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Can anyone here post the typical specs on a China 150 F8 achro objective?

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#1 largelenses

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Posted 16 May 2021 - 08:19 AM

....or post what your best guess is for such glass specs?

Thank you.


Edited by largelenses, 16 May 2021 - 08:20 AM.


#2 RajG

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Posted 16 May 2021 - 08:32 AM

Link to Mike Jones' design:

 

https://www.cloudyni...2#entry11094146



#3 largelenses

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Posted 16 May 2021 - 08:36 AM

Link to Mike Jones' design:

 

https://www.cloudyni...2#entry11094146

Thank you much indeed!



#4 largelenses

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Posted 16 May 2021 - 09:06 AM

Can somebody with OSLO please post a breakdown of that linked lens file here?

Thank you



#5 rflrs

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Posted 16 May 2021 - 10:31 AM

Guess @ Celestron C6-R - visual
 SRF      RADIUS      THICKNESS   APERTURE RADIUS       GLASS  SPE  NOTE
 OBJ       --        1.0000e+20    5.2360e+17             AIR    

 AST   727.194584     16.000000     78.000000 A         H-K9L C  
  2   -436.352363      0.127000     78.000000             AIR    

  3   -440.912035      9.000000     75.000000            H-F4 C  
  4   -1.7911e+03    1.1873e+03     78.000000             AIR    

 IMS       --            --          6.292900 S                

 

Straight out of OSLO EDU.

 

Richard



#6 Star Shooter

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Posted 16 May 2021 - 01:21 PM

I have noticed that the Aperture Radius of surface #3 is not the same as the others.

It is 75mm, should it be 78mm like the others?



#7 Mike I. Jones

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Posted 16 May 2021 - 01:24 PM

L2 R1 is concave and light is converging into it, so I trimmed its aperture down some to give a flat land for an airspace ring.



#8 largelenses

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Posted 16 May 2021 - 01:45 PM

Thanks a bunch guys!!



#9 largelenses

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Posted 16 May 2021 - 02:56 PM

Just so I got this right:

 

First surface crown:  Radius    727.194584mm     16.000000mm thick     78.000000 A         H-K9L

Rear surface crown:  Radius  -436.352363mm  

 

 

With a .127 mm air gap between it and

 

 

First surface flint:  Radius     -440.912035mm      9.000000mm thick     75.000000            H-F4
 

Second surface flint: Radius -1791.1mm

 

Is it ok?



#10 Mike I. Jones

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Posted 16 May 2021 - 03:11 PM

Yes, it's fine but...

JUST TO BE SURE>>>>>  This was just a fictitious lens I made up based on my experience that gave Bob Yoesle a hint or guide on about how much extra shim to add to the airspace in his Celestron R6 lens.  It is NOT the exact prescription for the Celestron R6 lens.  The real prescription is proprietary to Celestron and I don't have it.  

 

However, this lens in the OSLO file is a real design and could be made, and it would work fine, if you're wanting to make it, and if you can get the glass blanks.  And, it's just a garden variety achromat, not an apo with costly glass, and will have the usual secondary color.

Mike



#11 lylver

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Posted 16 May 2021 - 03:19 PM

With 0.2mm and tin / tin silvered spacer, coma near canceled at F ray. Very thin lens

Units mm :

r1=734, r2=-437, t1=16, glass H-K9L

e=0.137 (0.2 on edge)

r3=-440.9, r4=-1749, t2=10, H-F4

------------------

coma corrected near Oiii rays or visual deep sky/scotopic peek (507-510) may be more probable for wide angle use.

It is a guess like Mike does : to complete what it could be.


Edited by lylver, 16 May 2021 - 04:01 PM.

  • jkmccarthy likes this

#12 largelenses

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Posted 16 May 2021 - 03:23 PM

Yes, it's fine but...

JUST TO BE SURE>>>>>  This was just a fictitious lens I made up based on my experience that gave Bob Yoesle a hint or guide on about how much extra shim to add to the airspace in his Celestron R6 lens.  It is NOT the exact prescription for the Celestron R6 lens.  The real prescription is proprietary to Celestron and I don't have it.  

 

However, this lens in the OSLO file is a real design and could be made, and it would work fine, if you're wanting to make it, and if you can get the glass blanks.  And, it's just a garden variety achromat, not an apo with costly glass, and will have the usual secondary color.

Mike

Thanks again!

  The free vs of Winlens3d does not let you open the included lens database and start examining their achros in the list too closely, which is kinda weird.  Can't break down the spot diagrams by color, for instance.



#13 largelenses

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Posted 16 May 2021 - 03:29 PM

With 0.2mm and tin / tin silvered spacer, Coma near canceled at F ray. Very thin lens

Units mm :

r1=734, r2=-437, t1=16, glass H-K9L

e=0.137 (0.2 on edge)

r3=-440.9, r4=-1749, t2=10, H-F4

Cool. Thanks!




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