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The ZWOptical ADC

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#1 John Boudreau

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Posted 21 November 2015 - 09:11 PM

Here's a few views of the upcoming ZWO ADC. This is a pre-release unit sent to me for testing a few weeks ago. As far as I know, the only changes in the final versions will be white prism levers instead of the black ones shown here (better visibility against the black scale ring), and a different plastic screw on that rotating scale ring. The plastic screw on the rotating scale ring serves to secure the ring in position after being referenced (leveled) to the horizon, and it also would then serve as the 'zero correction' point on the scale ring--- when the levers are adjusted that screw should be located between them as closely as possible using the scale ring as a guide, as seen in the image with the dashed yellow line.

 

In testing, I found that this design was the best 'out of the box' ADC that I've used for imaging and visual observation. The levers are threaded into the prism cells, and O-rings are used between the base of the levers and the ADC's body--- this allows varying the drag, or 'feel' of the lever movement. The lever travel slots are quite long, allowing hours of use without having to loosen and rotate the ADC in the focuser. The prisms are made of BK7 glass, and a pleasant surprise was that their AR coatings allow most of the UV light passed by special UV Venus filters like those from Astrodon and Baader, making this one of the best ADCs for imaging Venus in the UV. 

 

So things are looking a bit better for imagers and visual observers despite some of the planets being low in altitude over the next several years. And for those in locations where the planets culminate high in the sky, you can increase your observation periods too as such a device greatly improves the view when the planets are low hours before or after culmination.

Attached Thumbnails

  • ZWO ADC 01.jpg
  • ZWO ADC 03.jpg

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#2 John Boudreau

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Posted 21 November 2015 - 09:13 PM

Here's a test of the ZWO ADC with Jupiter in good seeing (maybe Pickering 6) on the morning of November 18. Scope was my 14.5" f/18 D-K Cassegrain. Camera was a test unit of the cooled version of the ASI224MC. Jupiter had just attained 49° altitude, and is presented such that the line of dispersion occurs vertically. Processing in AutoStakkert, RegiStax 6, PhotoShop, and Maxim DL were as identical as possible. Unfortunately some trees currently block my view of the morning planets until they have gained some decent altitude but you can still see plenty of the distortions due to atmospheric dispersion.

 

The left image is actually with the ADC in place, but tuned to the 'zero' correction point so it was essentially OFF. The middle image is with the ADC properly corrected. The right image is an RGB channel realigned version at sub-pixel accuracy of the left image. I think even at 49°, the improvement of the ADC corrected image is easily apparent.

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  • ZWO_ADC_jupiter.jpg

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#3 John Boudreau

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Posted 21 November 2015 - 09:14 PM

Here is a test result of the ZWO ADC with Mars @ 44° altitude, taken shortly after the Jupiter sequences. Mars was only 4.5" in angular diameter at the time. Seeing was quickly deteriorating and so ADC adjustment was difficult. I didn't attain a perfect correction setting as on the middle ADC corrected image you can still see a thin red fringe on the bottom edge of Mars and a thicker blue fringe on the upper edge (blue being a shorter wavelength disperses more than red). However this test shows that even less than perfect correction is far better than no correction at all!

Attached Thumbnails

  • ZWO_ADC_mars.jpg

Edited by John Boudreau, 22 November 2015 - 09:32 AM.

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#4 John_K

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Posted 21 November 2015 - 09:48 PM

Great images John and another innovative product from ZWO!


Edited by John_K, 21 November 2015 - 09:48 PM.

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#5 PiotrM

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Posted 21 November 2015 - 10:02 PM

Great images John and another innovative product from ZWO!


They aren't first with an ADC. Price will be important. Current ADC start at around 300 EUR, and it's hard to do it any cheaper.
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#6 Guest_djhanson_*

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Posted 21 November 2015 - 10:57 PM

Great review John - shows the merits of using an ADC quite well!  Looks nice and if I didn't already have my Pierro Astro ADC I would consider it.  ZWO is thinking ahead here - many low planets for the next 10 yrs in the northern hemisphere (like a great ice age :D ).  cheers, DJ


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#7 Xeroid

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Posted 21 November 2015 - 11:10 PM

Ok, so I'm a nubie, what is an "ZWO ADC"? 


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#8 Dark Night

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Posted 21 November 2015 - 11:24 PM

ZWO is the company and ADC stands for atmospheric dispersion corrector... compensates for the extra atmosphere when viewing/imaging low on the horizon. 


Edited by Dark Night, 21 November 2015 - 11:25 PM.


#9 Kokatha man

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Posted 21 November 2015 - 11:25 PM

Comprehensive review John...& the ideal person to write up a "first light" appraisal also, excellent..! :waytogo:  :waytogo:  :waytogo:  :waytogo:  :waytogo:

 

Both middle images show a marked improvement over the others either side...I've bookmarked your thread on ADC operation & I reckon Sam must've taken close note of it also ;) - the variable drag O-rings for example. :)

 

Fwiw I'm sure the figure will be adjusted from early estimates but if it is even in the ballpark of the previous estimates it'll blow your comments re pricing out of the water Piotr! :grin:

 

It'll get plenty of work on Jove with us in a month or two despite the other planets being at neck-ricking elevations... :)


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#10 moxican

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Posted 21 November 2015 - 11:42 PM

This is an amazing review. ZWO was testing ADC for a while now I am glad that it seems to come to an end. I can't wait to see it on their website. I'll put the order down immediately. Thanks for the review and heads up.


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#11 Foehammer

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Posted 22 November 2015 - 02:05 AM

I have been waiting for the release of the ZWO ADC since July when Sam also disclosed the approximate price in our correspondence. All I have to say is, it will do to the ADC market exactly what the ASI series cameras did to the planetary camera market!
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#12 DesertRat

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Posted 22 November 2015 - 02:17 AM

Very well done John, excellent review.  Sam did good to get you to test this ADC! :waytogo: :waytogo:

 

Glenn


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#13 Xeroid

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Posted 22 November 2015 - 09:36 AM

Dark Night

 

Thank you for that explanation!



#14 PiotrM

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Posted 22 November 2015 - 10:24 AM

Fwiw I'm sure the figure will be adjusted from early estimates but if it is even in the ballpark of the previous estimates it'll blow your comments re pricing out of the water Piotr! :grin:


Would be good, as most of the price of an ADC are two very high quality prisms. They would have to get them or make them on below normal prices which is hard to do on optics.

#15 sfugardi

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Posted 22 November 2015 - 12:41 PM

John, thanks for posting your ADC experience here. The ADC improved results are clear. This will be my next purchase assuming the price is reasonable.

 

I have few questions if you don't mind. How often do you have to tweak the levers as the planet changes altitude? I see you are using your chroma L filter instead of the ZWO IR cut filter. I am thinking of putting my Astronomik Type2 L filter back in my wheel, do you think it matters? Finally, I see that you are also testing the new cooled 224 and was wondering if you found any noise advantage at the fast frame rates? Sam was smart to pick you to test his new equipment. Thanks again for sharing your expertise here

 

Regards,

Steve


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#16 PiotrM

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Posted 22 November 2015 - 02:15 PM

ADC doesn't need many adjustments during imaging - depends how fast the planet is rising. During 2-3 hours of Jupiter imaging I corrected the ADC around once after initial setup. I also used L (IR/UV cut) and yellow longpass filters with ADC and they work very very well. Yellow is the brightest for Saturn (cuts blue, adds IR).
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#17 MvZ

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Posted 22 November 2015 - 04:21 PM

Nice review John!

 

I have had the chance to play around with an earlier version of the ZWO ADC for quite some time now, and am already quite pleased with that one (read: I use it all the time for planetary imaging since I got it). I never used any other ADC before, so I didn't know how to compare it, but the build quality of this one seems to be better than what I tested, and I already had no complaints about that one to be honest.I had the same impression about the high transmission for UV imaging, but I only tried it once , and with a W47/BG39 combo, so I didn't know how well it really performed in UV. 

 

Do you know how low the ADC can go (at what altitude it can still correct for the dispersion?). I think mine could go to about 15 degrees or so...


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#18 John Boudreau

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Posted 22 November 2015 - 09:49 PM

Thanks guys! I'm glad this product is finally so close to release.

 

For those who haven't used an ADC yet, I think you may find them a bit awkward at first, but I think that the learning curve is very quick as you see how they work first hand. Scopes of 8" and up have enough resolution in good seeing to make the improvement obvious both visually and for imaging. I can't imagine imaging or observing now without one unless the target is over 60° high.

 

Steve, I agree with Piotr that one doesn't have to constantly adjust the device. 90% correction is difficult to distinguish vs. 100%, and in time you'll get a feeling on how often you want to adjust the prism levers. Within an hour or so of a target's culmination, time between adjustment can be over an hour or more without a problem. When a planet is on the rise or going down the period will be less. Larger apertures, and better seeing will mean atmospheric dispersion effects are easier to detect, so one may want to tweak the settings more often in those conditions. With deep red and near-IR imaging, since those longer wavelengths are distorted the least, you can go much longer between adjustments. The latest Firecapture 2.5 beta has an ADC tuning toolbar action for color cameras that appears to do a nice job in the limited time I've had using it--- time will tell how accurate it is, but it's a nice added feature to an already awesome program!

 About the filter--- I'm using the Chroma L as it acts as an effective UV/IR-blocker, and has a somewhat deeper UV cut-off that any other L-type filter I know of. I'm thinking that the more B light in my 2016 Mars images with a OSC cam the better. But other fine UV/IR blocking filters include the Astronomik, Baader and certainly the ZWO versions. Since the ASI224MC (w/wo cooling) has such good near-IR performance the built-in filter in this model is a wider ranging clear filter without the typical UV/IR cutoff points.
 As for the cooling--- With our current temperatures here in New England there is certainly no advantage over a regular ASI224MC for planetary imaging (It was 22°F/-5.5°C at the time of the Jupiter captures). There well may be in longer exposures for Uranus and Neptune during Summer or for heat build-up during prolonged, very high fps rates. I haven't tested truly high fps yet, but I have a new laptop on order that should allow me to find out! I also plan some deep sky imaging with it soon, which is the main reason I have interest in the cooled version.

 

Emil, according to Sam the prisms have high transmission down to about 340nm where the drop-off is fairly quick. While that would still cut off part of the shorter wavelength end of a typical Venus UV filter bandpass or the W47/BG39 combo, the CWL zone and all of the longer wavelength part of the bandpass will be essentially unhindered. I've tested both the BK7-equipped Aries and ASH ADCs before with the Astrodon UVenus filter, and while they were usable in the UV, they didn't come close to the performance of the ZWO ADC. The UV friendly Pierro-Astro with fused silica prisms is still the best in that regard though, but the ZWO is a surprisingly strong UV performer!
 As far as how low in altitude it can correct, it should do as well as the ASH ADC I had tested earlier this year as they both are using 2° beam steering prisms. ADCs create more corrective dispersion with projection distance to the eyepiece or sensor, which of course would include the filter wheel light path, so if it appears to fall short in correction in a particular application you just need to add a T-thread extension. Without my filterwheel in place when I was using the cooled ASI224MC, I found I had to use my 25mm extension to easily get down to 20° when checking out Jupiter through the trees. It may have needed less extension that that, but I didn't really check that out. Fortunately there are plenty of sources for T-thread extensions of various lengths and other such adapters.


Edited by John Boudreau, 23 November 2015 - 08:43 AM.

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#19 happylimpet

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Posted 23 November 2015 - 04:34 AM

Looks tremendous. Would I be right that the guts of the thing (for putting into an existing T-threaded optical train) as seen in the middle of the middle pic has a length of around 30-35mm, and has T threads?

 

Starting to make plans!


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#20 PiotrM

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Posted 23 November 2015 - 05:45 AM

Would I be right that the guts of the thing (for putting into an existing T-threaded optical train) as seen in the middle of the middle pic has a length of around 30-35mm, and has T threads?


You can, but the ADC must be oriented against horizon, so some T2 locking rings could be needed.

#21 John Boudreau

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Posted 23 November 2015 - 08:13 AM

Looks tremendous. Would I be right that the guts of the thing (for putting into an existing T-threaded optical train) as seen in the middle of the middle pic has a length of around 30-35mm, and has T threads?

 

Starting to make plans!

 

The ADC body is 29mm long, and has female T-threads at both ends. As Piotr mentioned, T-thread locking rings could be required, but shimming to taste is also a possibility (Baader makes Delrin spacer rings of various thickness).

http://agenaastro.co...r-ring-set.html

 

The ZWO unit has overlapping lever slots (~60° overlap) similar to the Pierro-Astro. This helps to make initial orientation of the ADC body in the imaging train less critical than some other ADCs, as it allows plenty of travel to set the levers with reference to the horizon. This is one reason why the adjustment scale is a rotating ring--- you rotate the ring so it's locking screw is horizontal, then the levers can be adjusted referenced to that locking screw.


Edited by John Boudreau, 23 November 2015 - 08:18 AM.

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#22 Quaternion

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Posted 23 November 2015 - 01:01 PM

Thanks for the great pics and info on the ZWO ADC, but as fate would have it, I just sprang for the Pierro Astro unit !  :(

 

Oh well, I guess even if I spent a bit more, maybe I'm at least supporting the French who need a bit of support right now :waytogo: . 

 

Do you think the Pierro Astro unit is on par with the ZWO unit?


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#23 Fossil Light

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Posted 23 November 2015 - 02:34 PM

Hi John,

Great review.

 

I tested a prototype ZWO unit a few months back and found the optical quality to be very good. From the pictures you supplied it looks like ZWO have made a number of really nice mechanical design changes to improve usability.

 

On Venus I got a pretty good transmission too with a Baader UV filter and this ADC. I have the PA ADC with quartz prisms and the ZW0 unit was not far behind- maybe 80% of the PA version's transmission. Pretty good for BK7 prisms.

 

For those who want to know more about ADCs and how to use them have a look at my webpage which should have a load more diagrams added by the end of the week (newly formatted website just about to go live);  http://www.skyinspec...DC(2587060).htm

 

Cheers

Martin


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#24 TonyStar

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Posted 23 November 2015 - 04:26 PM

 

Fwiw I'm sure the figure will be adjusted from early estimates but if it is even in the ballpark of the previous estimates it'll blow your comments re pricing out of the water Piotr! :grin:


Would be good, as most of the price of an ADC are two very high quality prisms. They would have to get them or make them on below normal prices which is hard to do on optics.

 

a coupe of BK7 prisms for ADC application is not not very expensive, <100$ 



#25 John Boudreau

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Posted 23 November 2015 - 05:11 PM

Thanks for the great pics and info on the ZWO ADC, but as fate would have it, I just sprang for the Pierro Astro unit !  :(

 

Oh well, I guess even if I spent a bit more, maybe I'm at least supporting the French who need a bit of support right now :waytogo: . 

 

Do you think the Pierro Astro unit is on par with the ZWO unit?

 

The Pierro-Astro is a fine ADC, I own one and am very happy with it although I've added a couple of tricks to it. It's fused quartz prisms with UV friendly AR coatings still give the Pierro-Astro an advantage in UV imaging of Venus, although The ZWO still does quite well there too. The P-Astro also has the elongated and overlapped lever slots which are a nice touch. But I think the knurled finish of the unit's body causes the lever adjustment feel to be quite rough unless you use them set very loose. Here's what I did to mine:
http://www.cloudynig...turn/?p=6749439

 

You'll notice that the ZWO also sports the O-ring drag trick for it's levers. Shortly after that photo of my Pierro-Astro ADC was taken I also made a rotating scale ring for it that works very well.  Besides what is expected to be a noticeably lower price, the ZWO comes with what I consider these user-friendly features "out of the box" along with it's male and female 1.25" T-Threaded adapters.




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