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SkyWatcher’s 20" goto truss dob!

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#101 Pierre Lemay

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Posted 22 January 2017 - 01:26 AM

I can understand not posting the optical specifications.   if your company was proud of the specifications you would list them. 

That's an unfounded statement. Zambuto and Lockwood, among other premium mirror makers, also don't provide Strehl and other test results, yet no one questions their pride and reputation. 


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#102 starman876

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Posted 22 January 2017 - 10:04 AM

You really need to read this from Zambuto

 

http://zambutomirror...oopticalca.html


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#103 CHASLX200

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Posted 22 January 2017 - 11:01 AM

Testing a mirror at low power don't cut it.  I had a 18" Tectron with a bad Nova mirror that looked fine at low powers.  Once i jacked the power up to view planets it was ugly.



#104 skyward_eyes

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Posted 22 January 2017 - 11:51 AM

Star tests are generally done with a 2.3mm eyepiece and s test tunnel with an artificial star.

As I've said before, if you are looking for a optics that meets you strict needs and has documention to boot there are plenty of companies that will supply you with that.

Strehl numbers are great for internal use to keep track of quality. Releasing number does nothing but cause problems. Number get released and one guys optics are slightly dofferrnt than another and it becomes a 50 page discussion with no end. So Sky-Watcher will not release numbers for the same reason many another manufacturers do not.

If you are curious about these scopes we welcome you to attend TSP or any of major upcoming events where we will be demoing these scopes. Come by and use them. As I've said wth our high end triplet Apo refractor (which also got the same level of scrutiny, and surpassed it) I let our products speak for themselves.

Edited by skyward_eyes, 22 January 2017 - 11:52 AM.

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#105 starman876

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Posted 22 January 2017 - 12:01 PM

I would love to attend TSP and try one of these scopes out.   Are you going to NEAF?



#106 skyward_eyes

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Posted 22 January 2017 - 12:19 PM

Yes, we will be at NEAF but we won't have a demo sessions as everything will be at the booth.

#107 starman876

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Posted 22 January 2017 - 01:14 PM

Yes, we will be at NEAF but we won't have a demo sessions as everything will be at the booth.

that's a shame. would love to look through one just to see if I would be interested.  Have been thinking of buying a 20"  scope.  



#108 Pierre Lemay

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Posted 22 January 2017 - 03:33 PM

You really need to read this from Zambuto

 

http://zambutomirror...oopticalca.html

The part of the Zambuto website you refer to in your post confirms exactly what I said previously: ZOC refuses to provide any numbers with their mirrors. They rely only on their excellent reputation and simply follow their internal mirror making procedures.  Same for Lockwood and others. Skywatcher seems to be taking this approach as well. 


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#109 starman876

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Posted 22 January 2017 - 04:35 PM

 

You really need to read this from Zambuto

 

http://zambutomirror...oopticalca.html

The part of the Zambuto website you refer to in your post confirms exactly what I said previously: ZOC refuses to provide any numbers with their mirrors. They rely only on their excellent reputation and simply follow their internal mirror making procedures.  Same for Lockwood and others. Skywatcher seems to be taking this approach as well. 

 

If you carefully read the Zambuto specs you will see they refer to the scratch dig specs.  What they provide is an extremely smooth optical surface.   I think it is one of the best in the industry. It really makes a big difference in the optical quality of the mirror.  Once you look through a Zambuto mirror you will understand why. I am providing a link to the Edmunds web site which explains optical specifications. 

 

http://www.edmundopt...specifications/



#110 Polestar

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Posted 22 January 2017 - 09:08 PM

 

 

You really need to read this from Zambuto

 

http://zambutomirror...oopticalca.html

The part of the Zambuto website you refer to in your post confirms exactly what I said previously: ZOC refuses to provide any numbers with their mirrors. They rely only on their excellent reputation and simply follow their internal mirror making procedures.  Same for Lockwood and others. Skywatcher seems to be taking this approach as well. 

 

If you carefully read the Zambuto specs you will see they refer to the scratch dig specs.  What they provide is an extremely smooth optical surface.   I think it is one of the best in the industry. It really makes a big difference in the optical quality of the mirror.  Once you look through a Zambuto mirror you will understand why. I am providing a link to the Edmunds web site which explains optical specifications. 

 

http://www.edmundopt...specifications/

 

I had a read of the Zambuto specs; they were QUITE illuminating. I had thought that Strell ratio was a dandy reference point, but Zambuto's commentary on spec #4 really opened my eyes.


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#111 starman876

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Posted 22 January 2017 - 09:41 PM

 

 

 

You really need to read this from Zambuto

 

http://zambutomirror...oopticalca.html

The part of the Zambuto website you refer to in your post confirms exactly what I said previously: ZOC refuses to provide any numbers with their mirrors. They rely only on their excellent reputation and simply follow their internal mirror making procedures.  Same for Lockwood and others. Skywatcher seems to be taking this approach as well. 

 

If you carefully read the Zambuto specs you will see they refer to the scratch dig specs.  What they provide is an extremely smooth optical surface.   I think it is one of the best in the industry. It really makes a big difference in the optical quality of the mirror.  Once you look through a Zambuto mirror you will understand why. I am providing a link to the Edmunds web site which explains optical specifications. 

 

http://www.edmundopt...specifications/

 

I had a read of the Zambuto specs; they were QUITE illuminating. I had thought that Strell ratio was a dandy reference point, but Zambuto's commentary on spec #4 really opened my eyes.

 

I was wondering when someone would actually read the whole listing of specifications on their mirrors.  It is interesting how they compare a mirror with  a strehl ratio of better then 99.  I am not sure how one can do much better.  1/15 wave optics are pretty good also.  However, they clearly show how Zambuto goes that extra mile to make sure you get a top notch mirror.  You pay for this, but once you look through one you realize you got a bargain in the perfect images you see on nights of good seeing.


Edited by starman876, 22 January 2017 - 09:51 PM.


#112 smodtactical

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Posted 03 March 2017 - 01:56 PM

Are the skywatcher telescopes all made in the USA ?



#113 skyward_eyes

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Posted 03 March 2017 - 04:34 PM

All Sky-Watcher products are made by Synta in China. 



#114 macfly51

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Posted 03 March 2017 - 06:09 PM

Hi All, 

 

I've just sold my xx14g for a 18" or StarGate 20" Goto, but I'm afraid that the quality of polishing is less good on the 500 than the 450 frown.gif

 

I still hesitate ... I do not know which one to order ... My question may seem stupid, but I know the 250 are all excellent, the 350 very good ... and I'm afraid that the quality goes down with the diameter...

 

So ?

 

Thanks for the help smile.gif

 

Stéf from France.



#115 skyward_eyes

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Posted 03 March 2017 - 06:58 PM

All mirrors have to meet the same level of quality (defraction limited) before they ship. I would not worry about the debating between the 18" and 20". 



#116 macfly51

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Posted 03 March 2017 - 07:05 PM

Thank you for your reply :)

 

I thought above all of the softness of the surface.



#117 radicell2

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Posted 30 March 2017 - 09:26 AM

All Sky-Watcher products are made by Synta in China. 

On the new 18 and 20 incher,do you have any photos of the mirror blanks?Ad in S&T says fused conical.

 

Ric

TO



#118 skyward_eyes

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Posted 30 March 2017 - 09:50 AM

Here is an image of the unmounted 18" blank. Mirror surface is face down. 

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#119 Bram Weisman

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Posted 30 March 2017 - 08:29 PM

Has anyone used this design in high humidity?  Is dew a problem?  Is dew control possible?  Looks like custom heater pads would be required.

 

 

Bram Weisman

Katy, TX



#120 radicell2

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Posted 31 March 2017 - 08:31 AM

Here is an image of the unmounted 18" blank. Mirror surface is face down. 

Wow - it's a copy of my fused conical that I've had on my web site for years and made back in '88.

http://www.rokoszoptical.yolasite.com

Look under lightweight blanks.

 

Don't worry about dew - no problems there.

 

 

Bit of advise ..a  cracked piece of glass has a different crack pattern/signature if caused by an anneal issue versus a outside hit by  some event -blow or slight drop.

 

Just a bit of background on me...see my website on making /using fused blanks since '83.

 

Ric


Edited by radicell2, 31 March 2017 - 09:29 AM.


#121 skyward_eyes

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Posted 31 March 2017 - 01:26 PM

The blanks have gone through several generations of development to get to this point. The annealing process is done very slowly to ensure its done correctly.  


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#122 wolfli

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Posted 31 March 2017 - 09:19 PM

Really looking forward to seeing this scope in NEAF!! smile.gif smile.gif



#123 radicell2

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Posted 02 April 2017 - 02:29 PM

The blanks have gone through several generations of development to get to this point. The annealing process is done very slowly to ensure its done correctly.  

Could you show us an image of the stress pattern in one of the blanks?From what I see they still have some technical issues in the design that causes concern.I do wont to see these type of blanks  become a success not end up with another Stabilite situation.

Ric



#124 Relativist

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Posted 03 April 2017 - 10:15 AM

Could we see more high ISO short exposures? I'm curious if your 20" will work for EAA use.

Also, does the controls work with starsense and is it able to be pointed by software like SkySafari?

#125 skyward_eyes

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Posted 03 April 2017 - 10:50 AM

See page 2 of the forum to see some images through the 18" model using a 60Da. 




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