Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Brandt telescopes

  • Please log in to reply
36 replies to this topic

#1 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • topic starter
  • Posts: 21,454
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 21 June 2020 - 11:47 AM

Thought it was time to give Brandt a thread due to the recent ad on astromart for a 6" folded F15 Brandt refactor.

 

https://astromart.co...-refractor-6215

 

This ad on Astromart gives a good history on Brandt. 

 

I will look for more history.

 Maybe others who met Brandt can give some more insight to this mans accomplishments. 

 

Brandt made refactors and Maks.  I had one of his 8" Maks.  Great scope.  Guy I sold it to was very happy. 

 

https://astromart.co...olded-refractor

 

https://astromart.co...-cassegrain-f15

 

https://astromart.co...dt-8-mak-364171


Edited by starman876, 21 June 2020 - 11:53 AM.

  • tim53, Terra Nova and Bomber Bob like this

#2 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • topic starter
  • Posts: 21,454
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 21 June 2020 - 11:55 AM

also found this old thread

 

https://www.cloudyni...w-many-history/

 

there has to be more.



#3 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • topic starter
  • Posts: 21,454
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 21 June 2020 - 12:04 PM

https://www.google.c...=nnG4alZWokDTDM



#4 clamchip

clamchip

    Voyager 1

  • *****
  • Posts: 10,569
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 21 June 2020 - 01:07 PM

Most of the Brandt lenses ended up folded. 

To help understand a folded refractor I like Dave Trott's article:

http://davetrott.com...lded-refractor/

 

Robert


  • Bomber Bob likes this

#5 clamchip

clamchip

    Voyager 1

  • *****
  • Posts: 10,569
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 21 June 2020 - 01:21 PM

I built a telescope for a R.E. Brandt 6 inch f/13.3 lens/cell.

Remarkable how a fast 6 inch lens can perform this well.

His lenses were different as noted on this comparison plot.

Robert

 

post-50896-0-36135800-1547347053.jpg

Scan0009.jpg


  • Mr Magoo, plyscope, astro140 and 5 others like this

#6 clamchip

clamchip

    Voyager 1

  • *****
  • Posts: 10,569
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 22 June 2020 - 07:59 PM

Found a few more pictures of my Brandt 6 inch.

Top is my optics laboratory testing the lens spacing. I don't know if you can read the

eyepiece focal length it's 2.5mm giving me 810X. That's nothing I've used over 1000X

with this telescope, being silly of course but the Brandt didn't think I was silly it really

puts out the performance. 

Middle is mounted to my Edmund Extra Heavy Duty.

And I'm sure everyone has been wondering,

Do we dare ask Robert about the you know, the clamchip. Heaven forbid no not this

lens. Yes and it's a doozy, red arrow.

Robert

 

post-50896-0-21343200-1419821475_thumb.jpg

post-50896-1407390316388_thumb.jpg

post-50896-14073904174202_thumb.jpg


Edited by clamchip, 22 June 2020 - 08:10 PM.

  • Mr Magoo, beanerds, steve t and 6 others like this

#7 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • topic starter
  • Posts: 21,454
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 22 June 2020 - 08:02 PM

Found a few more pictures of my Brandt 6 inch.

Top is my optics laboratory testing the lens spacing. I don't know if you can read the

eyepiece focal length it's 2.5mm giving me 810X. That's nothing I've used over 1000X

with this telescope, being silly of course but the Brandt didn't think I was silly it really

puts out the performance. 

Middle is mounted to my Edmund Extra Heavy Duty.

And I'm sure everyone has been wondering,

Do we dare ask Robert about the you know, the clamchip, heaven forbid no not this

lens. Yes and it's a doozie, red arrow.

Robert

 

attachicon.gifpost-50896-0-21343200-1419821475_thumb.jpg

attachicon.gifpost-50896-1407390316388_thumb.jpg

attachicon.gifpost-50896-14073904174202_thumb.jpg

really nice scope



#8 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 22,235
  • Joined: 29 May 2012
  • Loc: Under the Blue Moon of Kentucky

Posted 23 June 2020 - 09:54 AM

It seems to me, and I'm just going from memory and may not have this correct, that he started building scopes in Southern California and later moved to Arizona. I seem to remember his name coming up at RTMC more than forty, (maybe fifty) years ago. I also seem to remember that our own Brian DeWelles wound up with some of his stuff and was selling it here in the CN classifieds some years ago. Maks maybe?


  • steve t likes this

#9 tim53

tim53

    Voyager 1

  • *****
  • Posts: 14,930
  • Joined: 17 Dec 2004
  • Loc: Highland Park, CA

Posted 23 June 2020 - 10:10 AM

It seems to me, and I'm just going from memory and may not have this correct, that he started building scopes in Southern California and later moved to Arizona. I seem to remember his name coming up at RTMC more than forty, (maybe fifty) years ago. I also seem to remember that our own Brian DeWelles wound up with some of his stuff and was selling it here in the CN classifieds some years ago. Maks maybe?

I wonder if you're thinking of Max Bray?  I never met him, but my late friend Dale Chesnut was often talking about him in the mid 80s when we were working on stuff together in his garage machine shop.

 

-Tim.



#10 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 22,235
  • Joined: 29 May 2012
  • Loc: Under the Blue Moon of Kentucky

Posted 23 June 2020 - 10:14 AM

I wonder if you're thinking of Max Bray?  I never met him, but my late friend Dale Chesnut was often talking about him in the mid 80s when we were working on stuff together in his garage machine shop.

 

-Tim.

You know Tim, I may very well be! Those darn mists of time and foggy memory may have struck again! :lol:



#11 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 19,715
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 23 June 2020 - 06:15 PM

Never had one of them scopes since i was a teen when they had ads in SKY&TELE and no way i could afford one back then. Even a Nag was well over my spending limit until the 90's.



#12 Dan /schechter

Dan /schechter

    Apollo

  • *****
  • Posts: 1,231
  • Joined: 21 Dec 2006
  • Loc: Long Beach, Calif.

Posted 23 June 2020 - 06:21 PM

I wonder if you're thinking of Max Bray?  I never met him, but my late friend Dale Chesnut was often talking about him in the mid 80s when we were working on stuff together in his garage machine shop.

 

-Tim.

I own a nice 80mm objective with both elements signed and marked as to glass type by Max Bray. The objective was mounted in a aluminum tube with an 1890's focuser. The tube came on a #3 Alvan Clark mount that Max had modified. His optical and machining skills were very very apparent.

 

Dan


Edited by Dan /schechter, 23 June 2020 - 06:22 PM.

  • Terra Nova likes this

#13 clamchip

clamchip

    Voyager 1

  • *****
  • Posts: 10,569
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 23 June 2020 - 08:36 PM

Found another picture of me fiddling around with the Brandt 6 inch.

Some of the best planetary views have been with this scope.

It seems impervious to atmospheric turmoil.

Robert 

 

post-50896-14073903142589_thumb.jpg


  • beanerds, steve t, Terra Nova and 3 others like this

#14 davidmcgo

davidmcgo

    Gemini

  • *****
  • Posts: 3,275
  • Joined: 09 Oct 2004
  • Loc: San Diego, CA

Posted 24 June 2020 - 08:55 AM

Part of the impervious to atmospheric turmoil is the bare aluminum tube.  Keeping it fairly shiny has a very low emissivity and avoids currents at the tube wall due to top half exposed to cold clear sky and bottom exposed to warm ground.

When I was rebuilding my 8” Meade, the best seeing was bare aluminum, then to get back close to that after powder coating needed the airspaced flocked liner from Protostar.

 

Dave


Edited by davidmcgo, 24 June 2020 - 08:56 AM.

  • clamchip, steve t and Bomber Bob like this

#15 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,531
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 24 June 2020 - 09:55 AM

" It seems impervious to atmospheric turmoil." which is most likely because the lens was figured to be good to a true 1/8 wave in green light or better. When the optics are good seeing has much less of an effect then what is believed.  When you have poor optics, when the seeing snaps you still only see a poor image. When the seeing is average to bad the image is even worse.  With excellent optics you have a higher percentage of the time viewing a sharper image hence the impression that the scope isn't effected by seeing.

 

                      - Dave 


Edited by DAVIDG, 24 June 2020 - 11:20 AM.

  • bobhen, clamchip, steve t and 1 other like this

#16 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • topic starter
  • Posts: 21,454
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 24 June 2020 - 10:05 AM

" It seems impervious to atmospheric turmoil." which is most likely because the lens was figured to be good to a true 1/8 wave in green light or better. When the optics are good seeing has much less of an effect then what is believed.  When you have poor optics, when the seeing snaps you still only see a poor image. When the seeing average to bad the image is even worse.  With excellent optics you have a higher percentage of the time viewing a sharper image hence the impression that the scope isn't effected by seeing.

 

                      - Dave 

I agree with you Dave.  It is better to have great optics so when the seeing is really good you can see everything you can.  



#17 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • Posts: 27,391
  • Joined: 03 May 2010

Posted 24 June 2020 - 10:11 PM

Here is the 200mm Brandt refractor of the Salt Lake Astronomical Society, donated by charter member Patrick Wiggins, discoverer of asteroid 4099wiggins.   I have used this scope many times, it is terrific on just about any target.  Planets, deep-sky, just wonderful, crisp, contrasty views.

 

8 inch Brandt 001a.jpg

 

 

 

 


  • davidmcgo, tim53, astro140 and 8 others like this

#18 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 19,715
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 25 June 2020 - 05:30 AM

Here is the 200mm Brandt refractor of the Salt Lake Astronomical Society, donated by charter member Patrick Wiggins, discoverer of asteroid 4099wiggins.   I have used this scope many times, it is terrific on just about any target.  Planets, deep-sky, just wonderful, crisp, contrasty views.

 

attachicon.gif8 inch Brandt 001a.jpg

That long tube would be a door bumber getting it outside.



#19 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • topic starter
  • Posts: 21,454
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 25 June 2020 - 06:53 AM

Here is the 200mm Brandt refractor of the Salt Lake Astronomical Society, donated by charter member Patrick Wiggins, discoverer of asteroid 4099wiggins.   I have used this scope many times, it is terrific on just about any target.  Planets, deep-sky, just wonderful, crisp, contrasty views.

 

attachicon.gif8 inch Brandt 001a.jpg

I will ad something meaningful to this threadsmirk.gif

 

Really nice looking scope.  I sure would like to be at the controls of that scope and viewing through it.   Thanks for sharing Chuck.



#20 photoracer18

photoracer18

    Gemini

  • *****
  • Posts: 3,387
  • Joined: 02 Sep 2013
  • Loc: Martinsburg, WV

Posted 25 June 2020 - 08:28 PM

Dick was in charge of the optical shop at Optical Craftsman from sometime in 1966 to about 1970. I have a 12.5" CC primary with his name on it from around late 1966 if I read the serial number right. It was used to replace the original primary in my Cave 12.5" Cass/Newt that was made in the early 60's.

 

I almost bought one of his 8" f13.3 refractors once but had no way to transport it. Most of Barry Griner's (D&G) larger refractors were folded also. Culminating in the folded 10" F34 he built for Dr. Green on LI (Also built a folded 12" F18 for him)


Edited by photoracer18, 25 June 2020 - 08:32 PM.

  • Bomber Bob likes this

#21 clamchip

clamchip

    Voyager 1

  • *****
  • Posts: 10,569
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 27 June 2020 - 06:25 PM

I thought today I would DPAC my Brandt shown previously.

I wanted to confirm my Williy-Nilliy spacer thickness change I made years ago.

Back then I just Kept replacing the spacers until the scope would take extreme high

power.

Today, rather than fly by the seat of my pants I have radar.

It looks as though I nailed the spacer thickness back then, nice straight lines with

a hint of outward bowing. This may be my 80deg upstairs because its outward

on the other side of focus too. Or it may be my apparatus is not all on axis.

I knew it must be close because of the way the scope performs.

Strangely though I think I might have a tiny zone in the middle, you can see the

central line(s) aren't the same thickness near the center, kinda get lumpy like a

ant body, hmm.

As you know DPAC is very sensitive, and it doesn't lie, and it doesn't have good days

or bad days. There is something in the center.

Because the telescope is so long I used my camera adapter as a stage for

holding my tester, worked fine. And just set the 6 inch flat centered in front of the

objective.

Robert

Attached Thumbnails

  • IMG_9857.jpg
  • IMG_9849.jpg
  • IMG_9842.jpg
  • IMG_9845.jpg

Edited by clamchip, 27 June 2020 - 06:43 PM.

  • tim53, starman876, Terra Nova and 2 others like this

#22 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,531
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 27 June 2020 - 07:00 PM

 Yep you have a zone in the middle of the lens and if your first image was taken inside of focus there some over correction as well. If the grating was outside then there is some undercorrection.  I estimate it is around 1/5 to 1/6 wave of pure spherical then you have to add in the fact that there is chromatic aberration  which is  increased with the additional spherical, so your looking at around a 1/4 wave of total aberration or maybe a bit worse. 

 

             - Dave 


  • tim53, starman876 and Bomber Bob like this

#23 clamchip

clamchip

    Voyager 1

  • *****
  • Posts: 10,569
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 27 June 2020 - 08:18 PM

Thanks Dave, I always look forward to your diagnosis because I'm pretty new at DPAC.

So as it sits it's roughly 1/4 wave diffraction limited?

If so that's not bad for a 6 inch achromat is it.

The zone in the middle, can you tell what's going on? and the affects it may create.

 

Robert



#24 Jeff B

Jeff B

    Fly Me to the Moon

  • *****
  • Posts: 6,793
  • Joined: 30 Dec 2006

Posted 27 June 2020 - 11:21 PM

 Yep you have a zone in the middle of the lens and if your first image was taken inside of focus there some over correction as well. If the grating was outside then there is some undercorrection.  I estimate it is around 1/5 to 1/6 wave of pure spherical then you have to add in the fact that there is chromatic aberration  which is  increased with the additional spherical, so your looking at around a 1/4 wave of total aberration or maybe a bit worse. 

 

             - Dave 

Dave, I agree with you on the zone and the 1/5 to 1/6 wave assessment but I don't understand the bolded section.  Could you please explain?  He is testing in green light with a green filter which uses its pass band twice.

 

Robert, try to capture an image at focus in green light.  That will reveal the zone.  Here is an example.

 

Jeff

Attached Thumbnails

  • T Istar, At Focus, White, Green.jpg

  • Bomber Bob likes this

#25 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,531
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 28 June 2020 - 09:20 AM

 A lens has two major types of optical aberrations, spherical and chromatic. As you know spherical aberration is when  the figure on the glass causes light not to come to the same focus position.  A  fully reflective system has no color error just errors caused by the figures. 

   In an achromat even if the lens is perfectly figured as per the design to have no spherical aberration, that only happens at one wavelength which is usually in the green. That is why  you test with a green filter to isolate that  wavelength. With the  blue and red  image, they  that don't come to the same focal position and  these  two wavelengths will show spherical aberration even thou the lens is perfectly figured in the green. This is called spherochromatism ie spherical aberration as a  function of wavelength. 

    So even if you have a perfectly figured achromat in the green you still have the problem that red and blue don't come to the same focus. So you have a wavefront error. You have a sharp image formed from the wavelengths that come to focus well enough to form a diffraction limited image swimming inside a blurry image caused by the other wavelengths that don't come to focus. That is what causes the purple halo around bright  objects.

    Now think about what happens  when the lens is not figured correctly ie it shows spherical aberration in the green. Now the image formed in green light has errors but this also translates to  the red and blue image which already have spherical aberration. So these wavelengths  have increased  in spherical  plus it causes more  defocus across all wavelengths.  You already have  chromatic aberration to start and now it  has also increased.

   So to summarize in a lens, spherical and chromatic go hand  in hand so if one changes so does the other. Hopefully this makes sense and explains my above statement. So when you see spherical errors when doing double pass testing in the green you have to factor in how they add to the other wavelengths and how they increase the total chromatic error. Hence my statement that errors in green look to be 1/5 to 1/6 wave but the total wavefront error from both spherical and color would be around 1/4 wave.

 

             - Dave 


Edited by DAVIDG, 28 June 2020 - 05:11 PM.

  • Jeff B, CharlieB, starman876 and 6 others like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics