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For users of the new ZWO ADC: Important!

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#1 John Boudreau

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Posted 25 January 2016 - 09:43 AM

A few days ago it came to my attention that Darryl's (Kokatha man) ADC is built with the wedge prisms mounted in a reversed manner to those in the ZWO ADC I was given to test back in early November. Thinking that it could possibly be my ADC that was the outlier as mine was a test unit, I asked a couple of others to check theirs--- Sean Walker's is like Darryl's, while Paul Maxon's is built like mine. So there are examples of both out there.

 

Either way of building the ADC is 100% correct--- both work equally well. But between them, the initial setup in a given scope is different: In several previous posts I've made describing how to use the ZWO ADC, I described that with an inverting scope that the prism levers and white nylon scale ring screw (a.k.a. datum screw) needed to be on the left side--- initially thinking that all were made like mine. However with the prisms mounted as in Darryl's, the prism levers and datum screw need to be mounted to the right in an inverting scope. The best way to describe this is that some are built left-handed, and others are right-hand ADCs. They simply have different dispersion correction polarity which is fixed by mounting the right-hand ADC to the scope with their bodies rotated 180° vs. the left-hand ones.

 

In notifying Sam Wen of ZWO about this, he thinks this occurred because of multiple staff members assembling the units. While they are working to standardize the assembly procedure from now on--- and I'm not sure which way will be the standard--- it's always possible that some opposite polarity ADCs will be produced. For background, I also own a Pierro-Astro which is right-handed, and have tested an ASH ADC which is left-handed. I do not know if the direction of those other brands is standardized though, and it's always possible that there are examples of both with those models too.

 

Attached is a ZWO ADC polarity test image that you can test your ADC's correction polarity with. The answer will determine if your levers should be pointed to the left or right when used in an inverting telescope--- please click on the thumbnail for the full size image.

 

In the center you'll see a large white disk with a small black center with subtle color fringes simulating spectral dispersion. To either side of the image there are also grey silhouettes of left-hand and right-hand ADCs shown with their levers spread apart and with the ring scale datum screw between them representing a proper horizontal reference.
Holding your ZWO ADC at arm's length from your monitor and while looking through the ADC with one eye, view the dispersed central disk and spread the levers to try to cancel out the color fringing. You should find that you'll correct the color fringes only with your ADC levers to one side and not the other, roughly matching either of the silhouettes.

 

So now you should know if your ADC is left or right-handed in a inverting scope. But what about use with a diagonal, which corrects the image vertically? First of all, using a diagonal complicates things so I don't recommend it. But if you have to, you'll find that an ADC with left-hand prism levers will need to be used with the levers to the right when used after a diagonal (the eye/camera end). The reverse is true with a right-hand ADC.

 

Comments and questions certainly welcomed.

Attached Thumbnails

  • ADC polarity test.jpg

Edited by John Boudreau, 26 January 2016 - 04:03 AM.

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#2 happylimpet

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Posted 25 January 2016 - 10:14 AM

Thanks John. Mine is a 'leftie'.


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#3 Sunspot

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Posted 25 January 2016 - 10:28 AM

I just re-double checked and like me, mine for sure is a lefty.


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#4 HowardK

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Posted 25 January 2016 - 11:27 AM

Very kind of you John to help us all like this.

 

my ADC is not here yet but I will be using your test as soon as I get it.


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#5 RAC

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Posted 25 January 2016 - 01:15 PM

Haha what if mine needs to be pointing down?


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#6 astrovienna

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Posted 25 January 2016 - 01:51 PM

Thanks John.  Mine is a rightie.  Ordered Dec 22.


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#7 Sunspot

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Posted 25 January 2016 - 01:57 PM

Haha what if mine needs to be pointing down?

In New Zealand is pointing down really pointing up? :lol:


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#8 mak5

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Posted 25 January 2016 - 02:48 PM

I don't own a ZWO ADC, but my Pierro Astro ADC needs to have the levers on the left side when used on my cassegrain, unlike the ASH ADC I had before which needed to have the levers on the right.
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#9 John Boudreau

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Posted 25 January 2016 - 03:32 PM

Haha what if mine needs to be pointing down?

 
Then we'd have left-handed, right-handed, and with yours, now underhanded! ;) 

 

:foreheadslap: 



#10 John Boudreau

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Posted 25 January 2016 - 04:01 PM

I don't own a ZWO ADC, but my Pierro Astro ADC needs to have the levers on the left side when used on my cassegrain, unlike the ASH ADC I had before which needed to have the levers on the right.

 

So now we have examples of other brands varying their prism setup, as my Pierro-Astro is right-hand. Thanks! :waytogo:

 

I know this issue doesn't effect performance, it's just that for some time now I've been giving advice both on CN and in private on use of the ZWO and wanted to correct some erroneous information that I had given.

 

I'm sure the guys at ZWO will be happy to know they are not the only ones who have stacked the prisms two different ways!



#11 Sunspot

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Posted 25 January 2016 - 05:03 PM

 

Haha what if mine needs to be pointing down?

 
Then we'd have left-handed, right-handed, and with yours, now underhanded! ;) 

 

:foreheadslap: 

 

down underhanded.... (couldn't resist...)


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#12 RAC

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Posted 25 January 2016 - 06:21 PM

You guys a just jealous haha.
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#13 Sunspot

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Posted 25 January 2016 - 06:33 PM

You guys a just jealous haha.

Does it show? :lol:


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#14 baron555

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Posted 25 January 2016 - 07:46 PM

I don't see any subtle color dispersions.

 

OK, I see them but with my bifocals, I have to tilt my head up and down to get them to appear.

 

I say mine is a righty.


Edited by baron555, 25 January 2016 - 08:03 PM.

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#15 DesertRat

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Posted 25 January 2016 - 10:31 PM

Thanks John for the additional info.

 

Some of the confusion about left vs right handed may also be due to the fact that some these units can be used front to back or back to front.  These devices have T2 connections on both ends.   When this is done the left handed or right handed property is reversed.  It will still work either way.

 

In general if increasing the correction makes dispersion worse, then it needs to be rotated 180 degrees.

 

Bifocals may make it difficult to assess correction in a monitor test.  Also blue does not show well on some monitors.  Here is an additional graphic one can employ.  It is simply a circle 1 pixel in breadth with green offset 1 pixel upwards from red, no blue layer.  IIRC increasing correction moves the image downwards when in the proper orientation.   If not rotate unit 180 degrees.  Depending on the image orientation this rotation may also be required depending on the scope and the image projection used.

 

ADC_test_image.png

 

It may help some to display this image full-screen.  Also some LCD monitors may bias the image slightly.

 

Glenn


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#16 Guest_djhanson_*

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Posted 25 January 2016 - 10:56 PM

I don't own a ZWO ADC, but my Pierro Astro ADC needs to have the levers on the left side when used on my cassegrain, unlike the ASH ADC I had before which needed to have the levers on the right.

My Pierro Astro ADC is the same - levers on the left side for both John and Glenn's test images.  I also have been imaging this way.  DJ


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#17 RAC

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Posted 26 January 2016 - 01:33 AM

Thanks John for the additional info.

 

Some of the confusion about left vs right handed may also be due to the fact that some these units can be used front to back or back to front.  These devices have T2 connections on both ends.   When this is done the left handed or right handed property is reversed.  It will still work either way.

 

In general if increasing the correction makes dispersion worse, then it needs to be rotated 180 degrees.

 

Bifocals may make it difficult to assess correction in a monitor test.  Also blue does not show well on some monitors.  Here is an additional graphic one can employ.  It is simply a circle 1 pixel in breadth with green offset 1 pixel upwards from red, no blue layer.  IIRC increasing correction moves the image downwards when in the proper orientation.   If not rotate unit 180 degrees.  Depending on the image orientation this rotation may also be required depending on the scope and the image projection used.

 

attachicon.gifADC_test_image.png

 

It may help some to display this image full-screen.  Also some LCD monitors may bias the image slightly.

 

Glenn

 

 

That test still proves that mine needs to point down lol.


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#18 John Boudreau

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Posted 26 January 2016 - 02:55 AM

 

Some of the confusion about left vs right handed may also be due to the fact that some these units can be used front to back or back to front.  These devices have T2 connections on both ends.   When this is done the left handed or right handed property is reversed.  It will still work either way.

 

 

Hi Glenn,

Your circle works nicely too, and may well be easier to see for some people/monitor situations.

 

I've mentioned in the past that both the latest ASH ADC (There was a 2nd redesign early last year) and the Pierro-Astro could be used completely reversed or flipped 180°--- IIR, Steve (Yock1960) had to reverse his ASH because of a gender situation with an adapter he already owned. The ASH and P-Astro have different gender T2 threads at each end, and when used with their optional adapters there is an intended direction.

The ZWO can be used reversed also, but then the rotating scale would be facing the scope so it's situation is a bit different. The T2 thread is female at each end.


Edited by John Boudreau, 27 January 2016 - 08:48 AM.


#19 HowardK

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Posted 03 February 2016 - 01:28 PM

Just received mine

 

it's a righty

 

thanks John for the neat tests


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#20 mikey cee

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Posted 03 February 2016 - 03:20 PM

If and when I ever get one I'm sure it will be ambidextrous! That's the kind of luck I've had my entire life. :smirk:   Mike


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#21 Billytk

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Posted 04 February 2016 - 06:42 PM

So mine's a righty. So when I use it in my Orion XT12G Dobsonian, does the datum screw go to the right or left side of the horizon as seen through my focuser?



#22 TonyStar

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Posted 05 February 2016 - 03:56 PM

If it's a righty the reference screw goes to the right by definition..



#23 AstroEthan

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Posted 05 February 2016 - 10:45 PM

Mine appears to work with the screw pointing to the right.

 

As someone who likes to see info-graphics and statistics, I thought it would be interesting to put the variants that have been posted here into a pie graph, so I put them in an Excel spreadsheet:

 

http://1drv.ms/23ORswX

 

Hopefully I got everything right. I had to infer some things from the first post.



#24 RAC

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Posted 05 February 2016 - 11:49 PM

Well with a little more playing around with my ADC it seems mine must be put together a little different to all the others.

 

Using the test pics in this thread mine needs pointing down as I already found out but there's more unless I'm thinking this wrong and every ones is like this?

 

This is the 100% neutral setting with no change to the test image no matter where you turn the adc around.

IMG_5182.JPG

 

 

The prisms are stuck in with silicon so it's not easy to change, if I swap the prisms top to bottom I just make it an uppy and not a downy. I don't really mind the way it is it's just a little different?

 

 



#25 John Boudreau

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Posted 06 February 2016 - 01:35 AM

Well with a little more playing around with my ADC it seems mine must be put together a little different to all the others.

 

Using the test pics in this thread mine needs pointing down as I already found out but there's more unless I'm thinking this wrong and every ones is like this?

 

This is the 100% neutral setting with no change to the test image no matter where you turn the adc around.

IMG_5182.JPG

 

 

The prisms are stuck in with silicon so it's not easy to change, if I swap the prisms top to bottom I just make it an uppy and not a downy. I don't really mind the way it is it's just a little different?

 

Sorry I didn't address your issue earlier Raymond--- with either a "haha" or "lol" in each of your earlier posts in this thread I had thought you were joking. :scratchhead:

 

The levers are intended to be put together to get the ADC in the neutral/zero correction setting. That's apparently not happening with yours.

 

To the best of my knowledge the wedge prisms are supposed to be marked on their edges at the thick ends--- mine had a red mark on each of the prisms. These marks are supposed to be aligned with the prism levers--- one prism has it's red mark facing and aligned with the lever; the other prism has it's red mark 180° from it's lever. Depending upon which prism is stacked on top or the bottom of the ADC during assembly determines if if the ADC is LH or RH.

 

It sounds like either the marks are in the wrong place on the prisms or that the prisms weren't properly aligned to the levers during assembly.


Edited by John Boudreau, 06 February 2016 - 10:07 PM.



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