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How hard is it to make a reflector as good as mid-price ED or Apo refractor?

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#126 gnowellsct

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Posted 03 May 2018 - 03:39 PM

didn't you post this a couple of years ago?

I post it every now and again so that people can see what horrors lurk when they are inattentive.



#127 Dzukielis

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Posted 05 May 2018 - 12:21 PM

 

 

 

Why is this? Is it just a market driven thing and that there is a limited desire for producing high quality premium reflectors outside of professional / research instruments?

 

I have no idea of actual numbers produced, but it seems that there one can readily buy nice refractors of 100-150mm aperture in the $1000-10,000 range, but there are few “refractor-like” reflectors in this space. Clearly there are small custom houses producing very nice instruments with precision figured mirrors that would probably meet or exceed the quality of good Apo, but there just don’t seem to be a lot them. At least I’ve never come across them, so I guess this means they are not produced in large numbers, or bought by a lot of people.  

 

It’s become a sort of quest for Holy Grail for me to find this balace of quality of aperture within the bounds of normal affordability - ideally I’d like an excellent quality reflector (both optically & mechanically) in the  10-12” range for the price of of 130mm Apo with the ssme image quality. Does it exist?

     Plenty of desire to manufacture amazing reflector , here is the list :

 

http://webstertelescopes.com/
https://www.teeterst...pes.com/ttstark
http://www.obsessiontelescopes.com/
http://www.loptics.c...scopeprices.htm
http://www.starstruc....com/index.html

 

  Orion, Skywatcher, Meade , all dobsonians coming from China are "poor man's"  instruments no matter what size  and everything you can expect is medium quality, some downsides and etc. If you have money, you can get royal excellence   from those linked telescope makers and personalize your dream. I am in Europe and i dream one day to be able to have one marvelous creation from those manufacturers, probably need just around 10 000 bucks, thats it...  Any  big APO for visual will be left in dust and forgotten in light gathering power and ease of use of extra large   ultra compact dobsonian and no need of  expensive equatorial mount. 

 

 Just two cents, nothing against reafractors ( i have one :))  )  . 



#128 Starman1

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Posted 05 May 2018 - 01:07 PM

A few makers of high-end reflector telescopes:

http://www.starstruc...ucture3_001.htm
http://www.planewave.com/
http://www.obsessiontelescopes.com/
http://www.astrosystems.biz/index.htm
http://www.jpastrocraft.com/index.htm
http://www.officinas...e.com/index.php
http://www.liteboxtelescopes.com/
http://www.sumerianoptics.com/en/
https://sites.google...edobsonfactory/
http://dobstuff.com/stt.htm
http://www.normandfullumtelescope.com/
http://www.teeterstelescopes.com/
http://sdmtelescopes.com.au/

http://newmoontelescopes.com

http://www.waiteresearch.com

 

And a few high-end mirror makers to put in those scopes:

http://www.veritasoptics.com/
http://zambutomirrors.com/
http://www.ostahowskioptics.com/
http://www.galaxyoptics.com/
http://www.kennedy-optics.com/
http://www.loptics.com/
http://www.normandfu.../mirror_en.html
http://www.opticalmechanics.com/
http://www.pegasusoptics.com/
http://www.lightholderoptics.com/
http://www.oldham-optical.co.uk/
http://www.waiteresearch.com/

Mark Harry

Mike Spooner

http://translate.goo...rro-sphere.com/

http://www.swayzeoptical.com

 

May have retired:

Mark Suchting (Australia)

Bob Royce (US)


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#129 Asbytec

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Posted 06 May 2018 - 12:00 AM

If you come in from a night of observing and are happy with the view, you 'effectively' have a reflector as good as an expensive ED refractor or quality Newt because of the impact it has on you. If not, get a premium one. That's "how hard" it is.

Edited by Asbytec, 06 May 2018 - 12:03 AM.

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#130 Starman1

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Posted 06 May 2018 - 12:20 AM

 

Easy there.  I'm lucky enough to observe at a popular place where a lot of other observers go, so I get a chance to look through lots of inexpensive scopes from China.

One of the finest 16" scopes I ever did a star test on was a Chinese made dob.  It was as close to perfect as I've seen in a star test.

 

On the other hand, the variability of optical quality from scope to scope with that same maker is also high.

China is certainly beating the US makers in sales, but that is largely related to price, which is related to the wages in the source factories.

 

I wouldn't argue that I haven't seen some dogs among US-made scopes, either, because I have.

But I have seen more, uh, unfinished optics among Chinese makers' scopes.

Ask just about any mirror maker in the US that does a re-figuring service for sub-adequate mirrors where most of those mirrors come from, and you won't hear the names of the premium makers

in the US.

 

Does that mean that most are inadequate for the observers who own them?  No, it doesn't.  But you certainly have been luckier than many of the scope owners whose instruments

I've tested that had 1/2 wave optics with turned down edges on the mirrors.

 

[No Chinese make I've seen so far is as bad as a number of Coulters I saw in the '80s and '90s.  Boy, most of those were really bad.]

 

So, decent scopes at decent prices are what you get.  As with any production product, the quality curve is going to resemble a bell-shaped curve.

If you get one with optics in the upper end of the curve, great.  Unfortunately, the bottom of the curve also exists.


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#131 Dzukielis

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Posted 06 May 2018 - 02:27 AM

 

 

 Congratulations, you are lucky !

 Cloudynights is world only  resourse having such a tremendous amound of information. And it  showed me clearly one thing:  plenty of unhappy or not satisfied  chineese scope owners. Especially a lot of  unhappy   catadioptrics users, i read also how people bring chineese mirros to recoute to  best USA mirror makers and etc.   And of course many happy people like you mister Barbie and i am happy for it. 

 

  Personal problem with me is:  i don't like how chineese dobsonians look, i do not like they are heavy , mobile but not to a level i want and etc.  And i choose not to own one . Better i build one some  day or buy from premium USA maker.  I go crazy about obsession ultra compact style.... 

  And mister Barby,  we even can't talk about quality when prices differ so much, simple example:

https://www.teleskop...uss-Design.html

and 

http://www.obsession.../12.5/index.php

 

Price difference is almost 3 times, so what are we talking about ??   Owning scope is not also about mirror, it's about feeling you happy or not, how it looks, how it feels , how performs when touched or moved , are enought of features and etc.

There is nothing to fight in this topic , but i continue to dream about scope which i made personally for me and my needs.

Thank you.



#132 Asbytec

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Posted 06 May 2018 - 03:12 AM

"And it showed me clearly one thing: plenty of unhappy or not satisfied chineese scope owners. Especially a lot of unhappy catadioptrics users, i read also how people bring chineese mirros to recoute to best USA mirror makers and etc."

I'm not saying you're wrong, there are unhappy CAT owners and more than a few Dob owners question their mirrors. I totally agree with the idea Chinese Dobs need some redesign work. Case in point is their altitude bearings, among other mods and threads discussing those mods.

But I don't get the impression there are "plenty" of unhapppy users with the connotation they are coming out of the woodwork. On the contrary, seems most comments are at least favorable. Once in a while someone will post an atrocious CAT star test or a warped secondary flat or they may complain about balance. My own Chinese CAT is, by no stretch, premium and I know it. But, it is good and probably in the production bell curve peak.

I think that's the truth of the matter, there is a bell curve probably centered on sensibly good performance. Whereas premium bell curve is shifted to the right and tgey are sensibly perfect. Maybe with a tighter grouping of samples, as well. Bottom line, in my view and experience, is a lot of sensibly good scopes are coming out of China (mechanics aside) and only a few sensibly perfect ones.

Edit: Whether anyone considers the Chinese bell curve good or not is another point.

Edited by Asbytec, 06 May 2018 - 03:37 AM.


#133 gazerjim

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Posted 06 May 2018 - 05:00 AM


On the other hand, the variability of optical quality from scope to scope with that same maker is also high.

 

So, decent scopes at decent prices are what you get.  As with any production product, the quality curve is going to resemble a bell-shaped curve.

If you get one with optics in the upper end of the curve, great.  Unfortunately, the bottom of the curve also exists.

The crux of the matter, I would guess.   One usually gets what one pays for,  sometimes less and sometimes even more.  Big bucks for premium equipment is largely about consistency of excellence.  And the maker's reputation and individualized attention if expectations are somehow not met is a  guarantee of sorts.

 

I think the bell curve analogy is a good one regarding product quality.  It probably applies to consumer expectations of quality as well.



#134 CHASLX200

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Posted 06 May 2018 - 06:09 AM

     Plenty of desire to manufacture amazing reflector , here is the list :

 

http://webstertelescopes.com/
https://www.teeterst...pes.com/ttstark
http://www.obsessiontelescopes.com/
http://www.loptics.c...scopeprices.htm
http://www.starstruc....com/index.html

 

  Orion, Skywatcher, Meade , all dobsonians coming from China are "poor man's"  instruments no matter what size  and everything you can expect is medium quality, some downsides and etc. If you have money, you can get royal excellence   from those linked telescope makers and personalize your dream. I am in Europe and i dream one day to be able to have one marvelous creation from those manufacturers, probably need just around 10 000 bucks, thats it...  Any  big APO for visual will be left in dust and forgotten in light gathering power and ease of use of extra large   ultra compact dobsonian and no need of  expensive equatorial mount. 

 

 Just two cents, nothing against reafractors ( i have one smile.gif)  )  . 

Nothing i would ever buy.



#135 Lyuda

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Posted 06 May 2018 - 07:21 AM

I really don't think it's that hard. Ive never used an APO so do take my word lightly, but here's how I see it.

I was actually seriously considering buying a 102 apo... Until I saw Jupiter for "the first time" through my 10" dob. I never really gave Jupiter a chance in my dob because the few times I did, it was no better than my achromatic (the result of poor collimation, poor seeing, no cooldown, and impatience). The other night I really pushed Jupiter with everything done properly and the view was simply impeccable.

Now, it possibly wasn't as good as an apo -though I have my doubts - but I was able to push so much magnification and still resolve more detail than I ever imagined possible. Wisps and swirls, colors everywhere, big red spot, and even a barge on the northern hemisphere.

This was all done at 240x. With a 102, the best I would get is ~150x. So for me, even if an APO would give more detail, Jupiter would be much smaller and that's just not how I prefer to view. You could say that Im a man of high power.

DSO's come into play too. Even the largest APO's won't resolve as much detail as a reflector. Resolving globular clusters in a refractor? Forgetaboutit.

The only thing I feel like my refractor has over my dob is: aesthetics, wide FoV (which I'm not a fan of anyway), and portability.

Edited by Lyuda, 06 May 2018 - 07:24 AM.

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#136 Asbytec

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Posted 06 May 2018 - 07:42 AM

I was actually seriously considering buying a 102 apo... Until I saw Jupiter for "the first time" through my 10" dob. 

Exactly the way I feel. Not that a great APO is not a nice scope to have, but after a night of observing Jove I'm content with the images in my current scope. 



#137 Lyuda

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Posted 06 May 2018 - 07:58 AM

Exactly the way I feel. Not that a great APO is not a nice scope to have, but after a night of observing Jove I'm content with the images in my current scope.

Couldn't agree more. Maybe some can find little details without the use of maximum magnification, but why not make it as big as possible? Doesn't hurt to have a bigger picture :)

On nights of bad seeing, you can mask the dob to reduce noise from a turbulent atmosphere. You can't make an APO's aperture bigger....

Edited by Lyuda, 06 May 2018 - 08:00 AM.


#138 Pinbout

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Posted 06 May 2018 - 08:30 AM

 

I've tested that had 1/2 wave optics

32IN F3.3.jpg

 

and what the say they provide

 

14.5f4.5 star test.jpg


Edited by Pinbout, 06 May 2018 - 08:34 AM.


#139 Asbytec

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Posted 06 May 2018 - 08:47 AM

Couldn't agree more. Maybe some can find little details without the use of maximum magnification, but why not make it as big as possible? Doesn't hurt to have a bigger picture smile.gif

On nights of bad seeing, you can mask the dob to reduce noise from a turbulent atmosphere. You can't make an APO's aperture bigger....

I couldn't agree more, as well. For me, Jupiter maxes out at about 40x per inch. It's probably related to some reduced throughput due to the obstruction, meniscus, and three reflective surfaces more so than the limitations of the optics. That's about a 0.6mm exit pupil (or 240x in 6" aperture).

 

I think the "image breakdown" of smaller low contrast detail is due to the exit pupil and my own physiology rather than the scope. We just need more light throughput in the image to go higher magnification and smaller exit pupil. I've heard some refractors can reach 0.3mm exit pupil, and I am sure that is due to their more efficient throughput. 

 

As Mel Bartel likes to say, if a scope can do 50x per inch it's a good one. I presume he means a crisp image of the moon or similar. The proof lies in the sharp high contrast detail visible on the moon at 50x per inch, Mars at 70x per inch with no problem, double stars at 80x per inch and higher and 150x per inch on Arcturus a couple times just to see what's up that high. The scope will keep going, but as the exit pupil diminishes my own ability to detect bright low contrast Jovian detail at 0.5mm exit pupil and smaller also wanes. 

 

But, yes, I maximize the image scale to the point I begin to lose soft contrast detail (on DSO, too). I think it actually helps to have a larger image, so long as it retains sufficient surface brightness to be seen. Not unlike ludicrous magnification used on small, bright planetary nebula. Sure. 



#140 Starman1

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Posted 06 May 2018 - 09:00 AM

attachicon.gif 32IN F3.3.jpg

 

and what the say they provide

 

attachicon.gif 14.5f4.5 star test.jpg

Like the first one, only fuzzier.



#141 Pinbout

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Posted 06 May 2018 - 09:13 AM

Like the first one, only fuzzier.

then its worse cause to add a tde the inside would be woolly on the outside ring



#142 Jeff B

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Posted 06 May 2018 - 09:15 AM

Circling back to the original question, it is not that difficult to make a reflector that will perform as good as a mid priced APO of equal aperture, and, especially, focal ratio.

 

Any vendor that pushes glass and scopes out the door, has the capacity to make really good, first rate ones.  They just have to decide to do it.  Not all decide to do it.  And they have their reasons.

 

But it can, and is done, sometimes by "accident", sometimes on purpose, and sometimes consistently on purpose.  

 

Then it's your choice as to which one you want and can get.

 

Jeff



#143 gwlee

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Posted 06 May 2018 - 09:27 AM

A few makers of high-end reflector telescopes:

http://www.starstruc...ucture3_001.htm
http://www.planewave.com/
http://www.obsessiontelescopes.com/
http://www.astrosystems.biz/index.htm
http://www.jpastrocraft.com/index.htm
http://www.officinas...e.com/index.php
http://www.liteboxtelescopes.com/
http://www.sumerianoptics.com/en/
https://sites.google...edobsonfactory/
http://dobstuff.com/stt.htm
http://www.normandfullumtelescope.com/
http://www.teeterstelescopes.com/
http://sdmtelescopes.com.au/

http://newmoontelescopes.com

http://www.waiteresearch.com

 

And a few high-end mirror makers to put in those scopes:

http://www.veritasoptics.com/
http://zambutomirrors.com/
http://www.ostahowskioptics.com/
http://www.galaxyoptics.com/
http://www.kennedy-optics.com/
http://www.loptics.com/
http://www.normandfu.../mirror_en.html
http://www.opticalmechanics.com/
http://www.pegasusoptics.com/
http://www.lightholderoptics.com/
http://www.oldham-optical.co.uk/
http://www.waiteresearch.com/

Mark Harry

Mike Spooner

http://translate.goo...rro-sphere.com/

http://www.swayzeoptical.com

 

May have retired:

Mark Suchting (Australia)

Bob Royce (US)

Lots of bigger scopes here, but only found two 8” scopes and no 6” scopes. Only one of the 8” scopes is a tube design. There’s not much available for the person who wants a premium quality small reflector. 



#144 Lyuda

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Posted 06 May 2018 - 09:42 AM

I've heard some refractors can reach 0.3mm exit pupil.

Not unlike ludicrous magnification used on small, bright planetary nebula.

Why would you even want a .3 exit pupil though, especially on a refractor? Even at 500x for planetaries I can stay at .5 with my reflector. It's hard enough looking through that...

When it comes to imaging, refractors are king. But, I don't do imaging, so I'll take as much aperture and magnification as I can get :)

Edited by Lyuda, 06 May 2018 - 09:44 AM.

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#145 Asbytec

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Posted 06 May 2018 - 09:45 AM

attachicon.gif 32IN F3.3.jpg

 

and what the say they provide

 

attachicon.gif 14.5f4.5 star test.jpg

What they provided me, I'm happy. (The defocus is in error due to the focal length being not as advertised.) The shadows are closer to 80% as measured by an image of both at 10 waves. Looks a lot like the 1/6th above. 

 

8 Waves.jpg


Edited by Asbytec, 06 May 2018 - 09:47 AM.

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#146 Starman1

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Posted 06 May 2018 - 10:27 AM

Lots of bigger scopes here, but only found two 8” scopes and no 6” scopes. Only one of the 8” scopes is a tube design. There’s not much available for the person who wants a premium quality small reflector. 

For better or worse, 6" isn't going to be a popular size for better scopes, where reflectors are concerned.

 

The Teeter STS is a high-end full-tubed dob series but, by and large, tubes are considered a sign of low quality on the better dobs.

I think there are many reasons for that:

1) Most people transport their scopes to get to darker sites, and tubes are just plain inconvenient to transport.

2) Mirrors are often transported in the scopes, and vertical isn't as safe a way to transport a large mirror as horizontal.

3) Most tubed scopes have very inexpensive tubes, like a wrap-around steel or cardboard.

4) The tubed scopes have much higher centers of gravity, necessitating much taller rocker boxes, making the bases harder to transport, tippier, and a lot more flexible.

5) With one notable exception, tubed dobs have small diameter side trunnions, making them far more sensitive to imbalance.  It's harder to make a tubed dob with a large

diameter trunnion.

 

So I think most people looking for a premium quality small reflector will likely be looking at a truss-tubed 8".  I know if I were looking for something in that size, that is where I'd look.

I might have to put mirrors and structure together from different sources. When I built my 6" f/5 in the '80s, that's exactly what I did--pieces from a dozen different sources.

But a 10" is barely larger so it's likely the market just skips right away to 10".  There is a lot more choice at that size.

It seems the best way to get a premium 6" or 8" is either to build it yourself or have the mirrors on a lower-priced scope refigured and buy a better structure for it.



#147 Asbytec

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Posted 06 May 2018 - 11:54 AM

"...(mass produced) tubed dobs have small diameter side trunnions, making them far more sensitive to imbalance."

Emphasis mine, but this is one reason I shy away from them. Just got tired of fideling with balance and other mods. They need a better structure. I like to think Bresser/ES was onto something with their Messier/Firstlight series. And ES truss series. I mean, finally, right?

Edited by Asbytec, 06 May 2018 - 11:56 AM.

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#148 gwlee

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Posted 06 May 2018 - 02:05 PM

For better or worse, 6" isn't going to be a popular size for better scopes, where reflectors are concerned.

 

The Teeter STS is a high-end full-tubed dob series but, by and large, tubes are considered a sign of low quality on the better dobs.

I think there are many reasons for that:

1) Most people transport their scopes to get to darker sites, and tubes are just plain inconvenient to transport.

2) Mirrors are often transported in the scopes, and vertical isn't as safe a way to transport a large mirror as horizontal.

3) Most tubed scopes have very inexpensive tubes, like a wrap-around steel or cardboard.

4) The tubed scopes have much higher centers of gravity, necessitating much taller rocker boxes, making the bases harder to transport, tippier, and a lot more flexible.

5) With one notable exception, tubed dobs have small diameter side trunnions, making them far more sensitive to imbalance.  It's harder to make a tubed dob with a large

diameter trunnion.

 

So I think most people looking for a premium quality small reflector will likely be looking at a truss-tubed 8".  I know if I were looking for something in that size, that is where I'd look.

I might have to put mirrors and structure together from different sources. When I built my 6" f/5 in the '80s, that's exactly what I did--pieces from a dozen different sources.

But a 10" is barely larger so it's likely the market just skips right away to 10".  There is a lot more choice at that size.

It seems the best way to get a premium 6" or 8" is either to build it yourself or have the mirrors on a lower-priced scope refigured and buy a better structure for it.

Solid-tubed scopes have proved to be better suited to my observing style than a truss-tube scope. Although truss-tubed scopes have some obvious advantages for travel, my scopes are used at my rural home most clear nights and seldom travel anywhere, and I quickly tired of spiders spinning webs in my permanently set up truss-tubed scope as well as pollen and sap dropping onto the optics while observing despite installing a shroud. 

 

The incessant tree dodging required at this forested site means that my 6-inch scope gets far more use than my 8-inch scope, so a 10-inch scope wouldn’t be much use to me here. The Teeters 8” solid tube scope weighs 41#, the same as my 8” Synta scope, so it has no advantage with respect to this key parameter. Instead, I am experimenting with a new base for the Synta 8” to see if it can be lightened enough to be more useful here without compromising its stability too much. If so, it might be worth upgrading its optics. 

 

At the moment, my 34#, 6” Synta, solid-tube Dob seems to offer the best compromise for this site and my observing style, especially its optical performance versus its weight. It isn’t as refined as I would like for my primary scope though, so I am looking at various options, but want to avoid building a scope myself. 



#149 barbie

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Posted 06 May 2018 - 03:19 PM

Easy there.  I'm lucky enough to observe at a popular place where a lot of other observers go, so I get a chance to look through lots of inexpensive scopes from China.

One of the finest 16" scopes I ever did a star test on was a Chinese made dob.  It was as close to perfect as I've seen in a star test.

 

On the other hand, the variability of optical quality from scope to scope with that same maker is also high.

China is certainly beating the US makers in sales, but that is largely related to price, which is related to the wages in the source factories.

 

I wouldn't argue that I haven't seen some dogs among US-made scopes, either, because I have.

But I have seen more, uh, unfinished optics among Chinese makers' scopes.

Ask just about any mirror maker in the US that does a re-figuring service for sub-adequate mirrors where most of those mirrors come from, and you won't hear the names of the premium makers

in the US.

 

Does that mean that most are inadequate for the observers who own them?  No, it doesn't.  But you certainly have been luckier than many of the scope owners whose instruments

I've tested that had 1/2 wave optics with turned down edges on the mirrors.

 

[No Chinese make I've seen so far is as bad as a number of Coulters I saw in the '80s and '90s.  Boy, most of those were really bad.]

 

So, decent scopes at decent prices are what you get.  As with any production product, the quality curve is going to resemble a bell-shaped curve.

If you get one with optics in the upper end of the curve, great.  Unfortunately, the bottom of the curve also exists.

I think the same can be said of U.S. telescopes as well.  Case in point being the Coulters from the 80's and 90's.  I also observed through a Zambuto not long ago that I thought was less than  stellar considering its reputation.  An Orion set up nearby was delivering a better star test and planetary performance so you can certainly get a dog from a U.S. telescope maker as well.  



#150 CHASLX200

CHASLX200

    Hubble

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Posted 06 May 2018 - 03:52 PM

No one has got a dog Zambuto that i know of.




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