesser aperture with better optics. I’m sure there is a point the two equal out at.

Yep. I agree with that and time will tell.  Need to remember that a 7" versus a 6" gathers 52% more light and a bit more resolution.

 

But this scope is actually cheaper versus a SW Esprit and other 150mm scopes.

 

Time will tell.

Edited by Joe G, 31 January 2024 - 11:09 PM.

[SandyHouTex]

Yep. I agree with that and time will tell.  Need to remember that a 7" versus a 6" gathers 52% more light and a bit more resolution.

 

But this scope is actually cheaper versus a SW Esprit and other 150mm scopes.

 

Time will tell.

 I have flatteners on all of my Taks and it improves the field nicely.  ALL triplets have significant field curvature.  You can browse the spot plots here:

 

https://takahashi-eu...alog/refractors

 

If I was in your shoes, I would get the flattener for the 185, and the reducer as well to see if either one improves the images.  Maybe even DPAC them in place.  The flattener is $299 preorder and the reducer is $306 preorder.

 

Good luck.  I hope everything works out.

[scoale]

Well, this an interesting issue.  My carbon fiber Esprit tests very well in DPAC.  I have posted the results.  It puts up great visual images.  I have used it for photography.  I think visual is the best test.

 

I have owned a lot of various scopes over the years.  Most seemed okay.  One stood out which it seemed that it was obviously not great.  That was a Meade Lightbridge 16" Dob.  I had it side by side next to an Orion XT12i Intelliscope.  It was clearly inferior. I had that BK7 mirror refigured and it was an obvious improvement.

 

I then had my 12" Orion Intelliscope refigured by John Hall of Pegasus optics.  I couldn't tell the difference.

 

I now have a 16" Mike Lockwood 1" thick quartz mirror in a Dob.  It is really nice and in my environment cools quickly. 

 

I have really nice seeing at times.  Has to be some of the best in the country otherwise I would not be between Mt Wilson and Mt Palomar geographically. 

 

My point is that obsessing about perfection may not be the best way to evaluate telescope optics.  I will say that I was hopeful that the DPAC was better.  It seemed very close to the SV 180 that Paul evaluated. 

 

I don't know whether Askar intentionally figured this lens in Red, as StellarVue did for their scope.  I do wonder whether Stellarvue just let the scopes they sold, where no one complained, just sit out there.  It seems improbable they would have sent a notice out saying, "Doh, we used a red laser interferometer to figure your lens.  If you want us to look at the DPAC results in green, please send it back."

 

But who knows?

 

I knew this purchase would be a risk.  And my expectations were that it would be okay on Jupiter and show more on deeper stuff.  One night is not going to determine this.  I need to look thru it for a few more nights.

 

But it seems there are not a lot of options in a 7" plus refractor and the price seemed good.  So is it going to be a dud like my Meade Lightbridge 16?  I doubt it.

 

Yeah, of course, there are various other telescope designs in this range.

 

I don't know whether Askar intentionally designed this to be used with their reducer/flatteners to give good astrophotography results at the expense of visual.  It seemed that StellarVue didn't.  They just optimized in red because that is what their Zyogo IF did.

 

I have owned a ES AR152 achromat and compared it to my 150mm Esprit.  I did not like that scope.  Too much color.

 

I thought that the Askar would be closer to an APO than a Achro.  Another 1" of aperture.

 

So far that seems to be the case.  Time will tell.

 

All scopes have price/performance compromises.

 

Hi, Joe.  In the Askar 185 thread you mentioned:

 

"Not expecting it to be perfect.  Just acceptable planetary views and better at deep sky with no central obstruction. I would hope that it puts up nice views of the planets and the extra aperture works well on globs and open clusters".

 

I would stay with your above-mentioned success criteria.  You've already confirmed improvement on DSO.  Planetary views will be the question.  For planets, you should see an aperture difference, but I would expect a scope that DPAC's as poorly as this one to be quite soft at higher magnification - but let's see!  I think your expectation is that it outperforms your Esprit and I look forward to hearing whether or not it does.  If it does, you have a scope that outperforms your Esprit on DSO and planets at a lower price.  If not, you always have the option to pay 4X 

[scout]

I knew this purchase would be a risk.  And my expectations were that it would be okay on Jupiter and show more on deeper stuff.  One night is not going to determine this.  I need to look thru it for a few more nights.

 

But it seems there are not a lot of options in a 7" plus refractor and the price seemed good.

Hi Joe, thanks for all of the details you've given.

 

Your signature says you own an 8" Askar apo and a 6" triplet apo. Other than curiosity and testing, what made you decide to buy this 7" refractor?

[lylver]

Yep. I agree with that and time will tell.  Need to remember that a 7" versus a 6" gathers 52% more light and a bit more resolution.

 

But this scope is actually cheaper versus a SW Esprit and other 150mm scopes.

 

Time will tell.

My two cents *** sarcastic ***
52% more, sure, but with commercial level at 88 to 92% strehl,

55% of 152% does not match 88%

 

It should be better at lower magnification than the maximum.

 

Anyway, red is at 90%, so as I have guessed the optic formula, I suppose a better intermediate behaviour in orange and yellow

Edited by lylver, 01 February 2024 - 01:38 AM.

[planedriver]

Hi Joe, thanks for all of the details you've given.

Your signature says you own an 8" Askar apo and a 6" triplet apo. Other than curiosity and testing, what made you decide to buy this 7" refractor?

I think 200mm APO is a 200mm f4 wide field small telescope used for AP. I have the 185mm version.

[Maciek_Cz]

As an "imaging" refractor, with today's post processing, digital capabilities, it will do okay. If Paul's estimates are close (and they will be), as a visual refractor with 1/4 wave in the green, I do not think this scope is worth the money, even at $4,799.

 

The reason to buy a "visual" refractor is for a refractor's high contrast, low scatter, high definition, suburb sharpness and the ability to take high magnification and retain those qualities. For visual, one would be better off with an 8" Newtonian of mid FL with a high-quality mirror. The Newtonian would also cost a few thousand dollars less than even this low cost refractor. 

 

Bob

This is the holy truth!
Any Newton with this aperture, even with a large obstruction, will work better. It's not for me to say whether it's worth buying or not, but even as a refractor guy, I'd rather save about $4,000 and buy a Newtonian with a high Strehl mirror. Why does the manufacturer create such a telescope?

[Ben the Ignorant]

Could it be the lens spacers have been swapped? They make the triplet well and test it but they have to handle it, so a little dust enters between the lenses. Then they take it apart for a final cleaning but they mismatch the spacers. 

 

That seems more likely than issueing a scope with decadent strehls.

[Maciek_Cz]

This is exactly what Paul wrote about in the DPAC SVX180 thread. The error is due to the design of the lens and the testing method (red).

[900SL]

This is the holy truth!
Any Newton with this aperture, even with a large obstruction, will work better. It's not for me to say whether it's worth buying or not, but even as a refractor guy, I'd rather save about $4,000 and buy a Newtonian with a high Strehl mirror. Why does the manufacturer create such a telescope?

Because big and cheap will always find a market. 'Never mind the quality, feel the width!'

I'm with you on the Newt. This Askar makes absolutely no sense to me, as an imager.
The weight and length makes handling and mounting a challenge, necessitating a mount upgrade, and likely a permanent mount in an Observatory.
Guiding will be a challenge. And the DPAC doesn't convince me as to performance.
I could do better, for less, with a good quality Newt and coma corrector.

Edited by 900SL, 01 February 2024 - 03:24 AM.

[fate187]

As an "imaging" refractor, with today's post processing, digital capabilities, it will do okay. If Paul's estimates are close (and they will be), as a visual refractor with 1/4 wave in the green, I do not think this scope is worth the money, even at $4,799.

 

The reason to buy a "visual" refractor is for a refractor's high contrast, low scatter, high definition, suburb sharpness and the ability to take high magnification and retain those qualities. For visual, one would be better off with an 8" Newtonian of mid FL with a high-quality mirror. The Newtonian would also cost a few thousand dollars less than even this low cost refractor. 

 

Bob

That's an excellent summary to the whole cheap vs expensive discussion and should be pinned somehow as it underlines why there are these expensive refractors and also the discussions between refractors and mirrors ...

 

[...]

 

My point is that obsessing about perfection may not be the best way to evaluate telescope optics.

 

[...]

 

All scopes have price/performance compromises.

Quoting what I think is important, that bold statement even more so. 

 

There are questions coming up on DPAC and maybe the respected forum members could do a youtube about the ins and outs 

 

Oh btw: all them manufacturers when they here about CN doing DPAC with there scopes right now:   

 

Best,

Michael 

[Ben the Ignorant]

Or at least one of the spacers has been flipped? Assuming they have that kind of profile, flipping a spacer or both can change the spacing.

 

[Maciek_Cz]

That's an excellent summary to the whole cheap vs expensive discussion and should be pinned somehow as it underlines why there are these expensive refractors and also the discussions between refractors and mirrors ...

 

Quoting what I think is important, that bold statement even more so. 

 

There are questions coming up on DPAC and maybe the respected forum members could do a youtube about the ins and outs 

 

Oh btw: all them manufacturers when they here about CN doing DPAC with there scopes right now:   

 

Best,

Michael 

If I had such an Askar, the first thing I would do is look at Jupiter and compare it with Mac 180 and Newton 180 - 200. If I got a better image in Askar, I would keep it. DPAC is DPAC, observations are the best test.