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Equipment Discussions >> Refractors

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NHRob
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Loc: New Hampshire
Re: TEC140 or TMB130 new [Re: BillP]
      #6604567 - 06/27/14 01:50 PM

How about a TMB140??


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Jeff B
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Re: TEC140 or TMB130 new [Re: Alan French]
      #6604588 - 06/27/14 02:00 PM

Quote:

Also TEC (and AP) have Yahoo groups where Yuri (and Roland) are quite happy to answer questions about their products.

Clear skies, Alan




And they frequent each others forum too, which can be quite entertaining at times.


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snommisbor
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Reged: 06/15/09

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Re: TEC140 or TMB130 new [Re: dvb]
      #6605006 - 06/27/14 07:07 PM

Quote:

Thanks, all, for your comments.

All in all, I think I'll go for the TEC140. My interest is mainly visual. I think I can spread the sting of the purchase price over a several months - I understand it is 20% down, the rest on delivery (from the OPT site),





I don't believe OPTcorp is selling TEC anymore even though it is on their site. Yuri stated on the Yahoo group that you could only get it direct from TEC. And it you go to the TEC website OPTcorp is no longer listed as a dealer. So I would call before I put any money down. But you have made a great choice and you will not be disappointed.


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MrGrytt
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Reged: 07/28/05

Loc: Upstate Cuomostan
Re: TEC140 or TMB130 new [Re: BillP]
      #6606716 - 06/28/14 11:55 PM

Quote:

I conducted extensive enough tests to narrow down the difference to the optic and not the eyepiece (and a year worth of tests). And the differences with the LOMO performance were fairly obvious compared to the Tak on several levels, and subtle compared to the Chinese scope. And yes of course conditions were ripe for comparisons -- I don't conduct compares in marginal conditions. As far as lemons, quite true that this may have been the case. But of course that logic applies to good results as well and perhaps good samples are not representative! And important to note that the presumption that a *premium* scope has less QC variation is completely anecdotal...so again, nothing to bank on.





My apologies for the delay in getting back to this but you have left me curious about a few things. Time-Warner gave me some serious modem problems that had to be resolved and it took a while.
I am curious about your "LOMO" 80/600 and where you got it. The reasons I'm curious are because you are saying things that have never been heard before and also because about 5 or 6 years ago Astronomics found an old stash of supposedly "LOMO" 80mm lenses and weren't sure where they had come from. They were selling them at discount prices and assumed they were LOMO optics. They could even have been lenses that didn't make the grade for normal sale. Never did find out and because of that I didn't buy one of them. In addition, before Thomas Back was ever involved with designing LZOS optics they had made some 80mm optics that were known to not be very good, at least not compared to the present stock of real LOMO 80mm optics. Hopefully you know for sure what the origin of that lens is before saying things that cut down one of the premier 80mm optics ever made.

Quote:


So the bottom line (for me) is that brand names do not impress. Not at all. The proof is in the testing...and I've had supposed premium brands fail and supposed mass produced just beat the pants off of premiums (as far as the optic performance is concerned). So in the end, it's all the luck of the draw. So if one wants to eliminate that problem, then stop relying on luck and brand presumptions.





There are brands you can have a great deal of confidence in. If you chose not to have confidence in them that is totally up to you. Regardless, I have no doubt that no matter where optics originate they will be highly scrutinized by the majority of people who obtain them. I also have no doubt that those who chose to buy from a known manufacturer with an excellent reputation will have far fewer legitimate complaints.


Quote:


At any rate...if folks want to hand their hats on a brand, that's of course perfectly fine. But one must realize that it is not a good scientific or engineering or political ot consumer practice to simply trust without verifying! So where spending my money is concerned, brand means nothing, tested performance means everything.




Does this mean you never buy a new scope from some of the more reputable manufacturers? It seems highly unlikely that you can have some of them in your possession to undergo your personal quality control prior to purchasing. It seems to me that you, like most people, will often be forced to determine the actual quality of the optics after you have shelled out your money. If not, you are very fortunate or only buy used equipment. Regardless of new or used, a person always has the option of not keeping the scope. That brings up another question. Why do you still have the LOMO 80/600 if it is sub-par performer?

Harvey


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Scott99
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Re: TEC140 or TMB130 new [Re: MrGrytt]
      #6607317 - 06/29/14 12:11 PM

re: TEC's minimum Strehl - after poking around the Yahoo group archives it doesn't appear that TEC ever stated a minimum Strehl ratio, however, Yuri has said the lenses are 1/8 or 1/10 PV, and RMS 1/50 or better - 1/50 RMS converts to 98.4% Strehl ratio…..

https://groups.yahoo.com/neo/groups/tec-scopes/conversations/messages/1738

https://groups.yahoo.com/neo/groups/tec-scopes/conversations/messages/2628

again though, this doesn't mean that everyone needs to buy and use a TEC! It seems to be a common attitude that the refractor needs to be a perfect apo or else the scope is bad. I've been hearing this at star parties too. Nonsense - I'm happy to have a couple of "premium" apos right now, but I've had lots of fun with simple achromats, one of my favorite ones was the 1980's University Optics 80mm F/6.6, that's the one that hooked me on the refractor experience.

With today's machine-polishing methods, decent quality small and mid-size refractors are more affordable than ever. IMO the message should be, get the obstruction out from in front of your objective and start observing, let the rest of us obsessed apo-philes argue about Strehl ratios & such in these forums, don't worry about it!

the high-strehl lens will get the image quality a little bit cleaner, but most refractors will show nice tight star images and good contrast compared with obstructed scopes. All of the ED triplets will do a good job with color correction.


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BillP
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Re: TEC140 or TMB130 new [Re: MrGrytt]
      #6607441 - 06/29/14 01:17 PM

Hello Harvey. Yes, the LZOS was a Tom Back inspected one. Know that for sure as I used to correspond with him. Didn't say it was bad. It was a basic "good" optic...nothing special. Some like to attribute mystical qualities to brands, but nothing mystical really goes on and with the good comes the bad, that's just the way it is as people make mistakes and machines that are programmed and built by people make mistakes also. And no, I choose no brand with confidence. Sorry, but I assume nothing when I purchase and inspect everything. One really has to accept the premise that people make mistakes. That being the case, branding is no substitute for due diligence by the consumer IMO.

More reputable than manufacturers? Sure...there are plenty. As example, a manufacturer direct warranty may require you pay for shipping, but a reseller warranty on top of that may require no shipping charges. Resellers have their own terms and conditions for purchase, and many have much better terms than the manufacturer...like allowing a return just because you are not happy with the product. Manufacturer directs most of the time have no such policy. So invariably I will gravitate to a reseller because they have better terms. And yes, one shells out the cash first. But that is never a worry when you get a confirmation of the policy from them. And no I do not have the just fine LOMO that was bested by the Chinese scope. I have the Chinese scope of course. In no way was the LOMO "sub-par". It performed excellently in all respects. Another scope simply beat it and that one I kept.


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SteveC
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Reged: 06/15/06

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Re: TEC140 or TMB130 new [Re: hottr6]
      #6608244 - 06/29/14 09:53 PM

Quote:


It is interesting to note that most of the TEC140 owners that have written in this thread have moved on to something else. So much for a lifetime instrument, but I guess it was a key point to be made when discussing the purchase with one's partner.




I've owned my TEC140 for about 7-8 years and it's not going anywhere. Now, I'm not about to suggest one scope over another, but if l were considering buying a bigger scope,I'd have no problem with getting another TEC product.

Edited by SteveC (06/29/14 10:09 PM)


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MrGrytt
scholastic sledgehammer


Reged: 07/28/05

Loc: Upstate Cuomostan
Re: TEC140 or TMB130 new [Re: BillP]
      #6608278 - 06/29/14 10:14 PM

Quote:

Hello Harvey. Yes, the LZOS was a Tom Back inspected one. Know that for sure as I used to correspond with him. Didn't say it was bad. It was a basic "good" optic...nothing special.





I was asking about the LOMO optic, not the LZOS optic.

As long as you brought it up, which LZOS optic was involved?

Harvey


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peleuba
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Reged: 12/01/04

Loc: Southern PA
Re: TEC140 or TMB130 new [Re: Paul G]
      #6611699 - 07/01/14 05:26 PM

Quote:

Quote:

And yes, there is a very firm and tangible definition of TEC's premium optics - guaranteed Strehl ratio of 98.4% or higher




Source?




I dont have the link handy, but its on the Yahoo group that Yuri states that for the 140 and larger telescopes the minimum quality is 1/8 wave in green light - have no idea what the equivalent Strehl ratio is but I can tell you it would be lower then .984 as this fugure is more akin to 1/10 wave. When I tested both my TEC160ED and later the TEC160FL, both scopes were better then 1/8 wave with the 160FL approaching 1/10 wave in green Interestingly in was also quite good in red, not so much in blue.

Now, my TEC110FL was no where near as good and TEC has backed off on the "1/8 wave in green" standard on the 110FL. I was ultimatly very unhappy with the performance of my 110FL on the bench and under the stars and Yuri explained that he "relaxed the standards" on the 110FL due to the compexity of the design, curves, glass melt etc and that there is no routine hand asperizing any of the surfaces. My 110 was barely diffraction limited and the star test was an utter mess.


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RAKing
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Reged: 12/28/07

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Re: TEC140 or TMB130 new [Re: peleuba]
      #6612558 - 07/02/14 08:08 AM

Quote:

Now, my TEC110FL was no where near as good and TEC has backed off on the "1/8 wave in green" standard on the 110FL. I was ultimatly very unhappy with the performance of my 110FL on the bench and under the stars and Yuri explained that he "relaxed the standards" on the 110FL due to the compexity of the design, curves, glass melt etc and that there is no routine hand asperizing any of the surfaces. My 110 was barely diffraction limited and the star test was an utter mess.




Ouch! I am very sorry to hear that news.

Ron


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peleuba
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Reged: 12/01/04

Loc: Southern PA
Re: TEC140 or TMB130 new [Re: RAKing]
      #6612636 - 07/02/14 09:15 AM Attachment (43 downloads)

Quote:



Ouch! I am very sorry to hear that news.

Ron




Me too. I was incredibly bummed. I have owned large APOs up to 160mm in aperture and for me and APO refractor really shines in the smaller apertures up to 130mm. Above that and I really prefer using my Portaball-8 on the Tom O. platform.

I bought based on my experience with the 160ED and the 160FL, both really excellent. I was lead to beleive that the 110FL would be manufactured to the same level - it was not. I sent the telescope back to Yuri and he said that he was unable to do any better based on the design and current glass melt - mine was the first scope from the second run. He did refund my money and I would not hesitate to puchase another TEC if in the future. Star Test images from my TEC110FL below...


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t.r.
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Re: TEC140 or TMB130 new [Re: peleuba]
      #6612772 - 07/02/14 10:35 AM

Paul, I've read about your TEC110 before and just noticed you have a Tak Sky 90II which is of similar short focus design using fluorite as well...how is its quality compared to the TEC?

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tomcody
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Reged: 07/06/08

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Re: TEC140 or TMB130 new [Re: t.r.]
      #6612801 - 07/02/14 10:49 AM

Quote:

Paul, I've read about your TEC110 before and just noticed you have a Tak Sky 90II which is of similar short focus design using fluorite as well...how is its quality compared to the TEC?



+1 t.r. I was just wondering the same thing?
Rex


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Tank
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Reged: 07/27/09

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Re: TEC140 or TMB130 new [Re: tomcody]
      #6612853 - 07/02/14 11:29 AM

FYI
My TEC 140 has a awesome figure in and out focus is virtually identical at 300x
Too bad on the TEC110 is sure theres great ones out there!


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dedo
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Reged: 06/04/10

Loc: Italy, Rome
Re: TEC140 or TMB130 new [Re: Tank]
      #6613213 - 07/02/14 02:46 PM

At F5.6 it's really hard...also remember the sky90 is a....well, a 90. Differences in aperture does counts in that subject too.

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jrcrillyAdministrator
Refractor wienie no more
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Re: TEC140 or TMB130 new [Re: t.r.]
      #6613242 - 07/02/14 03:03 PM

Quote:

just noticed you have a Tak Sky 90II which is of similar short focus design using fluorite as well...




The designs aren't very similar. One's an oiled triplet and the other's an airspaced doublet.


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jrbarnett
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Re: TEC140 or TMB130 new [Re: peleuba]
      #6613261 - 07/02/14 03:12 PM

Looks very normal for a very fast triplet, TBH. Similar to how Travelers star test.

You might find this interesting:

http://geogdata.csun.edu/~voltaire/roland/startest2.html

I can see that if you were expecting Suiter results on the bench or on the star test, you'd be disappointed. But given that yours performed poorly in focus, you probably did the right thing.

My point though is that anyone expecting matched patterns inside and outside of focus with very fast triplet refractor optics is barking up the wrong tree. Great standard for slower doublets. Lousy for complex systems like SCTs and fast triplets.

- Jim


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ryderc1
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Re: TEC140 or TMB130 new [Re: jrbarnett]
      #6613314 - 07/02/14 03:41 PM

If my Traveler's star test patterns looked anything like those I'd be concerned too! Fortunately, they don't.

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peleuba
scholastic sledgehammer


Reged: 12/01/04

Loc: Southern PA
Re: TEC140 or TMB130 new [Re: t.r.]
      #6613321 - 07/02/14 03:44 PM Attachment (29 downloads)

Quote:

Paul, I've read about your TEC110 before and just noticed you have a Tak Sky 90II which is of similar short focus design using fluorite as well...how is its quality compared to the TEC?




Hi Tim - I really like the SKY90. The star test is certainly better then the TEC110FL but color correction is better in the TEC. Frankly, the TAK is not as bad as I have read it to be. I was expecting worse.

Takahashi manages spherical aberration by adjusting the spacing between the elements. This degree of freedom also has a downside as it makes collimation and centering a real PITA. And, it calls for a robust lens cell.

Regarding the TEC110FL - to be able to control SA in the design employed by TEC you would have to hand aspherize one of the surfaces. TEC does not do this routinely on any telescope they produce.

The star test in my post above and the focault images below show the issue… It looks like an edge problem but really its gross amounts of HSA. Foucault #1 shows issue at the edge of lens; Foucault #2 shows a hill at ~83% radius, and then a very steep fall-off from there to edge. Star tests with a 3mm eyepiece + green filter showed a significant halo around the Airy disk extending to many (about 5-10) disk diameters. Masking off the outer radius of the lens improves the view a lot. Reducing the aperture to 100mm using a mask shows nice improvement; using a larger mask, reducing clear aperture to 85mm (77% clear diameter) shows a near-perfect star test.

Anyway, so I like my Sky90-II more then my sample of the TEC110FL, aperture notwithstanding.


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t.r.
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Re: TEC140 or TMB130 new [Re: peleuba]
      #6613332 - 07/02/14 03:52 PM

Thanks Paul, I found my Tak Sky 90II to be very good as well in the star test but yes, residual CA remained. Still, a good optic and fine visual performer, CA and all. The collimation is indeed an issue.

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