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Permanent collimation is here. Or is it?

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#1 jgroub

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Posted 29 January 2016 - 04:41 PM

Skywatcher has introduced its Star Discovery 150P, a six-inch newtonian reflector made mostly of ABS plastic, a very hard, stiff, long-lasting plastic.  What's unusual about this scope is that it is designed so as not to permit the owner to collimate it, as it is collimated permanently at the factory.  

 

Astronomy and Nature TV has done an excellent in-depth review here:  

 

https://www.youtube....h?v=mhhs65AWdCk

 

At 7:30, the presenter discusses the collimation issue.  He goes on to defend it because this collimation-free feature is coming from a reputable company like Skywatcher, not some off-brand no-name.  He says that because of the thermal expansion qualities of ABS plastic, or more particularly, the lack thereof, the mirror cell does not shift as the temperature changes.  He concludes that the scope is "essentially collimated for life."  

 

What do you think?  Is it really possible to have a newt with a primary that doesn't need collimation, or is this just so much hokum?  How are they able to do this?  How permanent is permanent?  Will this spread to other newts/dobs?  

 

(A tip of the hat to Ed (aeajr) for coming across this.)  


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#2 Jason D

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Posted 29 January 2016 - 05:05 PM

I find it difficult to accept. I am at work now. I will watch the whole video tonight. By scanning over the video, I see that the primary mirror is cemented but I do see adjustment screws for the secondary. This part I do not get. So, there is a chance for the scope to be miscollimated and if that happens they expect owners to recollimate by only using the secondary mirror adjustment screws -- impractically interesting!!!! Anyway, I need to be careful not to say too much until I watch the whole video tonight.

Jason


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#3 jgroub

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Posted 29 January 2016 - 05:10 PM

The Edmund Astroscan had no means of collimation. Ask someone who owned

one which went out of collimation how that worked out...

Yeah, but that was a 40-year old design.  Is it possible that Skywatcher has figured out something new in the meantime?  Or is superglue still superglue, 40 years old or not?



#4 Astrojensen

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Posted 29 January 2016 - 05:18 PM

I have a newtonian that is *at least* 60 years old. When I picked up, it hadn't been used for at least two decades. After a long car trip home, it was still in *perfect* collimation. It is quite heavy, though, with a refractor-like cell for the primary mirror and a super strong secondary holder. Think TOA 150 meets newtonian... Okay, it's not THAT bad, but you get the idea. 

 

So yes, it's entirely possible to build a newtonian that is essentially collimated for a lifetime. 

 

 

Clear skies!

Thomas, Denmark


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#5 Astrojensen

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Posted 29 January 2016 - 05:28 PM

BTW, did anyone bother to watch the video at all? The scope is CLEARLY described as being collimatable, just that it's made so that it shouldn't be necessary in most cases. It's NOT glued together. 

 

It's a bit more primitive than on my 1950'ies newtonian, which has a push-pull cell with screws, like on a refractor, but the idea is the same. Make it solid and adjust it once, and it will hold collimation. Just like on a refractor.

 

 

Clear skies!
Thomas, Denmark 



#6 jgroub

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Posted 29 January 2016 - 05:35 PM

Well, he says that it can be adjusted slightly.  "The holes here . . . do allow for a tiny amount of movement."  That sounds a lot different to me than a scope that is fully collimatable.  The whole thrust of the discussion is that this just won't be necessary.  


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#7 Vic Menard

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Posted 29 January 2016 - 07:26 PM

I watched the collimation portion of the video and I see adjustments for both the secondary mirror and the primary mirror. The primary mirror adjustments are rudimentary, but they should work. The secondary mirror adjustments appear to be common 3 push, 1 (central) pull--but one of the push screws may be fixed--this would provide basic tilt alignment but would "lock out" rotation and fore and aft adjustment.

 

I believe both the rear mirror cell and the front spider "cell" are ABS--the tube appears to be metallic. To achieve optimal performance (up to 50X per inch of aperture), the axial alignments for a 6-inch f/5 Newtonian are pretty tight. The out going laser beam will need to be aligned to the primary mirror center spot (does this scope have one?) within 3- to 4-percent of the primary mirror diameter (around 0.2-inch +/-). The return (Barlowed laser) alignment will need to be considerably closer, (about 0.05-inch +/-).

 

Of course, if the scope is only used at moderate (less than 25X per inch of aperture) and lower magnifications, the allowable errors can be increased a bit (perhaps as much as 50-percent or more), especially if the seeing and/or user expectations are somewhat diminished.

 

I'm reticent to pass judgement either way given the limited amount of information provided in the video. I did additional research online, but the specifications and manual I found provided little useful information. 

 

Can a small Newtonian be collimation "free" like a refractor, of course. This scope seems to be trying to make that leap by limiting some adjustments and beefing up other mechanicals that would otherwise require more frequent adjustment. Is this scope essentially "collimated for life"? Or is it just a sales pitch? I'm skeptical, but willing to be convinced...  :shrug:


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#8 bobaloo2

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Posted 29 January 2016 - 08:26 PM

There's an old saying in engineering, "if you make something that's impossible to break, it means that it's impossible to fix when it does break..."


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#9 jgroub

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Posted 29 January 2016 - 09:02 PM

So, no consideration is given to the fact that, as the presenter said, this is coming from the respected name of Skywatcher?  

 

Or is Synta always just Chinese-made Synta, no matter what name is silk-screened on the tube?  



#10 Vic Menard

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Posted 29 January 2016 - 10:08 PM

So, no consideration is given to the fact that, as the presenter said, this is coming from the respected name of Skywatcher?  

 

Or is Synta always just Chinese-made Synta, no matter what name is silk-screened on the tube?  

 

 

I don't see this as a "high end" Skywatcher scope. I think this scope was designed to target the economy go-to market. Reducing the number of precision mechanicals is one way to minimize production costs. Of course, I could be wrong, but that's my first impression...


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#11 havasman

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Posted 30 January 2016 - 12:07 AM

The only thing certain for me is that I don't want one.


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#12 Astrojensen

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Posted 30 January 2016 - 04:19 AM

 

So, no consideration is given to the fact that, as the presenter said, this is coming from the respected name of Skywatcher?  

 

Or is Synta always just Chinese-made Synta, no matter what name is silk-screened on the tube?  

 

 

I don't see this as a "high end" Skywatcher scope. I think this scope was designed to target the economy go-to market. Reducing the number of precision mechanicals is one way to minimize production costs. Of course, I could be wrong, but that's my first impression...

 

This is my impression as well. A name means nothing, if it isn't followed up by action. The scope here looks like an honest attempt, albeit in the low budget end of the market. How it will perform in the long run remains to be seen. Perhaps the reflector forum will be buried under a colossal avalanche of "how do I collimate this scope"-threads in a few years, perhaps not. For Sky-Watcher's sake, let's hope not.

 

 

Clear skies!
Thomas, Denmark


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#13 Jon Isaacs

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Posted 30 January 2016 - 08:57 AM

So, no consideration is given to the fact that, as the presenter said, this is coming from the respected name of Skywatcher?  

 

Or is Synta always just Chinese-made Synta, no matter what name is silk-screened on the tube?  

 

Skywatcher is the house brand for Synta Optical.  They also own Celestron and provide most of Orion's products.  They got their start back in the 1990's when Celestron stopped importing Japanese products, mostly Vixen, and had them cloned in China. There is a certain irony to the fact that Synta became the largest telescope maker in the world and ended up purchasing Celestron when they were going bankrupt.  

 

Synta manufacturers some very nice telescopes, their Esprit apo refractors are one example.  But they also manufacture some stuff best categorized as toys. 

 

The fellow doing the video. I have seen his collimation video.  He uses a laser and does not get the importance of the Barlowed Laser for adjusting the tilt of the primary mirror.  They would benefit everyone if they were to consult, Vic, Jason or Nils.. 

 

Generally one would not want to use plastic for a mirror or for the spider vanes. EJN discussed the thermal properties and they are part of the equation.  Plastics are not very strong nor are they very stiff/rigid.  We are all very well aware of this, a plastic fork versus a steel fork, there is a huge difference.  Young's modulus is the normal measure of material stiffness.  ABS with 30% glassfilled has about 12% the stiffness of aluminum, about 4% the stiffness of steel. It is also brittle.  For something like a mirror cell, stiffness is a virtue, for the spider vanes supporting the secondary, stiffness and strength are important, if you look at the secondary support, the vanes are thick.  

 

I did have chuckle at the suggestion that this mount was capable of supporting 5kg.. 

 

:shrug:

 

Jon Isaacs

 

Jon


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#14 KerryR

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Posted 30 January 2016 - 09:20 AM

Most Astroscans held collimation very well. Those that 'lost it' usually only needed to have the foam mirror support replaced, which is responsible for pushing the mirror snugly against the primary retaining ring. Worked well for the low to moderate powers the scope was designed for.


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#15 howard929

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Posted 30 January 2016 - 09:38 AM

It seems IMO that the ABS is used just as a way to save money as is the loss of 6 primary collimation screws that it doesn't have. It looks like a cheap telescope and a hard one to recommend to a new user, again IMO.


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#16 jgroub

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Posted 30 January 2016 - 12:58 PM

 

So, no consideration is given to the fact that, as the presenter said, this is coming from the respected name of Skywatcher?  

 

Or is Synta always just Chinese-made Synta, no matter what name is silk-screened on the tube?  

 

Skywatcher is the house brand for Synta Optical.  They also own Celestron and provide most of Orion's products.  They got their start back in the 1990's when Celestron stopped importing Japanese products, mostly Vixen, and had them cloned in China. There is a certain irony to the fact that Synta became the largest telescope maker in the world and ended up purchasing Celestron when they were going bankrupt.  

 

Synta manufacturers some very nice telescopes, their Esprit apo refractors are one example.  But they also manufacture some stuff best categorized as toys. 

 

The fellow doing the video. I have seen his collimation video.  He uses a laser and does not get the importance of the Barlowed Laser for adjusting the tilt of the primary mirror.  They would benefit everyone if they were to consult, Vic, Jason or Nils.. 

 

Generally one would not want to use plastic for a mirror or for the spider vanes. EJN discussed the thermal properties and they are part of the equation.  Plastics are not very strong nor are they very stiff/rigid.  We are all very well aware of this, a plastic fork versus a steel fork, there is a huge difference.  Young's modulus is the normal measure of material stiffness.  ABS with 30% glassfilled has about 12% the stiffness of aluminum, about 4% the stiffness of steel. It is also brittle.  For something like a mirror cell, stiffness is a virtue, for the spider vanes supporting the secondary, stiffness and strength are important, if you look at the secondary support, the vanes are thick.  

 

I did have chuckle at the suggestion that this mount was capable of supporting 5kg.. 

 

:shrug:

 

Jon Isaacs

 

Jon

 

So. I'll put you down for a "no", then.  



#17 Cotts

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Posted 31 January 2016 - 10:11 AM

Permanently collimated in the factory?  Check.

 Zero means of adjustment provided?  Check.

Maintains collimation at all times?  Check.

 

Meet the no-longer-available Ceravolo HD 145.

 

IMG_7717.jpg

 

And it is optically perfect.  Literally perfect.

 

Dave


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#18 Jon Isaacs

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Posted 31 January 2016 - 10:43 AM

Permanently collimated in the factory?  Check.

 Zero means of adjustment provided?  Check.

Maintains collimation at all times?  Check.

 

Meet the no-longer-available Ceravolo HD 145.

 

attachicon.gifIMG_7717.jpg

 

And it is optically perfect.  Literally perfect.

 

Dave

 

And only about twice the price of the Skywatcher 6 inch F/5.. :)   Rare.. since 2009 there have been 5 of them offered on Astromart, the price ranges from $3000 to almost $5000, that was Markus Ludes..  The other thing about a Mak-Newt is that the mirror is spherical.. 

 

That said, my 130mm F/5 Synta Newtonians hold their collimation quite well.  

 

Jon



#19 Cotts

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Posted 31 January 2016 - 11:05 AM

Jon, I only posted because there seemed to be a trend in the thread implying that 'permanent collimation' is not possible.  It is, but, as you have correctly pointed out, it doesn't come either cheaply or commonly.

 

Dave


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#20 Vic Menard

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Posted 31 January 2016 - 12:17 PM

To be fair, the OP asked if it was, "...possible to have a newt with a primary that doesn't need collimation..." and whether or not the Skywatcher collimation is "permanent". The OP also included a video that proclaimed the Skywatcher was, "...essentially collimated for life."

 

I think the responses to the OP were specific to the claim in the video regarding the Skywatcher Star Discovery 150P, a 6-inch f/5 economy Newtonian. I don't believe the commentary was directed at all Newtonians and certainly not at a singular high end Mak-Newt. 


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#21 Vic Menard

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Posted 31 January 2016 - 12:36 PM

And only about twice the price of the Skywatcher 6 inch F/5.. :)   Rare.. since 2009 there have been 5 of them offered on Astromart, the price ranges from $3000 to almost $5000, that was Markus Ludes..  The other thing about a Mak-Newt is that the mirror is spherical.. 

 

The current price I found (FLO) for the Skywatcher Star Discovery 150P with Go-To mount was 349 pounds (about $500)--I'm guessing the scope is about half of that (maybe less). So I'm wondering how you arrived at "twice the price"?

 

And I agree, a spherical primary shifts much of the collimation load to the corrector, and the meniscus corrector in a Mak-Newt is typically mounted in a precision cell, similar to what's found on a refractor. The single weakness in a Mak-Newt (assuming the focuser alignment is fixed) is the secondary mounting, so I'm very impressed that the Ceravolo secondary is both "permanent" and "with zero means of adjustment".



#22 TG

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Posted 03 February 2016 - 11:44 AM

 

The other thing about a Mak-Newt is that the mirror is spherical.. 

 

Jon

 

Alas, a spherical primary does not remove the need for collimation and Mak-Newts tend to be harder to collimate than a Newt due to the corrector. I think Ceravolo had the right idea as does Roland with his recent MNs.

 

Tanveer.



#23 Deep13

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Posted 03 February 2016 - 03:12 PM

The reviewer is really gushing over that thing. Skywatcher is not a manufacturer. It's an importer of mass-produced Chinese optics. So his reliance on their reputation or prestige is a bit misplaced.
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#24 Juan Rayo

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Posted 03 February 2016 - 03:24 PM

The reviewer is really gushing over that thing. Skywatcher is not a manufacturer. It's an importer of mass-produced Chinese optics. So his reliance on their reputation or prestige is a bit misplaced.

 

I thought the same of their 90mm Mak and virtuoso mount combo review. My wife got me one, very much based on that review, and to be honest there are many things that are not mentioned in the video that could knock the needle towards the "waittaminute not so good" field. I should probably write those down for CN...

 

Anyways, I´d like to think that this is because the reviewer is very enthusiastic about amateur observing and the different telescopes they get to play with. In any case, I am certainly taking into account their enthusiasm when I see their videos, and not letting myself be too excited about the scopes.


Edited by Juan Rayo, 03 February 2016 - 03:25 PM.

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#25 jgroub

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Posted 03 February 2016 - 04:02 PM

 

The reviewer is really gushing over that thing. Skywatcher is not a manufacturer. It's an importer of mass-produced Chinese optics. So his reliance on their reputation or prestige is a bit misplaced.

 

I thought the same of their 90mm Mak and virtuoso mount combo review. My wife got me one, very much based on that review, and to be honest there are many things that are not mentioned in the video that could knock the needle towards the "waittaminute not so good" field. I should probably write those down for CN...

 

Anyways, I´d like to think that this is because the reviewer is very enthusiastic about amateur observing and the different telescopes they get to play with. In any case, I am certainly taking into account their enthusiasm when I see their videos, and not letting myself be too excited about the scopes.

 

Yeah, I have to agree with both of these assessments.  It's interesting that someone in his position - working in a telescope shop for quite some time, someone who ostensibly knows the score, someone who is making videos - is saying something like this, when a relative newb like me whose primary source of information is the wisdom gleaned from these boards, knows better.  


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