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

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#76 RajG

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Posted 05 August 2020 - 04:49 PM

The 80mm f/5 design can be scaled up to larger apertures and the performance is still very good after a slight re-optimization. I am attaching the Olso files for 100mm (503mm fl) and 120mm (605mm fl) aperture.

 

The 100mm f/5 is diffraction limited (Strehl > 0.8) from 435nm-656nm. Performance is still very good at 404 nm & 707nm (Strehl ~0.78).

 

SRF      RADIUS      THICKNESS   APERTURE RADIUS       GLASS  SPE  NOTE
OBJ       --        1.0000e+20    4.3634e+17             AIR    

AST   356.912266 V   12.500000     50.000000 A         N-BK7 C  
  2    155.411420 V    3.700000     50.000000             AIR    

  3    125.899454 V   22.500000     50.000000         S-FPL53 C  
  4   -132.342983 V   12.000000     50.000000             AIR    

  5   -112.117385 V   12.500000     50.000000           N-BK7 C  
  6   -347.593046 V  455.105000     50.000000             AIR    

IMS       --            --          2.214479 S

 

The 120mm f/5 is also diffraction limited from 435nm-656nm, but performance falls off beyond that range.

 

SRF      RADIUS      THICKNESS   APERTURE RADIUS       GLASS  SPE  NOTE
OBJ       --        1.0000e+20    4.3634e+17             AIR    

AST   430.687830 V   15.000000     60.000000 A         N-BK7 C  
  2    185.191924 V    4.000000     60.000000             AIR    

  3    150.995147 V   27.000000     60.000000         S-FPL53 C  
  4   -160.303364 V   14.500000     60.000000             AIR    

  5   -135.626983 V   15.000000     60.000000           N-BK7 C  
  6   -410.521760 V  548.220000     60.000000             AIR    

IMS       --            --          2.669500 S

 

Attached File  TripletFPL53NBK7100mmf5.len   1.46KB   7 downloads

 

Attached File  TripletFPL53NBK7120mmf5.len   1.52KB   7 downloads

 



#77 RajG

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Posted 05 August 2020 - 06:10 PM

Here is a 140mm f/7 air-spaced triplet (984mm fl) design, using FCD100 and N-BK7. It is diffraction limited (>0.8 Strehl) from 420nm - 710nm.

 

The e-line (546nm) Strehl is 0.99. Strehl at 435nm (g-line) is 0.93. By comparison, the TEC 140FL has g-line Strehl of 0.7.

 

S-FPL53 or S-FPL55 can be used instead of FCD100, and performance is comparable after re-optimization.This design can be scaled up to 160mm & 180mm apertures, and performance remains diffraction limited from 435nm-656nm.

 

Comment on this thread: 

 

https://www.cloudyni...triplet-design/

 

Spots are shown for 435nm-656nm.

 

sml_gallery_326571_14014_27217.pngsml_gallery_326571_14014_256.pngsml_gallery_326571_14014_180.png

 

Attached File  TripletFCD100NBK7 140mmf7.len   1.5KB   5 downloads



#78 RajG

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Posted 05 August 2020 - 08:32 PM

Improved version of the 80mm f/5, now fully diffraction limited over 404nm-710nm.

 

Attached File  TripletFPL53NBK780mmf5Improved.len   1.46KB   4 downloads



#79 RajG

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Posted 07 August 2020 - 09:06 AM

Here is my attempt at designing a 130 f/6.3 (819mm fl) air-spaced apo triplet using S-FPL53 and N-BK7. It is diffraction limited from 400nm-706nm. Chromatic focus variation over this range of wavelengths is less than +/- 0.0051%.

 

For comparison, the AP130GTX has focus variation less than +/- 0.006% from 400nm-706nm.

 

Rays and spots from 400nm-706nm are shown below.

 

This was a really challenging exercise due to the very wide range of wavelengths, large aperture & fast focal ratio, it took many attempts. The large air space between the second and third element is a key ingredient in this design.

 

BTW, S-FPL53 can be replaced with S-FPL55 (requires re-optimization). That version is diffraction limited from 404nm-706nm but not at 400nm.

 

Post your comments on this thread: https://www.cloudyni...triplet-design/

 

sml_gallery_326571_14028_4486.pngsml_gallery_326571_14028_5372.pngsml_gallery_326571_14028_55706.png

 

Attached File  TripletFPL53NBK7 130mmf6_3.len   1.53KB   3 downloads


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#80 Mike I. Jones

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Posted 10 August 2020 - 07:32 PM

200mm aperture Chief, using f/6.2 primary and giving a system focal ratio of f/5.6. Primary conic is -1.0717, slightly hyperboloidal. Flat secondary mirror. Interesting solution as Zemax changed the second lens element to fused silica. I constrained field tilt to 2º. I tried equal radii on the lenses but it wasn't having it. If there is interest I will run tolerances, which are likely going to be fairly tight in alignment.

8f6_2 prescription.jpg

8f6_2 layout.jpg

8f6_2 full-field spots.jpg

Attached Files


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#81 RajG

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Posted 12 August 2020 - 04:13 PM

100mm f/6 (604mm fl) Apo Petzval astrograph. Diffraction limited on-axis from 435-707nm. Flat well-corrected field over a full-frame sensor. Spots shown over 22mm radius (44mm dia) over 435nm-707nm. (At 546nm, this is diffraction limited over the entire image circle.). Ample backfocus (211 mm).

 

This design scales up very well, being diffraction limited over 435-707nm even at 170mm f/6. Even scaled up to 200mm f/6 it is very close to diffraction limited, falling only slightly short (better than .75 Strehl) for a few wavelengths. Of course that would be impractical & very expensive as it uses two full-aperture S-FPL53 lenses.

 

S-FPL55 or FCD100 can be used instead of S-FPL53, performance is nearly identical (with re-optimization of course).

 

sml_gallery_326571_14088_7575.pngsml_gallery_326571_14088_24627.png

 

Attached File  Petzval100f6 S-FPL53.len   1.68KB   5 downloads


Edited by RajG, 12 August 2020 - 04:36 PM.


#82 cuzimthedad

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Posted 20 August 2020 - 02:23 PM

Just a reminder: This is a no-discussion thread.


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#83 Ed Jones

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Posted 20 August 2020 - 06:15 PM

Well let me try this again, this is the Zemax prescription for the 8 inch F/7 Chief group build.  (I had a radius from a measured primary instead of exactly F/7 primary and a few other lesser issues).  It's for a 90 degree fold although other layouts are possible.  I also converted it to millimeters for all the metric users.  I'm also posting this on my web site.

Attached Thumbnails

  • 8inchF7ChiefCNwlayout.jpg

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#84 Ed Jones

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Posted 20 August 2020 - 06:18 PM

Here is the point spread function and the spot diagrams. 

Attached Thumbnails

  • 8inF7ChiefSpots.jpg

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#85 Ed Jones

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Posted 23 August 2020 - 07:06 PM

This page has links to Google Drive with CAD files of the design, Zemax files, a drawing of the correctors and coordinates and a 3D lens cell holder.  (#165)


Edited by Ed Jones, 23 August 2020 - 07:17 PM.

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#86 RajG

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Posted 24 August 2020 - 07:44 PM

Here is a 100mm f/8 air-spaced triplet using FPL51. It uses the same mating glasses (N-BK7 & N-SK5) as Dave Shafer's f/10 Super Apos (#57 & #58 on this thread). This is also diffraction limited (>0.8 Strehl) from 400nm-707nm.

 

sml_gallery_326571_14200_10136.pngsml_gallery_326571_14200_31038.png

 

Attached File  TripletFPL51NBK7NSK5100mmf8.len   1.46KB   1 downloads

 

 

 

 


Edited by RajG, 24 August 2020 - 08:14 PM.


#87 RajG

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Posted 24 August 2020 - 08:09 PM

And here is a 150mm f/10 triplet using S-FPL51, N-BK7 and N-SK5. It is diffraction limited from 404nm-707nm (scaled down to smaller apertures, it would be diffraction limited at 400nm as well). 

 

sml_gallery_326571_14200_18470.pngsml_gallery_326571_14200_36441.png

 

Attached File  TripletFPL51NBK7NSK5150mmf10.len   1.47KB   1 downloads


Edited by RajG, 24 August 2020 - 08:15 PM.


#88 Mike I. Jones

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Posted 25 August 2020 - 03:02 PM

William Herschel's 40-foot telescope made observational history in the late 1700's and early 1800's.  Funded by King George to the tune of £4000 and operational in 1780, its primary mirror was 48" in diameter and had a focal length of 40 feet or 480", making it f/10.  Herschel did not want a Newtonian configuration due to the very low reflectance of two speculum mirrors, and opted to delete the Newtonian diagonal mirror and tilt his primaries for viewing off the the side.  This form of telescope will always be referred to as the Herschelian.  

 

Oh, if only Herschel had thought of the idea of using a corrector lens or two to correct the strong aberrations that severely limited the 48" resolution!  Per a suggestion by "hamishbarker" in the 8" f/7 Chief thread https://www.cloudyni...ild/?p=10450130, I have applied Ed Jones's Chief idea to Herschel's 40-foot telescope, and the image improvement is remarkable!  I don't know the refractive indices of the various crown glasses used in early refractors by Fraunhofer and others, so I simply used good old N-BK7.

 

Attached is the Zemax lens file, set up in two configurations: (1) without corrector lenses and (2) with corrector lenses.  This is the prescription, field map, multi-configuration editor and Zemax lens file, minus the merit function operands to make the file size fit.  

 

For those of you with Zemax experience, you'll notice that I did the lens tilts/decenters exactly per the method shown in the Zemax KnowledgeBase articles on the subject.  There are simpler ways to do tilt/decenter with just two coordinate breaks, but you have to be careful to do them properly and watch tilt commutivity, otherwise thicknesses, positions and angles can be wrong.  Using the preferred Zemax method requires two extra surfaces per lens but removes any ambiguities in lens angles or positions.  I can start a new thread on this subject in the ATM Forum if desired.  

 

Herschel 48in f10 telescope  - LDE.jpg

 

Herschel 48in f10 telescope  - Field editor.jpg

 

Herschel 48in f10 telescope  - multiconfig.jpg

 

Attached File  Herschel 48in f10 telescope without, with Chief corrector - no MF.zmx   9.12KB   2 downloads

 

Herschel 48in f10 telescope  - layout.jpg

 

Herschel 48in f10 telescope  - spots at 1000um.jpg


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#89 Mike I. Jones

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Posted 25 August 2020 - 03:04 PM

The corrected spots are so small in the above spot plots that no detail can be seen.  These are the spots the corrected 48" Herschelian gives, plotted 10X larger.  The on-axis performance is diffraction limited.  Herschel would have fallen off his ladder!

 

Herschel 48in f10 telescope + Chief corrector - spots at 100um.jpg


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#90 hamishbarker

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Posted 26 August 2020 - 09:56 PM

Nice one! Are the lenses spherical or aspherical? I can't read the zemax detail on my phone.


William Herschel's 40-foot telescope made observational history in the late 1700's and early 1800's. Funded by King George to the tune of £4000 and operational in 1780, its primary mirror was 48" in diameter and had a focal length of 40 feet or 480", making it f/10. Herschel did not want a Newtonian configuration due to the very low reflectance of two speculum mirrors, and opted to delete the Newtonian diagonal mirror and tilt his primaries for viewing off the the side. This form of telescope will always be referred to as the Herschelian.

Oh, if only Herschel had thought of the idea of using a corrector lens or two to correct the strong aberrations that severely limited the 48" resolution! Per a suggestion by "hamishbarker" in the 8" f/7 Chief thread https://www.cloudyni...ild/?p=10450130, I have applied Ed Jones's Chief idea to Herschel's 40-foot telescope, and the image improvement is remarkable! I don't know the refractive indices of the various crown glasses used in early refractors by Fraunhofer and others, so I simply used good old N-BK7.

Attached is the Zemax lens file, set up in two configurations: (1) without corrector lenses and (2) with corrector lenses. This is the prescription, field map, multi-configuration editor and Zemax lens file, minus the merit function operands to make the file size fit.

For those of you with Zemax experience, you'll notice that I did the lens tilts/decenters exactly per the method shown in the Zemax KnowledgeBase articles on the subject. There are simpler ways to do tilt/decenter with just two coordinate breaks, but you have to be careful to do them properly and watch tilt commutivity, otherwise thicknesses, positions and angles can be wrong. Using the preferred Zemax method requires two extra surfaces per lens but removes any ambiguities in lens angles or positions. I can start a new thread on this subject in the ATM Forum if desired.

Herschel 48in f10 telescope - LDE.jpg

Herschel 48in f10 telescope - Field editor.jpg

Herschel 48in f10 telescope - multiconfig.jpg

Herschel 48in f10 telescope without, with Chief corrector - no MF.zmx

Herschel 48in f10 telescope - layout.jpg

Herschel 48in f10 telescope - spots at 1000um.jpg


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#91 RajG

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Posted 01 September 2020 - 10:42 AM

80mm f/5 (398mm f.l.) quad element wide-field astrograph. Diffraction limited on-axis over 435-707nm; e-line (546 nm) Strehl of 0.95. Spots are excellent over an APS-C sensor. It is also usable over a full frame sensor with only slight deterioration in the corners. Ample backfocus (~126mm).

 

sml_gallery_326571_14277_83926.png

 

Spots (435-707nm) over a 28mm diameter field (4-degree fov) (covers APS-C):

 

sml_gallery_326571_14277_19913.png

 

And here are the spots (435-707nm) and MTF vs field over a 44mm diameter image circle (covers a full-frame sensor):

 

sml_gallery_326571_14277_13218.pngsml_gallery_326571_14277_4696.png

 

Attached File  Quad80f5 S-FPL53.len   1.33KB   2 downloads

 

 


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#92 rflrs

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Posted 12 September 2020 - 07:00 AM

Title: baker10-85
165 mm f/7 Baker-Cooke Triplet (with field flattener)

 

Surf      Radius   Thickness    Glass    Clear Diam

 

   1     846.513        20.5   N-BAK4           180
   2    -1166.54       158.1                    180
STO    -1252.37           9    N-SK5           140
   4     193.294          34   N-FK58           140
   5    -193.294           9    N-SK2           140
   6    -954.745       215.3                    140
   7     -489.31          15   N-BAK1           150
   8    -273.874    490.1619                    150
   9      620.49         9.5    N-BK7           100
  10       -1086         136                    100
  11     -337.33         6.5    N-BK7            65
  12      550.69       212.2                     65
IMA    Infinity                               43.3

 

Field: 2.1454 degrees
Band: 334.15 to 1334.15 nm

 

Diffraction limited except about 3 nm in the UV end of the band.

 

Richard


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#93 BKSo

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Posted 12 September 2020 - 10:04 AM

80mm f/5 (398mm f.l.) quad element wide-field astrograph.

 

See post #17



#94 Millyon

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Posted 13 September 2020 - 12:48 PM

    Here is a Autodesk Fusion 360 design I worked up using Stellafane newt design site. This design was for a 16" newtonian as an astrograph. Being an astrograph, I used a four inch secondary mirror in order to get max illumination for my ZWO ASI 16000MM. If I ever step up to a larger format camera, there will be a reasonable amount of full Illumination available.

    Making sure one understands visually what the design implys can minimize making mistakes (one hopes smile.gif The carbon fiber tube prompts me to get as many components as possible before ordering the CF tube to minimize it's cost of about 2k dollars at ~64 inches.

    Any questions feel free to ask. Just not here.

 

Attached is the Stellane .newt file if your interested in playing. Just rename it to .newt extension for Stellafane importing.

Attached Files


Edited by Millyon, 13 September 2020 - 01:12 PM.


#95 rflrs

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Posted 14 September 2020 - 10:30 AM

Here's another Petzval.  This one was derived from the design
given in the 2017 Solstice Design note.

 

Title: Ptz23-15
100 mm f/7 Petzval Refractor

 

Surf     Radius   Thickness    Glass    Diam

 

STO   Infinity   -2.500251              100
   2      501.2         6.5    N-BK7     105
   3      345.3        13.5   N-FK58     105
   4     -345.3         6.5    N-BK7     105
   5      -5380         439              105
   6      561.9           6    N-BK7      95
   7      262.3          13   N-FK58      95
   8     -262.3           6    N-BK7      95
   9     -911.7    436.2633               95
IMA    -737.77                         43.3

Field: 3.544 degrees (+/- 1.772 degrees)

It is diffraction  limited from h (404.7 nm) to r (706.5 nm).  I
still think one of the major advantages of the Petzval over the
simple objective is the reduced field curvature and astigmatism.

 

Richard


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#96 Mike I. Jones

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Posted 19 September 2020 - 03:21 PM

This is a 10" aperture f/11 Chief I designed for J.T. Senghas.  It uses off-the-shelf lenses from Ross Optical, which I'm hoping are readily available.  Tolerances are fairly tight, especially for L1 and L2 placement, but they are within 3D printing capabilities.

 

10f11 Chief.jpg

 

10f11 Chief lens details.jpg

 

 


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#97 Mike I. Jones

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Posted 19 September 2020 - 03:23 PM

These are the MTF plots for the nominal (perfectly made) system, and both Gaussian and Uniform distributions of manufacturing errors using the tolerances given.

 

10f11 Chief MTF runs.jpg



#98 Mike I. Jones

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Posted 20 September 2020 - 11:35 AM

This was a fun project I worked on back in the mid-90s.  A work friend that I knew was VERY skilled with tools asked me if I could design him a telescope, and he would build it.  I don't how the idea got into my head, but this is what I proposed to him: a Texas telescope.  I designed the 5" f/15 achromat, Optico Fabrication made the lens (very nicely, I might add), and Glenn built the whole thing.  It was so novel that it had a story and pictures done on it.  These are the most rewarding kinds of projects I can think of!  That's me on the left and Glenn in the middle, at a star party near Cleburne State Park in October of 1997.  I also suggested he make the alt-azimuth fork look like a Texas Longhorn!

 

Texas telescope layout.jpg

 

Texas Telescope.jpg


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#99 Mike I. Jones

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Posted 20 September 2020 - 11:36 AM

The Whittenberg Texas Telescope.

DCP01234.JPG


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#100 Mike I. Jones

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Posted 20 September 2020 - 11:37 AM

View of the Texas telescope with the front cover removed.  I sized the two Newtonian diagonal mirrors he used to fold the path.  His TelRad finder is not shown.

 

DCP01241.JPG


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