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In Defense of Towa

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#51 deSitter

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Posted 21 February 2018 - 10:44 AM

Well, sometimes I get a pleasant surprise. 

 

Tonight I tested one of my 80mm Towas, a very beat-up Meade that came my way.  It is restorable and I've kind of worked on it whenever a needed part came along, or I got a bright idea.  The EQ-3 mount also came with the 120VAC motor drive.  The glass is in good condition.

 

I put it up to the flat and turned the Ronchi on it.  133lpi.   This objective is not bad!  With three bands showing, nice and straight, regular.  There was a bit of turned edge evident.  I made sure the lens was loose in the cell and tested it at three rotational orientations.  The turned edge is real, but not severe enough to condemn the lens.  You could mask it off if it bothered you, and have essentially a perfect achromat.

 

Still can't get decent photos but will keep trying.

 

I have the Orion version as well, in excellent (showroom new) condition.  I'll test that one in coming days.  But so far the news is good.

 

Here is the objective, in front of the 8" test flat.  Nice, collimateable cell. 

attachicon.gif 80mm Towa 002.jpg

 

The focuser had problems so it got a new pinion shaft & knobs donated from a recently-made Meade.  They mate up pretty well.  This one has a brass thread-on 1.25" eyepiece holder.

attachicon.gif 80mm Towa 001.jpg

I should send you mine to test. I'm sure they'd test well. They'd have to, they test well with stars. I'd like to see you point that Meade at a test double and report. Good deal! I've always wanted one of those (no more, have the 3" space covered).

 

-drl



#52 deSitter

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Posted 21 February 2018 - 10:54 AM

The widger scope is a Towa, in its original form , it was, well, not good at all, but thats because some one took it apart and well just through everything haphazardly in. Carol bless her heart, shipped it all the way from cal. 

 

The lens after several attempts at indexing the lenses , now has the tightest, pin point stars I've ever seen from a Towa. 

 

So wonder if that might be part of the reason Towa has a bad name???

I had a similar experience with a 50/600mm early 60s Towa. On arrival it had some astigmatism that kept it from the better class but otherwise the star test was excellent. I figured this was a case of misalignment caused by a sloppy cell and sure enough it was. After some trial and error I found an orientation of the elements in the cell and with respect to each other that resulted in all the astigmatism being eliminated. That scope is now a prized possession!

 

Compared to my Astro and SYW scopes, the mechanics on the Towas are 2nd rate and should always be seen to before giving up.

 

-drl


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#53 BigC

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Posted 21 February 2018 - 10:58 AM

 

 

 

 

The lens after several attempts at indexing the lenses , now has the tightest, pin point stars I've ever seen from a Towa. 

 

So wonder if that might be part of the reason Towa has a bad name???

 

I can't speak for anyone but myself.  I formed my opinion based solely on DPAC testing of some two-dozen or so 60mm objectives, along with a handful of 40mm and about a dozen 50mm, sometimes paired with  observational star-testing to see what the various testing defects do to the Airy disk.  Rotational adjustment is always part of my testing.

 

Rotation can help eliminate wedge but it won't eliminate gross zonal errors or a rough surface.  Usually the changes are subtle.

 

I'm looking forward to testing my Orion Towa 80mm, after the good results with the Meade.  Makes me think Towa sourced the 80mm objectives from someplace other than the 60mm and under.

 

It could also be a case of sub-80mm scopes just not bringing in enough money to hand-figure each lens.  The small ones were probably all just machine polished and left at that while the 80mm might have had some hand figuring done.  Who knows?

 

That doesn’t explain the good (older) 50mm x 600mm Towas. Admittedly the 60mm Towas are horrible but I have a 50mm that is quite good.

 

 

Actually it can explain it.  Just random chance alone would probably generate some good ones, over the tens of thousands made.  I have a few good 50mm and 60mm myself, it's just that they are few, and far-between.

 

I haven't tested a large enough sample of "old" Towas yet, to begin to form an opinion.  Also some of these brands we have just assumed are old Towa, without positive ID.  I would love to eventually be able to say something like "Towas made before 19XX have a much better chance of being good optically".  We are seeing some anecdotal evidence to this effect, but still need to do the tests with a decent-sized sample.

 

My opinion is that Towa were and are "good enough" for the intended market and pricepoints. Too many here have unrealistic expectations. Not only that but I dare to say a majority of casual stargazers would be adequately served by Towa  and are happy never owning Televue or Takahashi. Many of us have not the skies,time, or money for premium optics.The list of what can be seen in a 4.5 Towa reflector is enough to occupy MANY hours.


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#54 Chuck Hards

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Posted 21 February 2018 - 10:58 AM

 

Well, sometimes I get a pleasant surprise. 

 

Tonight I tested one of my 80mm Towas, a very beat-up Meade that came my way.  It is restorable and I've kind of worked on it whenever a needed part came along, or I got a bright idea.  The EQ-3 mount also came with the 120VAC motor drive.  The glass is in good condition.

 

I put it up to the flat and turned the Ronchi on it.  133lpi.   This objective is not bad!  With three bands showing, nice and straight, regular.  There was a bit of turned edge evident.  I made sure the lens was loose in the cell and tested it at three rotational orientations.  The turned edge is real, but not severe enough to condemn the lens.  You could mask it off if it bothered you, and have essentially a perfect achromat.

 

Still can't get decent photos but will keep trying.

 

I have the Orion version as well, in excellent (showroom new) condition.  I'll test that one in coming days.  But so far the news is good.

 

Here is the objective, in front of the 8" test flat.  Nice, collimateable cell. 

attachicon.gif 80mm Towa 002.jpg

 

The focuser had problems so it got a new pinion shaft & knobs donated from a recently-made Meade.  They mate up pretty well.  This one has a brass thread-on 1.25" eyepiece holder.

attachicon.gif 80mm Towa 001.jpg

I should send you mine to test. I'm sure they'd test well. They'd have to, they test well with stars. I'd like to see you point that Meade at a test double and report. Good deal! I've always wanted one of those (no more, have the 3" space covered).

 

-drl

 

 

You pay the shipping both ways, and I'm happy to test anything for anybody, up to about 7" aperture, no charge.  Give me a couple of weeks turnaround in case I get super busy at work.

 

PM me if interested.  



#55 Terra Nova

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Posted 21 February 2018 - 11:22 AM

 

 

 

 

The lens after several attempts at indexing the lenses , now has the tightest, pin point stars I've ever seen from a Towa. 

 

So wonder if that might be part of the reason Towa has a bad name???

 

I can't speak for anyone but myself.  I formed my opinion based solely on DPAC testing of some two-dozen or so 60mm objectives, along with a handful of 40mm and about a dozen 50mm, sometimes paired with  observational star-testing to see what the various testing defects do to the Airy disk.  Rotational adjustment is always part of my testing.

 

Rotation can help eliminate wedge but it won't eliminate gross zonal errors or a rough surface.  Usually the changes are subtle.

 

I'm looking forward to testing my Orion Towa 80mm, after the good results with the Meade.  Makes me think Towa sourced the 80mm objectives from someplace other than the 60mm and under.

 

It could also be a case of sub-80mm scopes just not bringing in enough money to hand-figure each lens.  The small ones were probably all just machine polished and left at that while the 80mm might have had some hand figuring done.  Who knows?

 

That doesn’t explain the good (older) 50mm x 600mm Towas. Admittedly the 60mm Towas are horrible but I have a 50mm that is quite good.

 

 

Actually it can explain it.  Just random chance alone would probably generate some good ones, over the tens of thousands made.  I have a few good 50mm and 60mm myself, it's just that they are few, and far-between.

 

I haven't tested a large enough sample of "old" Towas yet, to begin to form an opinion.  Also some of these brands we have just assumed are old Towa, without positive ID.  I would love to eventually be able to say something like "Towas made before 19XX have a much better chance of being good optically".  We are seeing some anecdotal evidence to this effect, but still need to do the tests with a decent-sized sample.

 

Chuck, I think you will also remember, that my (grandson’s) ‘good’ one was certainly not a random sample, not by me anyway. It was sent to me by a fellow CNer, (completely unrequested), to prove a point that there were good ones out there, as I had gotten something of a ‘rep’ for dogging them the way I do.


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#56 Chuck Hards

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Posted 21 February 2018 - 11:24 AM

My opinion is that Towa were and are "good enough" for the intended market and pricepoints. Too many here have unrealistic expectations. Not only that but I dare to say a majority of casual stargazers would be adequately served by Towa  and are happy never owning Televue or Takahashi. Many of us have not the skies,time, or money for premium optics.The list of what can be seen in a 4.5 Towa reflector is enough to occupy MANY hours.

 

I would agree with you, for the most part.  60mm scopes will never be looking at subtle details on Mars or Jupiter at 400X.  I've made the point in other threads that the diffraction limit is pretty easy to hit with small objectives, and most users of these scopes aren't pushing the power to the upper limits very often.

 

Many of the ones I've tested with sub-par objectives are just fine for most beginners, or even more experienced observers for a "grab-n-go".

 

HOWEVER, I have come across some real dogs.  Not even close to pinpoint stars, not really usable except at very low powers.  Towa does have a high percentage of those.  Makes me wonder why some brands didn't have the quality problems Towa had.

 

I think the real value of all of this is for the potential collectors among us, who want to pick up something nice from the old days, not pay a premium price for something with sub-par optics.   For the kid who found it under the Christmas tree in 1961, it was no doubt absolutely amazing.


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#57 deSitter

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Posted 21 February 2018 - 12:41 PM

 

My opinion is that Towa were and are "good enough" for the intended market and pricepoints. Too many here have unrealistic expectations. Not only that but I dare to say a majority of casual stargazers would be adequately served by Towa  and are happy never owning Televue or Takahashi. Many of us have not the skies,time, or money for premium optics.The list of what can be seen in a 4.5 Towa reflector is enough to occupy MANY hours.

 

I would agree with you, for the most part.  60mm scopes will never be looking at subtle details on Mars or Jupiter at 400X.  I've made the point in other threads that the diffraction limit is pretty easy to hit with small objectives, and most users of these scopes aren't pushing the power to the upper limits very often.

 

Many of the ones I've tested with sub-par objectives are just fine for most beginners, or even more experienced observers for a "grab-n-go".

 

HOWEVER, I have come across some real dogs.  Not even close to pinpoint stars, not really usable except at very low powers.  Towa does have a high percentage of those.  Makes me wonder why some brands didn't have the quality problems Towa had.

 

I think the real value of all of this is for the potential collectors among us, who want to pick up something nice from the old days, not pay a premium price for something with sub-par optics.   For the kid who found it under the Christmas tree in 1961, it was no doubt absolutely amazing.

 

I'll repeat the story of the 4 NOS Milben click-zoomers. One went to a friend. The other three 60mm f/7 objectives were outstanding, very good, and mediocre. I cut them down for finders/side scopes. Same exact objective from the same time. One of these guys was fitted with a beautiful old Tasco .965 focuser and is one of my favorite telescopes. The mediocre one was truly mediocre and could not do 20x per inch, but even that one makes a great 10x finder compared to the typical cemented 50mm finder.

 

-drl


Edited by deSitter, 21 February 2018 - 12:44 PM.

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#58 droid

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Posted 21 February 2018 - 01:12 PM

but...but...but... my Jimi Hendrix Special (Meade 291) has a awesome lens!

 

attachicon.gif post-50896-0-39733100-1493422989.jpg

Totally righteous



#59 clamchip

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Posted 21 February 2018 - 01:21 PM

I call it the Jimi Hendrix Special because Mr. Hendrix being a lefty played a right side

guitar upside down.

My Meade is upside down too because I rotated the focuser so I can have the finder

on the right. Top photo standard configuration, middle photo the Special, bottom photo

you can see what it did to the tube by the Meade name out by the objective.

 

post-50896-0-50399400-1493422917_thumb.jpg

post-50896-0-07395900-1493422957_thumb.jpg

post-50896-0-39733100-1493422989.jpg


Edited by actionhac, 21 February 2018 - 01:35 PM.

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#60 deSitter

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Posted 21 February 2018 - 01:30 PM

Good, I thought it might be because of purple haze :)

 

-drl


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#61 droid

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Posted 21 February 2018 - 01:40 PM

I've found one in 25 years or so, fixin and donating that was garbage, that lens was horrid, and I just gave the owner another one in its place and explained why. they were happy and the land fill got its one and only junk scope, the rest were passable , the one in the widger is outstanding , stars are pinpoints, 


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#62 droid

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Posted 21 February 2018 - 01:42 PM

I call it the Jimi Hendrix Special because Mr. Hendrix being a lefty played a right side

guitar upside down.

My Meade is upside down too because I rotated the focuser so I can have the finder

on the right. Top photo standard configuration, middle photo the Special, bottom photo

you can see what it did to the tube by the Meade name out by the objective.

 

attachicon.gif post-50896-0-50399400-1493422917_thumb.jpg

attachicon.gif post-50896-0-07395900-1493422957_thumb.jpg

attachicon.gif post-50896-0-39733100-1493422989.jpg

 

I love  it being blind in my right eye, its perfect.


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#63 Chuck Hards

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Posted 21 February 2018 - 03:44 PM

I hate it when you can't get the finder to the side you need it on.  #1 justification for rotating tubes.  Whoops, wrong thread.  :lol:


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#64 Tenacious

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Posted 21 February 2018 - 04:54 PM

 

 

 

 

The lens after several attempts at indexing the lenses , now has the tightest, pin point stars I've ever seen from a Towa. 

 

So wonder if that might be part of the reason Towa has a bad name???

 

I can't speak for anyone but myself.  I formed my opinion based solely on DPAC testing of some two-dozen or so 60mm objectives, along with a handful of 40mm and about a dozen 50mm, sometimes paired with  observational star-testing to see what the various testing defects do to the Airy disk.  Rotational adjustment is always part of my testing.

 

Rotation can help eliminate wedge but it won't eliminate gross zonal errors or a rough surface.  Usually the changes are subtle.

 

I'm looking forward to testing my Orion Towa 80mm, after the good results with the Meade.  Makes me think Towa sourced the 80mm objectives from someplace other than the 60mm and under.

 

It could also be a case of sub-80mm scopes just not bringing in enough money to hand-figure each lens.  The small ones were probably all just machine polished and left at that while the 80mm might have had some hand figuring done.  Who knows?

 

That doesn’t explain the good (older) 50mm x 600mm Towas. Admittedly the 60mm Towas are horrible but I have a 50mm that is quite good.

 

 

Actually it can explain it.  Just random chance alone would probably generate some good ones, over the tens of thousands made.  I have a few good 50mm and 60mm myself, it's just that they are few, and far-between...


 

I have a Towa 50mm x 600mm 6TE-5 that rides on an EQ-2.  The quality of the image is very good.  Unfortunately, the focuser is of a poor design.  The rack is actually on the inside of the focus tube and it tends to bend away from the pinion, loosing engagement.

 

Is there some evidence that Towa's 50 x 600 glass was sourced or made differently?



#65 Chuck Hards

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Posted 22 February 2018 - 05:15 PM

As far as I know, nobody can say for sure what optics came out of what company, across-the-board.  Did some make in-house?  Certainly, that is known.  But there were optical shops putting out just lenses, prisms, and mirrors, and they were probably supplying everyone at one time or another, even the ones with in-house fabrication, if a large order came in and swamped them I'm sure they would just buy optics to fill the order.

 

I have some Towa 50x600mm that test very well.  An old Milben is good, it is in every way a Tasco 6TE clone.  And I have a very early 6TE OTA that tests very well.  But I also have some that don't test as well and they far outnumber the really top-notch ones.  More have come through my hands for testing that weren't of Swift or Royal Astro quality.

 

The thing to remember is that an imperfect lens in these small apertures can still produce imagery that all of us would consider excellent (see the first post in this thread).  Very few people can say with certainty that an optic is good just based on the images it's produced, with nothing at hand for comparison.  What finally turned around my thinking was the side-by-side test.  A known excellent scope is used alongside an identical scope with a less-than-perfect lens.  Both must use identical diagonals and eyepieces, and the images compared on nights of excellent seeing.  It is only then that the difference is noticed, typically at higher magnifications and on subtle details.  You have to swap diagonals and eyepieces to make sure what you are seeing is a result of the objective alone.  (It almost always is.)

 

This backs up what Dave G. has been telling us.   Experience and many hours spent observing aren't a guarantee that we can judge optical quality with anything other than generalities.  The difference between "good" and "as good as it gets" can be very hard to judge with certainty if you don't have a top-notch reference at the time.  The only way I know how to tell them apart sans bench testing, is the side-by-side observing test, and I've got nearly 52 years of experience at this now.   It takes the bench test to remove all doubt, and see just how close we really are to having that "as good as it gets" objective if you can't do a side-by-side observational comparison.  

 

But the good news is, those in the "second tier" are still eminently usable and some of them have given me terrific views.  Just not the sharp views of low-contrast details.  The rave-worthy stuff that a true 1/8-wave optic can produce.  The "good" scope will show some nice details in Jupiter's bands, for example, while the "excellent" scope might show you those little blue festoons and other details not seen in the other scope.

 

The seeing itself is a huge factor in observational optical evaluation, especially without that reference optic.  I like that bench testing removes the elephant from the equation.

 

Some of the old Towas that could make a better showing under DPAC are still leaps and bounds better than a lot of modern telescopes I've tested.   


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#66 Kasmos

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Posted 22 February 2018 - 06:23 PM

I tested my Towa/Crescent against my two SYW Mayflower 814's, my APL Manon, and also with my Selsi (Carton?), objective threaded onto the Crescent's tube. I used the same diagonal and eyepieces in the same evening session. Since I was switching the OTAs out of the same mount, it wasn't exactly a side by side. But, whenever I'd switch back it was the same result. Using this somewhat imperfect method, the two Mayflowers, the APL and the Selsi all gave basically indistinguishable superior views. (They will need a true side by side test to pick a winner). The Crescent was not just lesser but obviously far inferior. If I had to quantify it, I'd say it was two to three steps down in quality.

 

I had formally tested it against one of the Mayflowers with the same results. The Crescent/Towa was not only inferior, but to my way of thinking, may not even be usable. I tried changing the lens spacing (made it worse), and indexing which might have helped some. I keep (illogically), hoping another test session will show it to be better than it is. frown.gif 

 

I like the kit so I have to ask. Does anybody have a good 60mm x 800mm objective they can spare? 


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#67 clamchip

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Posted 22 February 2018 - 07:58 PM

You might check with Sheldon (MASILMW) here in classifieds I bought a 60mm x 700mm lens from

him recently, a air-spaced coated in cell made by the company that supplies Meade for $13 shipped!

 

Nippon Kogaku made/makes their own lenses and they are excellent. NK learned a lot during WW2

about coatings. Lens coatings were extremely important for the demanding sea and air duties.

Zeiss makes their own glass too.

 

Robert


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#68 Bomber Bob

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Posted 22 February 2018 - 08:19 PM

"Does anybody have a good 60mm x 800mm objective they can spare?"

 

Well, I gave the all-black Stein Towa 60x800 to the Boy Scouts, but maybe they would loan it to you.  It was Old Towa in the Asahi style with a perfect star test and well-controlled CA.  Or at least, they'd let me DPAC it.

 

"nobody can say for sure what optics came out of what company, across-the-board"

 

I think Old Towa (1950s & early 1960s) is generally good because they sourced from the better makers -- maybe even Asahi, or Royal at least (or their suppliers!).


Edited by Bomber Bob, 22 February 2018 - 08:23 PM.

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#69 clamchip

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Posted 23 February 2018 - 12:01 PM

The bench DPAC test is great and scientific , a controlled environment, double sensitive. And I like star testing too

which is my favorite.

I can have incredibly stable air here in the valley during the day, I wish it was as good at night!

And thats when the the 'Perforated thingy' is my resolution test. It's on a cell tower 2-1/2 miles from my

house.

Its really only for 4 inch aperture and smaller. Resolving the ventilation perforations that cover this gray cylinder

at the yellow arrow, the wire snaking up the mast at the red arrows, and the green ground wire at the green arrow. 

The perforated cylinder is tough, it takes a very good 80mm to resolve, and a outstanding 60mm.

A 4 inch will resolve it, and how well it resolves it is what I'm looking for with a 4 inch.

Robert

 

post-50896-0-35176200-1516589154_thumb.jpg



#70 Chuck Hards

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Posted 24 February 2018 - 04:46 PM

The thread has been edited and restored.  Let's all do our best to keep it light.  Factual, but light.  No comments on moderation or removed posts.  Thanks.  There's some good info here.


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#71 deSitter

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Posted 24 February 2018 - 05:14 PM

Thanks Chuck.

 

-drl



#72 Chuck Hards

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Posted 24 February 2018 - 06:20 PM

I tested the Orion version today.  A little less turned edge than the Meade, but there is a center zone problem, not as clean a null as the Meade.  It uses 2 plastic spacers and the lens looks to have been messed with before I got it, both spacers are not between the elements (the Crown was flipped when I got it).  But even so, the lines are much better than the typical 50mm & 60mm Towa and I'd call this one perfectly capable of some sharp images.  I'll play with spacing and see if I can improve things, but I doubt it.  Will let you know.

 

So far the two Towa 80mm objectives I've looked-at have been a breath of fresh air.  I had to go through a lot of 60mm before I found a good one.  Two decent ones right off the bat is a good sign for the 80mm.


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#73 deSitter

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Posted 24 February 2018 - 06:28 PM

There should not be 2 spacers I think - one goes between the lenses and the other between lens and retaining ring. My Towa objectives are like that.

 

-drl


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#74 Chuck Hards

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Posted 24 February 2018 - 06:46 PM

Thanks.  I used one spacer and stuck the other between the flint and the cell seat.  I'll move it next time I clean it.  

 

Edit:  Now I feel the urge to try some .003" spacer material.  The plastic ring seems hugely thick.



#75 Terra Nova

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Posted 24 February 2018 - 07:14 PM

Okay, we are playing nice now! smile.gif

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