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#26 djgilley

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Posted 27 March 2020 - 05:04 PM

Here's a follow up to my previous post , this one uses plain ol BK-7 as the first element, the other elements are the same as the previous design. This one, at this aperture and F ratio, is a true apo, wavefront error at the following wavelengths:

4358- .159

4860- .217

5413- .0895 ( a bit of spherochromatism)

6563- .112

7070-  .148

6 inch BK7 quadruplet

 

 

Attached Files



#27 djgilley

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Posted 13 April 2020 - 01:57 PM

Another 4 element design, this time using BSM-14. 

 

RMS error:

 

5460-.002675 (1/90 wave)

4861- .0348 (between 1/8 and 1/9 wave)

6563- .0172 (1/18 wave)

4358- .0333 (between 1/8 and 1/9 wave)

7070- .077 (just a bit over 1/4 wave)

6 inch BSM14 quad

 

Attached Files


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#28 djgilley

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Posted 14 April 2020 - 02:35 PM

I was searching the forums a few days ago and came across a thread in which Mike Jones mentioned a design for a full aperture corrector for the 6 inch F10 achromat he built. https://www.cloudyni...6-f10-achromat/ I downloaded the OSLO file, did some puzzling, and came up with a design. This one uses PHM-52 and NBM-51, which makes a somewhat better corrected achromat, but still with quite a bit of violet error, especially at F10. Using two ordinary glasses (TIM-28 and BAH-28) I designed a corrector that improves the F/C correction by about 2.4 times and reduces the violet error by a factor of 4.75. The color crossing looks somewhat similar to the old Astrophysics 6 inch F10 that used KZFS1, this has better violet correction but doesn't correct far red as well. As Mike's corrector does, this increases the focal length to about F14. It's interesting to fiddle around with this design principle on OSLO, though I don't fully understand the math behind it, even after reading McCarthy's patent. 

6 inch PHM52 quad achromat corrector

Attached Files


Edited by djgilley, 14 April 2020 - 02:36 PM.

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#29 lylver

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Posted 23 April 2020 - 06:01 PM

An approximation of the SAF asymetric plössl aka the Clavé.

The reference scope at this time was a newton 8" f7, the eyepiece was made to work with the Marcel Paul barlow for planetary.

Flat field design @f/14 modified from the A.Konig patent and fit Parra-Mantois baryum glass at the time it was calculated.

A poly-strehl evaluation make it very useful up to 40° AFOV. under 8mm focal length, if objective speed is low at f/14.

SAF recommendation was to preserve eye relief construction even if only 43° field was directly accessible.

Color correction matches well eye resolution : top saturated color, subtles hues are well perceived.

Was designed as a replacement eyepiece to the orthoscopic that was difficult to built at this time. The design lasted long and could still be used today when combined in the powerful enough barlow.

Eye relief is 73% fl. and focus to sky lens around 80%

The exit pupil has low aberration @f14 and is still usable at f/6 with few eye fatigue (~3 dioptries) for deep sky watching.

For the 10mm, diffractiong limited field is 8° off axis at f8. (AFOV central 16°), 18° at f/14 (36° AFOV), 2° off axis at f/6

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#30 lylver

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Posted 30 April 2020 - 05:35 PM

Masuyama, a retroengineering try.

+ Clave update

Due to geometry, I was surprised by the heavy index needed, should be lanthanum glass anyway.

The eyepieces has limited curvature, should be comfortable.

masuyama2-post-36-1407091554409.jpg

masuyama75f7-15D.JPG

Attached Files


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#31 djgilley

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Posted 04 May 2020 - 03:33 PM

Thought I would see what I could do to improve a design posted from a thread last year https://www.cloudyni...chromat-design/ This design is a Petzval/sub aperture corrector. The primary doublet is over corrected and about F17.5 with a 6 inch corrector at a bit over half the primary focal length. The resulting combination operates at ~F8.9, though the tube would of course be longer, perhaps 125 inches as guess? The F/C color correction is 1/7900, so a good improvement over a standard achromat, though there is still quite a bit of G-line error, about the same as a standard 4 inch F12.5 achromat. 

 

10 inch Petzval OSLO
10 inch Petzval spots

 

 

Attached Files


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#32 Mike I. Jones

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Posted 04 May 2020 - 06:32 PM

300mm Loveday scope, with some tweaks by me.

 

Attached File  300mm Loveday.len   634bytes   34 downloads

 


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#33 Mike I. Jones

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Posted 04 May 2020 - 06:44 PM

"Hypergraph" 400mm f/8 giving 50x50mm sensor format.

 

Attached File  HypergraphV2.len   837bytes   18 downloads

 


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#34 Ed Jones

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Posted 05 May 2020 - 01:10 PM

This is a 10 inch Dilworth type of relay telescope.  It's all spherical F/7.  

Attached Thumbnails

  • Dilworth.jpg

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#35 djgilley

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Posted 05 May 2020 - 09:25 PM

Just out of curiosity I thought I'd try substituting a different flint glass in my previous Petzval design. When I did the first iteration I was surprised to see that this combination has much better color correction, I'd call this a semi-apo. 

10 inch Petzval LAL8
10 inch Petzval spot

 

 

 

 

Attached Files



#36 Mike I. Jones

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Posted 15 May 2020 - 09:18 PM

10" f/11 Dual-primary Gregorian.  How to make a Gregorian look like a Cassegrain.

 

Attached File  10in f11 Dual Primary Gregorian.len   1.21KB   20 downloads

 

10f11 dual-primary Gregorian - layout.jpg

 

10f11 dual-primary Gregorian - spots.jpg


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#37 Mike I. Jones

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Posted 18 May 2020 - 07:26 PM

The process for adding text, lens files and pictures is:

1. First, click "More reply options".  You'll then see "Attach Files" button. 

2. You can start off the post with an introductory or descriptive text (but you don't have to).

3. Do "Choose Files" and pick your lens file (*.len or *.zmx) or picture files (*.jpg, *.gif).  Just pick one at a time to attach. 

4. Do "Attach This File" to attach it to the post, but you have to do "Add to Post" for it to show up in the post.  

5. Do "Add to Post" to place the lens file or picture wherever you want in the text stream.  You can put it anywhere in the post, before or after text, or before or after a picture.

6. Add more text as desired, or load up another picture and do "Add to Post" wherever you want it in the text stream.

 

Looking forward to seeing your designs here, they will be most welcome.

Mike


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#38 Get Sirius

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Posted 19 May 2020 - 07:46 AM

This is a post for those with a big budget. It is my Kilometer Scope. The primary mirror is f/1.0 and one kilometer in diameter.

With just two conic mirrors and three reflections this design has incredible performance. Unfortunately it is almost impossible to baffle.
Kilo #1.png

Kilo #2.png

For those with a more modest budget the design can be made with a 100 meter diameter f/.7 primary mirror and give a diffraction-limited field size of about 800 mm in diameter, on a slightly curved image.
To make this design easier to use you might want to add a 10 meter diameter finder scope. Both conic mirrors here are very close to being pure parabolas.
My pledge to you - other designs I will be posting are smaller than this one.

- Dave

#39 Mike I. Jones

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Posted 19 May 2020 - 08:43 AM

Dave, you can add your OSLO  *.lens files exactly like pictures.  A lot of folks here know how to use OSLO-EDU with its 10-surface limit, and would love to have your designs here!



#40 Get Sirius

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Posted 19 May 2020 - 09:23 AM

quad picture.png

This is a quad-schiefspiegler design done with an interesting constraint - the output axis is parallel to the input axis.
No rays crossing over each other as in the usual tri-schiefspiegler designs. Here is the OSLO file.

Attached File  Quad Schiefspiegler.len   35.44KB   10 downloads

This 6 inch f/12 design is diffraction limited over a 1.0 degree diamter field, with no image tilt. If the ptimary mirror is made a parabola then better performance results but a slight retouch of the design is then necessary. It can then be made in a 12" f/12 design.
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#41 djgilley

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Posted 19 May 2020 - 06:51 PM

This design is a modification of the design in a thread I started about 3 weeks ago https://www.cloudyni...hromat-design/ 

I wanted to see what I could come up with by replacing the FPL-51 with a less expensive and much easier to work with substrate, BK-7. This uses a fairly new glass from Ohara, TIH-57, I'm not sure of it's diameter availability. The melt chart shows it as 5.5x the cost of BK-7, so it's somewhat more expensive than the other titanium flints. The 4th element, NBH-56 is 7x the cost of the BK-7, but it's half the diameter of the 1st element. Though the F/C correction is somewhat unequal, it averages ~1/5 wave. G is .36 wave and R is similarly corrected. The track length is 1.4x the focal length, so a bit of a disadvantage in mounting. 

BK7NBH56
BK7TIH57spots

 

Attached Files


Edited by djgilley, 19 May 2020 - 06:53 PM.

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#42 Get Sirius

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Posted 19 May 2020 - 08:16 PM

Here is an 8 inch aperture f/1.0 astrocamera design with a 10 degree flat field diameter.

pix.jpg

Attached File  May 19, 2020 astrocamera.len   5.33KB   15 downloads

The OSLO file shows that for most of the field 80% of the polychromatic energy from .45u to .65u falls within a 8 to 10u diameter circle.

The lenses are all BK7 glass and all surfaces are spherical.

Edited by Get Sirius, 19 May 2020 - 08:17 PM.

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#43 Get Sirius

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Posted 20 May 2020 - 07:28 AM

Here is the design prescription for the f/1.0 Astrocamera in my previous post.


f/1.0 Astrocamera with 10 degree field diameter

All spherical surfaces


SRF RADIUS THICKNESS APERTURE RADIUS GLASS


OBJ -- 1.0000e+20 8.7489e+18 AIR


1 638.516100 25.000000 105.000000 BK7 aperture stop

2 flat 101.006918 105.000000 AIR

3 -355.827257 30.000000 107.000000 BK7

4 -694.462798 3.000000 109.000000 AIR

5 398.216736 34.999994 112.000000 BK7

6 447.405712 123.025997 112.000000 AIR

7 -398.374692 -123.025997 115.000000 REFL_HATCH

8 447.405712 -34.999994 112.000000 BK7

9 398.216736 -3.000000 112.000000 AIR

10 -694.462798 -30.000000 109.000000 BK7

11 -355.827257 -2.000000 107.000000 AIR

12 -68.806711 -16.063653 28.000000 BK7

13 -- -3.000000 28.000000 AIR

Image 17.5 height

Focal length = 200 mm at .5200u

Edited by Get Sirius, 20 May 2020 - 07:30 AM.

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#44 Get Sirius

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Posted 20 May 2020 - 09:32 AM

Here is a very compact quad-schiefspiegler design with all spherical surfaces and no image tilt. This is for a 6 inch aperture f/10.3 design
The OSLO file is given here too. I am not familiar with everything that has been done in quad-schief designs and don't know if this is new.



[attachment=Attached File  Compact Quad-schiefspiegler.len   8.45KB   19 downloads


1498451:ast.jpg].

Attached Thumbnails

  • ast.jpg

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#45 Get Sirius

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Posted 21 May 2020 - 04:56 PM

Catadioptric telescope designs with subaperture lens correctors for spherical primary mirrors usually have lenses that are about ¼ to 1/3 of the diameter of the primary mirror. There is variation in that size ratio but it is true for most designs. By contrast there is a wonderful design by Peter Ceravolo where the corrector lenses are only in the 8% to 10% range of the primary mirror’s diameter. Furthermore the design works well for fast speed spherical primary mirrors in the f/2.0 to f/1.5 range. For really large aperture telescopes, like 1.0 meter or larger, that makes the corrector lenses still be a reasonable size and cost. The design requires a Gregorian configuration to work. Here is an example of a 20 inch aperture f/10 design with an f/2.0 spherical primary mirror. The corrector lenses are only 1.6 inch in diameter!

cer.png



cer2.png




The secondary mirror gives 35% diameter obscuration and the corrector lenses fall inside that central hole in the beam.Attached File  Gregorian with 3 corrector lenses, May 21, 2020.len   5.17KB   12 downloads

Edited by Get Sirius, 21 May 2020 - 05:10 PM.

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#46 ed_turco

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Posted 23 May 2020 - 10:15 AM

+1



#47 Mike I. Jones

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Posted 24 May 2020 - 12:19 AM

This is a very fast J-band infrared camera I did for Caltech a few years ago.  300mm f/1.0, 1.15-1.35µm spectral band, 10 degree field, three aspheres, imaging onto a 2K x 2K cooled InGaAs sensor with 18µm pixels (36x36mm).  Predicted to reach 17th magnitude in J-band in 5-10 seconds integration time for nightly all-sky surveys.  The requirement was to give 80% ensquared energy within each 18µm square pixel anywhere over the format, which this design achieves with some margin.  The SF8 window covers the sensor, which is cooled to 77ºK.  Maximum distortion is +6 pixels at the extreme corners, which is easily removed with little image degradation.  This is an extremely difficult design to manufacture, with very tight tolerances.  The cost quotes forced the design to fall back on Valery Terebizh's 300mm f/1.46 all-spherical design, which cost them longer integration times to reach the same magnitude but at a fraction of the cost of the f/1 system.  I sure would have liked to have seen this built.

 

Attached File  300mm f1.len   1.11KB   9 downloads

 

300mm f1 layout.jpg

 

300mm f1 prescription.jpg

 

300mm f1 spots.jpg

 

The cutoff frequency for 18µm pixels is 1 / (2 * 0.018) = 27.78 cy/mm, so the MTF plot stops at 30 cy/mm.  The system is within about 10% of being diffraction limited at f/1 at the extreme corners.

 

300mm f1 MTF.jpg


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#48 lylver

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Posted 26 May 2020 - 05:30 PM

Brandon eyepiece ?

brandon10.JPG

Violet (405nm) not focused compared to another asymetrical plössl

brandon10violet405s.jpg

Strengths : spherical aberration is low, field curvature positive, no annoying ghost image.

Attached Files


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#49 Mark Harry

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Posted 27 May 2020 - 08:12 AM

Good match for Gregorian?



#50 Josef-cz

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Posted 30 May 2020 - 01:47 PM

https://www.cloudyni...telescope-r2881

The best optical construction that exists is simple, easy to make, I attach live recordings.

https://www.youtube....h?v=SKsrIpI9lwE

https://www.youtube....h?v=J684xshhx8s

https://www.youtube....h?v=v34mTPSosok

https://www.youtube....eature=youtu.be


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