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Amici Prism OK for High Mag?

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#1 coopman

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Posted 19 March 2020 - 04:56 PM

I'm looking at this one (for budgetary reasons):
https://agenaastro.c...al-2956152.html
and the description indicates that it is good for high magnification planetary viewing. I have always heard that these amici diagonals were not very good for astronomy purposes. I would love to be proven wrong and be able to star hop and view with correctly oriented views. Can anyone provide some user input on this particular diagonal...or the acceptability of amici prisms for astro purposes? Thanks for your comments.

#2 Bomber Bob

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Posted 19 March 2020 - 05:04 PM

My understanding is there's a bit more light loss with the Amici vs. traditional 90* prism diagonal -- and aren't are a good idea for fracs smaller than 4" aperture.  I haven't used this particular prism, but I have seen the slight dimming with that Unitron 142 (3" F15) that I owned for a while comparing a rare high-quality spectros 35mm barrel Amici with an excellent Baader 1.25" prism.


Edited by Bomber Bob, 19 March 2020 - 05:05 PM.

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#3 junomike

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Posted 19 March 2020 - 05:09 PM

IME I loved it for the Moon (correct Image) and the  one I had (Olivon) didn't seem to exhibit the dreaded "Amici line" some commonly associated with them.

 

Not sure about Baaders claim to high power but this Amici looks similar and is $100 cheaper.

 

EDIT:  Looks like the Olivon linked above is no longer available.


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#4 Jon Isaacs

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Posted 19 March 2020 - 05:28 PM

"Full 38mm clear aperture"  Full aperture for a 2" is at least 46mm.

 

When you look at the split light path of an Amici prism, the light travels in two separate paths, you see why there might be some image degradation. 

 

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

 

Good quality binoculars with Amici/roof prisms have phase coatings because there is a phase shift between the two sides which affects the contrast when the two light paths are joined put back together.  It can never be made perfect but it can be improved substantially. 

 

"The multiple internal reflections cause a polarization-dependent phase-lag of the transmitted light, in a manner similar to a Fresnel rhomb. This must be suppressed by multilayer phase-correction coatings applied to one of the roof surfaces to avoid unwanted interference effects and a loss of contrast in the image."

 

I see no mention of phase coatings in the Baader prism page so I assume the prism is not phase coated.  

 

Regardless of what they say, I wouldn't spend that kind of money on a Correct Image diagonal if I wanted to use it for viewing the planets and splitting double stars. 

 

Jon


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#5 Shorty Barlow

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Posted 19 March 2020 - 05:45 PM

It's pretty good up to 100x.

 

med_gallery_249298_5348_86680.jpg

 

I have the 2" Baader Zeiss as well. The APM and the Baader Zeiss are good higher than 100x. There's a lot of bollocks written about Amici prisms. Things have changed now we are in the 21st century. I use Amicis a lot. 

 

gallery_249298_5348_100387.jpg

 

 

Don't believe the bollocks.

 

med_gallery_249298_5348_49982.jpg


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#6 jjack's

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Posted 19 March 2020 - 06:08 PM

I never saw the airy pattern looking into amici prisms. So they can't be high definition diagonals.

I use a 2"baader one on the moon and landscape but at low to medium power.



#7 Jon Isaacs

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Posted 19 March 2020 - 06:17 PM

 

I have the 2" Baader Zeiss as well. The APM and the Baader Zeiss are good higher than 100x. There's a lot of bollocks written about Amici prisms. Things have changed now we are in the 21st century. I use Amicis a lot.

 

Phase coatings have been standard on decent quality root prism binos since the 1990s. That's really the big change in the technology. 

 

I use 300x and more with star diagonals. I'd hope for that with any diagonal.

 

Jon



#8 jeffreym

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Posted 19 March 2020 - 06:49 PM

I think the a correct image diagonal is just another tool.  If it improves your experience, use it.  I have a $250 mirror and Baader's top of the line amici.  I like them both.  I like amici diagonals on the moon and star hopping, life is easier.  I never noticed any issues with magnifications above 300x with either of them.  I also rarely have a sky that would support those magnifications so that critical comparison does not happen frequently.  On dim objects, you might go to the mirror in hopes of seeing just a little deeper. 

Have fun,

Jeff


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#9 BillP

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Posted 19 March 2020 - 08:12 PM

I am in the middle of a write up on the more expensive Baader 2"/90° Astro Amici-Prism with BBHS ® coating.

https://agenaastro.c...al-2456120.html

 

Yes, very slightly less throughput, but minimal and only noticeable on fainter DSO like M1 in a 4" showing it with just very slightly less extent.  Of course, due to the split prism there is a horizontal diffraction spike on very bright objects, like Rigel as example.  But on other bright stars like the Belt stars of Orion no spike.  Image quality was fantastic in this unit and took it to 326x in my TSA-102 and 480x and 600x in my 152 Apo and view just as sharp as using my 2" Zeiss prism.  So it really performed like a champ!  Impressive.  Heavier than even the Zeiss 2" Prism.  Made observing so much nicer though with everything in correct orientation.  Slewing around was way more intuitive.  Made observing the Moon much nicer too as up was up and left was left so easy navigating around to features.  Ran it with Binoviewer and on Solar and worked just as good as my Zeiss 2" prism in those configurations as well.  Also turned my 80mm Apo into a really fun spotter with everything in correct orientation.  Never liked that scope it in that role before but with this was fabulous - and with the 40XW the terrestrial views were simply jaw dropping!  Recommend you talk to Bob at Alpine Astro to find out exact technical differences between the unit the OP linked and the more expensive one I tested.


Edited by BillP, 19 March 2020 - 08:19 PM.

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#10 Shorty Barlow

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Posted 20 March 2020 - 05:02 AM

The Baader Zeiss Amici is heavy. I weighed my 2" Amici prisms and it is 50 grammes heavier than the APM Amici and a whole 195 grammes heavier than the less expensive Baader Amici. I can't vouch for the accuracy of my scales but the weight difference between the two Baader Amici prisms is substantial. 

 

Comparative weights

 

Baader Zeiss Amici: 650g

 

APM Amici: 600g

 

Baader Standard Amici: 455g

 

med_gallery_249298_5348_100990.jpg

 

It's difficult to determine who actually manufactures the less expensive 2" Baader. There seem to be identical units with other brand names. It's possible they all originate from the same OEM.

 

med_gallery_249298_5348_11249.jpg

 

I used mine regularly with an ST80 and an Evostar 72ED DS Pro predominantly for rich field observing. However, it would perform well on the Moon and other objects at 130x and over.


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#11 25585

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Posted 20 March 2020 - 08:35 AM

I am in the middle of a write up on the more expensive Baader 2"/90° Astro Amici-Prism with BBHS ® coating.

https://agenaastro.c...al-2456120.html

 

Yes, very slightly less throughput, but minimal and only noticeable on fainter DSO like M1 in a 4" showing it with just very slightly less extent.  Of course, due to the split prism there is a horizontal diffraction spike on very bright objects, like Rigel as example.  But on other bright stars like the Belt stars of Orion no spike.  Image quality was fantastic in this unit and took it to 326x in my TSA-102 and 480x and 600x in my 152 Apo and view just as sharp as using my 2" Zeiss prism.  So it really performed like a champ!  Impressive.  Heavier than even the Zeiss 2" Prism.  Made observing so much nicer though with everything in correct orientation.  Slewing around was way more intuitive.  Made observing the Moon much nicer too as up was up and left was left so easy navigating around to features.  Ran it with Binoviewer and on Solar and worked just as good as my Zeiss 2" prism in those configurations as well.  Also turned my 80mm Apo into a really fun spotter with everything in correct orientation.  Never liked that scope it in that role before but with this was fabulous - and with the 40XW the terrestrial views were simply jaw dropping!  Recommend you talk to Bob at Alpine Astro to find out exact technical differences between the unit the OP linked and the more expensive one I tested.

BillP that is the one I own, and I agree. Its my most expensive visual accessory, but well worth its price. Looking forward to your full review. waytogo.gif

 

I also have the APM roof prism 90° CI Shorty Barlow has. That too has great light transmission. Its not so good as the Baader but way better than any other Amici or roof prisms for astronomical use.



#12 gwlee

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Posted 20 March 2020 - 10:44 AM

I bought the 2” Baader T2 AMICI prism about two years ago for terrestrial viewing with my AT72ED2. As expected, it works fine for terrestrial use. To me, it seems to work as well my 2” TeleVue Everbrite mirror diagonal for astronomy use so it’s replaced the Everbrite for all uses of this scope.

Found that I like the AMICI much better for star hopping. Charts, naked eye, bino, and telescopic views all match. Haven’t seen the “artifacts” you read about on the internet, but don’t often use this scope much above about 62x.

Negatives: very expensive and narrow field stop begins to vignette with EPs wider than 27 Panoptic, but very satisfied with the diagonal and glad that I decided to try it for myself.
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#13 emilslomi

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Posted 20 March 2020 - 03:02 PM

The APM Amici is great too. Resolution just as good as the Baader T2 prism or Baader 2" mirror or the regular 2" APM mirror or prism. Spikes not visible at mags below 3 in my 140. The only thing I don't like to use it for is the bright planets, which get "smeared". I like it best for the moon and galaxy hunting.

 

Emil


Edited by emilslomi, 20 March 2020 - 03:03 PM.

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#14 Bomber Bob

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Posted 20 March 2020 - 06:32 PM

My vintage 1980s spectros Amici RA prism with 35mm barrels.  I have a set of 3 spectros Kellners that fit it -- 50mm, 40mm, 30mm.  The extension tube let me use it with the Unitron 142 that I tested against my Astro Optical 76mm F15 frac.

 

spectros Diagonal Prism to Unitron Sleeve S01.jpg

 

 


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#15 BillP

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Posted 21 March 2020 - 11:47 AM

I bought the 2” Baader T2 AMICI prism about two years ago for terrestrial viewing with my AT72ED2. As expected, it works fine for terrestrial use. To me, it seems to work as well my 2” TeleVue Everbrite mirror diagonal for astronomy use so it’s replaced the Everbrite for all uses of this scope.

Are you talking about the less expensive Baader AMCI?  Just asking because I got zero vignetting with my 40 XW in the more expensive Baader AMCI and it has a field stop larger than 27 Pan.  46.5mm (larger than 41 Pan's).



#16 25585

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Posted 21 March 2020 - 02:53 PM

Interesting thread on the T2 Zeiss here  https://stargazerslo...-correct-image/



#17 Shorty Barlow

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Posted 21 March 2020 - 04:12 PM

I found these 1.25" William Optics Amicis with helical focusers performed as well as the cheaper Baader 2".

 

med_gallery_249298_5348_82560.jpg

 

The 'Omegon' below was the same. Unfortunately the Omegon eyepiece holder appears to only be brazed on. 

 

gallery_249298_5348_32757.jpg

 

I've had the entire holder detach on a couple of them.

 

gallery_249298_5348_92037.jpg

 

Both the Omegon and the WO Amicis were very good for lunar and rich field viewing.


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#18 coopman

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Posted 21 March 2020 - 04:14 PM

I e-mailed Bob at Alpine Astro and he said that both the $299 and the $719 models are good enough to support at least 200X.  The $719 model is obviously higher quality and would have a higher mag. limit.  He said that he has never had a customer return either type of the amici diagonals for a refund.   


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#19 Shorty Barlow

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Posted 21 March 2020 - 04:38 PM

I e-mailed Bob at Alpine Astro and he said that both the $299 and the $719 models are good enough to support at least 200X.  The $719 model is obviously higher quality and would have a higher mag. limit.  He said that he has never had a customer return either type of the amici diagonals for a refund.   

I've had around 180x with the less expensive Baader Amici on the Moon, Jupiter, Saturn and Mars. I certainly couldn't complain about the image quality.

 

You might find this link interesting: https://www.telescop...al/p/106656.uts


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#20 gwlee

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Posted 21 March 2020 - 05:21 PM

Are you talking about the less expensive Baader AMCI?  Just asking because I got zero vignetting with my 40 XW in the more expensive Baader AMCI and it has a field stop larger than 27 Pan.  46.5mm (larger than 41 Pan's).

Bill,

 

Believe you are testing the “AMICI-DX2” version, and I am using the “AMICI-DX1.” Look forward to reading your review.

 

I have the Baader #2456130 (Baader T2/90 degree  Roof Prism with BBHS coating). It’s specified “clear aperture” is 31mm. Claimed to be “Zeiss spec prism.” The specified field stop of my 27Pan is 30.5mm. 

 

Price without the required nose pieces was $319. I set it up with 2” nose pieces to work with a 27 Pan in my AT72ED2. I seldom use my 35 Pan with my AT72ED2 because the EP is so large, and it shows obvious distortion in terrestrial views, but haven’t noticed any light fall off in casual use. 
 

Have used the prism regularly for about 2 years now for terrestrial viewing and also for astronomical viewing with the AT72ED2 without noticing any spikes or other prism artifacts that people mention, but seldom use this scope above 62x. Use a 2x barlow occasionally and haven’t noticed any problems with the prism at 124x. 

 

Gary

 

 

 

 

 

 

 

 

Gary


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#21 godoflurking

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Posted 22 March 2020 - 03:28 PM

Sorry this is tangential to the topic: Has anyone tried a 90° Amici followed by a pentaprism to give a 0° correct image? I was thinking a high quality diagonal like the Baader Astro Amici with 31mm clear aperture, coupled with the Orion pentaprism with 29mm clear aperture. Or would it be better to try to custom fit a binocular-like double porro-prism for a 0° correct image? I'm mostly concerned with high mag viewing.

 

Hmm, after some searching it seems the Vixen erecting lens is the way to go. I'm having trouble finding reviews for this thing though.


Edited by godoflurking, 22 March 2020 - 04:53 PM.


#22 Shorty Barlow

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Posted 22 March 2020 - 05:21 PM

 

 

Hmm, after some searching it seems the Vixen erecting lens is the way to go. I'm having trouble finding reviews for this thing though.

I've seen that Vixen lens but I thought it was for Newtonians and gave an upright image. A Newtonian image is inverted but not mirror-reversed, erecting image adapters produce an upright, non-reversed image. 

 

I've used an erecting eyepiece in an Amici prism (in a Maksutov) to give an inverted, non-reversed image of the Moon. 

 

Surely using that Vixen erecting lens in a conventional diagonal will give a mirror-reversed, inverted image?



#23 godoflurking

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Posted 22 March 2020 - 06:24 PM

I've seen that Vixen lens but I thought it was for Newtonians and gave an upright image. A Newtonian image is inverted but not mirror-reversed, erecting image adapters produce an upright, non-reversed image. 

 

I've used an erecting eyepiece in an Amici prism (in a Maksutov) to give an inverted, non-reversed image of the Moon. 

 

Surely using that Vixen erecting lens in a conventional diagonal will give a mirror-reversed, inverted image?

I think everything you said is correct, but I meant using the Vixen erector without a diagonal since I wanted a 0° correct image. It should give an upright and non-mirrored image.


Edited by godoflurking, 22 March 2020 - 06:25 PM.


#24 Shorty Barlow

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Posted 22 March 2020 - 06:39 PM

I think everything you said is correct, but I meant using the Vixen erector without a diagonal since I wanted a 0° correct image. It should give an upright and non-mirrored image.

Ermmm ... I don't know, I'm too confused now lol. It sounds about right.



#25 godoflurking

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Posted 22 March 2020 - 07:22 PM

All these terms are confusing me too... upright, inverted, flipped, mirrored, reversed, MIRROR-REVERSED! I like thinking of it in algebra terms by keeping track of the number of reflections in total: an odd number of reflections will produce text which is not readable no matter how I orient my head. All that's left now is figuring out the rotation of the image, for which I need to trace only one off-axis point waytogo.gif




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