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Tele Vue Renaissance #1778

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#1 Peter Ceravolo

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Posted 28 August 2020 - 11:59 PM

A few months ago a Tele Vue Renaissance refractor was offered for sale by a fellow Canadian. One could tell from the photos that the brass tube had acquired some nice-looking patina. I recently became enamored with brass, I had acquired and started dissecting, documenting and restoring an antique Cooke refractor. Seeing the add I pondered the notion of modern brass. The current owner mentioned that the finish on the brass tube was not quite ideal, the original owner had tried to polish it and left some residue on the OTA. We made a deal and I had the scope shipped across the country.

 

The Renaissance brings back memories of very early 1980’s Stellafane. I had some one-on-one observing time with Al Nagler and his MPT and prototype Nagler eyepieces. The wide-rich-field views of the Milky Way were amazing compared the “peep hole” eyepieces I was used to. I have always been impressed with Tele Vue’s ground breaking and high-quality products, so it’s a treat to finally acquire a Tele Vue instrument of that heritage to use with the dozen or more Tele Vue eyepieces I have accumulated over my four and half decades doing astronomy.

 

Here is the Renaissance mounted on a Losmandy 200 for testing.

 

IMG_2600.JPG

 

As soon as I could, I spent some time with the telescope under the stars on nights of good seeing. Although the collimation was a bit off, I was impressed with the image quality, a clean Airy disc and diffraction rings at 344x. That high power is achieved with a 8mm Radian and 5x Powermate. What struck me the most was the color correction; it was much better than I was expecting. I must admit I am not a refractor aficionado, with talk of the number of crossings etc, but I don’t see much difference in the Renaissance’s faint blue halo when compared to my Stellarvue 110mm f/7 ED’s faint blue halo. There is perhaps a bit more spurious red in the Renaissance image. David Nagler says that the 4” f/5.5 Renaissance has the color correction of a 4” f/8 achromat.

 

David tells me that the Tele Vue Renaissance #1778 was born April 12, 1993 and was the 5th from the last one made. Upon opening the case I saw that the black anodized cell and end ring had faded from exposure to the sun. The brass patina was blotchier than expected and the polish residue was a lot more obvious than I would like in instrument that I would want to display as much as use. Some might be annoyed - I saw an opportunity - let’s rip the scope apart and see what’s inside while we clean it up!

 

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#2 Compressorguy

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Posted 29 August 2020 - 03:42 AM

Congrats Peter! Boy, am I going to enjoy this thread! I have a 1985 Renaissance and a Genesis. My Renaissance is the earlier version with the bolt on focuser and both front and rear cells thread on. I’ve had it apart to polish the tube as well. Both are beautiful to look at and great performers to look through. My Renaissance has very good color correction also but the newer Genesis edges it out with the addition of its rear flourite element. The pinpoint, wide field views through both are mesmerizing. 


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#3 Peter Ceravolo

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Posted 29 August 2020 - 04:18 AM

Scott  (Compressorguy)! I'm curious to know how the earlier and later Renaissance differ. I'll post all the pics of the refurb shortly. Please post what ever pics you have. I'm particularly interested in your experience polishing the tube.

Peter


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#4 Peter Ceravolo

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Posted 29 August 2020 - 04:29 AM

The first part to extract from the tube was the objective cell. The three button head screws holding the cell in place have some gunk in the socket to prevent people from messing with the optics. Well... a sharp tipped knife is all it took to flick the filling out of the screw.

 

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The cell in this scope was encrusted with the dried up polishing gunk and needed a bit of persuasion to let go. A few taps with a hammer on a wooden brush butted up to the cell was all that was needed to free the cell.

 

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The rear cell/focuser threads on, and there is a set screw to keep it in place so one can line up the focuser with the bolts holding the objective cell in place.

 

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#5 Peter Ceravolo

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Posted 29 August 2020 - 04:41 AM

Four bolts hold the rack and pinon pressure plate in place. Note the section of plastic tube that I assume provide a "bearing" surface between the pressure plate and the brass shaft.

 

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The last owner did say that the focuser knob shaft was bent. I tried messing with it to straighten it out without much success. I decided that would be revisited another day.

 

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The draw tube slides on what looks like a teflon sheet in the focuser body. This does not compare with the technology today of course, but other that a bit of image shift at 300x, the old style rack and pinion focuser felt smooth with little backlash.

 

IMG_2520.JPG


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#6 Peter Ceravolo

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Posted 29 August 2020 - 04:52 AM

The focuser body threads on to the rear end ring/lens cell. Again a set screw locks it in place.

 

IMG_2522.JPG

 

The rear focal reducing/field correcting cemented doublet lens, what makes this instrument a Petzval telescope, is mounted in the rear end ring. It took no effort to rotate the threaded retaining ring, that was a surprise. Normally these retaining rings are locked in place to prevent things from coming loose in handling over the years. The other surprise was that the ring was a very sloppy fit. When I reassembled the telescope I applied a drop of Loctite to keep it from coming loose.

 

IMG_2527s.JPG

 

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#7 Peter Ceravolo

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Posted 29 August 2020 - 05:02 AM

The objective lens was a bear to get out. In this case the retaining ring was secured in place with a Loctite type substance. Before messing with it I marked the lenses on their polished faces to preserve their respective orientation.

 

I then injected acetone in the threaded portion of the cell to free up the Loctite. Ultimately I had to fashion a "wrench" from scrap aluminum plate to retract the retainer ring. It's not visible in this image below, but one has to curve the bottom of the "wrench" in order to clear the convex glass surface. A few layers of tape on the edge will also help to ensure no scratching the lens.

 

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With the widely spaced doublet extracted, I marked the edges to preserve alignment. Given the quality of optics nowadays, this is probably not necessary, but I did it anyway just in case...

 

IMG_2533.JPG


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#8 Compressorguy

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Posted 29 August 2020 - 06:54 AM

I think optically the early and later model Renaissace scopes were the same. Both are 101mm x 550mm. Mechanically, my early model, s/n 1093, mfg Jan 7, 1985 has very finely threaded on front and rear cells. The focuser mounts to the rear cell via 4 screws vs being screwed on like the later models. Also the s/n plate on the early models is located on the clamshell vs the focuser body. Lastly the clam shell on the early models is constructed as a single piece with one split and tightening screw. The later models are a much better two piece design which aides removal of the ota without having to remove one of the cells and sliding the clamshell off the tube. 

 

Regarding polishing, I believe my tube was in a little better shape but not much better. I used Flitz metal polish and an old cotton tee shirt by hand to polish it. Lots of elbow grease. I also taped off the ends so as to not get polish in the tube and or in the fine threads. Not sure what all is in the polish (acidic?) but don’t want it near the objective coatings in case it could react. The coatings on my scope are pristine. I do remember that I polished in one direction consistently and would recommend the same for a really good result. Either go length wise or radially, which ever you prefer but keep your strokes consistent in the same direction, like sanding wood grain. The Flitz polish worked great and was easy to use and doesn’t smell as bad as Brasso. Fortunately there was very little to no pitting on my tube. I guess if there were some bad pitting it could be removed with some 1,000 to 2,000 grit paper and polished out. These tubes appear to be pretty thick. It must be if your front cell is threaded into it, lol. Here’s some photos of the focuser and before and after.

 

Focuser held on with 4 screws. Also before polishing.

 

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#9 Compressorguy

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Posted 29 August 2020 - 07:00 AM

After polishing. Also I was VERY lucky to find a TV screw on dew shield on eBay and snapped it up as soon as I saw it. I know they were offered with the very early design Genesis before the sliding dewshield but not sure they were ever offered with the Renaissance. 

 

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#10 Compressorguy

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Posted 29 August 2020 - 07:07 AM

The only other difference may be the coatings. The 1985 Renaissance has purplish coatings while my Genesis s/n 1608 (not sure of year but probably very early 90’s) has more bluish coatings. It’s my understanding that the Genesis directly followed the Renaissance but interesting to surmise there was some overlap as my Genesis s/n is 170 before your Renaissance. 

 

Renaissance

 

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Genesis

 

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#11 25585

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Posted 29 August 2020 - 01:27 PM

Thank you for this thread and your photos waytogo.gif

 

My 102 & 85 Renaissances have black draw tubes, not the nice brass one yours has. 

 

What polish did you use? 



#12 Peter Ceravolo

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Posted 29 August 2020 - 03:37 PM

IMG_2606b.JPG

 

Here is a pic of the assembled Renaissance on it's display tripod in the backyard.

 

Reassembly was a breeze, this is after all a relatively simple telescope. The cell is some what oversized for the tube, there is significant play, David suggested I would have to play with the objective tilt and screws to achieve optimal collimation. So I started out by simply pressing the cell against the tube and tightening the screws in the shop. I mounted the telescope on the big 'ol Losmandy and was prepared to fiddle with the objective cell while looking a star close to the zenith.

 

Well, the diffraction pattern was nearly perfect! Beautiful Airy disk and rings at 340x, way better than when the scope arrived. The seeing was quite good that night and I thought that there might be a bit of reddening to one side of the diffraction pattern so I played with the screws to see if I could tweak it out. Well, I was back to the offset diffraction rings. I tried messing with it some more and got no where. I then backed off all the screws and simply pressed the cell against the tube to re-tighten the screws. It was then I noticed that the lens rocked a bit on the end of the tube. At one tilt the collimation was off, at the other it was bang on again.

 

Scott how do you collimate the older version if the cell threads on? Or is the machining so good that no collimation is required?


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#13 Bonco2

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Posted 29 August 2020 - 04:37 PM

Love this thread. The early Renaissance is what got me back into refractors in the late 80's. After my first view seeing the veil neb and North American neb for the first time, I bought a new Genesis. MY favorite telescope. You mention 344X. When I write reports about the Genesis I usually write something like, "It's good up to 250X+. But the truth is I have used it successfully splitting double stars with stacked 2.4X and 2X barlows at  more than the 344X you reported. I figured if I posted that people would think I was nuts. But your testimony gives credibility to my observations. Thanks for your sharing the assembly/disassembly. Beautiful telescope and a superb performer. BTW you looked thru my Genesis in a late 80's Winter Star party. If my memory serves me I think you were impressed. Everybody else was including Al Nagler....What a great guy he is.

Bill


Edited by Bonco2, 29 August 2020 - 04:38 PM.

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#14 Peter Ceravolo

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Posted 29 August 2020 - 06:08 PM

Bill I know what you mean about talk of high power observing past 200x. The reality is that a lot of telescopes can't handle it, but a surprising number of commercial telescope can. But I think it's what you're looking at that makes all the difference. On the planets, yes, empty magnification is a reality and seeing just reinforces that fact. When the seeing is excellent, and I have actually seen "perfect" seeing from here on our mountain top home, I love looking at stars - diffraction patterns. I get in a physical optics kind of mood :-) During those times one can jack up the power past what one would think reasonable. Last night I was looking through the Renaissance at 530x but the seeing was mediocre. But given that the telescope still held it's own, meaning that even with the seeing one could tell the optical quality could handle the high power.

 

A bunch of years back I was observing with a 212mm f/4 aplanatic Mak Newt I had recently finished (started it 25 years ago... :-). I labored over the optics, the wavefront was well corrected and very smooth. I used that scope past 800x looking at doubles. I even looked at a tiny planetary nebula in Cygnus, over head, at 800x and could decern the bi-lobed structure. The seeing that night was in fact "perfect". I was focusing by varying the distribution of energy from the Airy disk to the diffraction rings. But it's a Newt, so you have to be careful of where you stand otherwise ones breath will waft in the light path and destroy the image. And don't get me started on open truss telescopes...

 

Of course with this talk of "ludicrous power", one cannot ignore the need for a driven solid mount with slow motion control to make the experience pleasurable.


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#15 Bonco2

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Posted 29 August 2020 - 08:14 PM

Peter,

You've expressed my thoughts better than I could ever do and you have more credibility than I will ever have. Last thing I want is this thread to get into an argument over ludicrous magnification. I'm happy that an expert such as you is recognizing and revealing the qualities of these early Al Nagler products.  Maybe I or someone else will start a thread about ludicrous magnification with classic scopes. Should be a very controversial and possibly interesting thread. Or not.

Best wishes, Bill



#16 Peter Ceravolo

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Posted 30 August 2020 - 01:09 AM

The old, caked on polish compound was hard a rock and required a lot of rubbing to remove. It wasn't a big deal really, but the big brass tube is a lot of work to make pretty, setting it up for the next round of patina making.

 

IMG_2510.JPG

 

I am fundamentally lazy and impatient, so I was casting around for a way to speed things up. I scrounged the shop for bits and pieces and was able to mount the tube on a vertical spindle I use for rough grinding glass.

 

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I tube is only taped in place, so I had to be careful not to press too hard on the surface. I hold a pin on the top plate taped to the tube to stabilize it. I used a scotch scrub type pad to remove the encrusted gunk, and that did mar the surface some so it will take some more work to smooth out the fine scratches. I was looking for a more satin type finish. One of the Antique Telescope Society members suggested fine steel wool, it seems to work well but it take a long time and I wanted to re-assemble the scope and get on with other things. The last step was to apply a protective wax coating. I had ordered "Conservator's Wax" recommended to for antiques, but I needed something now so I applied Mother's California Gold - Pure Brazilian Carnauba wax. If it's good enough for my 'vette, it's good enough for the Renaissance - at least for now... :-)

 

Because it is so easy to disassemble I plan to revisit the tube finish as time permits.


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#17 RichA

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Posted 30 August 2020 - 01:42 AM

TeleVue's decision to leave the tube uncoated probably stemmed from the fact few people know how to lacquer brass like they used to with 1800's microscopes, some of which survive with surface in good condition today.  I'd probably look for a way to do it, just to prevent the tube from reverting in a few years.



#18 RichA

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Posted 30 August 2020 - 01:47 AM

A few months ago a Tele Vue Renaissance refractor was offered for sale by a fellow Canadian. One could tell from the photos that the brass tube had acquired some nice-looking patina. I recently became enamored with brass, I had acquired and started dissecting, documenting and restoring an antique Cooke refractor. Seeing the add I pondered the notion of modern brass. The current owner mentioned that the finish on the brass tube was not quite ideal, the original owner had tried to polish it and left some residue on the OTA. We made a deal and I had the scope shipped across the country.

 

The Renaissance brings back memories of very early 1980’s Stellafane. I had some one-on-one observing time with Al Nagler and his MPT and prototype Nagler eyepieces. The wide-rich-field views of the Milky Way were amazing compared the “peep hole” eyepieces I was used to. I have always been impressed with Tele Vue’s ground breaking and high-quality products, so it’s a treat to finally acquire a Tele Vue instrument of that heritage to use with the dozen or more Tele Vue eyepieces I have accumulated over my four and half decades doing astronomy.

 

Here is the Renaissance mounted on a Losmandy 200 for testing.

 

attachicon.gifIMG_2600.JPG

 

As soon as I could, I spent some time with the telescope under the stars on nights of good seeing. Although the collimation was a bit off, I was impressed with the image quality, a clean Airy disc and diffraction rings at 344x. That high power is achieved with a 8mm Radian and 5x Powermate. What struck me the most was the color correction; it was much better than I was expecting. I must admit I am not a refractor aficionado, with talk of the number of crossings etc, but I don’t see much difference in the Renaissance’s faint blue halo when compared to my Stellarvue 110mm f/7 ED’s faint blue halo. There is perhaps a bit more spurious red in the Renaissance image. David Nagler says that the 4” f/5.5 Renaissance has the color correction of a 4” f/8 achromat.

 

David tells me that the Tele Vue Renaissance #1778 was born April 12, 1993 and was the 5th from the last one made. Upon opening the case I saw that the black anodized cell and end ring had faded from exposure to the sun. The brass patina was blotchier than expected and the polish residue was a lot more obvious than I would like in instrument that I would want to display as much as use. Some might be annoyed - I saw an opportunity - let’s rip the scope apart and see what’s inside while we clean it up!

 

Thanks for that.  First time I've ever seen the sub-diameter correcting element in its cell. 



#19 Peter Ceravolo

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Posted 30 August 2020 - 08:38 PM

TeleVue's decision to leave the tube uncoated probably stemmed from the fact few people know how to lacquer brass like they used to with 1800's microscopes, some of which survive with surface in good condition today.  I'd probably look for a way to do it, just to prevent the tube from reverting in a few years.

Rich, my spider sense suggests that it would be easier for most to simply buff/polish and wax the tube every few years when the patina gets out of hand. A few hours effort at most.

 

You are absolutely right, the skills associated with spraying lacquer on brass to preserve the finish is tough to acquire, and then there is the recipe for the lacquer. A member of the ATS has gone through the process, guided by a conservator in Italy - it was a bigly job!



#20 walter a

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Posted 30 August 2020 - 09:47 PM

I needed a little elbow grease on this one.

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#21 Peter Ceravolo

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Posted 31 August 2020 - 12:58 AM

Another Canadian Renaissance!

 

Walter, don't hold back...



#22 Compressorguy

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Posted 31 August 2020 - 06:18 AM

 

Scott how do you collimate the older version if the cell threads on? Or is the machining so good that no collimation is required?

Hi Peter, you are correct. There is no collimation other than any rotational differences between the front and rear cells and I believe collimation is finding the best rotational balance and spacing of the two. That said, the machining is so accurate that there is very little if any rotational difference, at least in mine. I will say the threads are extremely fine and I found it extremely difficult to get the cells started on the threads. Even rotating it backwards and listening/feeling for the “click” was difficult. There is a single, small, set screw in each cell, that if over tightened may introduce some very slight tilt to the cell but also distorts the tube and creates a gap between the cell and tube if used in that manner. So my thought is they are intended to only secure the cell in place. 

 

27169F9E-E76C-4EE4-8892-DBBC6C3515E5.jpeg


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#23 Compressorguy

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Posted 31 August 2020 - 06:20 AM

I needed a little elbow grease on this one.

WOW! Beautiful! 


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#24 Peter Ceravolo

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Posted 31 August 2020 - 03:49 PM

I did an image search for Tele Vue Renaissance, I see that a lot of the brass tubes have blotchy patina, some really bad.

 

Maybe we should start a thread on how to rework brass tubes!


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#25 B l a k S t a r

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Posted 07 September 2020 - 12:30 PM

Peter, what a beautiful job you've done.  Bravo on the view(s).




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