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Post your Optical Design! (This is a no-discussion thread!)

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#101 rflrs

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Posted 25 September 2020 - 10:12 PM

In the thread:

 

   https://www.cloudyni...l/#entry8151208

 

a design suggested in 2000 was brought up.  That design was a 280 mm (or so)
f/7.5 Petzval utilizing only two glass types (K5 and F2).  This is an
alternative to that design, substituting BK7 for one of the K5 lenses.

 

Title: Ptz24-67
280 mm f/7.5 Petzval Refractor

 

Surf     Radius   Thickness   Glass   Diam

 

 STO   Infinity   -5.904512            280
   2     1662.7          25    N-K5    290
   3    -1662.7          18      F2    290
   4      50300      1833.2            290
   5     1045.3          18   N-BK7    190
   6    -1045.3         4.6            190
   7    -1045.3          12      F2    190
   8     -23525    1117.642            190
 IMA    -2093.8                       43.3

But, that doesn't mean that anyone will actually try to implement this design,

either.

 

Richard


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#102 RajG

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Posted 14 October 2020 - 08:26 PM

Here is a 200mm f/4.6 (927mm fl) Houghton Cassegrain Astrograph. Spots are shown over a 1 degree field radius (32 mm diameter image circle), over 334nm-2400nm range i.e., from near UV to deep IR. This is essentially the entire usable range for BK7 glass.

 

On-axis it is diffraction limited from 334nm-2400nm. Strehl >0.99 over all wavelengths between 380nm-2400nm (Strehl at 334nm is .83). Insane! 

 

All spherical surfaces, corrector lenses are ordinary N-BK7. 

 

I had to magnify the scale for the spots, for some annoying reason OLSO defaulted to showing the spots on a very small scale. If you open the OLSO file, remember to manually set the scale for the spot diagram to 0.02mm.

 

sml_gallery_326571_14702_1880.pngsml_gallery_326571_14702_19450.png

 

Attached File  HoughtonCass200f4.65.len   1.57KB   5 downloads


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#103 RajG

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Posted 17 October 2020 - 11:19 AM

250mm f/4 (1002mm fl) Houghton Astrograph. On-axis Strehl is >0.99 for all wavelengths from 365-1900nm, and >0.98 from 330-2400nm.

 

Spots (magnified) and MTF shown from 365-1152nm over a 22mm field radius, covering a full frame sensor. Diffraction limited performance over the full field.

 

All spherical surfaces, corrector lenses are BK7 glass.

 

sml_gallery_326571_14727_16721.pngsml_gallery_326571_14727_9571.png

 

 

sml_gallery_326571_14727_20179.png

 

Attached File  Houghton250mmf4.len   1.61KB   7 downloads


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#104 Nodda Duma

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Posted 17 October 2020 - 06:19 PM

Hi folks,

What a great thread.  I've been a lens designer for ~ 20 years now ... half of that for the US Navy and then half in the private sector.  Most of my designs aren't pertinent to astronomy, but I do have one which is fielded / being fielded (I've lost track on when the upgrade was taking place) on ISS.

 

In any case, I own a Vixen VC200L and about 4 years ago I worked on the optical prescription based on what I've gleaned on the internet and my own measurements.

You can compare to the layout on Vixen's page on the VC200L.  https://www.vixenopt...cope-p/2632.htm

 

50498886408_530d07bfce_k.jpg

I know it's not quite correct (field curvature is slightly different), but it's pretty close.  I assume all BSL7 singlets for the corrector group -- changing glass-types doesn't have a significant effect on color correction. 

-Jason

Edited by Nodda Duma, 17 October 2020 - 06:42 PM.

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#105 djgilley

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Posted 19 October 2020 - 07:55 AM

 

This is a bit of a kludge I suppose, it needs a high index meniscus lens ahead of the focus to somewhat alleviate lateral color... and it's F16. In what are ostensibly three crown glasses the BSM-14 is acting like the flint. It's diffraction limited from 4358nm - 6567nm.

 

4 inch F16
 

 

 

4 inch F16 spots
 

 

 

Attached Files



#106 RajG

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Posted 23 October 2020 - 08:02 AM

This is a 100mm f/10 (1000mm fl) fluorite quintuplet using N-BAK1  & N-BAF4 as mating glasses. 

 

Spots are shown from 400-707nm, Strehl >0.995 for all wavelengths in that range.  (It is diffraction limited from 375nm-904nm.)

 

All spherical surfaces, no aspherics.

 

med_gallery_326571_14785_66200.png

 

 

Attached File  QuintupletBAK1BAF4CAF2.len   1.58KB   3 downloads



#107 catalogman

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Posted 23 October 2020 - 08:48 AM

The design of a Pfund telescope and its variations was discussed in this CN thread:

 

https://www.cloudyni...opes/?p=6380524

 

-- catalogman



#108 RajG

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Posted 23 October 2020 - 04:51 PM

Following on to my post #106: you can replace N-BAF4 with N-F2 and get virtually identical performance with a little re-optimization.

Note: not F2, but the lead-free glass N-F2 which is slightly different. Using F2, you get a very good apo but not the extreme Strehl values.

 

As in post #106, spots are shown from 400-707nm, Strehl > 0.995 over this entire range. It is diffraction limited from 365nm-880nm, but note that N-F2 & N-BAF4's transmittance falls off rapidly below 400nm.

 

All spherical surfaces.

 

 

med_gallery_326571_14785_59039.png

 

Attached File  QuintupletBAK1NF2CAF2.len   1.57KB   3 downloads




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