73 replies to this topic

[denis0007dl]

Here is startest of Askar 203mm APO and Ronchi.....

 

Kind regards,

Denis

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[CHASLX200]

I wanna see Jup.

[Gert]

I wanna see DPAC.

[salico]

I wanna have two for Binoscope.

[bobhen]

Here is startest of Askar 203mm APO and Ronchi.....

 

Kind regards,

Denis

Just for comparison. Below is a star test from a Takahashi TSA 120.

 

Bob

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[Astrojensen]

Doesn't look very impressive at all. There appears to be significant undercorrection, in combination with spherochromatism. The in-focus star image is far too overexposed to show the diffraction rings. 

 

The Ronchi is blurry and difficult to interpret. 

 

A video of a star, slowly racking it through focus at very high power (600x or so) would be a LOT more revealing. 

 

 

Clear skies!

Thomas, Denmark

[Julio]

Here is startest of Askar 203mm APO and Ronchi.....

 

Kind regards,

Denis

Ronchi looks good, it looks like a green filter wasn't used showing CA on one side of focus obscuring the star test.

Edited by Julio, 09 January 2025 - 09:13 AM.

[Kitfox]

Hmmm.  That looks like a cheap achromat, especially if that Ronchi image is single pass...

[Jeff B]

I wanna see DPAC.

This.  Single pass Ronchi with many bands does not do much for me.

 

I see some astigmatism.  I won't comment on the other stuff as I don't know the magnification involved and it's obvious a deep green filter was not used.

 

If anyone has one in the US and is willing to send it to me, I'll give it a proper optical health check.

 

Jeff

[peleuba]

Here is startest of Askar 203mm APO and Ronchi.....

 

Denis - Thanks for posting.   I am not sure why others who test scopes do not have the Ronchi screen vertical!     Its too hard for me (and perhaps others) to judge curvature of the Ronchi bands when the screen is not in a straight up/down orientation.  I have enlarged and rotated the Ronchi image 63° to make easier to interpret the curvature of the bands.  

 

A couple of important questions/clarifications: 

 

(1)  Is the Ronchi image in double pass?

 

(2)  I do not think a green filter was used - the images appear to be in white light.   Can anyone confirm if a filter used for these images?   

 

(3)  Was the the Ronchi image taken inside of focus or outside?

 

 

 

Doesn't look very impressive at all. There appears to be significant undercorrection, in combination with spherochromatism. The in-focus star image is far too overexposed to show the diffraction rings. 

 

The Ronchi is blurry and difficult to interpret. 

 

A video of a star, slowly racking it through focus at very high power (600x or so) would be a LOT more revealing. 

 

Hi Thomas - Objectively speaking, yes - agree -  this is not going to be a top performing APO when comparing it to other high-end scopes from TAK/TEC/LZOS/AP and maybe even StellarVue.  Might it be better then we think, though?  Perhaps, but as you stated, we would need more information as the photos are not terrific captures from a test bench.   The largest error is spherochromatism.  Pure spherical correction might be OK but its difficult to judge because of the smear from the unfocused color.  Both outer rings look to be the same size - however, the brightness is vastly different as is the texture; the outside of focus image has a much "harder" outer ring.  Spherochromatism can be negated if a green filter is used.  But even so, this is unavoidable in a spherical triplet using a single piece of lower-end ED glass in such a large aperture.  Clearly, this scope was made to a price point; it was not made to attain a certain performance level.  This is an important distinction and necessary consideration when comparing telescopes.   You almost NEVER get performance if you do not pay for it.

 

To be sure, its likely this telescope will produce better images then an 8" SCT.  Admittedly, that is a rather low performance bar to exceed.  But, that's the market for these big, Asian-built, inexpensive APO's. 

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Edited by peleuba, 09 January 2025 - 01:52 PM.

[SandyHouTex]

Here is startest of Askar 203mm APO and Ronchi.....

 

Kind regards,

Denis

The  Ronchi looks pretty good.

[denis0007dl]

Wolfi says:

optical test is made in autocollimation - doublepass.

Every error is therefore displayed twice as strongly as in reality.

The Apo will not only show clean stars, it will also perform very well on the moon and planets.

[garret]

Wolfi says:

optical test is made in autocollimation - doublepass.

Every error is therefore displayed twice as strongly as in reality.

The Apo will not only show clean stars, it will also perform very well on the moon and planets.

Wolfi?? 

Wolfi by Tex Avery: 

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[Maciek_Cz]

Job is very simple.

Here you have decomposition of ronchigram to red, green and blue channels.

Green has the best correction. Red is quite good.

Ronchigram looks like a single pass.

 

red

 

green

 

blue

Edited by Maciek_Cz, 09 January 2025 - 12:37 PM.

[salico]

Wolfi?? 

Wolfi by Tex Avery: 

Wolfi is Wolfgang Ransburg, owner and founder of TS, Telescope Service Ransburg, Germany

 

Cheers,

 

Sal

[denis0007dl]

Correct!

[Villa_il_Gioiello]

Thanks for posting this. I ordered the 185 APO in December. It's arriving tomorrow. I'll be doing a star test tomorrow night if the SoCal winds calm down before then.  

 

I wonder why Askar decided to offer a 203mm. It's only 20% more light than the 185. That's like offering at 100mm and a 109mm. A 210mm probably would have made more sense given they already have the 185. 

[denis0007dl]

Thanks for posting this. I ordered the 185 APO in December. It's arriving tomorrow. I'll be doing a star test tomorrow night if the SoCal winds calm down before then.  

 

I wonder why Askar decided to offer a 203mm. It's only 20% more light than the 185. That's like offering at 100mm and a 109mm. A 210mm probably would have made more sense given they already have the 185. 

Congrats on beast!!!

 

Keep us posted with nice images of mechanics, lenses, and any test you will do.

 

Denis

[SandyHouTex]

Well 203mm is 8 inches and 185mm is 7 inches.

[Villa_il_Gioiello]

Well 203mm is 8 inches and 185mm is 7 inches.

Yeah, I don’t think so. Recheck your math. 

[Martinbruce]

Well,

 I read the following “To be sure, its likely this telescope will produce better images than an 8” SCT. Admittedly, that is a rather low performance bar to exceed. “. I’m ok with the first sentence but hey hey hey, the second?

[bobhen]

If you are an imager, today you can get very satisfactory images with mediocre optics. The digital revolution, frame selection and stacking and the "ever-improving" post processing software can add contrast, sharpness, etc. that is just not there in the telescope's optics. That was not the case years ago. 

 

If I were a "deep sky" imager, I would save money and grab one of these less expensive refractors coming out of Asia. For my planetary imaging, I would grab a C11 or C14. Then I would get the best software and learn the best possible post processing techniques. 

 

For the visual astronomer, there is nothing the brain can do in real-time to improve image quality like what a computer can with today's imaging software. For the visual astronomer, high optical quality plays a much more important role in seeing deep sky and planetary details. If I were a visual astronomer only, I would be looking for something with better optical quality.

 

Bob

[CHASLX200]

I would be scared  to pay 8k and not like the image.

[davidc135]

Let's see how it compares to Denis' 180mm LZOS in practice.

 

David

Edited by davidc135, 10 January 2025 - 11:57 AM.

[peleuba]

Yeah, I don’t think so. Recheck your math. 

 

Here's the math...

 

185 / 25.4 = 7.28 Inches.  Round down and you get 7 inches 

 

203 / 25.4 = 7.99 Inches.  Round up and you get 8 inches.

 

But I don't think it really matters as these scopes are made to a price point.  It may be that the aperture size is a function of the availability of inexpensive lens blanks...   If the blanks from Chengdu Glass Company (CDGM) don't have to be machined, then that is a huge cost savings relative the uber-thin margins on a scope like this.   To wit:  I was speaking to a friend who makes lenses for APO's here in the U.S. back when Askar originally announced these big APO's.   After a quick back of the napkin calculation based on prevailing costs of the raw materials, specifically - the ED glass, mates, cost of  the Chinese mechanics (OTA/focuser/rings/paint/anodizing/lens cell) and the cost of polishing and figuring to a ¼ wave, the retail price was still lower then the sum of its parts.  Also, keep in mind the wholesale cost (the price Askar charges its retailers) would be ~20% lower then the selling "list" price to consumers.    

 

In any event, the true cost of something is what you pay while the value of something is what you receive.  At this price point, the cost seems universally positive for the consumer.  I think the jury is still out on the relative value, IMO.  I come at this from a visual astronomer's perspective.   As Bob said above, for imaging this could be a terrific low cost larger aperture platform.   And for general use, I would certainly prefer it to an 8" SCT.

 

Looking forward to seeing more user test reports on these Askar APO's.

Edited by peleuba, 10 January 2025 - 02:04 PM.