10 replies to this topic

[Maciek_Cz]

Hello to all DPAC folks.

At the request of Tomasz (Vroobel), I am publishing ronchigrams from the test of his freshly purchased Starwave 102 f/11 ED.

Tomasz built a beautiful set for the analysis of optics in the autocollimation system using the Ronchi screen.

The photos were taken in and out of focus. The only weak point of the set is the Ronchi screen itself. It is printed with a laser printer on transparent foil.
The screen has 4 lines per millimeter. For such a focal ratio it is sufficient, I think.

The flat mirror is the surface of the oil, and the Ronchi screen and the RGB LED diode are placed in a special holder designed by Tomasz.

The artifacts visible in the photos are dust pollen deposited on the surface of the oil.
The slight curvature of the bands may be due to the Ronchi screen inaccuracy.

As far as I know, these are the first such measurements for such a telescope.

The colors of the photos and the position of the Ronchi screen can be found in the names of the image files.

 

I encourage you to discuss.

Maciek

 

Blue

Attached Thumbnails

• 
• 
• 
• 

Edited by Maciek_Cz, 15 September 2022 - 07:44 AM.

[Maciek_Cz]

Green

 

Attached Thumbnails

• 
• 
• 
• 

[Maciek_Cz]

Red

 

 

Attached Thumbnails

• 
• 
• 
• 

[Maciek_Cz]

Setup

Attached Thumbnails

• 
• 
• 
• 

[Maciek_Cz]

I am posting another batch of photos.

This time Ronchi's screen was at focus. I look forward to an interesting discussion.

 

P.S. Colors in filenames.

 

 

Attached Thumbnails

• 
• 
• 

[Jeff B]

Excellent work Maciek!  

 

And a very nice lens in DPAC, smooth with a nice edge, slightly under corrected in green.

 

Have you run your DPAC simulator on the images yet?  I bet it comes out pretty good!

 

Jeff

[Maciek_Cz]

Thank you Jeff for your comment.
I only have analyzed green in detail because red and blue are almost perfect.
In green, the result is between 1/7 and 1/8 lambda closer to 1/8.
I still wonder if my software estimates it correctly ...

[Jeff B]

Thank you Jeff for your comment.
I only have analyzed green in detail because red and blue are almost perfect.
In green, the result is between 1/7 and 1/8 lambda closer to 1/8.
I still wonder if my software estimates it correctly ...

I think so for figures that are smooth with simple over/under corrections, no significant issues or zoning, all of which will degrade the real Strehl relative to what your program estimates. 

 

But I find it does require practice/skill at the tweaking of the parameters (which came quickly for me) and, above all else, user honesty (which is sometimes not so quick  .).   

 

I base the software's Strehl correctness on my ability to get good agreement between my inside/outside simulations (see attached images for my LZOS 254 F9 objective) but also with some test reports that I trust, like the attached LZOS report for the same lens.  Additional LZOS documentation shows for this objective they calculated a low and a hi Strehl value based upon a statistical read on their IF.  They always quote the "low" reading.

 

I consider the overall level of strehl agreement between your software and the LZOS report to be very good.  

 

Jeff

Attached Thumbnails

• 
• 
• 

[areyoukiddingme]

Sounds like they could be reporting error bars on a Strehl. It would be good to see that become a norm.

[vroobel]

Hi,

 

I am an owner of the ASCENT 102ED F/11. Tonight I performed a star test, so can share its result here, respectively In and Out

 

Edited by vroobel, 16 September 2022 - 08:33 PM.

[CHASLX200]

Looks good enough for me. I gotta use Jupiter to really know how good a scope is. Stars do nothing for me.