23 replies to this topic

[Jeff B]

This one is Serial Number 05098, speculating is was made in ~2006, and like the previous sample I tested:

 

https://www.cloudyni...optics-110-flt/

 

has the TEC oil coupled, F6.5 triplet objective.  I acquired it about a month ago.

 

The OTA is really in very good overall cosmetic shape with some minor wear, like mild scratches, scuffs and very small chips all to be expected with a well used scope of this age.  The rings are a bit beat up but are quite robust.  This is a heavy OTA.  Most importantly though, the glass and coatings look almost brand new, love the coatings.

 

Jeff

 

 

 

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[Jeff B]

This scope is robustly built and after over 17 years, the laser still fired through the hole in the center of the mask.

 

But I have to say, I dislike the stock Crayford focuser, and yes, I know it is old, but it is low capacity for use with bino-viewers.

 

It comes with a removable spacer and without it, using an AP diagonal, 1.25" adapter and standard Plossel eyepiece, I have 70mm of back focus left.  Not enough to be bino-friendly with the AP diagonal, but enough when using my Baader T2, quick changer diagonals, with their much shorter light paths.

 

Jeff

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[Jeff B]

Here are the preliminary inside/at/outside of focus shots with a green LED.

 

The at-focus shot was terribly difficult to take as there is just not that much to see in terms of artifacts unless I really hyped the contrast to bring out some features such as that smooth mild zone at the 80% span which is not uniform in magnitude circumferentially but still there.  Any micro-whatever you might think you see is mostly noise from the image contrast enhancement.   This is a smooooth polish.

 

The center 80% of the images seem quite neutrally corrected with a smooth transition towards mild overcorrection from 80% out to the good edge.

 

Jeff

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[RichA]

That's the beauty of fluorite.  It's expensive, so manufacturers tend to lavish a bit more effort on it than regular glass.  So you are less likely to see some of the flaws in it that you might see in regular efforts.  Plus, it's a TEC product.

[Jon Isaacs]

 

But I have to say, I dislike the stock Crayford focuser, and yes, I know it is old, but it is low capacity for use with bino-viewers.

 

Jeff:

 

My WO 80 mm Megrez 2 FD that you tested was of the same vintage and it's focuser was weak and I had replaced it with an Astro-Tech 106LE steel track focuser that just happened to fit.

 

Jon

[Jeff B]

That's the beauty of fluorite.  It's expensive, so manufacturers tend to lavish a bit more effort on it than regular glass.  So you are less likely to see some of the flaws in it that you might see in regular efforts.  Plus, it's a TEC product.

Actually Rich, it is an FPL-51 center element, with, perhaps, BK7 surrounding it. 

 

WO caught, perhaps rightfully so, a whole bunch of garbage for using the words "Fluorite", and even "Fluoro-Star",  in its advertising and printing on the scope's "beauty ring".  Some folks thought it strongly implied a real FL element, when, in fact, they were really "just" fluoro-crowns.

 

Seems to have tricked you too.  

 

Jeff

[RichA]

Actually Rich, it is an FPL-51 center element, with, perhaps, BK7 surrounding it. 

 

WO caught, perhaps rightfully so, a whole bunch of garbage for using the words "Fluorite", and even "Fluoro-Star",  in its advertising and printing on the scope's "beauty ring".  Some folks thought it strongly implied a real FL element, when, in fact, they were really "just" fluoro-crowns.

 

Seems to have tricked you too.  

 

Jeff

Then there should be noticeable colour error in the white light image.  Is that why you only posted the green-light image of the bands?

Edited by RichA, 11 June 2024 - 12:16 PM.

[SandyHouTex]

Here are the preliminary inside/at/outside of focus shots with a green LED.

 

The at-focus shot was terribly difficult to take as there is just not that much to see in terms of artifacts unless I really hyped the contrast to bring out some features such as that smooth mild zone at the 80% span which is not uniform in magnitude circumferentially but still there.  Any micro-whatever you might think you see is mostly noise from the image contrast enhancement.   This is a smooooth polish.

 

The center 80% of the images seem quite neutrally corrected with a smooth transition towards mild overcorrection from 80% out to the good edge.

 

Jeff

That's a nice looking test.  Excellent correction.

[Jeff B]

Here are my usual white light LED images along with their color montages, generated by separating out the R,B,G channels and displaying them individually.   The yellow image was generated by deleting the blue channel and slightly reducing the intensity of the red channel.   There has been some good discussions here on CN's about using this process to generate the individual colors, especially the yellow blending, as opposed to using individual colored LEDs and/or filters.  As I understand it, there perhaps can be some camera, software split processing and LED related artifacts that might creep in.  Before I started this current procedure, I made extensive comparisons between split RGB images and those using discrete RGB LEDs and filters, concentrating on the green channels, and saw only maybe some subtle differences.  I will continue with my present process as data capture and processing is so much faster with fewer variables and all colors are captured at the same distance from the lens, which gives me some insights concerning secondary spectrum for the objective.

 

In the white images, I can immediately see some secondary spectrum, particularly in blue, as blue fringing of the two outer black ronchi screen shadows that flips to the other edge on the other side of focus.  To a lesser extent, there is some of that in red too as a red tint but on the opposite side of the shadow as blue.  I also see the spherochromatism in blue as brighter and wider blue fringing at the tips of the line shadows, most easily seen in the outside of focus image.

 

The montages clearly show spherochromatism with the biggest "misses" in spherical and secondary spectrum relative to green/yellow are in the blue. There are much smaller misses in the red.  The slightly different focus of the red and green is also seen as subtle red/green borders to the shadow lines that flip to the  other edge on the other side of focus in the blended yellow images.

 

Jeff

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[Jeff B]

There there should be noticeable colour error in the white light image.  Is that why you only posted the green-light image of the bands?

Correct!  See above Rich.

 

Jeff

[RichA]

Here are my usual white light LED images along with their color montages, generated by separating out the R,B,G channels and displaying them individually.   The yellow image was generated by deleting the blue channel and slightly reducing the intensity of the red channel.   There has been some good discussions here on CN's about using this process to generate the individual colors, especially the yellow blending, as opposed to using individual colored LEDs and/or filters.  As I understand it, there perhaps can be some camera, software split processing and LED related artifacts that might creep in.  Before I started this current procedure, I made extensive comparisons between split RGB images and those using discrete RGB LEDs and filters, concentrating on the green channels, and saw only maybe some subtle differences.  I will continue with my present process as data capture and processing is so much faster with fewer variables and all colors are captured at the same distance from the lens, which gives me some insights concerning secondary spectrum for the objective.

 

In the white images, I can immediately see some secondary spectrum, particularly in blue, as blue fringing of the two outer black ronchi screen shadows that flips to the other edge on the other side of focus.  To a lesser extent, there is some of that in red too as a red tint but on the opposite side of the shadow as blue.  I also see the spherochromatism in blue as brighter and wider blue fringing at the tips of the line shadows, most easily seen in the outside of focus image.

 

The montages clearly show spherochromatism with the biggest "misses" in spherical and secondary spectrum relative to green/yellow are in the blue. There are much smaller misses in the red.  The slightly different focus of the red and green is also seen as subtle red/green borders to the shadow lines that flip to the  other edge on the other side of focus in the blended yellow images.

 

Jeff

Wow!  That is worse (though exposure and illumination source varies) than a 120mm f/8.3 achromat I've got.  Thanks for posting it!  You've got to contrast this against more modern scopes that probably would not be as nicely figured and polished, even though they might have better glass in them.  

Edited by RichA, 11 June 2024 - 07:41 PM.

[Jon Isaacs]

Actually Rich, it is an FPL-51 center element, with, perhaps, BK7 surrounding it. 

 

WO caught, perhaps rightfully so, a whole bunch of garbage for using the words "Fluorite", and even "Fluoro-Star",  in its advertising and printing on the scope's "beauty ring".  Some folks thought it strongly implied a real FL element, when, in fact, they were really "just" fluoro-crowns.

 

Seems to have tricked you too.  

 

Jeff

 

About that same time, WO was engraving Fluorite on the objective cells of FPL-53 doublets and OK-4 triplets. Fluorostar was a sideshow.

 

Jon

[Jeff B]

About that same time, WO was engraving Fluorite on the objective cells of FPL-53 doublets and OK-4 triplets. Fluorostar was a sideshow.

 

Jon

And now for my next trick...

[peleuba]

Some folks thought it strongly implied a real FL element...

 

You think?   

[PhotogTom]

Those white light shots remind me of my low-cost binoculars.

[LLEEGE]

They got me with that marketing tool when I bought one in 2006. It was still a nice scope with TEC optics.

[Jeff B]

Geeze, you are a rough bunch.  Been hanging out in the ATM forum too much?  

 

 

This sample is waaaay better than any achromat so just stop that snarkiness right there.   But it does have a bit more secondary spectrum and spherochromatism than my friend Paul's first sample.  I've attached a comparison montage, white LED, inside of focus and from left to right:  This sample, WO 110 sample one, Orion 110 ED F7 FPL-51 doublet, AP 110GTX, and Istar  6" F10.

 

All are excellent spherically in green/yellow and the real differences between them are a minor one in the red but more pronounced ones in the blue.  

 

Looking at the color montages, inside of focus, for the two WO 110 samples shows subjectively very little difference compared to the white light difference.  But that's the power of DPAC, small differences are magnified.  There is to me a difference in color balance between the two, but Paul's sample just nails it spherically and secondary spectrum wise, especially in comparison to the AP 110GTX, making me wonder if Paul's sample is made around FPL-53, though I do know that these objectives were made to a price point too and it is a bit sporty at F6.5, so I expect sample-to-sample variations, just like I got with my SW 150ED and 120 ED samples.

 

Jeff

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[LLEEGE]

I was very happy with my FLT110 w/ TEC optics. I only sold it to finance a larger APO.  I often thought about buying a used one but they are few and far between. Thankfully, I was one of the lucky AP110GTX lottery winners.

[peleuba]

They got me with that marketing tool when I bought one in 2006. It was still a nice scope with TEC optics.

 

Yes, I agree.  The WO branded TEC110 is a very fine telescope.   Its better corrected then the TEC110FL for two main reasons:   (1) Focal ratio; (2) All spherical design.  The 110FL was a F/5.6, oil spaced, spherical design.  Leaving the lens spherical means there was significant residual high order spherical aberration present.  The only way to mitigate this design-induced HSA is to moderately aspherize at least one surface or go to an air spaced design.  But even air spacing may require a mild asphere.

[Jeff B]

On the bench in double pass, this sample of WO 110 TEC looks a whole lot like a SW 120ED F7.5 FPL-53 doublet that I have and recently tested

 

https://www.cloudyni...o/?hl=dpac test

 

Here are the white light and color montages, all inside of focus.

 

I find it interesting considering how very different the two objective designs are.

 

Some information and indoor and outdoor star testing and lunar observations with this WO/TEC sample will follow.  Hint:  It was an interesting journey.

 

Jeff

 

 

 

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[Jeff B]

Star Testing Round One

 

As Paul, Scott, myself and others have said, DPAC along with quality star testing will give us pretty much what we need to know about an optic for visual use.  Interferometer and Roddier testing would be good cross checks but I've found the former two to be completely adequate for my wants and needs, and they are my primary screening tools.  Good results from DPAC and star testing have always resulted in very high quality views of astro-objects, especially solar system objects.  Note that I have not mentioned imaging, which can have its own set of requirements for good work.  

 

I use star testing primarily for judgements concerning coma, astigmatism, and visible HSA 

 

I did not take photos as it is a bit of a PITA process.  However, I did make extensive use of the freeware program Aberrator to simulate what I saw and got very good subjective simulations IMO.

 

Indoor Star Testing

 

This was done with my TEC 160ED supplying a collimated light source from a 50 micron artificial star, who's image was further reduced using high quality barlows.  As there are refractive optics in the light path, I used a deep green filter for most assessments with magnifications up to 360X.  A picture of the "rig" is below.  Note that the WO's dew shield is removed.....more on that later.

 

Short version is that, in green, I detected no coma, but, about 1/5 to 1/6 wave of astigmatism and what seemed like 1/10 wave-ish mixture each of 3rd and 5th order spherical, both most easily seen a few waves outside of focus above ~150x.  I was a little disappointed.  I rechecked all of my set up and alignments but the results stayed.  At focus, even at 360X, the airy disk was nice and round with no obvious "X" pattern but the first ring did display four equally spaced brighter spots/arcs around its circumference.  But I was still a little disappointed.

 

Outdoor Star Testing

 

That very night was clear and calm so I set up outside, letting the scope acclimate for a couple of hours (warm up a few degrees actually) using my AP600GTO as the OTAs ride.  I chose Arcturus and Spica as they have different tints and are well placed for me.  I had my laptop with me, with Aberrator running.  The short version is I got basically the same result as indoors but perhaps less "severe": No coma, ~1/6 to 1/7 wave of astigmatism and that bit of HSA.  Outside though in real air upstairs, the airy disks looked really good with the circular dance of the first ring with the seeing only allowing occasional glimpses of the minor "lobing" of that ring.  I did see a bit of red/blue splashing around the airy disk, which is something I see with almost all fast APOs.  Interestingly, the red and blue splashing, at times, seemed to occur at 90 degrees to each other, perhaps being a sign of the mild astigmatism.

 

The other thing was the astigmatism would vary in intensity from maybe 1/5 wave to 1/8 wave (which was functionally invisible at focus).

 

So the scope seemed maybe better behaved outside.  Also, if I was not specifically looking for this stuff, I may have ignored it, however, I was looking for it.

 

But as Kylo Ren said to Rey: "We're not done yet!"

 

Jeff

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[peleuba]

Indoor Star Testing

 

This was done with my TEC 160ED supplying a collimated light source from a 50 micron artificial star, who's image was further reduced using high quality barlows.  As there are refractive optics in the light path, I used a deep green filter for most assessments with magnifications up to 360X.  A picture of the "rig" is below.  Note that the WO's dew shield is removed.....more on that later.

 

 

That's the way to do it!

 

Regarding the astigmatism you see - I had an FS152 that demonstrated some noticeable astig on the bench when tested horizontally.   It went mostly away when using the scope outdoors and the OTA was pointing up.

Edited by peleuba, 14 June 2024 - 03:09 PM.

[Jeff B]

Star Testing Round Two

 

The primary off axis aberration in refractors is typically astigmatism, which can develop quite quickly in fast APOs (don't believe me?  Just look at any off axis spot diagrams....or mis-collimate your scope).  I originally neglected to check the objective's collimation with the focuser using my Cheshire "eyepiece".  After bringing the scope back in from outside, I did that after an hour of it sitting around. Sure enough, the reflection dots did not line up, the circles only half overlapping forming a sort of figure "8" pattern. 

 

So, since this might be the source of mild astigmatism I'm seeing, I removed the dew shield (really easy) and found that the objective's cell assembly had three nice sets of push/pull collimation screws.  Gently loosening up the three "pull" screws, and tweaking the push screws, I quickly had the reflection dots in the Cheshire all lined up.  Securing everything and redoing the indoor star testing did indeed show an improvement with a residual 1/7 to 1/8 wave astigmatism. 

 

I reassembled everything and took the scope out the next night, which had even better seeing.  Using the same everything, yes there was an overall improvement from before with about 1/8 wave residual astigmatism.   That's pretty good really, but then I had the idea of tweaking those collimation screw sets to perhaps dial out that residual. I've done that several times before with my achromat ATM projects, so why not here?  I was using about 180X about 3-4 waves outside of focus when I removed the dew shield and then had a look to recenter Arcturus.  And the astigmatism was gone.  Really!?  I went to ~300X.  Still gone...but it started to slowly creep back in....then slowly leave.  This went on for about a half an hour before settling back down to ~1/8 wave.  I tweaked the collimation screws and indeed, I basically dialed it out to below 1/10 wave on average, which is below my personal level of detection.  Just for fun, I slid the dew shield back on.  No effect.  Took it back off later....no effect.  And as a bonus the HSA, or what I was calling HSA, was much reduced as well.  The at focus images looked great, with no ambiguity at focus and with reduced color splashing  too.

 

I redid the DPAC images the next day.  Those are the ones shown above, with the PCT label, meaning Post Collimation Tweak.   They are to me, identical to the originals shots I took, demonstrating the value of a quality star test to go along with DPAC testing.  The Cheshire retest showed a mild misalignment of the reflection dots, which to me is further proof that the best optical axis may not be precisely normal to the objective's physical axis. 

 

Subsequent lunar viewing has shown this objective to be very sharp indeed, giving that etched 4K HD look with the impression of vast detail, staying nice and sharp all the way up to ~220X before dimming took place.  At low powers, color tint was quite neutral, almost clinical.  Only with powers advancing above ~100X did I pick up a warmth to the image, especially with the excellent Denk II viewers I also used (which filter the blue to a degree) and especially combined with my Clave pairs....too warm for me actually.   

 

To many, the moon is not a good test object for contrast as it's so high on the moon with the stark and intense shadows.  However, I've also noticed it has many subtle color/tint contrast variations over the surface.  This lunar color and contrast pallet was readily seen by me with this scope and very enjoyable.

 

This is a high fidelity objective.  It's just too bad I'm too old and lazy to get up in the morning for the planets.

 

Now, eventually, I will compare this WO/TEC sample to my most excellent Orion 110ED F7 doublet sample and my SW120ED, both of which are very sharp  visual scopes, maybe updating this thread later.

 

Jeff

[Steve D.]

Excellent post.  Thanks for taking the time to write this up in such detail.