Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Announcements and News >> Discussion of CN Articles, Reviews, and Reports

Pages: 1 | 2 | 3 | (show all)
Olivier Biot
Amused
*****

Reged: 04/25/05

Loc: 51°N (Belgium)
Discovery vs. Zambuto Optical Shoot-out
      #4934549 - 11/25/11 03:46 PM

Discovery vs. Zambuto Optical Shoot-out

By Tim Neubert.


Post Extras: Print Post   Remind Me!   Notify Moderator  
gatorengineer
Carpal Tunnel
*****

Reged: 02/28/05

Loc: Hellertown, PA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Olivier Biot]
      #4934887 - 11/25/11 08:48 PM

Pictures of both scopes would have been interesting. Was the custom a home brew? Relative cage ID's and cage heights. Rear end mirror box open or closed. Shrouds.... All of these things and this is literally a stream of thought list could have made differences. No slight to Carls optics in anyway, but fair needs to be fair....

Post Extras: Print Post   Remind Me!   Notify Moderator  
Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Olivier Biot]
      #4934944 - 11/25/11 09:46 PM

Actually Discovery makes some pretty nice mirrors. I've tested several and was quite surprised. They're just an inch too thick though and they need to be that way for counter weight issues from what they told me when I visited the factory. I told them they really should thin their mirrors down. Really nice people though. All my scopes are Zambuto and Taks and that's enough to put a grin on my face.

Post Extras: Print Post   Remind Me!   Notify Moderator  
James Bielaga
Vendor (Aurora Astro)
*****

Reged: 11/14/06

Loc: Washington, USA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Daniel Mounsey]
      #4935078 - 11/25/11 11:44 PM

Hi Tim,

I would say you have to test them on the planets. I have 13.1" dob yep old coulter but Carl Zambuto refigured the mirror in 1995 and it's 1/11th wave where before it was 1/2 wave. My scope performs better on planets 312x is easy and have pushed it to over 700x before. It rivals 6" APO refractors on planetary detail. It also does better on globulars and detail on nebulas.

I am not surprised the discovery scope was brighter it has more aperture in the review and more surface area. Carl Zambuto does make some fine mirrors and never seen a bad one. You can get to that 50x magnification per inch if the seeing is right with his optics. But with a dob without tracking sometimes that is hard to do.

Good article enjoyed the review. One of our club members has a discovery premium dob 17.5" and enjoys it and it does have good optics too.

James Bielaga


Post Extras: Print Post   Remind Me!   Notify Moderator  
deepskydarrell
member


Reged: 03/09/08

Loc: Abbotsford, BC Canada
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: James Bielaga]
      #4935162 - 11/26/11 01:27 AM

Thanks for the comparison Tim.

Wished you would have tested it on more objects. Such as the faint companions of NGC 7331, or Sephan's Quintette, or even (in winter) NGC 2024-- the Flame Nebula --- How would they both perform with the bright star Alnitak just out of the field. Or even the central star in the Ring.

It would be useful to hear more on this.

Thanks.

DSD.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: James Bielaga]
      #4935667 - 11/26/11 12:18 PM

Quote:

Hi Tim,

I would say you have to test them on the planets. I have 13.1" dob yep old coulter but Carl Zambuto refigured the mirror in 1995 and it's 1/11th wave where before it was 1/2 wave. My scope performs better on planets 312x is easy and have pushed it to over 700x before. It rivals 6" APO refractors on planetary detail. It also does better on globulars and detail on nebulas.

I am not surprised the discovery scope was brighter it has more aperture in the review and more surface area. Carl Zambuto does make some fine mirrors and never seen a bad one. You can get to that 50x magnification per inch if the seeing is right with his optics. But with a dob without tracking sometimes that is hard to do.

Good article enjoyed the review. One of our club members has a discovery premium dob 17.5" and enjoys it and it does have good optics too.

James Bielaga





Certainly a longer target list would be interesting, but the logistics of getting the weather, people, and equipment together (not to mention the self esteem of the Discovery owner) all need to be considered.

On the brightness, by my math it looks like a 7% light gathering difference. That should be subtly noticeable all by itself, but the large difference in coating age (7 years and in favor of the larger aperture) would be an even bigger factor. Presumably, the diagonal mirror coatings are of the same age as the respective primaries.

But most revealing was the consistent sightings of the faintest stars which were not visible in the larger aperture. That would indicate to me the smaller aperture was doing a better job of getting all the light on target, and not smearing portions of it randomly around the field.


Post Extras: Print Post   Remind Me!   Notify Moderator  
chollman
sage
*****

Reged: 04/24/08

Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Jeff Morgan]
      #4935743 - 11/26/11 01:04 PM

If you add pricing as the eight criteria. Would that make the discovery mirror more attractive being that it is $1000.00 cheaper? Charlie

Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: chollman]
      #4935852 - 11/26/11 02:07 PM

The brightness difference can be easily explained as the standard coatings on Discovery mirrors are enhanced, whereas Zambuto mirrors always have standard coatings.
The visibility of faint stars is often determined by superiority of focus, and the Zambuto optics may have had a superior Strehl ratio, putting more light into the star's spurious disc, and, hence, making fainter stars more visible.

I discovered the same thing when using a Paracorr. It obviously cuts the light by a tiny percentage, but fainter stars were visible WITH the Paracorr than without for exactly the same reason--a better concentration of the star's light in a tiny point.

So the results, to me, imply that, whereas the Discovery was an excellent mirror, the Zambuto was a tad better.
This seems to conform to what I've seen through the years.
My current mirror is from the Ostahowski era of Discovery and my next scope will have a Zambuto mirror.

No question the Discovery optics are a bargain among the premium mirror makers. It would be interesting to know if the Discovery mirror was from Terry Ostahowski, or made after that period.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sean Cunneen
Let Me Think
*****

Reged: 08/01/07

Loc: Blue Island Illinois
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Starman1]
      #4935865 - 11/26/11 02:14 PM

A great comparo, truly enlightening! You always wonder exactly what you are going to get with those mirrors ground with pixie dust... No I have an idea!

Sean


Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Olivier Biot]
      #4935902 - 11/26/11 02:32 PM

Thanks for the write-up.

Do you happen to have notes as to which eyepieces were used in each scope for the observations of each target?

Regards,

Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tim Neubert
newbie
*****

Reged: 08/09/11

Loc: San diego, CA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: jrbarnett]
      #4938888 - 11/28/11 10:36 AM

Thanks for the feed-back guys!!

As for comparing on planets, Saturn was very low in the sky when we did the comparison and just wasn't worth it.

We used both eyepieces (Explore-100 degree and Ethos) on each target. We spent a lot of time back and forth between scopes on each target moving each eyepiece back and forth in an attempt to eliminate variability. We should have also done and Ethos versus Explore Scientific shoot-out as well!!

The differences between the optics was subtle but clearly observable. I actually owned the Discovery and I have to say it is amazing the quality you get for the money with Discovery. The owner of the Zambuto scope was truly taken by surprise. He thought it wouldn't be much of a comparison and was really impressed with views the Discovery produced.

One other thing to take into account is that this only one comparison and it is nearly impossible to take out all the variability. So, get out there and do a comparison of your own. Comparisons from multiple owners that show a clear trend is the only way to prove that Zambuto optics consistently outperform the competition by meeting the seven criteria.

Sincerely,

Tim Neubert


Post Extras: Print Post   Remind Me!   Notify Moderator  
Project Galileo
scholastic sledgehammer
*****

Reged: 11/14/07

Loc: Jefferson County, Colorado
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Tim Neubert]
      #4939157 - 11/28/11 12:57 PM

Thanks for taking the time to compare these two mirrors. Very interesting and insightful.

Post Extras: Print Post   Remind Me!   Notify Moderator  
LivingNDixie
TSP Chowhound
*****

Reged: 04/23/03

Loc: Trussville, AL
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Tim Neubert]
      #4939159 - 11/28/11 12:58 PM

Put the scopes through this on the planets or Moon, and I would expect the Zambuto will pull further ahead. And I have owned a Discovery and love the products they make.

Post Extras: Print Post   Remind Me!   Notify Moderator  
bob irvin
sage


Reged: 03/22/11

Loc: Greater Los Angeles, CA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Olivier Biot]
      #4939379 - 11/28/11 03:38 PM

Thanks for putting the review together Tim. I know it takes time to do the work and write it up and it's a value to us readers.

bob


Post Extras: Print Post   Remind Me!   Notify Moderator  
Qi Dang
newbie
*****

Reged: 02/18/08

Loc: California
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Olivier Biot]
      #4940299 - 11/29/11 04:16 AM

This should be a double blind comparison.

Post Extras: Print Post   Remind Me!   Notify Moderator  
hoof
Carpal Tunnel
*****

Reged: 04/07/05

Loc: Redmond, WA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Qi Dang]
      #4940643 - 11/29/11 10:41 AM

A few thoughts:

1) Were the two 'scopes equally thermally acclimated? If the Discovery is considerably thicker, it could have had some extra thermal distortion effects degrading it's contrast if it hadn't had time to come to ambient temperature.

2) What is the status of the secondaries? Even the best primaries can have their capabilities degraded by a less-than-stellar secondary. If the secondary was noticably better on the Zambuto 'scope vs the Discovery, this alone could explain the difference even if the Discovery's primary was actually better.

Without knowing the situation for the above two situations, it's harder to really judge the situation.

Finally, a dimmer image (due to smaller area and more-degraded coatings) could actually increase perceived contrast in certain situations.

Why? Because the background would be darker. I have observed many times DSOs that were more easily observable when the magnification increased. Since this darkens the overall view, this seems counterintuitive, but it's the darkening of the background vs the DSO that can make the difference. This could easily be affecting the results between the two optics in this test.

Finally, we are only observing with one sample of each manufacturer's optics. That means we can only know how these particular optics performed, which tells us almost nothing about how any other optics would compare from both manufacturers.

So I'd say we can't draw any real conclusions yet based on this comparison. Both are obviously great optics. But which one is better? Hard to tell.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tim Neubert
newbie
*****

Reged: 08/09/11

Loc: San diego, CA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: hoof]
      #4941139 - 11/29/11 03:27 PM

Jonathan,

You are correct that this only one comparison and it is nearly impossible to take out all the variability. So, get out there and do a comparison of your own. Comparisons from multiple owners that show a clear trend is the only way to prove that Zambuto optics consistently outperform the competition by meeting the seven criteria.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: hoof]
      #4941228 - 11/29/11 04:18 PM

Quote:


Finally, we are only observing with one sample of each manufacturer's optics. That means we can only know how these particular optics performed, which tells us almost nothing about how any other optics would compare from both manufacturers.




Small sample size is an inherent problem in testing of astro equipment. Especially since the effort and expense of statistically proper tests are immense, and the profit motive none. If there was a telescope in every garage, maybe someone like Consumer Reports would step in. But of course we know that our small hobby will never generate that type of interest. (Their loss, no?)

But let me turn this around for you: When a significant "sampling" of amateur astronomers over a number of years are universally praising the work of a particular optician (Christen, Zambuto, Royce, etc) in comparison to mass-produced work, and then back up words with a product order, there is something real and significant going on.

I suppose it is possible that very rarely one of the premium makers has a "bad one" get out of their shop. And mass-produced mirrors can be consistently good, and be good value for the money. Maybe a random selection could result in a mass-market optic equalling or bettering a premium one (manufacturing is after all a statistical process). But if you think the odds of this are any more than "remote" you're kidding yourself.

Each type of optic has a place in the hobby, and free-market pricing has sorted it out - as it always does.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tim Neubert
newbie
*****

Reged: 08/09/11

Loc: San diego, CA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Jeff Morgan]
      #4942347 - 11/30/11 10:15 AM

Jeff,

Your right in saying there are clear levels of optics and that their optical performance directly correlates with their price tag. However, what I am trying to answer is different.

My question is about the Zambuto seven criteria. Do they translate to an observable difference in contrast over other premium optics? Does perfection of the small scale features of the mirror truly make a difference? This is a hard concept to grasp and something that I really only noticed on those special nights of good viewing when I saw detail in specific targets that I never saw before with other optics on equally good nights of viewing. Others have had similar experiences, but is it real?

Tim Neubert


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Tim Neubert]
      #4942520 - 11/30/11 11:58 AM

Quote:

Jeff,

Your right in saying there are clear levels of optics and that their optical performance directly correlates with their price tag. However, what I am trying to answer is different.

My question is about the Zambuto seven criteria. Do they translate to an observable difference in contrast over other premium optics? Does perfection of the small scale features of the mirror truly make a difference? This is a hard concept to grasp and something that I really only noticed on those special nights of good viewing when I saw detail in specific targets that I never saw before with other optics on equally good nights of viewing. Others have had similar experiences, but is it real?

Tim Neubert



It's hard to evaluate.
1) Extremely good seeing, where differences in premium mirrors are in evidence, are rare.
2) Cooling, collimation, and cleanliness have to be identical in the two scopes.
3) The difference would result in a "slight" increase in contrast only, which would take some time to establish.
Star images might be the easiest to use to see a difference.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BillP
Postmaster
*****

Reged: 11/26/06

Loc: Vienna, VA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Tim Neubert]
      #4942974 - 11/30/11 05:03 PM

Tim,

Excellent report

Thanks!!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: BillP]
      #4943043 - 11/30/11 05:51 PM

Reminds me of the old saying..."one robin does not herald Spring..."

n of 1 is not a significent sample...period.



Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Mr. Bill]
      #4943096 - 11/30/11 06:27 PM

Quote:

Reminds my of the old saying..."one robin does not herald Spring..."

n of 1 is not a significent sample...period.





Bill,
You're right. I've looked through about a dozen Discoverys, most of the Ostahowski mirror vintage, and almost twice that number of Zambutos over the years.

Collimation and cooling have not been optimum in most of the scopes I've looked through. Judging from what I've seen, I would not say that I was all that impressed with Zambuto mirrors in most of the samples I've looked through.

In the ones that were optimized, though, I've generally seen that the star images are a little tighter and have a little less "fuzz" in the edges and/or diffraction rings in the Zambuto-mirrored scopes--obviously less light scatter.

The difference hasn't been overwhelming, but the star test reveals a slightly better correction, in general, on the Zambuto mirrors in the optimized scopes.
Ostahowski's mirrors are right up there, though. The ones I've seen were definitely in the "premium" class.

What I find it hard to understand, though, is why not everyone who pays the price of a Zambuto mirror bends over backwards to learn collimation or even use fans to cool the mirror! That's a little like buying a Ferrari and never exceeding 30mph.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Wing Eng
newbie
*****

Reged: 09/18/07

Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Starman1]
      #4943185 - 11/30/11 07:20 PM

I tried a somewhat similar "Shoot-out" that involved comparing my 12 year old Celestron Starhopper 8 inch f/6 with my 24 year old Coulter Odyssey Red Tube 10.1 inch f/4.5. The images of globulars and open clusters seems about identical for the brightness of these objects - probably due to the coatings on the Celestron being only half the age of the Coulter - even though the Coulter has around 59% more intrinsic light gathering ability.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Wing Eng]
      #4943395 - 11/30/11 09:49 PM

Hi Wing- have seen & read your "web" reviews for a long time! Glad to see you here on CN- your input is appreciated!
mike b


Post Extras: Print Post   Remind Me!   Notify Moderator  
deepskydarrell
member


Reged: 03/09/08

Loc: Abbotsford, BC Canada
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Starman1]
      #4943629 - 12/01/11 01:27 AM

Carl Z's 7 criteria are very convincing. The 4th one is excedingly so. http://zambutomirrors.com/zambutoopticalce.html

Optical companies don't / won't talk about surface roughness. There doesn't seem to be a statistical test for it. But boy can you see it when you take a look at it on a focault testor. And it shows up in glare or fog next to a bright object.

I still believe the visual test in contrast is in faint objects near brighter ones. Such as the galaxies hidden within M 44.

DSD.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Darenwh
Carpal Tunnel


Reged: 05/11/06

Loc: Covington, GA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: deepskydarrell]
      #4944095 - 12/01/11 10:58 AM

Even if it comes down to Zambuto mirrors being better than those in Discovery scopes it becomes apparent based on how close the two mirrors were that anybody who owns a Discovery dob (at least an Ostahowski vintage) should be very happy with the scope they have for the money they spent. Discovery scopes are easily premium scopes at bargain prices.

I happen to be one of those people who have one and I am quite happy with it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: James Bielaga]
      #4948493 - 12/03/11 06:49 PM

Quote:

Hi Tim,

I would say you have to test them on the planets. I have 13.1" dob yep old coulter but Carl Zambuto refigured the mirror in 1995 and it's 1/11th wave where before it was 1/2 wave. My scope performs better on planets 312x is easy and have pushed it to over 700x before. It rivals 6" APO refractors on planetary detail. It also does better on globulars and detail on nebulas.

I am not surprised the discovery scope was brighter it has more aperture in the review and more surface area. Carl Zambuto does make some fine mirrors and never seen a bad one. You can get to that 50x magnification per inch if the seeing is right with his optics. But with a dob without tracking sometimes that is hard to do.

Good article enjoyed the review. One of our club members has a discovery premium dob 17.5" and enjoys it and it does have good optics too.

James Bielaga




I would bet big bucks that your reflector would out perform any 6" apo on a night that allows its potential to be realised. On common so so nights it might seem rivaled, but on a better night with 1/11 on the wavefront in that aperture youd also best a 7" apo.

Pete


Post Extras: Print Post   Remind Me!   Notify Moderator  
oldtimer
Pooh-Bah
*****

Reged: 11/13/08

Loc: Lake County Illinois
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Olivier Biot]
      #4951477 - 12/05/11 01:38 PM

I have read several 'good' reports as to Discovery's mirror quality, however the 14" I bought several years ago is nothing to brag about. Oh its fine for deep sky, which is what I use it for, but fails badly on planetary.

Yes yes I know all about alignment, seeing conditions, cool down time and mirror cell pinch but its just not that good. My 10" newt with a mirror produced by an 'acomplished amateur' kicks its butt on the planets.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bowmoreman
Clear enough skies
*****

Reged: 09/11/06

Loc: Bolton, MA
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: oldtimer]
      #4966989 - 12/14/11 08:55 PM

Fascinating review, and it pretty much mirrors my review experience and thread earlier this year... There is something hard to quantify about the 'smoothness' of Zambuto that is hard to quantify... That said, I am sold...

Disclaimer: I have not viewed thru other premiums... Only a Tak M300... And FSQ106... The key to me was the contrast delta... Darks darker, lights lighter.. And linear in between...

Nice review


Post Extras: Print Post   Remind Me!   Notify Moderator  
Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: oldtimer]
      #4969824 - 12/16/11 03:46 PM

Quote:

I have read several 'good' reports as to Discovery's mirror quality, however the 14" I bought several years ago is nothing to brag about. Oh its fine for deep sky, which is what I use it for, but fails badly on planetary.



What vintage is the Discovery scope?


Post Extras: Print Post   Remind Me!   Notify Moderator  
photiost
scholastic sledgehammer
*****

Reged: 12/14/06

Loc: Montreal, Canada
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Starman1]
      #4983821 - 12/25/11 12:15 AM


The quality of the secondary plays a significant roll in the systems overall image quality.

This has to be taken into consideration.


Post Extras: Print Post   Remind Me!   Notify Moderator  
VĂ­ctor MartĂ­nez
sage


Reged: 02/05/07

Loc: Cadiz - Spain
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: photiost]
      #4983952 - 12/25/11 05:27 AM

Hi,
Has anyone compared directly one mirror Zambuto mirror with a recent Ostahowski mirror (since he set up his own business) on same conditions?


Post Extras: Print Post   Remind Me!   Notify Moderator  
oldtimer
Pooh-Bah
*****

Reged: 11/13/08

Loc: Lake County Illinois
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Calypte]
      #4985460 - 12/26/11 12:25 PM

The 14" size miiror was one of the last they produced...maybe 1998???

Post Extras: Print Post   Remind Me!   Notify Moderator  
ScumotheUniverse
sage


Reged: 12/02/08

Loc: first dark primordial pool.
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Starman1]
      #4985496 - 12/26/11 12:59 PM

Quote:


In the ones that were optimized, though, I've generally seen that the star images are a little tighter and have a little less "fuzz" in the edges and/or diffraction rings in the Zambuto-mirrored scopes--obviously less light scatter.





Justifying Zambuto's decision not to use enhanced coatings. Apparently his rationale for using only standard coatings. Or at least that is what he used to say. Is he still recommending standard coatings only? I belong to the ZOC yahoo group, but have not kept up with the most recent posts.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: ScumotheUniverse]
      #4985947 - 12/26/11 06:57 PM

The point about secondaries is interesting. Discovery made their own secondaries (note that this was a "diagonal" in my day, and Terry still uses that terminology, as do I), but at one point they considered buying some from China, to cut costs. They rejected an entire shipment and went back to making their own, but another scope maker was using those same secondaries in production scopes.

Post Extras: Print Post   Remind Me!   Notify Moderator  
deepskydarrell
member


Reged: 03/09/08

Loc: Abbotsford, BC Canada
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: ScumotheUniverse]
      #4986429 - 12/27/11 02:15 AM


Justifying Zambuto's decision not to use enhanced coatings. Apparently his rationale for using only standard coatings. Or at least that is what he used to say. Is he still recommending standard coatings only? I belong to the ZOC yahoo group, but have not kept up with the most recent posts.




Carl Z told me: "We use a standard aluminum with one layer of silicon dioxide overcoat. Its a good coating. Provides 92% in the visible
and it preserves our contrast."

I believe one concern might possibly be that enhanced coatings don't last as long and are harder to remove for recoating, sometimes requiring refiguring (which defeats the whole purpose for the excellent figure) The single overcoating keeps the micro finish from getting too bulky / lumpy? and that would defeat contrast.

Darrell Abrahams.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: deepskydarrell]
      #4986842 - 12/27/11 12:00 PM

Quote:


Justifying Zambuto's decision not to use enhanced coatings. Apparently his rationale for using only standard coatings. Or at least that is what he used to say. Is he still recommending standard coatings only? I belong to the ZOC yahoo group, but have not kept up with the most recent posts.




Carl Z told me: "We use a standard aluminum with one layer of silicon dioxide overcoat. Its a good coating. Provides 92% in the visible
and it preserves our contrast."

I believe one concern might possibly be that enhanced coatings don't last as long and are harder to remove for recoating, sometimes requiring refiguring (which defeats the whole purpose for the excellent figure) The single overcoating keeps the micro finish from getting too bulky / lumpy? and that would defeat contrast.

Darrell Abrahams.




Carl may be right about the multi-layer aluminum "enhanced coatings" of the 1980s. But today's dielectric-layer enhanced coatings (usually 2 or more transparent layers added to the silicon dioxide) will not fail earlier than a standard coating.and are no more difficult to remove. The thickness of the coatings will still be in the small number of nanometer thickness area, so what it really boils down to is the quality of the coating, and most coaters who offer enhanced coatings are pretty good at it. The ones we've tested here were very good.

What is a matter for debate in the physics arena is the nature of how multiple dielectric layers handle off-axis light. There is the possibility of increased scatter and constructive/destructive interference with off axis rays.
I haven't seen lab reports that show spectral results or photometry of light scatter, so I think those "reports" are anecdotal and suspicious from the standpoint of the physics of reflective surfaces and likely to be related to a justification to keep costs down rather than a true examination of the results of the enhanced coatings.

From the standpoint of failure of the aluminum surface, enhanced coatings should be MORE durable than simple silicon monoxide (which becomes silicon dioxide) overcoating.

What is true, though, is that the slight difference in reflectivity for the enhanced coatings would be sub-visual (i.e.not noticeable), and might not be justifiable from the cost standpoint.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Starman1]
      #4987063 - 12/27/11 02:29 PM

Quote:

.... so what it really boils down to is the quality of the coating, and most coaters who offer enhanced coatings are pretty good at it. The ones we've tested here were very good.





Are there coaters in the Pacific northwest that offer (and are good at) enhanced coatings?

Shipping mirrors isn't cheap and has to be reflected in the mirror price.

And if you haven't noticed shipping costs have gone up dramatically in the last year or so.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: Jeff Morgan]
      #4987103 - 12/27/11 03:05 PM

Here are some links. There are information articles about coatings as well as coaters:
http://www.alcoat.net/
http://www.majestic-coatings.com/reflective-coatings.html#ProtectedAluminum
http://c-optical.com/
http://www.clausing.com/
http://www.dentonvacuum.com/
http://www.evaporatedcoatings.com/
http://www.flabegusa.com/front_surface_mirrors.html
http://www.galaxyoptics.com/reflectivecoatingservices.html
http://www.llopt.com/mc.html
http://www.majestic-coatings.com/
http://articles.adsabs.harvard.edu/full/seri/PASP./0109//0000303.000.html
http://www.newportlab.com/
http://www.nova-optical.com/Coating.htm
http://www.opticalmechanics.com/technical_articles/Demystifying%20Mirror%20Coating.pdf
http://www.opticalmechanics.com/technical_articles/coating_primer.html
http://www.opticwavelabs.com/
http://www.emf-corp.com/
http://www.astronomy.net/astroguide/ag373.html
http://www.quantumcoating.com/
http://www.glasscoater.com/id2.html
http://www.reynardcorp.com/thin_film_coatings.php
http://www.sciencedirect.com/science/article/pii/S0168900204001627
http://www.opticalsputtering.com/Characterization%20of%20silver%20and%20aluminum%20coatings.pdf
http://www.gemini.edu/documentation/webdocs/rpt/rpt-te-g0073.pdf
http://www.page.sannet.ne.jp/mazmoto/emsultima.htm
http://www.page.sannet.ne.jp/mazmoto/silvertest.htm
http://www.spectrum-coatings.com/Telescope-Mirror-Prices.htm
http://www.youtube.com/watch?v=_ToAkH7u3lY
http://www.thinfilmsinc.com/thin-film-services.php#Evaporated
http://www.vaculayer.com/?gclid=COm3oYaa3pwCFSNQagodOUoxKg
http://zcrcoatings.com/?gclid=CPGnobf_waICFRekiQod6y3_QQ


Post Extras: Print Post   Remind Me!   Notify Moderator  
RAKing
Postmaster
*****

Reged: 12/28/07

Loc: West of the D.C. Nebula
Re: Discovery vs. Zambuto Optical Shoot-out new [Re: ScumotheUniverse]
      #4987293 - 12/27/11 05:35 PM

Quote:

Justifying Zambuto's decision not to use enhanced coatings. Apparently his rationale for using only standard coatings. Or at least that is what he used to say. Is he still recommending standard coatings only? I belong to the ZOC yahoo group, but have not kept up with the most recent posts.




Carl Zambuto is not the only mirror maker who uses standard coatings.

I had a long discussion about this with another one of the top quality mirror makers. He told he that he would use enhanced coatings if the cutomer demanded it, but he considered it a "matter of pride as an optician" that he could create a mirror good enough that you wouldn't need any enhancements. He asked me to test his mirror with the standard coatings and if I didn't think it was good enough, he would fix it.

I haven't talked to Carl about this, but I suspect his philosophy is similar. My last two mirrors have come from Zambuto with standard coatings. The view through the eyepiece speaks for itself.

Cheers,

Ron


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | (show all)


Extra information
5 registered and 6 anonymous users are browsing this forum.

Moderator:  droid 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 6581

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics