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TEC APO250VT is Now Listed on The Tec Website

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#101 Mike Clemens

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Posted 27 April 2014 - 01:46 AM

In retrospect there are too many things I don't understand to say why they behave in those fashions.

1) They are both aluminum OTA, but the TEC tube is 400mm longer. The OTA shrinkage or growth would be considerably more on the TEC200 as temps vary?

2) but the focal ratio is longer on the 200 and as such the CFZ a bit deeper and a change in length would be less destructive. But perhaps not enough to accommodate #1?

3) The more massive lens will take longer to chase the current temperature.

4) Oil spaced lens design versus air spaced. Who knows how they shed heat differently. One is only loosely held in the cell right? One can radiate through easily front front to back.

In any case my star sizes make me want to run a half hourly focus star instead of hourly with the smaller glass.

I posted this because people were discussing the functional differences of some of these specific scopes I mention. I think it is on-topic in a TEC250 discussion though because you can bet this scope, like those big TMB, is going to have a personality of its own when it comes to thermal accommodation.

#102 Psion

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Posted 27 April 2014 - 03:02 AM

Aluminium is worst material for a tube of telescope because of a big thermal expansion. Are you sure?

200 F9 tube 2000mm : difference 9°F is a thermal expansion 0.0085 inch, Focus Zone is 0.0094 inch
200 F8 tube 1600mm : difference 9°F is a thermal expansion 0.0075 inch, Focus Zone is 0.0067 inch

#103 Mike Clemens

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Posted 27 April 2014 - 04:17 AM

Yes for sure the TEC and AP are all aluminum. TMB uses Kruppax Phenolic.

Those are mild changes you list (relative to CFV) for such a dramatic temp change! I didn't expect that! The lenses are said to change focal length in the opposite direction as they cool. For that reason, it is said that aluminum is the better choice, ( besides it's other superb characteristics for the job. )




#104 Edd Weninger

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Posted 27 April 2014 - 11:00 AM

I recall a comment by Roland Christen who responded to a query about why he did not use carbon fiber tubes. He said that the shrinkage of the aluminum tube somewhat compensated for the change in figure of the cooling lens.

#105 Psion

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Posted 28 April 2014 - 01:00 AM

I have similar result with AL tube only:

~30mk per °C, but for carbon is ~10mk per °C. (like Kruppax 50 for TMB tube)

This is a reason, why user have to refocus TEC 200 F8 every 2°C change.

#106 Patrik Iver

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Posted 28 April 2014 - 09:19 AM

I have similar result with AL tube only:

~30mk per °C, but for carbon is ~10mk per °C. (like Kruppax 50 for TMB tube)

This is a reason, why user have to refocus TEC 200 F8 every 2°C change.


I *think* what Yuri really said two posts up was that aluminium requires less refocusing than carbon fibre composites would. Just like Roland Christen also has said previously.

#107 Psion

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Posted 28 April 2014 - 09:52 AM

I understand, Yuri needs material with thermal expansion 150mk :)

Anyway, for calculations we need not only coefficient of thermal expansion, but we need know a time curves of a temperature changes both components.

#108 ken svp120

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Posted 28 April 2014 - 02:41 PM

I have similar result with AL tube only:

~30mk per °C, but for carbon is ~10mk per °C. (like Kruppax 50 for TMB tube)

This is a reason, why user have to refocus TEC 200 F8 every 2°C change.


I *think* what Yuri really said two posts up was that aluminium requires less refocusing than carbon fibre composites would. Just like Roland Christen also has said previously.


Right. You can find ads for some scopes actually promoting the "excellent thermal stability" of carbon fiber as if this were some kind of good thing when in fact it is exactly the opposite. Don't let the truth stand in the way of a good story right?

#109 JimP

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Posted 09 September 2014 - 09:30 AM

"I know the 10” TMB/APM air spaced scopes will cool, because I remember Jim Phillips’ (Damian Peach assisted) fantastic planetary images. However, I wonder how long it will take an air spaced 10” lens to get to optimum vs. an oil spaced or doublet fluorite lens. Perhaps an air conditioned observatory is the best for these beasts."


Derek,

 

I do have an air conditioned observatory for the TMB LZOS 10" F/9. The inside temperature is always cool compared to the outside during our hot summer.  I watch  the temperature carefully and turn of the AC to get the inside and outside temp as close as possible at dusk. It is not perfect but I have had no real trouble with cool-down with this scope. When the seeing is good here the temp remains constant for 1-2 or more hours then drops a degree then 1-2 hours it drops another degree. The key is how long does it take the outside temperature to stabilize?  
 

Jim


Edited by JimP, 09 September 2014 - 10:13 AM.


#110 Danny206

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Posted 10 September 2014 - 11:46 PM

Sorry to say, but we have changed design and parameters for APO250. 

It is going to be F/7.5, not 8.2.

So, all comparisons made here are not valid anymore.

Yuri

 

Yuri,

 

Is the design change toward a faster scope meant to accomadate astro-photography use as well ? Is there any tradeoff in visual use ?



#111 Astrojensen

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Posted 11 September 2014 - 02:27 AM

A 10" f/7.5 apo is going to be pretty special. It is, to my knowledge, the fastest apo above 8" ever made.

 

 

Clear skies!
Thomas, Denmark



#112 dothead

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Posted 11 September 2014 - 10:52 AM

Thomas,

 

there's the 12" f/7.5 LZOS lens - APM has sold a few of these during the past couple of years.

 

Clear skies,

Ralph, Germany



#113 Astrojensen

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Posted 11 September 2014 - 12:41 PM

 

there's the 12" f/7.5 LZOS lens - APM has sold a few of these during the past couple of years.

You're right, In had forgot about those. Anyone faster?  :grin:

 

I bet Markus and his gang could make a 10" f/5 Petzval apo if one wanted one badly enough and could cough up the medium-sized fortune it would cost.

 

 

Clear skies!
Thomas, Denmark



#114 GeneT

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Posted 11 September 2014 - 01:01 PM

 

I'd need a lot of gin at the bar to order that.


I believe copious amounts of gin/vodka/tequila are recommended accessories. In my case, a divorce attorney may be required. I just happened to mention the scope in a casual conversation with my wife and when I mentioned the price, she felt the need to do a preemptive, "don't even think about it". I wasn't even considering the scope, but in the end I just shut up. There was no way I could convince her that it was innocent small talk.

 

 

Now, hopefully you have finally learned.  :grin:



#115 t.r.

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Posted 11 September 2014 - 01:03 PM

 

 

there's the 12" f/7.5 LZOS lens - APM has sold a few of these during the past couple of years.

You're right, In had forgot about those. Anyone faster?  :grin:

 

I bet Markus and his gang could make a 10" f/5 Petzval apo if one wanted one badly enough and could cough up the medium-sized fortune it would cost.

 

 

Clear skies!
Thomas, Denmark

 

Why does it have to cost a fortune? Ten inch achro's are relatively cheap, the original Genesis Petzval had no fancy glass in the objective and it was made to F/12. The only cost in the the correcting elements in the back...one could design a modern version of the ChromaCorr with an integrated flattner and accomplish quite a bit at much lower cost. There is a writeup here on CN about the "TEC Big Eye" 10 incher Yuri made years ago... a chromacorr it is pretty descent for the visual user.



#116 GJJim

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Posted 11 September 2014 - 01:24 PM

 

 

 

there's the 12" f/7.5 LZOS lens - APM has sold a few of these during the past couple of years.

You're right, In had forgot about those. Anyone faster?  :grin:

 

I bet Markus and his gang could make a 10" f/5 Petzval apo if one wanted one badly enough and could cough up the medium-sized fortune it would cost.

 

 

Clear skies!
Thomas, Denmark

 

Why does it have to cost a fortune? Ten inch achro's are relatively cheap, the original Genesis Petzval had no fancy glass in the objective and it was made to F/12. The only cost in the the correcting elements in the back...one could design a modern version of the ChromaCorr with an integrated flattner and accomplish quite a bit at much lower cost. There is a writeup here on CN about the "TEC Big Eye" 10 incher Yuri made years ago... a chromacorr it is pretty descent for the visual user.

 

 

The alignment tolerances make these Petzval scopes extremely difficult in larger sizes. Going from 4" to 10" increases the weight of the glass by a factor of 16 and everything in the cell has to be overbuilt to handle the weight over a 2.5X larger physical separation. They are engineering nightmares compared to even an air spaced triplet.

 

If I had a dollar for every Chromacorr type gadget that was announced as "just around the corner", I could buy a nice steak dinner. IIRC the original Chromacorr used an odd glass that is not available (outside of a rogue lab).


Edited by GJJim, 11 September 2014 - 01:33 PM.


#117 SteveC

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Posted 11 September 2014 - 01:54 PM

 

 

I'd need a lot of gin at the bar to order that.


I believe copious amounts of gin/vodka/tequila are recommended accessories. In my case, a divorce attorney may be required. I just happened to mention the scope in a casual conversation with my wife and when I mentioned the price, she felt the need to do a preemptive, "don't even think about it". I wasn't even considering the scope, but in the end I just shut up. There was no way I could convince her that it was innocent small talk.

 

 

Now, hopefully you have finally learned.  :grin:

 

Jeesh, I was supposed to have learned something??? Aside from being a wimp? Ohhh, you mean order equipment discretely.



#118 jrbarnett

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Posted 15 September 2014 - 10:27 PM

"LZOS costs more and seems to be reasons for that."

 

1.  Middleman.  The LZOS scope is an OEM product.  LZOS has to make a profit on the OG, and then the retailer, APM, has to make a profit on the finished scope.  With TEC, there are no middlemen.  Everything is made by a single source.  Much more efficient.

 

2.  Euros.  The Euro is a highly leveraged and inflated currency.  Part of the problem is the economic inequality among EEA members.  The string industrial economies are having to prop up the weaker members.  Anything made and sold in Euros is inherently more expensive due to this value inflation than in other more deflated currencies like the Dollar.

 

- Jim  



#119 jrbarnett

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Posted 15 September 2014 - 10:37 PM

This thread is getting good.

Reminds me of BMW vs Audi arguements.

Jeff

BMW vs. Audi:  no argument possible if you've owned and driven both.  Only BMW is the Ultimate Driving Machine.  Audis show their front wheel drive roots when truly driven; Quattro can only do so much to turn a plow-er into a proper driver's car.

 

Much like TEC vs. LZOS:  TEC - the Ultimate Observing Machine.  The rest are just Frankenscopes and wannabes.  :grin:

 

- Jim



#120 GJJim

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Posted 16 September 2014 - 07:35 AM

Has any company ever offered an oil-spaced fluorite objective in this aperture? One of the issues with the large, air-spaced LZOS objectives is the significant time it takes to acclimatize. At these apertures all are observatory scopes and some might argue that a proper observatory will have climate control to make sure the heavy glass is not too hot or cold when night falls. An advantage of the TEC design is the inherently faster heat transfer of glass elements without insulating air spaces in between.



#121 JimP

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Posted 16 September 2014 - 08:13 AM

"Much like TEC vs. LZOS:  TEC - the Ultimate Observing Machine.  The rest are just Frankenscopes and wannabes"

 

 

Sorry Jim, but you just do not know what you are talking about.

 

I have owned TEC 140, TEC 160 Fl and TEC 200 Fl apos. I own an APM LZOS  80 F/6 , TMB/APM LZOS 8" F/9 and 10" F/9 apos plus AP 130 GT and soon, hopefully, an AP 155 F/7. In the past I have owned AP 9" F/15, 6" F/12 and 155 F/7 apos.

 

They are ALL excellent scopes. The optics in all three are superb.

 

best,

 

Jim



#122 SteveC

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Posted 16 September 2014 - 01:07 PM

 

This thread is getting good.

Reminds me of BMW vs Audi arguements.

Jeff

BMW vs. Audi:  no argument possible if you've owned and driven both.  Only BMW is the Ultimate Driving Machine.  Audis show their front wheel drive roots when truly driven; Quattro can only do so much to turn a plow-er into a proper driver's car.

 

Much like TEC vs. LZOS:  TEC - the Ultimate Observing Machine.  The rest are just Frankenscopes and wannabes.   :grin:

 

- Jim

 

lol, what  troll!! :lol:


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#123 Jeff B

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Posted 20 September 2014 - 07:30 AM

 

This thread is getting good.

Reminds me of BMW vs Audi arguements.

Jeff

BMW vs. Audi:  no argument possible if you've owned and driven both.  Only BMW is the Ultimate Driving Machine.  Audis show their front wheel drive roots when truly driven; Quattro can only do so much to turn a plow-er into a proper driver's car.

 

Much like TEC vs. LZOS:  TEC - the Ultimate Observing Machine.  The rest are just Frankenscopes and wannabes.   :grin:

 

- Jim

 

 

Not so fast (no pun intended) Jim.  There's the S4.  Wicked machine.

 

But the TEC 140 would be the 325i of the scope world.  A superb package. It does everything really, really well, dosen't disappoint in any way and there's hell to pay if the OEM changes it much.

 

Now if we expand the car analogies to include American muscle cars, particularly Mustangs, Roland might even join in.

 

Jeff 



#124 Kent10

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Posted 01 October 2014 - 06:19 PM

Today, Yuri mentioned on the Tec Yahoo forum that the new Tec 250 will be fluorite!



#125 vahe

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Posted 01 October 2014 - 08:16 PM

Today, Yuri mentioned on the Tec Yahoo forum that the new Tec 250 will be fluorite!

I had no doubt that it was going to be fluorite specially after the announcement that the speed was increased from F/8+ to F/7.5, a 10” apo with FPL-51 can not be made that fast.

 

Vahe




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