Correct Image Diagonal

[Alien 13]

I cant get on with the inverted left-right views of standard diagonals so am looking for a 90 degree corrected one. I would like a two inch version but do wonder if the extended light path would make focusing close to the end stop on my WO ZS71 so perhaps a 1.25 inch one might be better, the eyepiece would probably be low power similar like a 32 mm plossi. This observing lark is a bit new to me and have been so used to the correct orientated imaged through my DSLR screen.

Thanks in advance for any views/recommendations.

Alan

[Louis D]

There are a couple of 2" options like the Olivon or Baader units.

[Floater]

Hi, Alan. There was a long thread about this subject started by iPeace (Mike) some weeks back.

Not sure how to give you a link but the title was 

New Baader/Zeiss T2 prism - Correct Image!

maybe have a hunt for it?

p.s I've started to realise that correct image makes a lot of difference when viewing the Moon. ??

[Alien 13]

3 minutes ago, Floater said:

Hi, Alan. There was a long thread about this subject started by iPeace (Mike) some weeks back.

Not sure how to give you a link but the title was 

New Baader/Zeiss T2 prism - Correct Image!

maybe have a hunt for it?

p.s I've started to realise that correct image makes a lot of difference when viewing the Moon. ??

Thanks Gordon, I must have missed this post somehow.

Link here if anyone else interested 

Alan

[John]

Personally I'd try and get used to the left right reversed image. I feel that it's hard to find a fully correct image diagonal that does not in some small way impact the quality of the viewed image because of the additional glass needed.

Software such as the Virtual Lunar Atlas and Virtual Planet Atlas make it easy to flip the image to match the view through the scope.

It's just a matter of practice getting used to this as it is with the fully inverted newtonian image - no way to correct that so you just have to get used to it

 

[Alien 13]

2 minutes ago, John said:

Personally I'd try and get used to the left right reversed image. I feel that it's hard to find a fully correct image diagonal that does not in some small way impact the quality of the viewed image because of the additional glass needed.

Software such as the Virtual Lunar Atlas and Virtual Planet Atlas make it easy to flip the image to match the view through the scope.

It's just a matter of practice getting used to this as it is with the fully inverted newtonian image - no way to correct that so you just have to get used to it

 

For me its just wrong to have the image swapped left to right, its the same thing as looking in a mirror and trying to use scissors to cut your hair, impossible.

The strange thing was that I got on ok when I had a newt way back in the sixties.

Alan 

[michael.h.f.wilkinson]

I have an Orion 2" Amici prism, and it is fine at lower magnification (no issues focusing with the 80mm F/6), but for higher magnification it does degrade the image quality slightly.

[Alien 13]

2 minutes ago, michael.h.f.wilkinson said:

I have an Orion 2" Amici prism, and it is fine at lower magnification (no issues focusing with the 80mm F/6), but for higher magnification it does degrade the image quality slightly.

Thanks for that although the Orion and WO 2 inch versions seem to be as rare as hens teeth in the UK.

Alan

[celestron8g8]

You might check out this one :  http://www.eyepiecesetc.com/Olivon_2_BK7_Roof_Prism_Diagonal_w_1_25_adapter_p/7202200.htm

or WOs' : http://agenaastro.com/william-optics-2-45-erecting-prism-diagonal.html

Or Stellarvues : http://www.highpointscientific.com/stellarvue-2-quot-correct-image-45-deg-erecting-prism-d1035

Or check out here : http://agenaastro.com/optical-accessories/diagonals-prisms/2-diagonals-prisms.html?p=1

Or check here : http://www.skiesunlimited.com/telescope-accessories/diagonals/

Or maybe here : http://www.highpointscientific.com/telescope-accessories/diagonals

Or at Stellarvue : http://www.stellarvue.com/45-degree-correct-image-erecting-prism-2-d1035/

[John]

Good links above but all USA based so import duties etc will be payable to get the item to the OP in the UK.

This Baader unit is in the EU and seems to provide around the best astronomical optical performance of any fully corrected image diagonal, at a cost

http://www.teleskop-express.de/shop/product_info.php/info/p7947_Baader-2--90--Amici-Prism---astronomical-quality.html

[iPeace]

9 minutes ago, John said:

Good links above but all USA based so import duties etc will be payable to get the item to the OP in the UK.

This Baader unit is in the EU and seems to provide around the best astronomical optical performance of any fully corrected image diagonal, at a cost

http://www.teleskop-express.de/shop/product_info.php/info/p7947_Baader-2--90--Amici-Prism---astronomical-quality.html

I was interested in one of these at the time, but Baader did not have any in stock for a rather long period, after which I stopped checking - so availability may be an issue. 

[Peter Drew]

Alan. If you do go down the erecting prism route I would recommend a 90 degree version rather than the 45 degree one, for some reason the former always seems to perform better. Be prepared that your refractor star images will display a diffraction spike similar to a Newtonian with a single spider arm, the intensity of which will depend on the brightness of the star and how optically well the "roof" line of the prism has been formed.   

[Alien 13]

These types of diagonals do seem hard to get hold of which is hard for me to understand, surely everyone needs one of these  I just cant understand why people can be happy with a reversed view, it would certainly be enough to put me off astronomy for life.

Alan

[Alien 13]

3 minutes ago, Peter Drew said:

Alan. If you do go down the erecting prism route I would recommend a 90 degree version rather than the 45 degree one, for some reason the former always seems to perform better. Be prepared that your refractor star images will display a diffraction spike similar to a Newtonian with a single spider arm, the intensity of which will depend on the brightness of the star and how optically well the "roof" line of the prism has been formed.   

Why would there be a spike, the best ever view of stars was with a military spotting/tank scope that had a 60 mm objective or slightly larger with X 6 magnification, just pinpoints of light hanging in the blackness.

Alan

[Stu]

22 minutes ago, Alien 13 said:

These types of diagonals do seem hard to get hold of which is hard for me to understand, surely everyone needs one of these  I just cant understand why people can be happy with a reversed view, it would certainly be enough to put me off astronomy for life.

Alan

Thing is, I would not know most of the time which way round things really are, so it makes no odds to me. I do however want to see things at their optimum so prefer simpler mirror or Prism designs which put fewer (no) artifacts into the image.

Now newtonians, they really are the work of the devil, can't be doing with standing on my head all the time 

[Peter Drew]

14 minutes ago, Alien 13 said:

Why would there be a spike, the best ever view of stars was with a military spotting/tank scope that had a 60 mm objective or slightly larger with X 6 magnification, just pinpoints of light hanging in the blackness.

Alan

When the light enters a roof prism the light is split into two halves then reversed and recombined, this corrects the E/W orientation, the angle of the roof corrects the N/S orientation just as an ordinary star diagonal does. However sharp the roof of the prism appears to be it still has a finite edge, this acts as an obstruction causing the spike. As already mentioned the intensity of the spike depends on the quality of the prism. You won't believe how much military standard prisms cost!       

[John]

32 minutes ago, Alien 13 said:

... I just cant understand why people can be happy with a reversed view, it would certainly be enough to put me off astronomy for life.

Alan

You are kidding, surely ?

It's just a little thing to get used to along with the stuff like collimation, the motions of an eq mount, the newtonian image orientation etc, etc.

I guess I've been using scopes for 40 years now but I've never seemed to have found anything other than a small adjustment in thinking needed when switching between the visual view, the frac / cat / sct view and the newt view. Seems a very small price to pay for the most absorbing and abiding interest that I've ever had

I guess if folks really did find it difficult to live with in enough numbers, there would be more solutions on the market.

 

[Alien 13]

Just now, Peter Drew said:

When the light enters a roof prism the light is split into two halves then reversed and recombined, this corrects the E/W orientation, the angle of the roof corrects the N/S orientation just as an ordinary star diagonal does. However sharp the roof of the prism appears to be it still has a finite edge, this acts as an obstruction causing the spike. As already mentioned the intensity of the spike depends on the quality of the prism. You won't believe how much military standard prisms cost!       

I am quite aware of the price of military optics 15- 70K would get you a reasonable spotter a system for a submarine would run six figures.

Alan

[Alien 13]

13 minutes ago, Stu said:

Thing is, I would not know most of the time which way round things really are, so it makes no odds to me. I do however want to see things at their optimum so prefer simpler mirror or Prism designs which put fewer (no) artifacts into the image.

Now newtonians, they really are the work of the devil, can't be doing with standing on my head all the time 

I like Newts, its a bit like reading a book upside down, not easy but doable but reading right to left is much harder perhaps our brains are hard wired this way.

Alan

[Stu]

Just now, Alien 13 said:

I like Newts, its a bit like reading a book upside down, not easy but doable but reading right to left is much harder perhaps our brains are hard wired this way.

Alan

I guess it's what you get used to, or whatever your natural preference is. I've spent far more time with refractors, maks and SCTs than newts, so a left-right reversed image seems quite natural to me. I actually get more confused when using a RACI Finder now, I often push the scope the wrong way when using one!

[iPeace]

As I mentioned later on in "the other thread", I now find myself using both correct-image prisms and mirror diagonals, for various reasons.

Weight is one, important when traveling, as a high-quality 1.25" mirror diagonal can be a bit lighter.

The ability to check for loss of detail through the prism - at high magnification - is another. I have yet to notice any loss of image quality, but it surely must occur compared to a good mirror diagonal.

Finally, in spite of myself, I keep trying to learn to accept the reversed image, thinking: what if this was all there was? If that were indeed the case, I'm sure I would manage just fine. 'Tis but a niggle to me, at present. I would definitely recommend this. So if you can get used to it, by all means, do so. Pretend you're on the outside of the celestial sphere, looking in. Or something.

But my sympathy for those who prefer the correct image remains, and I am very happy to have my two very good amici prism diagonals - they produce no artifacts discernible to me and are very enjoyable. There is cost involved, and careful checking of each specimen for slight flaws within production tolerances - see the other thread - but I have managed and so dare hope that others who feel the need may do so as well.

[iPeace]

27 minutes ago, John said:

It's just a little thing to get used to along with the stuff like collimation, the motions of an eq mount, the newtonian image orientation etc, etc.

With the fullest respect for the profound truth of this, surely there is joy in the use of equipment that does not require getting used to such things - say a refractor on an alt az mount?

[John]

8 minutes ago, iPeace said:

With the fullest respect for the profound truth of this, surely there is joy in the use of equipment that does not require getting used to such things - say a refractor on an alt az mount?

It's a nice instrumental choice often I find but not so much when trying to spot mag 13 supernovae

 

[iPeace]

6 minutes ago, John said:

It's a nice instrumental choice often but hopeless for trying to spot mag 13 supernovae

 

Exactly - all about priorities. 

[Louis D]

20 hours ago, John said:

Good links above but all USA based so import duties etc will be payable to get the item to the OP in the UK.

The US has an $800 exemption amount on daily imports.  You'd think European countries would reciprocate in the name of free trade.