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Equipment Discussions >> Refractors

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Eddgie
Postmaster
*****

Reged: 02/01/06

Re: Refractor Anti Reflection Coating longevity. new [Re: Paul G]
      #5694877 - 02/22/13 02:37 PM

Quote:

Back to the op, the primary reason to get a dielectric diagonal is the ability to clean it without causing sleeks in the coatings. A little dust on the diagonal mirror surface will have a much greater adverse effect on the image than any difference in reflectivity or scatter. Keep in mind the image occupies the central 1/4 inch or so of the mirror, a little dust that would cause zero degradation in the image if on the objective surface causes noticeable loss of low contrast detail if on the diagonal mirror (as does dust on the surface of an eyepiece where the image is also concentrated in a very small area).




I absolutely agree.

Serious planetary observers should buy a good quality dielectric.

For the most serious planetary viewing, the diagonal should be cleaned immediately before use (eyepecies too).

As the light cone converges to the diagonal, the intensity for unit area increases greatly. Dust on the diagonal will indeed scatter this light.

I find cleaning a dirty diagonal makes far more difference in scatter than changing from A T6 Nagler to an Ortho for example. In the latter case, it is hard to see a difference, but if there is dust on the diagonal, it is easy to see the difference in performance.

And this is why people should use dielectric. It is the most robust coating available. it will withstand even sand (silica quartz) abrasion.

Silica Quartz dust is the benchmark because it is hard enough to scratch MgF2 which is the hardest substance that most optics are ever exposed to.

This is why the Military went to Dielectric long ago. Based on my own observations, Marines are excellent shots, but not gentle with optics.

With Dielectrics, they don't need to be. Even desert sand won't scratch dielectrics when wiped with a shirt sleeve.

Hard. Very, very hard.

To be fair, Enhanced Aluminum is quite hard as well. Much harder than most people realize (harder than the glass it is bonded too).

But as far as I know, dielectric is the hardest currently available commercial glass coating technology.


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: Paul G]
      #5694915 - 02/22/13 02:56 PM

Hi again Doug,la200o,BCNGreyCat, jrbarnett and Paul G

Thank you ever so much, once again.Lastly I need to seek a answer to this query..this may seem silly and minor,BUT... do the latest new Televue NP-101 Telescopes and their Eyepiece Holders use Rust free Alloy Screws throughout?

I read of Televue having an issue with Rusty Screws which is a pain due to the fact that having to replace Rusty Screws with Stainless Screws is actually quite an expensive endeavour.


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: Eddgie]
      #5694945 - 02/22/13 03:11 PM

Hi Eddgie

Thanks. Dielectrics are very tough,yes and there is also the longevity which is a serious positive,supposedly Dielectric Star Diagonals won't (dare I say ever) degrade or oxidise or lose brightness in-a human lifetime.

Secondly Anti Reflection Coatings are Dielectric.

Edited by Plane_Guru (02/22/13 03:12 PM)


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la200o
Carpal Tunnel


Reged: 09/09/08

Loc: SE Michigan, USA
Re: Refractor Anti Reflection Coating longevity. new [Re: Plane_Guru]
      #5695186 - 02/22/13 05:10 PM

Quote:

Hi again Doug,la200o,BCNGreyCat, jrbarnett and Paul G

Thank you ever so much, once again.Lastly I need to seek a answer to this query..this may seem silly and minor,BUT... do the latest new Televue NP-101 Telescopes and their Eyepiece Holders use Rust free Alloy Screws throughout?

I read of Televue having an issue with Rusty Screws which is a pain due to the fact that having to replace Rusty Screws with Stainless Screws is actually quite an expensive endeavour.




Dunno the answer to this one, but none of my TV scopes show any sign of such rust, and my 102 is an early one that's been covered with dew, ice, and water from melting ice many times.

Bill


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Refractor Anti Reflection Coating longevity. new [Re: Plane_Guru]
      #5695268 - 02/22/13 05:48 PM

I've never read about Televue scopes having rusty screw issues. There are a number of owners on this forum who have Televue scopes and live in maritime climates (in the UK). Perhaps one of them will read this and comment on the reality of the corrosion issue.

Televue scopes have very few exposed screws in actuality, compared to other refractors.

- Jim


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Sean Cunneen
Let Me Think
*****

Reged: 08/01/07

Loc: Blue Island Illinois
Re: Refractor Anti Reflection Coating longevity. new [Re: jrbarnett]
      #5695325 - 02/22/13 06:15 PM

Certainly the quality of the coating has everything to do with it's longevity, but to give you an example, I have a Brandon Objective from maybe 1946 which has MGF2 coatings in beautiful condition. So when applied correctly and taken care of properly, coatings can last a LONG time.

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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Refractor Anti Reflection Coating longevity. new [Re: Paul G]
      #5695895 - 02/22/13 11:46 PM

I've frankly never heard if refractors *givn it up* like mirror coatings . The ONLY time I've heard if refractors losing coating effectiveness is abrasive contaminants, ammonia , ie; windex and finally dew laden with salt from the sea or outright ocean spray.

Typically tho aside from that - I think they outlast the observer no?

Pete


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: azure1961p]
      #5696280 - 02/23/13 10:17 AM

Hi Paul G

Would you be able to inform what what would be used instead of Magnesium Fluoride for ED glass elements?


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Refractor Anti Reflection Coating longevity. new [Re: azure1961p]
      #5696292 - 02/23/13 10:25 AM

True, Pete, and with the exception of the FS-series from Tak, where the coatings on the front fluorite element protect the soft, reactive lens material from environmental or physical damage, failed refractor coatings have minimal impact on the performance of the instrument. I have four or five uncoated refractors that nonetheless perform like champs. Coatings don't fail catastrophically, so a coated objective with coating issues would be only partially uncoated. That would have even less of a detectable impact than having no coatings at all.

Telescopes are tools, and outside tools to boot. Maintaining them and not misusing them is sensible. Obsessing over having them not change in condition at all through time under ordinary use is not. That is better suited to the art collector. Worry about your Vermeer not degrading through the decades, not your Celestron.

Regards,

Jim


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: azure1961p]
      #5696302 - 02/23/13 10:30 AM

Hi Paul,

Would you be able to inform what what would be used instead of Magnesium Fluoride for ED glass elements?


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: Plane_Guru]
      #5696320 - 02/23/13 10:39 AM

Interesting input.I already stated that I love Science and have a keen interest in the Science of Optics.Thanks

Edited by Plane_Guru (02/23/13 11:18 AM)


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Refractor Anti Reflection Coating longevity. new [Re: Plane_Guru]
      #5696342 - 02/23/13 10:51 AM

You may find this informative on mating coating formulations to glass type:

http://tech.groups.yahoo.com/group/ap-ug/message/17280

"For best results of minimum reflectivity, each glass type should have its own
multi-layer formula. This can be expensive, and does impact the final cost in
things like multi-element eyepieces where there may be many different glass
types in each assembly. It is usually cheaper for the manufacturer to coat them
all with the same formula in a large batch. The end result is multi-colored
hues on the various surfaces."

Though it doesn't give you the actual chemical formulation of different coatings that are used for different glass types, it does indicate that different glass types benefit from different coating formulations. This is one of the high-cost features of the ZAO II Orthos - each air to glass surface has multicoatings optimized for the underlying glass type. Almost no one bothers to do this. I don't think that even A-P uses different coating formulations on different surfaces in its refractors.

Now Celestron does share what multicoatings it uses on its SCT corrector plates in this article:

http://www.celestron.com/astronomy/technologies/starbright-xlt/

The correctors are water white glass. Celestron's AR coating on the correctors is a combination of MgF2 and HfO2 (Hafnium Dioxide).

Regards,

Jim


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Refractor Anti Reflection Coating longevity. new [Re: azure1961p]
      #5698165 - 02/24/13 12:12 PM

Quote:

I've frankly never heard if refractors *givn it up* like mirror coatings . The ONLY time I've heard if refractors losing coating effectiveness is abrasive contaminants, ammonia , ie; windex and finally dew laden with salt from the sea or outright ocean spray.

Typically tho aside from that - I think they outlast the observer no?

Pete




Windex does not contain ammonia:

http://www.aossmedicalsupply.com/doc/msds/glasscleaner.pdf

It's actually quite safe on lens coatings.


Tanveer


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mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: Refractor Anti Reflection Coating longevity. new [Re: TG]
      #5698180 - 02/24/13 12:23 PM

Most windex products do contain ammonia.

From Windex website:

All but two Windex® Glass and Multi-Surface Cleaners contain detergents, solvents, fragrance, Ammonia-D®, and alcohol. They should not be used if ammonia is not recommended for use on surface. (Windex® Multi-Surface Vinegar and Windex® Outdoor Multi-Surface do not contain ammonia. They are safe to use in these cases.)

MSDS on Windex Ammonia D : http://www.btps.ca/files/PDF/MSDS/Windex_Ammonia-D.pdf

Notice there is no mention of "ammonia" in the ingrediants. MSDS are not required to list any component in which there is less than 1% of a hazardous component in the mixture. Ammonia is in there, it's just not a required listing in the MSDS.


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Refractor Anti Reflection Coating longevity. new [Re: mgwhittle]
      #5699045 - 02/24/13 10:34 PM

Quote:

Most windex products do contain ammonia.

From Windex website:

All but two Windex® Glass and Multi-Surface Cleaners contain detergents, solvents, fragrance, Ammonia-D®, and alcohol. They should not be used if ammonia is not recommended for use on surface. (Windex® Multi-Surface Vinegar and Windex® Outdoor Multi-Surface do not contain ammonia. They are safe to use in these cases.)

MSDS on Windex Ammonia D : http://www.btps.ca/files/PDF/MSDS/Windex_Ammonia-D.pdf

Notice there is no mention of "ammonia" in the ingrediants. MSDS are not required to list any component in which there is less than 1% of a hazardous component in the mixture. Ammonia is in there, it's just not a required listing in the MSDS.




Do you have a source for confirming that there is actually ammonia in there? From what I recall, Ammonia-D is not actually ammonia but marketingspeak for some other chemical.

Tanveer


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teelgul
sage


Reged: 09/02/11

Loc: Australia
Re: Refractor Anti Reflection Coating longevity. new [Re: Plane_Guru]
      #5699170 - 02/25/13 12:20 AM

Televue is a great scope optically and mechanically .
its only weak points if at all are its internal coating and its non airline portability . Its mechanical design is a mixture of old and traditional, but solid. But I dont believe that it can do things which no other 4 inch can do.
if we are a bit flexible with the 4 inch definition then TEC 110 will be way ahead in design,and portability with the same optical performance if not better.
Any way if you live in CON USA internal coatings should not be a worry as its a shorter distance to the Televue factory.
For me the coating peeeling off in 4 places with in three months in the not so humid sydney was a bad experience.
if i were a Televue owner i would be more concerned with the paper coating and a some times loose rack mechanism than with the lens coating which iam sure will outlive all of us. This is from first hand experience of two televue scopes.Hope Televue has a better resin and if the paper coating now is half as durable as their lens coating it will be fine for a life time .


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: teelgul]
      #5699249 - 02/25/13 02:27 AM

Hello teelgul ,

I reside in Queensland,Eastern Australia and I am also worried about the Televue NP-101 Internal Flocking Paper lifespan and durability because where I reside the Weather can also be very humid(Central Queensland).

I have a brand NEW Televue NP-101 on order from:

http://www.bintel.com.au/Telescopes/Refractor/TeleVue-NP101/136/productview.aspx



I phoned The Binocular and Telescope Shop and raised the issue of the Internal Flocking Paper de-flocking and I was told that Televue have changed their Adhesives now to try and combat this very rare? issue.

All my best

Edited by Plane_Guru (02/25/13 05:19 AM)


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teelgul
sage


Reged: 09/02/11

Loc: Australia
Re: Refractor Anti Reflection Coating longevity. new [Re: Plane_Guru]
      #5699306 - 02/25/13 04:47 AM

Hello guru
Televue did fix it up for me but i had to pay one way fare.
If the new resin has fixed it up then great. Televue should have done this long
Back .A slight debonding may not performance but it should not happen in a scope of this price range. . Any way if you are going to use it from a fixed location with occasional transport then it should be fine .
Cheers


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Plane_Guru
member


Reged: 02/17/13

Re: Refractor Anti Reflection Coating longevity. new [Re: teelgul]
      #5699316 - 02/25/13 05:24 AM

Quote:

Hello guru
Televue did fix it up for me but i had to pay one way fare.
If the new resin has fixed it up then great. Televue should have done this long
Back .A slight debonding may not performance but it should not happen in a scope of this price range. . Any way if you are going to use it from a fixed location with occasional transport then it should be fine .
Cheers





Hi ,I concur wholeheartedly..The Flocking paper De-Flocking and becoming unglued should never be an issue in a Premium Telescope of this price .I too hope that Televue's change to a new Adhesive/Resin fixes the De-Flocking issue.


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mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: Refractor Anti Reflection Coating longevity. new [Re: TG]
      #5699425 - 02/25/13 08:49 AM

Quote:

Quote:

Most windex products do contain ammonia.

From Windex website:

All but two Windex® Glass and Multi-Surface Cleaners contain detergents, solvents, fragrance, Ammonia-D®, and alcohol. They should not be used if ammonia is not recommended for use on surface. (Windex® Multi-Surface Vinegar and Windex® Outdoor Multi-Surface do not contain ammonia. They are safe to use in these cases.)

MSDS on Windex Ammonia D : http://www.btps.ca/files/PDF/MSDS/Windex_Ammonia-D.pdf

Notice there is no mention of "ammonia" in the ingrediants. MSDS are not required to list any component in which there is less than 1% of a hazardous component in the mixture. Ammonia is in there, it's just not a required listing in the MSDS.




Do you have a source for confirming that there is actually ammonia in there? From what I recall, Ammonia-D is not actually ammonia but marketingspeak for some other chemical.

Tanveer




Hi Tanveer, the quote above is directly from Windex's website regarding ammonia in their products. As you see they say specifically, except for two products, all their glass cleaners contain ammonia.

Here are all the ingredients in Windex with Ammonia D:
http://www.whatsinsidescjohnson.com/en-us/products-by-brand/windex-1/windex-w...

And the contents of original Windex (the stuff often recommended here):
http://www.whatsinsidescjohnson.com/en-us/products-by-brand/windex-1/windex-o...

Ammonium Hydroxide is listed in both.

I used the MSDS from Ammonia-D as an example that some ingredients are not listed on the MSDS even though they are in there. Ammonia-D is a trademarked marketing name and it is a 28% solution of ammonia present at .05% in their cleaners. Since it is only at .05% it is not required to be listed on the MSDS. You can gleen this information from the Windex website (http://www.windex.com/en-US/Pages/Faq.aspx ), and how to read an MSDS (many sites, this just happened to come up first on a google search http://www.ehso.com/msds_regulations.php )


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