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TEC 7 Mak First Light

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#126 elwaine

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Posted 22 November 2020 - 11:40 AM

I don't want to derail this thread, but after he made the 7" Maks, Yuri found a stack of 6" mirrors in the shop and also made a small batch of new 6" Maks.  He made some nice upgrades from the original model - new focusing micrometer, mounting points, dew shield, and dust cover.

 

They were also marked with the "2013" front plate and worked just as well as the originals.  When I asked Yuri how many he made, he simply said, "A handful", which I took to mean five or six.  So if you are looking for one of the nicest 6-inch Maks around, this is a candidate. cool.gif

 

Cheers,

 

Ron

 

 

 

Ron,

 

There were three runs of TEC 6" Maks. The first was in the early 2000's and consisted of a run of 50. In 2013, he made several 6" Maks, like the one shown in your photos. I don't know how many he made at that time, but the secondary cover, as shown in your photo, was printed with "6 . f/12 . 2013."  

 

In the Fall of 2016, I contacted Yuri looking for a TEC 7" Mak. That was out of the question. But he said he had 2 or 3 "left over 6" optical sets" and offered to make me a 6" Mak... which I jumped at. The secondary cover was printed "TEC 6   150mm   f/12" and no date. 

 

gallery_17233_3964_119765.jpg

 

This one is from the first run of fifty 6" TEC Maks.

gallery_17233_3964_10768.jpg

 

The TEC 7" - like the later runs of TEC 6" Maks, have no tube baffles and have no printing around the periphery... just on the secondary cover.

 

med_gallery_17233_3964_234261.jpg


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#127 RAKing

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Posted 22 November 2020 - 12:52 PM

Ron,

 

There were three runs of TEC 6" Maks. The first was in the early 2000's and consisted of a run of 50. In 2013, he made several 6" Maks, like the one shown in your photos. I don't know how many he made at that time, but the secondary cover, as shown in your photo, was printed with "6 . f/12 . 2013."  

 

In the Fall of 2016, I contacted Yuri looking for a TEC 7" Mak. That was out of the question. But he said he had 2 or 3 "left over 6" optical sets" and offered to make me a 6" Mak... which I jumped at. The secondary cover was printed "TEC 6   150mm   f/12" and no date. 

 

Thanks for the updated info.  waytogo.gif   Over the years, I owned #25 and #12 from the original run as well as the one pictured from the 2013 run.  It's great that you were able to get another one from him.

 

All of my TEC Maks have been incredible instruments!

 

Cheers,

 

Ron


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#128 vahe

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Posted 22 November 2020 - 02:15 PM

My two cents on your broken meniscus.

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The way that I see this your only option at this point is to find someone with the experience to make a new meniscus. Since the glass is not totally shattered they can use the broken meniscus to measure R1, R2, the central hole for the Rumak secondary and the thickness, this along with the glass type will give the maker a much needed info to start with.

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For the glass, in the older days TEC used B grade BK7, more recently with the environmental movement they tried H2 grade of NBK7. For 7” size this glass may be acceptable for internal quality, but for larger TEC Maks this glass did not pass the test. In fact the lack of availability of suitable glass killed both larger TEC Mak projects and their APO200ED & APO160ED refractors.

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Coatings: My TEC6 came with one page spec sheet, meniscus coatings are identified as BBAR anti-reflection coatings. (Coatings always scare me, to put a finished corrector in vacuum oven heated to 600 degrees and hope that it survives calls for someone with strong nerves).

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With all the above information the maker of meniscus should be able to Reverse Engineer the corrector without access to the original design.

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As was suggested in post #111 you can explore some other avenues as well, contact folks with the knowledge and see if someone would be willing to make a new meniscus for you, if you can get Zen to do it that would be ideal. Making one meniscus will definitely be COSTLY, but depending on the cost involved it is definitely something worth the effort assuming the rest of the OTA is in good shape. Going back to the cost, a 7” Questar is priced at about $10K and if I have to choose I would take a TEC7 any day over Q7, just for its smaller co.

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A few other options; place a new post in CN, “ATM, Optics and DIY Forum”, call it “Broken Meniscus” to attract attention.

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Another option is to contact Markus and see what he has to say about this, Markus knows everyone in optics business in this world.

.

And, finally do not give up, you never know.

.

Vahe


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#129 ch2co

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Posted 22 November 2020 - 06:50 PM

Here's the mess.mad.gif

 

5555.jpg IMG_5630 (1).jpeg


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#130 luxo II

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Posted 22 November 2020 - 06:56 PM

Well, the scope will still work like that except stars are going to show two diffraction spikes arising from the crack.



#131 Jeff B

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Posted 22 November 2020 - 08:14 PM

Here's the mess.mad.gif

 

attachicon.gif5555.jpgattachicon.gifIMG_5630 (1).jpeg

Owe, my eyes!!

 

Well  shoot.  But don't give up.

 

I would recommend a thin line of dark nail polish over the crack. and as others have said, it will still work and you may be surprised how sharp it is on solar system objects.  Shoot Tak Mewlons with their fat spider vanes work great. 

 

Just make the line as thin as you can to cover the entire width.  Then reassemble and collimate it, first with a Cheshire eyepiece, then star test.

 

Jeff


Edited by Jeff B, 22 November 2020 - 08:16 PM.

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#132 luxo II

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Posted 22 November 2020 - 11:49 PM

Hmm. Re the above - I'd forget about the nail polish. It will work as-is; making the obstruction wider will be negative, not a positive.

 

This is pure speculation..... cannibalise an Intes Micro M615, for its corrector and install that. Whether the Intes secondary or TEC secondary is a better match... who knows.

 

Highly unlikely, but it might "just work"™.


Edited by luxo II, 22 November 2020 - 11:53 PM.

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#133 Jeff B

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Posted 23 November 2020 - 10:14 AM

Hmm. Re the above - I'd forget about the nail polish. It will work as-is; making the obstruction wider will be negative, not a positive.

 

This is pure speculation..... cannibalise an Intes Micro M615, for its corrector and install that. Whether the Intes secondary or TEC secondary is a better match... who knows.

 

Highly unlikely, but it might "just work"™.

That's why I suggested nail polish as acetone can quickly remove it.  Left unmasked, the jagged edges will contribute the effects of active refractive aberration to the image versus that of a thin obstruction.

 

Easy enough to try it both ways.

 

Jeff


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#134 elwaine

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Posted 23 November 2020 - 12:21 PM

ryderc1 began this topic with a report on how his TEC 7" Mak performed on the Moon. So I'll give a very brief update on how that same TEC 7 ( grin.gif ) performs on the Moon 7 years later.

 

Last night, using my TEC 7" Mak under the light polluted skies SW of Houston, with average seeing and less than average transparency, the terminator zone in the 7 day old Moon offered heart stopping drama even for an old codger like me, who has seen the Moon more times than I can recall. I used the following Baader Morpheus eyepieces: 17.5mm (154x), 12.5mm (216x), 6.5mm (415x). I also used a Baader 8-24mm Zoom, which I preferred to use at a magnification of close to 300x.

 

The Alpine Valley was in high relief and looked like a fresh wound had been cut into the landscape. I looked at it for quite a while hoping to glimpse some portion of the central rile, but observing conditions weren't nearly good enough. Still, the details of the Lunar surface surrounding the Valley were so etched that I kept trying, without success, to see the rile.

 

Even more striking were the stark black shadows cast off of the bright white peaks of the Alpes mountains, just South of the Valley. They were like spikes and needles jabbing at the gray lava of the Imbrium Basin. Some shadows were razor thin and had to be considerably less than a mile wide. (None of the very thin shadows are captured in the photo below.)

 

But the real show stopper had to be the 25 mile wide crater Aristoteles. The sinuous ejecta stood out in rich detail, reminding me of the head of Medusa. The play of light and shadow was quite dramatic.

 

For high magnification officionados, I'm sure the TEC 7 can gobble up more power than 415x, but my eyes can't. Exit pupils smaller than .4mm brings out the floaters; and even on the brightly lit Lunar surface, the views start to get noticeably dim when exceeding about 350x - but they are still rich in detail. 

 

I'm including a picture just to show the region I described. It's a poor photo taken by a hand held, old iPhone. A fair analogy to what I saw vs. what is seen in the photo, would be to compare a perfectly cooked Chateaubriand to a hotdog.

 

med_gallery_17233_3964_173040.jpg


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#135 ch2co

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Posted 23 November 2020 - 02:25 PM

 

 

Re: The cracked "corrector" ie front element plate.

Thanks for all of your suggestions. Now remember, I picked this up as a piece of trash at an auction that I won with the high bid of $11 .  I and everybody else who saw this thing saw it as trash or maybe some usable parts. After getting it home, I removed the corrector from the insides of the tube. It was jammed, cocked sideways in the tube about 8" in front of the primary mirror. aaah!  It obviously had been taken apart by someone who after seeing the damage was discouraged (and possibly tearful) and just slipped the corrector into the bowels of the tube and gave up. The damage to the overall body of the scope is very minor with only very slight scratch marks on the front edge of the lens hood, the edge of the corrector plate holder, and the edge of the back plate. The primary mirror and the front secondary mirror looked to be in perfect condition. The focusing "micrometer" turned smoothly and showed no apparent damage. 

Now about the crack.  The crack is not a perfectly straight line. It "wiggles" a small amount AND the top edge and bottom edge wiggle differently. Also there are a couple of angular cracks that branch out from the main crack. It looks like the a possible point of impact that caused the crack is where a very small chip of glass missing. The chip fell out of the tube when I was rotating it. See pics.

When light hits the corrector plate it spreads out in many directions from around the crack, which is why I believe the best thing to do is mask off that area. It would affect the optics of course, but not to the same degree as the crack and its myriad reflections would produce.


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#136 Reid W

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Posted 23 November 2020 - 06:02 PM

Yes, mask it off. Plain blue painter's tape- the full width. Do this before precisely trimming it down.

Hopefully, all you would see would be a single spike in the diffraction ring.
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#137 twkelley

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Posted 01 December 2020 - 11:39 AM

ch2co - When I saw your picture, after wincing, it made me wonder if you could have those guys who fix cracks in car windshields inject that epoxy into the crack and if it would fix it well enough to make it usable?  The crack  may be too large and deep, but made me wonder. Just a thought for an unusual and unfortunate situation.

 

TK



#138 Jeff B

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Posted 01 December 2020 - 12:11 PM

ch2co - When I saw your picture, after wincing, it made me wonder if you could have those guys who fix cracks in car windshields inject that epoxy into the crack and if it would fix it well enough to make it usable?  The crack  may be too large and deep, but made me wonder. Just a thought for an unusual and unfortunate situation.

 

TK

An interesting idea.

 

However, introducing a compound that bonds to the glass may introduce stress of varying amounts along entire length of the crack, making it appear optically wider than it is now, especially as the thermal expansion coefficients of the two materials will probably be very different from one another.  The edges of the crack are right now in more or less of a free state, but with some contact stresses where the surfaces touch.  

 

Still, this is all conjecture and I would find it fun and interesting to reassemble and collimate the beastie and have a look through it.  

 

So ch2co, if you'd be willing, I'd like to have a crack at it....ooops, sorry, poor choice of words.

 

Jeff



#139 RalphMeisterTigerMan

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Posted 01 December 2020 - 12:50 PM

Wow! That TEC 7 looks like a work of art! I was considering hitting the like button, but with all those beautiful pics I was afraid of getting Carpul-tunnel syndrome (think I spelt that wrong). I have always had a thing for well made optics but there's something about Mak-cass's that really turn me on, whether it's a regular or a Rumak design they are still amazing.

 

I have to plead guilty to envy!

 

Even though I love "window shopping" on CN, I very much cherish my current telescope, a Celestron C5+. While I know that it cannot hope to compete with a 7" Mak I still enjoy the views I got thru it a while back.

 

You are very fortunate to have such an amazing scope. Good luck and I hope you have many wonderful viewing sessions to come.

 

Clear Skies!

RalphMeisterTigerMan




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