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What is the Thomas Back (TMB) connection with APM, LZOS & Astronomics?

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#1 25585

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Posted 17 November 2020 - 04:12 AM

I see APM, TMB, LZOS & Astronomics all have Thomas Back designed or influenced refractors past & present. So what direct association did the man himself have with those companies, & are there any others? 


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#2 nicknacknock

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Posted 17 November 2020 - 04:18 AM

Dropping my 2c: A quick read here. If I recall correctly, Astronomics purchased and currently owns most of the optical designs that Thomas created.


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#3 nicknacknock

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Posted 17 November 2020 - 04:22 AM

A couple of more links here and here. I believe with the 3 links provided, this ties APM, TMB, Astronomics and Thomas nicely together.


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#4 25585

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Posted 17 November 2020 - 04:33 AM

Thank you waytogo.gif


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#5 Muffin Research

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Posted 17 November 2020 - 05:09 AM

APM has a beautiful TMB 100/800 for sale with nifty looking machined parts and as good as perfect lens. 


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#6 j.gardavsky

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Posted 17 November 2020 - 05:13 AM

Fantastic read on Thomas M. Back!

 

As he is writing, it is the spherochromatism, whereas most people are talking about the chromatic aberration.

And the spherochromatism problem applies not only to the refractor lenses, but also to the eyepieces.

 

Thank you very much for sharing the links,

JG


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#7 YAOG

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Posted 17 November 2020 - 10:50 AM

Here is an even better read by Mr. Back: https://www.cloudyni...little-history/


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#8 payner

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Posted 17 November 2020 - 11:41 AM

Couldn't agree more JG. It is the spherical aberration (primarily spherochromatism) is most definitely the greatest aberration and not SC. The former affects the center of field; that most critical when viewing objects with low contrast details and double stars, for example. Refractor design and optical figure are critical here.


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#9 25585

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Posted 17 November 2020 - 11:47 AM

APM has a beautiful TMB 100/800 for sale with nifty looking machined parts and as good as perfect lens. 

115mm F7. https://ensoptical.c...?search=Apm tmb

 

That is the scope that triggered this thread.


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#10 Muffin Research

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Posted 17 November 2020 - 12:19 PM

Ah no, I meant an old TMB scope http://apm-telescope...em/333634313836



#11 25585

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Posted 17 November 2020 - 12:25 PM

Ah no, I meant an old TMB scope http://apm-telescope...em/333634313836

An oldie indeed. No photo of the lens.



#12 alphatripleplus

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Posted 17 November 2020 - 12:39 PM

A couple of more links here and here. I believe with the 3 links provided, this ties APM, TMB, Astronomics and Thomas nicely together.

Very interesting read, much of which I did not know.



#13 BillP

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Posted 17 November 2020 - 02:05 PM

Here is an even better read by Mr. Back: https://www.cloudyni...little-history/

Very sad reading that post.  I spoke and corresponded with Thomas back in the day.  A true gentleman, which is a rarity in today's world.  Certainly miss his continued presence in the hobby.


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#14 BRCoz

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Posted 17 November 2020 - 04:18 PM

Tom was a cool guy.  I talked to him only one time and had a few emails with him.  He was down to earth.



#15 John Huntley

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Posted 17 November 2020 - 08:46 PM

115mm F7. https://ensoptical.c...?search=Apm tmb

 

That is the scope that triggered this thread.

I feel very lucky to own the 130mm F/9.25 version of that design. Mine dates from 2006. It's superb smile.gif

 

Thanks for starting the thread - some of the links I have not read before.


Edited by John Huntley, 17 November 2020 - 08:47 PM.

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#16 Esso2112

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Posted 17 November 2020 - 10:23 PM

I love the original TMB/LZOS scopes with the silver focuser.  The 100 f8 is one of the best 4” scopes in my opinion.  It is a heavy scope, but I kind of like it that way and optically it is fantastic.  Between my TMB 100 and my AP Traveler, I can honestly say the TMB would be the one to stay if I had to go with only one 4” scope. 
 

877E5972-ABF2-4888-BF9E-09475DA78646.jpeg


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#17 Kunama

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Posted 17 November 2020 - 11:04 PM

I've been lucky to own some nice refractors but I think the nicest so far is my current TMB-LZOS 152 F7.9 bow.gif   

 

TMB  certainly knew a thing or 2 about optics waytogo.gif waytogo.gif

 

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#18 25585

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Posted 18 November 2020 - 04:16 AM

I love the original TMB/LZOS scopes with the silver focuser.  The 100 f8 is one of the best 4” scopes in my opinion.  It is a heavy scope, but I kind of like it that way and optically it is fantastic.  Between my TMB 100 and my AP Traveler, I can honestly say the TMB would be the one to stay if I had to go with only one 4” scope. 
 

attachicon.gif877E5972-ABF2-4888-BF9E-09475DA78646.jpeg

Maybe the reason Astro Tech scopes have a similar Aston Martin colour? 


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#19 j.gardavsky

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Posted 18 November 2020 - 05:47 AM

Maybe the reason Astro Tech scopes have a similar Aston Martin colour? 

It's the Aston Martin body-in-white way of design,

JG



#20 John Huntley

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Posted 18 November 2020 - 05:52 AM

I love the original TMB/LZOS scopes with the silver focuser.  The 100 f8 is one of the best 4” scopes in my opinion.  It is a heavy scope, but I kind of like it that way and optically it is fantastic.  Between my TMB 100 and my AP Traveler, I can honestly say the TMB would be the one to stay if I had to go with only one 4” scope. 
 

attachicon.gif877E5972-ABF2-4888-BF9E-09475DA78646.jpeg

I love the look of those. The only slight downside that I've read about the older CNC models is that they weigh a lot for their aperture. Is that the case with your TMB 100 ?



#21 CHASLX200

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Posted 18 November 2020 - 06:31 AM

I love the original TMB/LZOS scopes with the silver focuser.  The 100 f8 is one of the best 4” scopes in my opinion.  It is a heavy scope, but I kind of like it that way and optically it is fantastic.  Between my TMB 100 and my AP Traveler, I can honestly say the TMB would be the one to stay if I had to go with only one 4” scope. 
 

attachicon.gif877E5972-ABF2-4888-BF9E-09475DA78646.jpeg

I had the 105- 650 version. Tank like in size but it did have the best lens ever in any scope i owned.  Pure true color.



#22 Esso2112

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Posted 18 November 2020 - 08:16 AM

I love the look of those. The only slight downside that I've read about the older CNC models is that they weigh a lot for their aperture. Is that the case with your TMB 100 ?

Oh yes, it weighs a ton for a 4” scope.  I can easily put the AP Traveler on an IOptron Ieq30 pro and have a steady view. The TMB 100 rides on an AP Mach1 or a DM6.   I haven’t put the TMB on a scale, but with rings, accessories and all, I would estimate is weighs between 15 and 20 lbs. 


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#23 peleuba

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Posted 18 November 2020 - 01:04 PM

Couldn't agree more JG. It is the spherical aberration (primarily spherochromatism) is most definitely the greatest aberration and not SC. 

 

Randy - I think you meant to say that its Spherochromatism (SC) - spherical aberration as a function of wavelength - that is the most damaging and "greatest aberration" and not Chromatic Aberration (CA).   If so, I agree.  If I misunderstood what you meant, let me know but your original thought I quoted above did not make sense to me.  Though, admittedly, the problem may be on my end.  lol.gif     

 

TMB was a talented if not frustrated optical designer.  He had the computer skills and quick mind to master optical design software and the patience to sit behind a keyboard and design optics.  He lacked the manufacturing capability and the needed relationships with the glass companies to bring those designs to fruition.  The partnership with APM (Markus Ludes) changed that.  It's too bad that Markus and Thomas could not work well together over the long term.  Self interest got the better of both of them in this business deal.    

 

Both the TOA 130 and TOA150 you have will have no detectable spherochromatism in the star test


Edited by peleuba, 18 November 2020 - 03:34 PM.

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#24 ismosi

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Posted 18 November 2020 - 08:15 PM

At the time my TMB 152/1200 was on order, I had a chance to go with the newer design or stick with the CNC.

 

For the Mars opposition I 'unrigged' my setup from its imaging configuration. I knew Mars was Thomas's favorite so it seemed fitting. But more than that, no scope (including my 18-inch Dob) gave me better views. I even put a Paragon in the star diagonal for this picture smile.gif

 

I am very fortunate to own this ...

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Edited by ismosi, 18 November 2020 - 08:15 PM.

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#25 payner

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Posted 18 November 2020 - 08:30 PM

Randy - I think you meant to say that its Spherochromatism (SC) - spherical aberration as a function of wavelength - that is the most damaging and "greatest aberration" and not Chromatic Aberration (CA).   If so, I agree.  If I misunderstood what you meant, let me know but your original thought I quoted above did not make sense to me.  Though, admittedly, the problem may be on my end.  lol.gif     

 

TMB was a talented if not frustrated optical designer.  He had the computer skills and quick mind to master optical design software and the patience to sit behind a keyboard and design optics.  He lacked the manufacturing capability and the needed relationships with the glass companies to bring those designs to fruition.  The partnership with APM (Markus Ludes) changed that.  It's too bad that Markus and Thomas could not work well together over the long term.  Self interest got the better of both of them in this business deal.    

 

Both the TOA 130 and TOA150 you have will have no detectable spherochromatism in the star test

Thanks for catching that, Paul. I did mean to end with CA rather than and SC! Ha, what I get for looking in on CN when I should have had my nose still on the spreadsheet for work (hey, discretionary eye break).

Relative to image fidelity, SC is the most important aberration to be controlled for a very high performing, corrected refractor (and seems to be lost in most all discussions I see regarding critical aberration control).

Yes, the very wide, air spaced gaps of the TOA design has all but eliminated SA on a measurable scale (as I've read) and certainly below visual threshold. Another telescope series that seems to be penalized by the majority because of their weight (as often are the original TMB designs before APM changed OTA construction). There are both necessary (in the case of the TOAs) and other reasons an overbuilt OTA is a positive quality.

Best,


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