Optical quality OSG mirrors

[pastorgalactico]

ello;

I am Spanish and I am new to this forum and would like to start by asking about the optical quality of the GSO mirrors.

I am building a 406 mm F4,5 newton telescope and the date is coming to buy a mirrors for the telescope.

http://pastorgalactico.blogspot.com.es/

At first I had thought about the mirrors that the GSO brand sells.

But I would like to know if any of you have this kind of optics in your telescopes and you could tell me if the optics is acceptable and it is like the one mounted on Meade's dobsom telescopes of 16 "or better.

I can buy them in Europe for € 1399 with aluminized 93% and € 1699 with the aluminized to 97%.

https://www.teleskop-express.de/shop/index.php/cat/c91_Selbstbau-----Optiken---Spiegel--Linsen-.html

Have if someone can help me with this topic.

Greetings.

J.Tapioles

[AstroSylv1]

Hello there, welcome to Webastro,

I would first question your budget and your long term project or expectations : I had a GSO mirror on my 10” dob in the past, and it did the job. But after some years, you may want a gain in contrast, in light scatter control, in definition... then only a hand craft made mirror will bring you that, and then budget is double or triple the GSO mirror. Unless you can make the mirror yourself. We have a couple of good quality mirror makers in France : Mirro-sphere and SkyVision, you can find them online. My mirror now is from Mirro-sphere, and starts are super sharp, little tiny dots, sky is darker than on my GSO and it gives fantastic details on all objects.

[pastorgalactico]

Hello;

That I have clear, that if you want more quality, quality must be paid and vast.

But is it worth it to pay double €?

Do you see so much difference?

I have heard comments that the differences are only noticed by the very purists in optics.

I have also been told by amateurs who are experts in optics that to notice these differences you have to go to extraordinary optics and the same happens with aluminizados of 94% and the hilux to 97%.

I have two possible artisans who could give a good job. One is from here in Spain; Joan Lopez Vila and the other is English Nikol optis.

The prices of a 16 "F4.5 of these artisans would be for the € 2100 secondary included.

Maybe it's worth saving a little more?

 

Regards;

 

J.Tapioles

[Invité]

Hi

A friend owns a 16" gso dob. The mirror has been tested as "random", but I remember very beautiful visions thru that scope.

Apparently, the quality of GSO mirrors is very stable in production.

You could buy one and maybe have it resurfaced (is that english?) later if you're not satisfied or if you're willing to explore the envelope of best performance.

[pastorgalactico]

Hello;

 

The translations of google can be an inconvenience to understand us well jejjeje.

I have not understood that very last.

Do you mean to buy one and try it and if it does not work well return it?

There is the option to pay 229 € more and they send you one with better quality than they have in stok.

 

Greetings.

[sixela]

Teleskop Express also offers testing services (i.e. they’ll send the mirror to Wolfgang Rohr to test), BTW. On their larger mirrors and even some more mundane sizes in Pyrex, such an independent test report is always included.

[pastorgalactico]

Sixela, explain that to me about TS.

How much they charge for that service.

My intention would be to buy one at 97% aluminized hilux that they say they choose them with better quality but I do not know if that is true.

Greetings.

[Invité]

Hello;

 

The translations of google can be an inconvenience to understand us well jejjeje.

I have not understood that very last.

Do you mean to buy one and try it and if it does not work well return it?

There is the option to pay 229 € more and they send you one with better quality than they have in stok.

 

Greetings.

 

You can buy the GSO mirror, and later if you want, a miror maker ( like Mirrosphere for example)can grind it and make it a perfect piece of art. But it will cost you as much as the miror itself...

[sixela]

Ask them, or look on their site...

 

https://www.teleskop-express.de/shop/product_info.php/info/p5793_Interferometrical-Test-Report---complete-telecopes-and-mirrors.html

 

They offer it on most Pyrex and fused silica mirrors as an option, and on some larger mirrors it’s included:

 

https://www.teleskop-express.de/shop/product_info.php/info/p9094_TS-Optics-358mm-f-4-5-Lightweight-Newtonian-Primary-Mirror-with-conical-back.html

[pastorgalactico]

Hello;

 

And that test means that if the mirror that I bought is not of good optical quality, will they look for another one that does have that quality?

Or if I buy the mirror and tell them to perform that test and it turns out that it is not very good, they will send it to me anyway.

It's what I want to know.

Maybe we should discuss with those of TS that they have and know the guarantees they offer about the GSO optics they sell.

Greetings.

[pastorgalactico]

Bonjour;

 

Eh bien, j'ai déjà contacté TS et je leur ai demandé de me parler de cette question.

 

Salutations à tous et merci beaucoup.

 

http://pastorgalactico.blogspot.com.es/

Modifié 7 novembre 2017 par pastorgalactico

[jctfrance]

MERCI DE PARLER EN FRANCAIS SVP!!

il y a Google traduction pour nos amis étrangers, ce qui n'est pas compliqué et tout le monde ne parle pas anglais (dont moi)

[gehelem]

MERCI DE PARLER EN FRANCAIS SVP!!

il y a Google traduction pour nos amis étrangers, ce qui n'est pas compliqué et tout le monde ne parle pas anglais (dont moi)

Salut

Rien ne l'interdit ni ne l'autorise dans la charte... ce serait bien savoir l'avis des modos

En ce qui me concerne, je trouverai dommage de se donner cette contrainte...

Gilles

[Modération]

Bonjour pastorgalactico,

 

You can translate by means of Google.

 

Webastro est un forum francophone. Merci de vous exprimer en français à partir des prochains messages. C'est une règle à respecter pour poster sur le forum.

 

La Modération.

[OrionRider]

La différence entre 94% et 97% est minuscule et ne vaut pas vraiment la différence de prix.

 

Par contre, entre un miroir Synta (SkyWatcher) à 86% et un GSO à 94%, le gain est sensible.

[teddelyon]

C'es vrai que ça fait une belle différence car il faut compter les 2 miroirs... au final 74 % de lumière réfléchie d'un côté et 88 % de l'autre... mais est-on toujours certains de ces chiffres aujourd'hui, car ça fait un moment qu'ils circulent ?

[OrionRider]

Si Synta faisait des miroirs à 94% ils ne manqueraient pas de le dire.

 

D'expérience je dirais qu'on remarque réellement une différence à partir de 10% de lumière en plus, sinon ça passe inaperçu.

[pastorgalactico]

Salut;

 

Je vais prendre en compte les Français, mais je pensais que vous pouviez choisir entre le français et l'anglais.

Pardonnez-moi pour ça, mais c'est la même chose pour moi de traduire en anglais qu'en français.

En ce qui concerne les miroirs, je ne m'inquiète pas de l'aluminisé de 94% à 97%, sinon ce qui me préoccupe c'est que si la qualité optique est meilleure dans l'un et dans l'autre.

Si la qualité est la même dans les deux, j'opterais pour le prix le plus bas.

 

salutation

Modifié 7 novembre 2017 par pastorgalactico

[OrionRider]

La qualité est en principe la même, seule l'aluminure est différente.

[sixela]

Pare contre, même chez les GSOs, il y a différents matériaux (BK7, borosilicate proche du Pyrex/Suprax, verre de quartz --"fused silica") et les plus chers sont plus faciles à bien polir et ont moins de tensions résiduelles dans le verre (ce n'est pas un hasard que c'est sur ces miroirs là que TS offre une option de test indépendant!) qui peuvent induire des erreurs de forme sur les miroirs BK7 (dans un processus de fabrication de masse).

 

La rumeur veut que les plus chers sont meilleurs, mais je n'en ai pas encore vu beaucoup, des GSOs en verre de quartz.

[teddelyon]

Si Synta faisait des miroirs à 94% ils ne manqueraient pas de le dire.

 

C'est pas faux