23 replies to this topic

[Jeff B]

This is the last of my "Challenge" scopes (and the crowd goes wild   ), submitted by a long time, and most respected, CNs contributor.   

 

It is a vintage WO 80FD, F6.9 doublet design with FPL-53 for the ED element, and who knows what, for the mating element.   It has been well used, well travelled, and well liked over the past 17 to 18 years by the owner, who bought it new from WO.  

 

The original focuser has been replaced by a nice dual speed focuser.  The scope is very stout and robust in it's construction, is bino-friendly (which does not matter to the owner), and has a nice mounting shoe for tripod use. 

 

The scope has literally seen some mileage but also lots of star light too.  On arrival of a scope, one of the first things I do is to check the focuser alignment using my Glatter laser in the focuser shining on a paper objective mask with a hole in the middle.  This showed the laser dot on the mask to be ~.6 - .7 degrees off center.   Fussing with the rotation feature, I managed to reduce the error to ~.1 degrees and I locked the system there with the rotation adjustment screws.   The thing I checked next was the objective "alignment" with the Cheshire eyepiece to see if the reflection dots off of the rear of the objective's elements line up to form a single dot.   They did and the dot was concentric with the Cheshire aperture hole.   

 

Ok, time to test (and don't give me any garbage about using the AP diagonal).

 

Jeff

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Edited by Jeff B, 16 April 2023 - 05:24 PM.

[Jeff B]

Here are the inside and outside of focus images taken with a white light LED.  The Ronchi screen was my standard 133 LPI screen.

 

Right away, you see that overall, the objective is basically neutrally corrected (straight lines), low in secondary color (focus differences from blue to red as seen by minimal color fringing around the line shadows), and a narrow slightly turned edge.   

 

There is a hint of a mild central zone as can be seen best in the outside of focus image as a subtle inward "dent" in the middle of the outer lines.  Also, the differences in contrast and sharpness of the lines in both images are rather small.  I've found this indicates a basically smooth figure and polish.  

 

Both the mild center zone and smooth polish are confirmed when I see the attached at-focus image in green (which has had its contrast enhanced).

 

When sweeping through focus, keeping a shadow in the middle, I did not see any real indication of astigmatism, which would be a rotation of the center shadow line and a clocking of the outer lines when going from one side of focus to the other.  

 

Jeff

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[Mark9473]

Looks good to me. I still enjoy mine after 17 years - it's my most used scope.

 

It would be good if you could correct your title from 80ED to 80FD so as to correctly identify this model among the other WO 80 scopes from that era.

The ED had a triplet objective; this one is a doublet.

[Jeff B]

Looks good to me. I still enjoy mine after 17 years - it's my most used scope.

 

It would be good if you could correct your title from 80ED to 80FD so as to correctly identify this model among the other WO 80 scopes from that era.

The ED had a triplet objective; this one is a doublet.

Thanks for catching this Mark and you are quite correct.  I've contacted a CNs Administrator to change the title.

 

But you brought up a good bit of history too.  WO was a bit liberal by today's standards and definitions in using the word "Fluorite" on the nameplate ring and their advertising.  The FPL53 ED element is not made of pure CaF2 fluorite crystal, though some vendors did call it Fluorite at the time, causing some confusion and controversy. 

 

https://www.cloudyni...me-as-flourite/

 

Jeff

Edited by Jeff B, 16 April 2023 - 06:00 PM.

[Jeff B]

Title fixed!

[Mark9473]

Even WO called it fluorite - just look at the lens cell.
But they admitted pretty soon on their Yahoo Groups list that it is indeed FPL-53.

[Scott in NC]

This is the last of my "Challenge" scopes...

The last?  Say it isn't so.  I've really enjoyed these, and have learned quite a bit from each one.  Hopefully you're just taking a break for a little while.

[Jeff B]

The last?  Say it isn't so.  I've really enjoyed these, and have learned quite a bit from each one.  Hopefully you're just taking a break for a little while.

Thanks Scott.

 

I'm indeed taking a break.  It's a lot of time and work actually to do one of these as you and Paul know...and others are finding out.  I want to keep it fun for me.

 

But moving right along.

 

Here are my usual color montages derived from the white light images.

 

Best correction is in the green/green-yellow, right in the heart of the visual spectrum.  You see signs of the "normal" spherochromatism associated with well designed and made ED doublets, specifically, a bit of over correction in blue and under correction in red.  But that spherochromatism is very well controlled as is the secondary spectrum with just a small miss in the blue relative to green/yellow. 

 

Jeff

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[Scott in NC]

Jeff, I like how you present the images as a montage all in the same post. That really makes it easy to compare them at a glance, which makes it much easier to see what's really going on with the lens.  When I post the same data it's scattered over several posts, so I need to learn how to do this.  Just one more thing to figure out!

[Jon Isaacs]

A bit more to this story:

 

This scope is mine.. it has always seemed to have very good optics and reading one of Jeff's tests of a WO refractor, I thought maybe he would test it for me. He agreed. A couple of minor corrections.

 

I bought the scope used but the original owner had never used it because he hadn't purchased a mount. The original focuser was a two speed but the two speed failed..

 

Based on what little I know, I was pleased by the results of Jeff's testing. When Jeff emailed the results to me, he said he'd like to buy the scope. Given that I'd just purchased an older WO 90 mm F/6.2 Megrez 90 FD, it seemed like rational thing to do.

 

I called Jeff and we had a wonderful, lengthy conversation about many things.  We did agree on a price and shook hands over the phone.

 

However, that night, I had second thoughts about parting ways with a scope I'd had for so long, one involved with many fond memories. It was my first really good refractor. In the morning, I wrote Jeff saying that I needed more time to decide. Jeff wrote back saying that he was also having second thoughts, he was trying to reduce the number of scopes, not add more.

 

So the scope is back home where it belongs but I haven't had a chance to use it..

 

My wife viewing some Anasazi ruins at the Canyon de Chelly.

 

 

A highly paid professional model at Saddle Mountain.

 

 

I want to thank Jeff for his efforts on my behalf. 

 

 

Jon

Edited by Jon Isaacs, 17 April 2023 - 06:35 AM.

[Jeff B]

Thanks Jon  for chiming in.  It was my pleasure to chat with you, test the scope and thanks for the corrections.  I love your modeling comment.  I myself have since retired from that sideline.....

 

Star Testing

 

I star tested this scope a couple of ways.  First outdoors on an OK night on real stars with some comparisons to my good old Orion 80ED.  Then indoor star testing, again, in comparison with my Orion 80ED, but also some others while "validating" the indoor set up.  I chose the Orion 80ED as I am completely familiar with this sample, having used it extensively on real stuff in the sky and on the bench. 

 

Outdoor Star Testing

 

A reasonable night with reasonable seeing allowing me to reach high enough magnifications to do a good test.  The little WO was on an alt/az mount, while the Orion was on a driven vintage Vixen SP mount.  All viewing was done in boring old mono-vision.  I violated a couple of star testing "rules" by using on each scope a TV 2.5X barlow (rule break number 1)  and a good old Celestron 10 mm Silver Top Plossl (rule break number 2) which gave ~138x and 150x for the WO and Orion scopes respectively.  The rule infractions were minor for me as what I was primarily after were reads on coma and astigmatism with secondary spectrum being....secondary....since I already had a good handle on SA and secondary spectrum with my DPAC testing.  So no yellow penalty flags were thrown on the field. 

 

I used AP 2" Maxbright diagonals, and just to be a geek about it, I used the same diagonal with the WO scope that I've used for all of my indoor testing.  The scopes had acclimated a solid 3 hours before I got serious and Castor & Pollux and Betelgeuse were well positioned.  And no, I didn't look at Sirius.

 

Like a lot of testing, the set up and preliminaries took longer that the actual testing.  In short, I saw no astigmatism in the diffraction rings of the WO scope either inside/outside of focus (oval rings whose axis would flip by 90 degrees when sweeping through focus) or at focus (subtle X pattern in the airy disk & rings).  I saw none in the Orion either.  The airy disk looked very white in both scopes.

 

I did see a small amount of coma in the WO scope at focus with a solid, round white airy disk but the first ring had a gap that spanned maybe 90 to 120 degrees of the circumference.   I figured it was real, as I could also see the smaller amount of coma I know exists in my Orion 80ED as well.   I had to look carefully for the coma as those first rings at focus would do their customary circular dance with the seeing, moving the gaps around, but they were there.

 

Castor looked very nice in both scopes with nice round airy disks staring back at me.

 

Now, even though my primary goal was to look for coma and astigmatism, I did look at the diffraction patterns (inside/outside/at focus) using a deep green filter held up to the eyepiece.  The spherical correction in green looked pretty good really with the intra/extra focal hairy outer and first rings looking very similar to each other in both scopes, with smooth even descents towards and outward from focus in both scopes .  Only when getting really close to and at focus did the coma show itself in both scopes, a bit more so with the WO scope.  

 

Indoor Star Testing

 

Indoor star testing is really, really, really desirable as I can do it at will and in a controlled environment with minimal disturbances (basically thermal and seeing).  Again, my goal is to get a read on astigmatism and coma, not spherical or color corrections.

 

I've developed an indoor star testing capability using a concept I've seen being used with good success in the ATM forums.  Specifically I use a bright 50 micron artificial star and stacked high quality barlows all mounted on the focuser end of a scope of known high quality (in this case my TEC 160ED)  to construct a collimated light source.  The test scope is then placed and aligned in front of the TEC's objective.  The focus position of the test scopes are very similar to those in DPAC and on real stars so it seems the rig gives a reasonable facsimile of a point source.  I "validated" the rig for coma and astigmatism detection by running scopes from 80 to 120 mm aperture, some with known coma and astigmatism, through the rig.  Yup, I got what seemed like the same results I got from real and outdoor artificial star testing.  It's important to choose a scope and components of high quality as any aberrations each may have will be added to those of the test scope.  The TEC has no coma or astigmatism that I've been able to detect at any magnification I've ever used and it's spherical aberration in green and yellow is truly excellent.  But it does have some spherochromatism in red and blue so I used a deep green filter for visual and imaging as well as the green channel for some of the camera work.

 

So, again, the setup, prep, and "validation" of the rig took much longer that the doing the test.....except for getting good photos with my hand held phone, which was a real PITA. 

 

The coma seen during real star testing is clearly seen here in the images, one "full spectrum" with all of the chromatic warts and the other with just the green channel with contrast enhanced.  So right around 1/4 to 1/5 wave of coma.  These shots were take at 185X, eyepiece projection.  Visually, the images did not look as "bad", maybe 1/5 to 1/6 wave and "bluer" with a white airy disk but, as Mike Spooner and I have commented on before, digital cameras enhance contrast.  Mine is set to a more warmish color balance to keep from saturating the blue, and I popped the contrast even more with processing.

 

But, but, those radial ED element adjustment screws were right there, looking at and calling out to me.  And since they were not potted, and I'm a chronic tweaker, I answered their call.   It took me maybe a total of half an hour to get a feel for the adjustments and to effectively dial out the coma as you can see in the photos.  Visually, there was none, zero that I could see.  The "full spectrum" shot is color balanced to be more what I saw visually.

 

There was no astigmatism to be seen either.

 

I've also included a shot taken of the Orion 80ED.

 

Unfortunately, I did not take the time to do another outdoor star test or look at the moon before shipping it back to Jon. I hope the coma and focuser adjustments stay and maybe Jon will tells us later his post op impressions.

 

I really enjoyed my time with this scope, especially with the aftermarket focuser.  I was/am highly impressed with it, so much so I didn't want to let it go, but I really don't need another 80mm class aperture scope and Jon has such nice, fond memories from using it so we collectively reconsidered.

 

Now, how much do you want to bet that one shows up for sale here or on Amart?

 

Jeff

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[Maciek_Cz]

Jeff, great job as usual. A small amount of coma can also be seen in the DPAC inside of focus images.

The Ronchi bands at the top edge are closer together than at the bottom edge.
Your work is like an excellent textbook on experimental astronomy!

[Jeff B]

Jeff, great job as usual. A small amount of coma can also be seen in the DPAC inside of focus images.

The Ronchi bands at the top edge are closer together than at the bottom edge.
Your work is like an excellent textbook on experimental astronomy!

Thank you Maciek.

 

I'm not going to model the results with your software because, as you have pointed out several times, there is not much to model on a really good optic like this.

 

You are very observant my friend.  That small bit of top-to-bottom "keystoning" with the inside of focus shadows is most likely due a small misalignment of the camera over the screen.....which is why I throw out the majority of my shots, especially with faster scopes, but some of it may be the mild coma as well.  The other "artifact" with camera misalignment I need to be careful of is any right-to-left tilt.  That results in one of the outside vertical shadows being thicker and darker than the other.  You can also see a touch of that in the inside of focus images with the right side line being slightly thicker and darker than the left side line.

 

Jeff

[Joe G]

I have the optics from this scope.  I originally bought an Orion Express 80mm achro.  It came with that nice black anodized tube that the Orion EON 120 ED comes with.

 

William Optics sold an "Apograde" upgrade for the scope which included a new lens cell (as described it was a FPL 53 doublet), a new focuser, and an extension tube.

 

Huge improvement.  I still own it.  It is at a different location. 

 

Very nice scope.   I have owned it for about 17 years.  IMHO 80mm is not enough light grasp.  But the optics are very nice.

 

I have seen Jon's reviews over the years.  Spot on.

[fate187]

I think I like the story of Jon Isaacs telescope even more than those DPAC results - nah keep'em coming . Quite nice to read, that Jeff got second thought buying another scope and Jon getting second thoughts parting with it  . Good outcome.

[Maciek_Cz]

Thank you Maciek.

 

I'm not going to model the results with your software because, as you have pointed out several times, there is not much to model on a really good optic like this.

 

You are very observant my friend.  That small bit of top-to-bottom "keystoning" with the inside of focus shadows is most likely due a small misalignment of the camera over the screen.....which is why I throw out the majority of my shots, especially with faster scopes, but some of it may be the mild coma as well.  The other "artifact" with camera misalignment I need to be careful of is any right-to-left tilt.  That results in one of the outside vertical shadows being thicker and darker than the other.  You can also see a touch of that in the inside of focus images with the right side line being slightly thicker and darker than the left side line.

 

Jeff

Hi Jeff,
Something just didn't seem right to me, because I saw a similar effect in the pre-apo 152 f/8 triplet photos you took earlier. I have to be vigilant. Thanks for the explanation.
The telescope is very good and indeed modeling in AOS would be just art for art's sake. Although, in my tests of the new version of AOS, I will also focus on these ronchigrams.

 

Maciek

[Jon Isaacs]

It's nice reading comments like:

 

"The telescope is very good and indeed modeling in AOS would be just art for art's sake. Although, in my tests of the new version of AOS, I will also focus on these ronchigrams."

 

and 

 

"I'm not going to model the results with your software because, as you have pointed out several times, there is not much to model on a really good optic like this."

 

I'm am not much of a tester. Jeff and I discussed this a bit in our phone conversation. Clear sky locations breed observer's, cloudier skies breed opticians and "metrologists."

 

I recognize the basics, astigmatism, coma etc but generally judge an optic on my subjective evaluation of the infocus star image at high magnifications. This is incidental to my pursuit of close doubles. 

 

This scope has always seemed like it had very good optics so one of my primary reasons for asking Jeff if he would test it was to get an idea of how good the optics really are, basically to calibrate my subjective evaluation.

 

One thing that took me aback abit was the title "Vintage WO 80 FD."  Jeff had told me he was going to post the results soon but when I saw vintage in the title, I thought to myself,

 

"I wonder who owns a vintage WO FPL-53 doublet. 

 

 

Then it dawned on me, that's my scope..     At my age, a scope that's 18'years old seems modern, state of the art.

 

Jon

Edited by Jon Isaacs, 18 April 2023 - 05:42 AM.

[Jeff B]

I have to chuckle Jon as I really did debate in my head using that word "vintage" in the title.  Is it really vintage?  Why didn't I use "vintage" in the title for the "vintage" AP which is almost 40 years old?  What is "vintage" anyway?  Early vintage ED doublet?  Would somebody confuse it with wine...... 

 

And as that stuff continued, I found myself incapable of driving a car or operating heavy equipment.....so I left it alone.

 

Sorry if I offended.

 

But I am curious to see if you notice any improvements in sharpness or high power star images, basically, did it stay fixed, not that it was broken to begin with, just misadjusted.  Thinking about it, if that small bit of coma is the only optical artifact on such a well traveled and extensively used scope, well that seems pretty good to me for such a vintage...oops, I mean old....no wait...umm, I mean...oh never mind.

[Mike Spooner]

I used to know what vintage meant - but that was so long ago I forgot!

 

Mike

[Jon Isaacs]

I have to chuckle Jon as I really did debate in my head using that word "vintage" in the title.  Is it really vintage?  Why didn't I use "vintage" in the title for the "vintage" AP which is almost 40 years old?  What is "vintage" anyway?  Early vintage ED doublet?  Would somebody confuse it with wine...... 

 

And as that stuff continued, I found myself incapable of driving a car or operating heavy equipment.....so I left it alone.

 

Sorry if I offended.

 

But I am curious to see if you notice any improvements in sharpness or high power star images, basically, did it stay fixed, not that it was broken to begin with, just misadjusted.  Thinking about it, if that small bit of coma is the only optical artifact on such a well traveled and extensively used scope, well that seems pretty good to me for such a vintage...oops, I mean old....no wait...umm, I mean...oh never mind.

 

Jeff:

 

No offense taken.. I was laughing at myself for my confusion. 

 

As far as my seeing any difference your massaging and tuning might have made, I'm afraid my eyeballs are well into the "vintage" stage and I don't see the subtle differences I once did... One of the days i may have cataract surgery and things may change.

 

My philosophy/strategy has always been, "if I find a good scope, I keep it."   Reading your comments and Maciek's comments, they confirm this is a scope to keep.

 

I'm sure after reflecting on our conversation, you thought to yourself; "what was I thinking, I need another scope like I need a hole in my head."

 

For my part I was thinking, "Jeff has made this scope even better, why would I part ways with it?"

 

One thing about it is that it uses a 2 inch extension to come to focus. This allows for a small hard case, it's only 18 inches long. Great for travel.

 

Another fond memory. 2012. We're slowly traveling from Wisconsin to Washington state, camping in the back of a Nissan Frontier mini-truck.. I have the WO 80 mm FD as my only scope. We're in the Big Horn Mountains of Wyoming at about 9000 feet the day of the transit of Venus.

 

It's cloudy but we stop for the night. I setup the scope and right on schedule, the clouds part and I was able to see first contact and much of the transit.

 

 

Jon

Edited by Jon Isaacs, 18 April 2023 - 02:08 PM.

[RichA]

Here are the inside and outside of focus images taken with a white light LED.  The Ronchi screen was my standard 133 LPI screen.

 

Right away, you see that overall, the objective is basically neutrally corrected (straight lines), low in secondary color (focus differences from blue to red as seen by minimal color fringing around the line shadows), and a narrow slightly turned edge.   

 

There is a hint of a mild central zone as can be seen best in the outside of focus image as a subtle inward "dent" in the middle of the outer lines.  Also, the differences in contrast and sharpness of the lines in both images are rather small.  I've found this indicates a basically smooth figure and polish.  

 

Both the mild center zone and smooth polish are confirmed when I see the attached at-focus image in green (which has had its contrast enhanced).

 

When sweeping through focus, keeping a shadow in the middle, I did not see any real indication of astigmatism, which would be a rotation of the center shadow line and a clocking of the outer lines when going from one side of focus to the other.  

 

Jeff

I don't know what the illumination level was, but that does not look like a fluorite scope to me.

[Mark9473]

You didn't even get to the OP's second sentence?

[RichA]

Thanks Jon  for chiming in.  It was my pleasure to chat with you, test the scope and thanks for the corrections.  I love your modeling comment.  I myself have since retired from that sideline.....

 

Star Testing

 

I star tested this scope a couple of ways.  First outdoors on an OK night on real stars with some comparisons to my good old Orion 80ED.  Then indoor star testing, again, in comparison with my Orion 80ED, but also some others while "validating" the indoor set up.  I chose the Orion 80ED as I am completely familiar with this sample, having used it extensively on real stuff in the sky and on the bench. 

 

Outdoor Star Testing

 

A reasonable night with reasonable seeing allowing me to reach high enough magnifications to do a good test.  The little WO was on an alt/az mount, while the Orion was on a driven vintage Vixen SP mount.  All viewing was done in boring old mono-vision.  I violated a couple of star testing "rules" by using on each scope a TV 2.5X barlow (rule break number 1)  and a good old Celestron 10 mm Silver Top Plossl (rule break number 2) which gave ~138x and 150x for the WO and Orion scopes respectively.  The rule infractions were minor for me as what I was primarily after were reads on coma and astigmatism with secondary spectrum being....secondary....since I already had a good handle on SA and secondary spectrum with my DPAC testing.  So no yellow penalty flags were thrown on the field. 

 

I used AP 2" Maxbright diagonals, and just to be a geek about it, I used the same diagonal with the WO scope that I've used for all of my indoor testing.  The scopes had acclimated a solid 3 hours before I got serious and Castor & Pollux and Betelgeuse were well positioned.  And no, I didn't look at Sirius.

 

Like a lot of testing, the set up and preliminaries took longer that the actual testing.  In short, I saw no astigmatism in the diffraction rings of the WO scope either inside/outside of focus (oval rings whose axis would flip by 90 degrees when sweeping through focus) or at focus (subtle X pattern in the airy disk & rings).  I saw none in the Orion either.  The airy disk looked very white in both scopes.

 

I did see a small amount of coma in the WO scope at focus with a solid, round white airy disk but the first ring had a gap that spanned maybe 90 to 120 degrees of the circumference.   I figured it was real, as I could also see the smaller amount of coma I know exists in my Orion 80ED as well.   I had to look carefully for the coma as those first rings at focus would do their customary circular dance with the seeing, moving the gaps around, but they were there.

 

Castor looked very nice in both scopes with nice round airy disks staring back at me.

 

Now, even though my primary goal was to look for coma and astigmatism, I did look at the diffraction patterns (inside/outside/at focus) using a deep green filter held up to the eyepiece.  The spherical correction in green looked pretty good really with the intra/extra focal hairy outer and first rings looking very similar to each other in both scopes, with smooth even descents towards and outward from focus in both scopes .  Only when getting really close to and at focus did the coma show itself in both scopes, a bit more so with the WO scope.  

 

Indoor Star Testing

 

Indoor star testing is really, really, really desirable as I can do it at will and in a controlled environment with minimal disturbances (basically thermal and seeing).  Again, my goal is to get a read on astigmatism and coma, not spherical or color corrections.

 

I've developed an indoor star testing capability using a concept I've seen being used with good success in the ATM forums.  Specifically I use a bright 50 micron artificial star and stacked high quality barlows all mounted on the focuser end of a scope of known high quality (in this case my TEC 160ED)  to construct a collimated light source.  The test scope is then placed and aligned in front of the TEC's objective.  The focus position of the test scopes are very similar to those in DPAC and on real stars so it seems the rig gives a reasonable facsimile of a point source.  I "validated" the rig for coma and astigmatism detection by running scopes from 80 to 120 mm aperture, some with known coma and astigmatism, through the rig.  Yup, I got what seemed like the same results I got from real and outdoor artificial star testing.  It's important to choose a scope and components of high quality as any aberrations each may have will be added to those of the test scope.  The TEC has no coma or astigmatism that I've been able to detect at any magnification I've ever used and it's spherical aberration in green and yellow is truly excellent.  But it does have some spherochromatism in red and blue so I used a deep green filter for visual and imaging as well as the green channel for some of the camera work.

 

So, again, the setup, prep, and "validation" of the rig took much longer that the doing the test.....except for getting good photos with my hand held phone, which was a real PITA. 

 

The coma seen during real star testing is clearly seen here in the images, one "full spectrum" with all of the chromatic warts and the other with just the green channel with contrast enhanced.  So right around 1/4 to 1/5 wave of coma.  These shots were take at 185X, eyepiece projection.  Visually, the images did not look as "bad", maybe 1/5 to 1/6 wave and "bluer" with a white airy disk but, as Mike Spooner and I have commented on before, digital cameras enhance contrast.  Mine is set to a more warmish color balance to keep from saturating the blue, and I popped the contrast even more with processing.

 

But, but, those radial ED element adjustment screws were right there, looking at and calling out to me.  And since they were not potted, and I'm a chronic tweaker, I answered their call.   It took me maybe a total of half an hour to get a feel for the adjustments and to effectively dial out the coma as you can see in the photos.  Visually, there was none, zero that I could see.  The "full spectrum" shot is color balanced to be more what I saw visually.

 

There was no astigmatism to be seen either.

 

I've also included a shot taken of the Orion 80ED.

 

Unfortunately, I did not take the time to do another outdoor star test or look at the moon before shipping it back to Jon. I hope the coma and focuser adjustments stay and maybe Jon will tells us later his post op impressions.

 

I really enjoyed my time with this scope, especially with the aftermarket focuser.  I was/am highly impressed with it, so much so I didn't want to let it go, but I really don't need another 80mm class aperture scope and Jon has such nice, fond memories from using it so we collectively reconsidered.

 

Now, how much do you want to bet that one shows up for sale here or on Amart?

 

Jeff

Very nice diffraction image. A lot of scopes I've seen, even premium, have had discontinuous first rings, or evidence of mild astigmatism.  

[Monel76]

I have the possibility to buy this telescope at a very fair price, with a TS Crayford dual speed focuser. I would use it exclusively for photographs. Is it still valid or is it better to spend twice as much for a modern 80/480 triplet?