Jump to content


Photo

Herring

  • Please log in to reply
122 replies to this topic

#1 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 09:21 AM

Dave O sent me some OSLO designs on a Herrig 9.5inch f12 . Any one have a design to share ? Dave s is very good Just thought ask. I think my interlocking box with slots might work for the Herrig . One thing on this one is a 800inch RCcx :help:

#2 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 09:35 AM

The 9.5 inch could be made with two 14.5 quartz blanks. Only two spherical surfaces . If a box could be made to hold them perfect . I tried one 10 years back but failed .math error . The .7 inch thick quartz is light and strong . The optical box could be light weight 4.5 ft long Maybe a box like this

Attached Files



#3 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4724
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 December 2012 - 09:54 AM

Dave O and I have been playing around with this design for few months. There is a BASIC program that was written to calculate the design and one of the functions is to save the output in the format that WINSPOT can read. I modified the program a tiny bit so it it was easier to run. You need access to QBASIC to run the program. Luckly I was able to find and old complier.
For those that don't know what the Herrig design is, it uses a CONVEX primary and Conave secondary and the light bounce off each twice. It also unobstructed. The correction is excellent. The only issue is figuring the long focal length convex primary. My thought is to make it out of Quartz because the low thermal expansion but more importantly Quartz is pretty clear optically so you can test thru it. This would allow one to first grind and polish a concave sphere on the back surface, the purpose of which would be to cause a null condition when the long radius convex surface was also a perfect sphere and you tested thru the concave surface. Just like one does when testing a Schupmann corrector.
Here is a spot diagram for 7" f18 version for 0.5 degree field of view. The black circle is the size of the Airy disk. As one can see it is better then diffraction limited out the very edge of the field. There are very few optical designs that are this good. It definitely on the "bucket list" of designs I would like to make.

- Dave

Attached Files



#4 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4724
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 December 2012 - 10:00 AM

Here is the OLSO file for the above 7" version which could be made from 8" blanks.

- Dave

Attached Files



#5 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4724
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 December 2012 - 10:34 AM

Here is a link to the BASIC programs to calculate the Herrig design. By the way the correct spelling of the design is HERRIG, no "N". http://bhs.broo.k12....ck/software.htm

All the Best,
- Dave

#6 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 10:55 AM

Unobstructed /color free / Only two optical{ spherical} surfaces .Thanks Dave

#7 Mike I. Jones

Mike I. Jones

    Gemini

  • *****
  • Posts: 3206
  • Joined: 02 Jul 2006
  • Loc: Fort Worth TX

Posted 10 December 2012 - 11:44 AM

"THEN, you must chop down the mightiest tree in the forest wiiiiiiith.... A HERRIG!"

Definitely on my retirement bucket list as well! Even though Cuzzin Ed rightfully questioned my sanity for using two 12.5" blanks to make an 8" telescope, I just GOTTA see it work! The Herrig is one of those "that CAN'T work but it does" designs, a truly weird, non-intuitive root to an aberration polynomial for sure.
Mike

#8 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 12:26 PM

Seeing EDs design he posted on Marks thread got my one brain cell to think that my box with the slots would hold all his optics in perfect 3d . Then I thought about Herring only two mirrors on center line and just tilted .

#9 tim53

tim53

    Cosmos

  • *****
  • Posts: 9193
  • Joined: 17 Dec 2004
  • Loc: Highland Park, CA

Posted 10 December 2012 - 12:52 PM

What is this? A 'fractor or a 'flector?

#10 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 12:55 PM

4 reflections and maybe more after the Dave s And Jones get done :jump:

#11 MKV

MKV

    Vanguard

  • *****
  • Posts: 2462
  • Joined: 20 Jan 2011

Posted 10 December 2012 - 01:15 PM

The Herrig is one of those "that CAN'T work but it does" designs, a truly weird, non-intuitive root to an aberration polynomial for sure.
Mike

Hmmm, for sure. Looks good 'on paper". With four reflections, I can just imagine what the tolerance are....good luck! Does anyone know of a Herrig that was actually made and objectively tested? Or is it all (OMG!) ancedotal?

Mladen

#12 Mike I. Jones

Mike I. Jones

    Gemini

  • *****
  • Posts: 3206
  • Joined: 02 Jul 2006
  • Loc: Fort Worth TX

Posted 10 December 2012 - 01:25 PM

Oh yes, very real: November 1997 Sky & Telescope; p. 113,

and on Dave Stevick's site at

http://bhs.broo.k12....rrig/newtct.htm

I also put up the 8" design a LONG time ago here that I'm going to make here.

Although, I want to improve on Herrig's mailbox-like enclosure design. Seems very leaky from a stray light standpoint, and the aperture stop is steeply slanted rather than perpendicular to the optical axis, which is better.

Mike

#13 mark cowan

mark cowan

    Vendor (Veritas Optics)

  • *****
  • Vendors
  • Posts: 3977
  • Joined: 03 Jun 2005
  • Loc: salem, OR

Posted 10 December 2012 - 03:21 PM

My thought is to make it out of Quartz because the low thermal expansion but more importantly Quartz is pretty clear optically so you can test thru it.



This will only be true if the quartz (AKA fused silica) is of transmission grade. The majority of what I've seen from surplus sources isn't - it contains many tiny bubbles and won't pass a coherent wavefront. The only true test I know of to differentiate the two is to try it as a transmission piece. :shrug:

Best,
Mark

#14 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4724
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 December 2012 - 03:40 PM

Mark,
I've work with Quartz up to 5" in diameter that was pretty good but I understand that the bigger stuff might have issues in transmission. If worse comes to worse then there is always BK-7. While it doesn't have the thermal expansion coeff. that Quartz does, there are plenty of large optics, that have elements made of the stuff. Just going to need to wait longer to test and to let the finished scope cool down.

- Dave

#15 mark cowan

mark cowan

    Vendor (Veritas Optics)

  • *****
  • Vendors
  • Posts: 3977
  • Joined: 03 Jun 2005
  • Loc: salem, OR

Posted 10 December 2012 - 05:03 PM

Hi David,

If it's semiconductor surplus it just plain varies. You can spec it if you're buying new but the price goes nuts. The way it's made determines the bubbles.

The material from RecoLabs has a small % of transmission quality pieces and it's not hard to test for that as they typically are plane-parallel and polished (not optically though). If a laser shows no scatter I've just put them on the stand in front of a good mirror and check the Ronchi - scatter is immediately obvious.

Material from Five Star Optics (formerly Superior Optical) may or may not be - I haven't tested any of it yet as it requires working for transmission tests and SFAIK neither has anybody else...

Best,
Mark

#16 ccaissie

ccaissie

    Viking 1

  • -----
  • Posts: 630
  • Joined: 13 Sep 2010
  • Loc: Whitefield, Maine

Posted 10 December 2012 - 06:54 PM

There was some grumbling over the 4 surfaces, etc., in the earlier posts to Jones. Assuming the ability to make some nice spherical surfaces, how does this design tolerate angular misalignment? spacing? radius of curvature?

Relative insensitivity to tolerances could make this a desirable design.

#17 MKV

MKV

    Vanguard

  • *****
  • Posts: 2462
  • Joined: 20 Jan 2011

Posted 10 December 2012 - 07:52 PM

Hi Mike, I think you and Ed Jones covered all the points on your archived thread - except one: the four reflections. I mean if autocollimation doubles the the wave error, I can just imagine what will four reflections do to A 1/10 wave P-V error!

Mladen

#18 MKV

MKV

    Vanguard

  • *****
  • Posts: 2462
  • Joined: 20 Jan 2011

Posted 10 December 2012 - 07:57 PM

on Dave Stevick's site at

Great. And how did it perform? I can't open the "Examples" files.

Mladen

#19 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 08:49 PM

I think there are some that use a 3 mirror for the last reflection

#20 Mike I. Jones

Mike I. Jones

    Gemini

  • *****
  • Posts: 3206
  • Joined: 02 Jul 2006
  • Loc: Fort Worth TX

Posted 10 December 2012 - 09:00 PM

I'm not following the issue of transmission. The Herrig is all-reflective. It is true that bubbles that grind through will scatter some light. But the internal transmission of the mirror substrates is immaterial.
Mike

#21 kfrederick

kfrederick

    Mercury-Atlas

  • *****
  • Posts: 2926
  • Joined: 01 Feb 2008

Posted 10 December 2012 - 09:02 PM

Post deleted by kfrederick

#22 Mike I. Jones

Mike I. Jones

    Gemini

  • *****
  • Posts: 3206
  • Joined: 02 Jul 2006
  • Loc: Fort Worth TX

Posted 10 December 2012 - 09:03 PM

OHHH - "Never mind"! :rainbow:

#23 ccaissie

ccaissie

    Viking 1

  • -----
  • Posts: 630
  • Joined: 13 Sep 2010
  • Loc: Whitefield, Maine

Posted 10 December 2012 - 10:32 PM

I ran several scenarios of the file in OSLO. Relatively INsensitive to spacing, radii, and angles.

C

#24 ccaissie

ccaissie

    Viking 1

  • -----
  • Posts: 630
  • Joined: 13 Sep 2010
  • Loc: Whitefield, Maine

Posted 10 December 2012 - 10:55 PM

I'm not following the issue of transmission. The Herrig is all-reflective. It is true that bubbles that grind through will scatter some light. But the internal transmission of the mirror substrates is immaterial.
Mike


Testing the convex surface through the back as a concave?

A.Leonard wrote in ATMT 2 about this in making convex hyperboloids. pp57,58, and in making mak correctors.

Right, needs to be homogeneous to a high degree for testing through the back.

#25 MKV

MKV

    Vanguard

  • *****
  • Posts: 2462
  • Joined: 20 Jan 2011

Posted 10 December 2012 - 11:03 PM

I ran several scenarios of the file in OSLO. Relatively INsensitive to spacing, radii, and angles.

C

The spacing, angle and radii were never even mentioned. If you read Mike Jones' archived thread from 2006, he and Ed Jones mention the "cons", one being that you need a 12.6" and an 11.2" mirror for an 8-inch clear aperture and a substantial loss of transmission on each reflection x 4 Ed put is succinctly: "What do you like about it? Four reflections, 2 oversize optics, doesn't have much going for it."

I think four reflections will mulitply even the tiniest errors on the mirrors wavefront and make them stand out. It's a well know fact that in autocollimation testing you have doubling of the errors even with fewer reflections.

Mladen






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics