35 replies to this topic

[Jeff B]

Specifically, Serial number 017.

 

I am, I believe, the third owner of this OTA.  I have owned it now for about 5 1/2 years.  It is an F9 oiled triplet with FPL-51 as the ED element.  It's at least 10 or more years old.  I have written extensively about its visual optical performance several times here on CN's and will only say it is superb (!) visually with very low "CA", gives an excellent star test, one of the best I've seen in this aperture really, and takes high power with ease.  It is one of my Reference Standards by which I gauge other scopes both mechanically and, especially, optically.   My sample is bino-friendly with the appropriate combinations of diagonal, viewer and eyepieces.

 

The OTA is surprisingly lite weight for its size, coming in at around 49 pounds with the dovetail and rings (3 of them) attached, but still a nose heavy brute.  I did use it in the field.  Twice.  I will never do that again.  It has spent the last 4+ years outside, under cover (telegizmos 365 cover), sitting on a MI-250 GEM.  As part of my evaluation of my newly acquired Losmandy Titan mount, I took down the 200ED and the MI-250 and brought them indoors for a good look at them both.

 

Which brings me around to the purpose of this thread which is really to document how well the 200ED has withstood the test of time outside here in SW Ohio, USA, where we get three full seasons.  I will document its physical condition as well as its DPAC bench performance.

 

Jeff

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[Element79]

Naw, I wouldn't worry about the TEC weathering the climate.

 

What I would worry about, however, is someone else that might also live in SW Ohio that now knows what your house looks like and what wonderful prize there is underneath that "covered thing" in your side yard!  That might keep me awake at night...

Edited by Element79, 04 November 2019 - 01:23 PM.

[macdonjh]

Jeff B,

 

In addition to adding information about your TEC200 here, I hope you'll post your impressions of the Titan with respect to your MI-250 in a new thread.  I had considered a Titan as my next upgrade, but an MI-250 became available and I jumped on it.  I'm quite pleased, but am interested to hear how the two compare side by side.

[Jeff B]

Jeff B,

 

In addition to adding information about your TEC200 here, I hope you'll post your impressions of the Titan with respect to your MI-250 in a new thread.  I had considered a Titan as my next upgrade, but an MI-250 became available and I jumped on it.  I'm quite pleased, but am interested to hear how the two compare side by side.

Actually, that is precisely one thing I'm going to do.  Actually, I may be "fixing' something with the Titan that's just not broken as the MI-250 has worked great really with minimal maintenance/tweaking over the last four years.   That will be a future thread.

 

Jeff

[Jeff B]

So, here are some pictures of the 200ED OTA after spending over four years outdoors.  Overall excellent condition really but here is the scoop.

 

With the dew shield removed the lens and coatings are in excellent condition though I make a point of cleaning the lens once a year in the spring after all the pollen has cleared the air.  No cleaning needed right now....but I'll probably do it anyway as I can be compulsive.

 

As you can see, there were a couple of small old bug nests deep under the back of the dew shield sliding flange.  One is a very small spider nest and the other two may actually be dried up Asian Lady bug bodies rather than nests.  Not bad after four + years and shows the dew shiled and cap are doing its job.

 

But speaking of the dew shield cap, you can readily see the dents I've managed to put into the edges of it over the years with my butter finger dropping it from on top of the ladder.      

 

The tube's paint does show some wear though.  But one might ask, "How could that be as it's under cover?".   Actually, the paint chips were removed by the sticky stuff used to line the rings as it's so grippy.  Ok, how grippy is it?  It's so grippy that I actually have to use a screwdriver under the scope to pry it out of the rings.  During that process (not fun six feet off the ground, on a ladder with an irreplaceable scope) portions of the paint would actually pull away from the OTA.  So, the stuff works....but maybe a bit too well.  

 

Also, early last year I did clean the OTA insitu to remove a few years of stains from dead Asian Lady and Stink bugs.  Came right off but none this year.  

 

So, overall, the scope is in excellent condition really.

 

Next will be the DPAC test photos.

 

Jeff

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[Jeff B]

Oops, forgot the lens shot.  Plus a shot of the entire cell.  Note the centering screw holes, all filled with stuff.  I took off the crime scene, toxic and nuclear waste tapes that Yuri wrapped around the cell to ward off the curious.   It didn't deter me though. 

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Edited by Jeff B, 05 November 2019 - 03:54 PM.

[Jeff B]

The DPAC test set up.

 

 

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[Jeff B]

Ok, starting from left to right in the spectrum (hold the cursor over the image to see its title):

 

First BLUE 

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[Jeff B]

Green:

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[Jeff B]

YELLOW:

 

 

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[Jeff B]

RED:

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[LLEEGE]

I was never a fan of the rubber tube ring liner TEC uses. I always applied a strip of felt to my TEC rings.

 

 

 

 Actually, the paint chips were removed by the sticky stuff used to line the rings as it's so grippy.  Ok, how grippy is it?  It's so grippy that I actually have to use a screwdriver under the scope to pry it out of the rings. 

[LLEEGE]

Thanks for the report, Jeff!

[Jeff B]

Thanks for the report, Jeff!

You're welcome.  An excellent lens really for a "fast" FPL-51 based oiled triplet (but I knew this going in) with a touch of under correction in green, a bit more in red and some over-correction in blue, all of which I'm finding to be pretty "normal" for a well made triplet.

 

Here is an interesting comparison.  Again, hover the cursor over the images to see their titles.

 

Jeff

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[Jeff B]

Same comparisons in blue.

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[Jeff B]

Finally in red.

 

All three scopes are of similar vintage.  Yuri and company were consistent.  

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[Jeff B]

Now, these at focus DPAC images of the 200ED are the most interesting. 

 

But first, they are a bit different from what I've taken before with other lenses as I used 150 LPI gratings, more precise cell phone camera settings + focus and I've gotten better at nailing grating focus and positioning to really highlite the shadows associated with the surface.  

 

So there appears to be a uniform aspheric on the lens and, if you look carefully at the previous DPAC images, you can see it in the outer portions of the bands.  What is also interesting is how the shape and "strength" of the aspheric changes with the color of the light.  I had trouble getting a decent image at focus in red as red is always a difficult color for me to capture with lower contrast and the aspheric appears just not as strong in red to boot.

 

 

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Edited by Jeff B, 05 November 2019 - 04:42 PM.

[R_Huntzberry]

Thanks for posting this.

[Kent10]

Thanks Jeff.  I love this stuff.

[Erik Bakker]

Wonderful insights Jeff. Thanks for posting them here 

[moshen]

These last images are really excellent. I know how hard and touchy it is to get these null images.

[CHASLX200]

It would never last in my nasty weather right on the gulf.

[mtminnesota]

Very interesting thread, thanks for posting it.

[fate187]

Thanks a lot for the comparison! Your DPAC and explanations are always helpful. I have questions though:

Comparing the green DPAC results outside focus of the 140, 160 and 200 I notice, that the 160 seems to have the most contrast. There is also a different width of the green lines for each scope!? Is there a reason for that? I thought I read, that the better the contrast and the smaller the width of the lines the better the polish? Please correct me...

 

And second for the aspheration: You mean the "dent" in in the null pictures? There is also a very small dent in the middle, could that be a very small zone? 

As for the aspheric surface I thought they are necessary for really faster scopes. I know that CFF aspherizes there lens. The other method would be to use fluorite glass, which is being used in the 180FL and 200FL and thus they don't need to be aspherized. I know the process to aspherize is difficult and the optician would probably be reluctant to do it with an expensive fluorite element.

 

Regards

Michael

[Jeff B]

Michael, thanks for the compliment.

 

Regarding the 160 ED green image, it was taken a little closer to focus than the others which will subjectively make the lines thicker.  There could also be small differences in focus of the cell phone camera, ASA and shutter speed settings, all of which can affect the image contrast and noise.

 

Regarding the aspherization, yes, the dents and doughnut shapes.   When I say aspherize, I mean the surfaces are not entirely spherical, and deviates from it over some portion of the surfaces.  Actually, all of the lenses I have tested show some form of "aspherization" of some form or another, none have really been perfectly spherical, some have come close, but there is always a deviation from spherical, mostly in the center. Attached are some other lenses. Hover the cursor over the image to see its title.

 

I don't know if the 200ED's aspherization was intentional or not to, for example maybe help balance the higher order spherical stuff.  Also, remember, DPAC testing is a very, very revealing test.  I'm not concerned in anyway about the in focus DPAC images.  I care more about the overall nature of the out of focus lines.  Also, this lens is extremely sharp with an excellent star test, and surprisingly little "CA".

 

Jeff

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