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Experiences with erect image 'Amici' prisms ?

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#1 skysurfer

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Posted 30 April 2016 - 06:48 AM

Since a few years I have a Baader Amici prism.

http://www.teleskop-...-Anschluss.html

I use it beside a 'normal' William Optics Dielectric mirror diagonal.
For lower magnifications the Amici works perfectly on deep sky on my 80mm and 110mm refractors as no mirror image is rendered. I don't like mirror images as comparing to a star chart is tedious, unless I flip the chart app (Skysafari allows this). But even in the latter case, when looking up on the chart how it looks like with the naked eye I have to flip again.
When using at high power however, contrast decreases (which I expect) and a bright stripe through a bright object (e.g. Jupiter), but in that case I don't care about mirrored image so I use the WO.

But even the 80mm achro equipped with the Amici and a 4mm (130x) shows a crisp image of Jupiter (when seeing allows) including GRS, lunar shadow dots (when available) and festoons, all despite slight CA in a purplish halo.

Obviously, when the WO is used the image is slightly crisper.

But why are there no phase correctional coated Amici prisms available ? The white stripes and the loss of contrast is a result of phase difference of the reflected image. With roof prims binos this is rather standard, but not with Amici prisms,

Source : https://en.wikipedia...wiki/Roof_prism

Are there others using an Amici prism with refractors os SCTs ?

#2 junomike

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Posted 30 April 2016 - 06:59 AM

I had a 2"" Olivon Amici Prism and loved It for correct-Image Lunar viewing.  I only noticed the dreaded "Roof-Line" on very bright Stars (Vega, Sirius, etc).

I mainly used it with my larger SCT's.

 

 

Mike



#3 edwincjones

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Posted 30 April 2016 - 08:05 AM

I use the Baader Amici prism on my
Tak Sky90 with Leica  22-7mm zoom
for a grab and go scope;
and to compliment large binocular viewing.
 
I am happy with the setup,
no problems
 
edj

Edited by edwincjones, 30 April 2016 - 08:09 AM.


#4 Jon Isaacs

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Posted 30 April 2016 - 10:04 AM

 

But why are there no phase correctional coated Amici prisms available ? The white stripes and the loss of contrast is a result of phase difference of the reflected image. With roof prims binos this is rather standard, but not with Amici prisms,

 

 

I think if you were to use the roof prism binoculars at high magnifications you would see the line, It has to do with the discontinuous optical surfaces..  

 

I use star diagonals for birding and star gazing, the reversed image is not a problem.  Few RACI diagonals have sufficient clear aperture to support the good eyepieces with large field stops... And you have a Newtonian, that's where the good planetary and lunars views are and that image is reversed and inverted..

 

Jon


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#5 Jeff Morgan

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Posted 30 April 2016 - 10:18 AM

I used to have a 2" WO Amici. It's primary use was in 80mm f/6 scopes (both achro and apo) for star hopping. The eyepiece was a 27 Panoptic, making the refractor both a finder and aux scope.

 

The roof line really only was bothersome on bright stars. And star hopping was a breeze. At the time, it was awesome.

 

However, planetarium software such as SkySafari can reverse/invert the displays to match whatever your telescope or finder scope can show you, thus rendering paper atlases all but obsolete. Uranometria is nice for an occasional look on the coffee table and looks fabulous on my bookshelf, but field use? Forget about it.

 

And the falling prices and widespread availability of DSC's and GOTO systems are just about the final nail in the coffin of the traditional finder scope. It's just wasted mass on your scope that has to be balanced out.

 

In light of this, I can see why no manufacturer would want to make such a specialized prism.

 

The Amici found it's use primarily in military optics. Short of another major land war, they will probably be scare on the amateur market.



#6 skysurfer

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Posted 30 April 2016 - 12:11 PM

And you have a Newtonian, that's where the good planetary and lunars views are and that image is reversed and inverted..

Which cancels out the mirror image. Upside down is not an issue, just rotate the tablet / smartphone / paper atlas one is using. I do that when using my Dobson.

However, planetarium software such as SkySafari can reverse/invert the displays to match whatever your telescope or finder scope can show you, thus rendering paper atlases all but obsolete. Uranometria is nice for an occasional look on the coffee table and looks fabulous on my bookshelf, but field use? Forget about it.

And the falling prices and widespread availability of DSC's and GOTO systems are just about the final nail in the coffin of the traditional finder scope. It's just wasted mass on your scope that has to be balanced out.

Indeed, I use Skysafari as well and like you I don't use paper atlases anymore. But as I said, when I 'zoom out' (i.e. look on the chart whether an object is located properly, not too low and not behind trees) I have to flip SS again.
So for deep sky viewing with a refractor the Amici is excellent. When I use my Dobson, this is not an issue as a Dobson does not render a mirror image.

And I don't have Goto as that consumes lots of power. I do use push to by using a chartin app like Skysafari and setting circles.

#7 Redbetter

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Posted 30 April 2016 - 01:33 PM

Like Jon, I'm using an amici (no name) for a RACI finder diagonal.  The problem with them (other than the roof line down the middle) is the lack of clear aperture, 20-21 mm being typical because the bodies are the same size as standard 1.25" star diagonals.   

 

The Baader gets around this by using a larger body to provide 31mm of clear aperture.  This would likely make it a nice fit for an 80mm refractor finder, other than being heavier/bulkier for the purpose and costing considerably more than the ST-80 I have mounted at the moment.  The cheap amici I have starts to break down at high power, so I swap out with a standard diagonal if I want to use it that way.  With the Baader I don't think that would be a problem.




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