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Homemade 0,65m f 1.5

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#1 galaxy13

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Posted 20 September 2019 - 04:59 PM

Gennady Borisov discovered recently a comet with his 0.65m f1.5 home-made telescope. https://www.skyandte...eaded-our-way/ 

 

It would be interesting to know how he was able to grind and parabolizing a telescope with so an extremely low f-ratio. Also how did he took pictures of the comet? Any reference and links would be appreciated.


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#2 gatorengineer

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Posted 20 September 2019 - 07:21 PM

I doubt it's parabolic..... Most likely hyperbolic with a lot of corrector... No small feat either way....


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#3 Ed Jones

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Posted 20 September 2019 - 07:24 PM

Well if the effective F ratio is 1.5 it doesn't mean the primary is F number is 1.5. He's could be using a tele-compressor on a fast primary with a not so large field.


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#4 clivemilne

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Posted 20 September 2019 - 07:52 PM

From the author:

 

 

 

He uses a FLI ML16803 camera located in the direct focus of the telescope.
The FLI Atlas focuser and CCD are mounted on spiders.

Gennady-with-0.65-m-scope_S-768x735.jpg


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#5 clivemilne

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Posted 20 September 2019 - 07:55 PM

It's an impressive instrument if it can illuminate a 37mm CCD chip at F1.5 with anything approaching a well corrected and flat focal plane.

 

Very impressive indeed.



#6 Ken Watts

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Posted 20 September 2019 - 09:12 PM

I showed my wife the picture and she just said, "oh, no no no no no!"  There went my Saturday project!

 

My hat is off to the fine person who engineered this fine astrocamera.  I am sure he, and his team, are quite proud!


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#7 brebisson

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Posted 21 September 2019 - 09:42 AM

Hello,

 

i think I read that he was working for an optical company or something like this, which probably explains a lot...

 

  cyrille 



#8 Vla

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Posted 21 September 2019 - 11:41 AM

It is not completely homemade. Borisov says for these more complex systems he buys computerized components, and optics are custom made commercially. He is an engineer in a Crimean state observatory, but he says they trust him only to wash the mirrors (probably joking). He also works for Roscosmos, which monitors satellites and space debris. Building telescopes for four decades.


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#9 Mike I. Jones

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Posted 21 September 2019 - 12:11 PM

Other than a question asked after the S&T article, I didnt read anything stating it was f/1.5.  I even watched the video with captions turned on and still no f/1.5.

 

EDIT: OK I found the reference on the MPC discovery announcement, observer details: "L51 MARGO, Nauchnij.  Observer G. Borisov.  0.65-m f/1.5 astrograph + CCD."

 

Vla - is this a Terebizh design?



#10 Vla

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Posted 21 September 2019 - 12:46 PM

There is little about the telescope itself. It is f/1.5 Hamiltonian-type astrograph. From the Russian press:

 

[30 августа 2019 года в ходе поискового обзора в обсерватории MARGO (пгт. Научный, Крым) с помощью 650-мм f/1.5 телескопа-астрографа системы Гамильтона он сделал снимки, на которых обнаружил ту самую комету.]

 

From what he says, sounds as if he designed the system and had the optics commercially made. Perhaps a singlet in front, Mangin mirror and field corrector.


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#11 mconnelley

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Posted 21 September 2019 - 05:30 PM

Hello:

 

    From the picture, it doesn't seem to have a corrector lens that is common for a Hamiltonian.  I also noticed that the elevation/declination axis is near the middle of the tube.  Either the primary is very light, or he's expecting to put something really heavy on the top end.  It looks like there might be a hole through the middle of the spider, so perhaps the lenses are below the spider and the camera goes on top.  I would be very interested to see this optical design.

Cheers

Mike


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#12 clivemilne

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Posted 21 September 2019 - 05:52 PM

I would have thought that a spider would have been somewhat redundant in a Hamilton?



#13 Mike I. Jones

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Posted 21 September 2019 - 06:17 PM

I tossed this set of designs together this afternoon just for fun to see what could be done, and a nice sharp 650mm f/1.5 Hamiltonian is indeed feasible. The FLI ML 16803 sensor is 4096x4096 with 9µm pixels, giving a 36.864 mm square with diagonal of 52.13mm, so this system is corrected out to 26mm off axis (giving a total corner-to-corner FOV of 3.06º). I assumed a wavelength range of 0.438-0.90µm to more or less match the CCD QE curve, although I left off any shorter wavelengths due to increased atmospheric scattering and contrast reduction (detrimental to comet hunting). I optimized the reflective second surface of the Mangin mirror with a sphere, pure conic and 8th order aspheric. A single corrector lens didn't quite get there, but with glass substitution a doublet corrector worked nicely. Even the all-spherical design performed well.

I also tried 2-element and 3-element Rosin astrographs using a hyperboloidal primary, but this was a little out of the Rosin's league. The Hamiltonian is a good choice for this astrograph.

Too many surfaces for OSLO-EDU, so I'll just attach the Zemax file for those that want to play with it. Here's the layout plot.

650mm f1_5 Hamiltonian astrograph layout.png
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#14 Mike I. Jones

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Posted 21 September 2019 - 06:19 PM

For you spot diagram fans, these are the spots I achieved.  All have nice tight cores with just a little fuzz around them.  It took some games with weighting field positions and wavelengths to get the spots this uniform over the FOV.

 

650mm f1_5 Hamiltonian astrograph spots.png


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#15 Mike I. Jones

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Posted 21 September 2019 - 06:27 PM

Although the design is far from diffraction limited at f/1.5, it still gives good polychromatic image modulation out to 100 cy/mm. 9 micron pixels have a Nyquist cutoff frequency of 1/(2 * 0.009)=56 cy/mm, so image modulation is around 50-60% at this spatial frequency.

Tolerances on the design components and alignment are nightmarish-ly tight, especially the Mangin mirror. Maintaining performance over temperature borders on art rather than science. I see what look like carbon fiber spacer rods around Borisov's tube. I believe it, and Invar 36 is not out of the question, unless he doesn't mind refocusing all night.

Cool story, cool telescope!

650mm f1_5 Hamiltonian astrograph MTF.png.jpg
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#16 Mike I. Jones

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Posted 21 September 2019 - 06:34 PM

Here's the Zemax file if you're interested.

 

Attached File  650mm f1_5 Hamiltonian configs no MF.zmx   28.43KB   26 downloads


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#17 Vla

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Posted 21 September 2019 - 07:38 PM

I searched a bit more, just to make sure what goes as "Hamiltonian" in Russia. Turned out it is the same (more sophisticated) system. The spider is needed because the final image (and corrector) lies midway between the front singlet and Mangin mirror.

Here's a pic showing the astrograph fully mounted. It is likely made based on the Santel 650mm f/2 system made by Roscosmos (50x50mm chip). Here's what the design looks like (bottom). I'm pretty confident Mike could squeeze out more from this kind of configuration.


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#18 PrestonE

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Posted 22 September 2019 - 08:14 AM

I found the below interview with him below...

 

If you watch the whole thing, it gives a couple of Quick views

of the front end of the scope with camera and corrector assemble...

 

https://www.facebook...?type=3

 

Best Regards,

 

Preston


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#19 Rickster

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Posted 22 September 2019 - 08:56 AM

How significant is camera heat when the camera is in the light path?



#20 Mike I. Jones

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Posted 22 September 2019 - 09:58 AM

Kind of but not totally tangential to the thread, but I wanted to show you what a remarkable design the Hamiltonian is.  This is a 300mm f/1.0, 10º FOV J-band infrared telescope study I did for Caltech a few years ago.  The sensor was a cooled InGaAs camera with 18µm pixels, and the requirement was to concentrate all energy over the aperture into each pixel anywhere within the 10º FOV.  I studied several different configurations, and the Hamiltonian was the only system capable of meeting the requirements with minimum glass in the path.  Best thing is, it's only three elements and can fit into the OSLO 10-surface limit grin.gif grin.gif  Here's the prescription, OSLO file and layout plot.

 

Attached File  300mm f1 J-band astrograph.len   1.55KB   8 downloads

 

300mm f1 J-band astrograph prescription.jpg

 

300mm f1 J-band astrograph layout.jpg

 


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#21 Mike I. Jones

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Posted 22 September 2019 - 10:00 AM

And these are the spots, with 18µm pixels overlaid, and the MTF out to 30 cy/mm.  The Nyquist cutoff for 18µm pixels is 1/(2*0.018)=27.8 cy/mm.

 

300mm f1 J-band astrograph spots.jpg

 

300mm f1 J-band astrograph MTF.jpg

 



#22 555aaa

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Posted 22 September 2019 - 12:14 PM

The Newtonian version in the reference that vla provided looks intriguing as it shows only a single element corrector.

#23 Vla

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Posted 22 September 2019 - 03:30 PM

I found the below interview with him below...

 

If you watch the whole thing, it gives a couple of Quick views

of the front end of the scope with camera and corrector assemble...

 

https://www.facebook...?type=3

That's interesting, because it shows front lens before the camera (easier to handle, for sure). Still, it's a bit strange not to see any sign of a flange around the opening that has to be on it, more so considering that the field corrector has positive power, making the beam converge more strongly toward the image plane. It is possible that camera and field corrector are part of one assembly, mounted onto the ring held by spider vanes, and the hole is minimized.


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#24 izberdska

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Posted 22 September 2019 - 07:05 PM

Gennady Borisov: a homemade Hamilton telescope.

https://astronomy.ru...html#msg4827179


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#25 Mike I. Jones

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Posted 22 September 2019 - 11:52 PM

Our friend at TEC, Yuri Petrunin, regularly reads this and other Cloudynights forums.  He knows a load of Russian optical and astronomical folks, and wrote me with some additional information on Borisov's telescope.  Here's some of what Yuri wrote, with his permission to put on CN.  The only purpose here is to give proper credit where credit is due.

 

Start this with a Google search on "valery terebizh".  You will be amazed.

 

All of Borisov's comets were discovered with telescopes designed by Dr. Valery Terebizh (VT), an excellent optical designer of a number of different wide-field, low focal ratio astrographs.  Many of Terebizh's designs have been built, including all the instruments Borisov used to discover comets listed below.  

 

Comet              Instrument     Design
C/2013 N4 (Borisov)  GENON        VT78-A  (First comet of independent Ukraine)
C/2013 V2 (Borisov)  GENON        VT78-A
C/2014 R1 (Borisov)  GENON Max    same but scaled 1.5X or other VT design
C/2014 Q3 (Borisov)  GENON Max    same but scaled 1.5X or other VT design
C/2015 D4 (Borisov)  GENON Max    same but scaled 1.5X or other VT design
C/2016 R3 (Borisov)  GENON Max    same but scaled 1.5X or other VT design
C/2017 E1 (Borisov)  GENON Max    same but scaled 1.5X or other VT design
C/2019 Q4 (Borisov)  no name yet  VT-8b scaled (Hamilton)

 

This site is interesting, but fails to mention that the optics for all the GENON scopes above were designed by Terebizh:

 

https://uk.wikipedia...орисов_Геннадій

 

Yuri said that the optics for Borisov's 650mm F1.5 system were made by highly skilled professional opticians.  Borisov evidently made and assembled the telescope mechanical parts, but he did not make the optical components.

 

The telescope is installed in the dome that belongs to Roscosmos, a company that does government military orders for satellite tracking programs.

 

https://www.roscosmos.ru/26801/   

 

When translated to English the first paragraph states: "Director General of Roscosmos State Corporation Dmitry Rogozin met with an employee of the Crimean Astrophysical Observatory Gennady Borisov. Using a telescope reflector of his own manufacture, the astronomer made the discovery of the first interstellar comet."

 

Borisov really put Ukraine on the map by discovering this interstellar comet.  But to clarify, "...of his own manufacture" does not mean Borisov made the optics, rather he had them made and integrated them into his telescope structure.

 

I don't know if any of this really matters, except to give Valery Terebizh proper credit for all the telescope optical designs used for Borisov's comet discoveries.


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