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iPeace

New Baader/Zeiss T2 prism - Correct Image!

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Confession time. I'm not a reverse-image person, or have yet to become one (it's been a year now). One of the great things about using binoculars is that they show me what's in the sky as it actually is, both up there, and down here in my Pocket Sky Atlas, or in Stellarium on the phone...you get the picture. The correct-image picture.

I have tried; there are a lot of tools out there, such as reverse-image lunar maps, etc. And they're great. And they do help. And I'm still not completely content.

I'm aware that the only way is a correct-image prism diagonal. And I'm aware that they are evil. Bad. Inferior. They ruin everything. Why else would everyone put up with reverse-image observing? They're fine for terrestrial observing, everyone maintains, but after dark they belong at the bottom of the case.

Then again, perhaps there's two sides to this. Maybe? Not sure. Just like there are those who swear by achromatic refractors, even shorter ones. They're not in denial; they acknowledge there's a bit of colour, or whatever else is inherently "wrong" with achros, it just doesn't bother them enough to make them look elsewhere. I wouldn't know my own experience of this, because I have only ever used an apo. Well, I use bins. And an occasional RACI finder. But anyway, I take no stance on the achro/apo thing, I like my apos and that's enough. The point is, what if there's a way for me to do correct-image observing, that just works for me, even if it doesn't work for everyone?

I have owned a Baader correct-image prism diagonal for a while now. A nice, big, 2" job. Baader does everything to make it perfectly clear that it's not meant for astronomy. They almost engrave it on the side. I've used it anyway, the thinking being that I would combine it with the smallest of my scopes (also an apo) to create the biggest of RACI finders. It worked. Very nice indeed. Whatever was inherently wrong with a correct-image prism, it wasn't bothering me. I did notice that my Baader Zeiss prism was nicer, apart from the reverse image, but couldn't quite explain why. Oh well.

Baader also supplies what they call "astro-quality" correct-image prism diagonals. I have carried the 2" ClickLock version in the back of my mind for some time now. And there it stayed, because Baader have not had them in stock for several months. Reading up on SGL, it seems the Baader T2 diagonals are very popular, especially the prisms. Hadn't really considered them before, but I delved into the details, and they are pretty cool...you can configure them as 2" or 1.25", just a matter of screwing in the appendages in your chosen size. And...Baader does an "astro-quality" prism in T2...and they actually have them in stock...cheaper - well, less expensive - too.

So it arrived quite recently, complete with 2" ClickLock, safely before Doris (the storm), and it's a great-looking and -feeling piece of kit. And tonight was the night.

Never have done Venus before; it's always been there, I've just never...well, you've all said that Venus has little to offer besides phases, and...well, anyway, it was high time I did something about it. So out with the AZ8 and the 120ED, new correct-image T2 prism inserted, still well before total darkness. Venus, as usual at this time, was the only thing bright enough to be seen. Starting at 100x, it was a very clear crescent, and very bright indeed. Had to work the Moonlite very gently to get the focus as good as possible in all that brightness, but it was a great view... nothing wrong at all. And as I was tracking, left was left and right was right...

My current site is residential in nature, such that individual targets often disappear behind a building for a short time before reappearing again. By now, it was properly dark - at least as dark as it ever gets, here - so I could turn to other targets. Orion was not doable - street light - so up to snag an open cluster. M35 was great, started at 29x, on to 53x and 90x with the view as nice as it ever was reverse-image. Where has this correct-image prism been all my life?

Venus reappeared and I returned to it, moving the whole setup back a bit to get a view over the high hedge. Time to see just what the limit was. At 191x, focus was even more critical, but certainly worth the bother. Yes, it's just a crescent phase on display, but really, really nice. More to be had? At 243x, we were really hanging out there. Getting proper focus was very difficult, and either side of perfect focus, Venus definitely had rainbow edges. But when the focus was just right...the image was as good as I've ever seen Jupiter - for comparison - at high power (keep in mind, before now, I've never done any serious planetary with the 120ED, so I'm comparing with a TV85 at 162x-200x on Jupiter, which is great, but can certainly be outdone). But Venus was dimming...what the...ah, the clouds had returned.

So, first session was pretty good! No direct comparisons done with other diagonals, but that can still happen. My best skies are yet to come, this year, so plenty to play for, but for now, no indication that this won't work for me. Can't wait to try it on the Moon at high power - correct-image Lunar observing is just one of those things for me.

Thanks for reading.

:happy11:

Edited by iPeace
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Excellent post and interesting stuff, iPeace.

I love to see 'accepted wisdom' being challenged and tested. After all, where would be had others not challenged the accepted view. (Take the pun, or not. ?)

I look forward to reading what others may have to say on the subject.

 

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1 minute ago, Floater said:

Excellent post and interesting stuff, iPeace.

I love to see 'accepted wisdom' being challenged and tested. After all, where would be had others not challenged the accepted view. (Take the pun, or not. ?)

I look forward to reading what others may have to say on the subject.

 

Thanks. To be sure, I'm quite content to be a deviant nutter - the peaceful type. But yes, we all need to discover the universe on our own terms.

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Very interesting report Mike :icon_biggrin:

I like my finders to present an image that matches what my eyes see but I can cope with what the scopes present.

Apparently our eyes present an upside down image to the optical nerve but the brain turns it the other way up.

 

Edited by John
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An interesting post iPeace.

My take on things is that the right way to do things is the way that gives YOU the most satisfaction and keeps you doing it.

I'm new to this game and inverted views is all I know when using a scope. I have previous experience of optics from my law enforcement and military past so know and use correct image equipment frequently.

Anyhow- keep on keeping on.

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I had the Baader Amici prism, in 1.25" flavour. It came with a second hand MiniBorg achro and worked well with that scope as a super RACI finder and ultra portable travel scope but it was very good indeed in my long focus achros. I would say that it was close to the Tak prism in performance but with much better construction and versatility with its T2 threads. 

Another item I really shouldn't have sold, I would certainly have one again but probably not at normal retail price.

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Traitor! Expel the traitor!!! 

;);) 

Tee hee, nice report Mike. If you are going to get an Amici, may as well get the best! I've read that the Zeiss Amici is as good as a standard Zeiss Prism so I'm not totally surprised by your report.

I've got totally used to reversed images, infact when I use a correct image Prism in a scope I ended up pushing it the wrong way!

Now, as for upside down Newt images, you have to be seriously crazy to put up with them! ;) 

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3 minutes ago, Stu said:

I've got totally used to reversed images, infact when I use a correct image Prism in a scope I ended up pushing it the wrong way!

Fortunately, for me, at the moment, this effect is somewhat drowned out by me still getting used to using the slo-mo knobs on the AZ8.

:grin:

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I understand that a lot of Japanese observers prefer to view "straight through" with their refractors, mak-cassegrains etc. That sort of explains the accessories that are supplied with Japanese made scopes like Vixen's and Taks eg: long extension tubes for the focuser to ensure that focus can be reached with no diagonal.

When using a correct image prism diagonal the poor old photons are being really messed about after their long journey - inverted and reversed by the scope, corrected by the diagonal, magnified by the eyepiece, inverted again by the human eye lens and finally corrected again by the human brain !

 

 

 

 

Edited by John
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Apart from the stigma caused by the lesser quality correct image diagonals, many refractor "purists" dislike the vertical star spike that can be introduced by the Amici prism roof. I use one on occasion for lunar viewing where the spike would not show.  :icon_biggrin:

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15 minutes ago, John said:

I understand that a lot of Japanese observers prefer to view "straight through" with their refractors, mak-cassegrains etc. That sort of explains the accessories that are supplied with Japanese made scopes like Vixen's and Taks eg: long extension tubes for the focuser to ensure that focus can be reached with no diagonal.

When using a correct image prism diagonal the poor old photons are being really messed about after their long journey - inverted and reversed by the scope, corrected by the diagonal, magnified by the eyepiece, inverted again by the human eye lens and finally corrected again by the human brain !

I truly appreciate this, and it makes perfect scientific sense not to go down this path in order to get the best quality image.

I like simplicity; it tends to work well and require less maintenance. And it is indeed my brain that is making all this unnecessarily complex.  :rolleyes2:

I see this often; the old chestnut that it takes 80% of the effort to realize the last - marginal - 20% of the desired gain. Is it worth the cost? Good question, and I'll deal with it - as it applies to me - in due course.

By the way, is this basically true for all observers who use binoculars? Even the big, mounted ones? Are all the bin users also giving the photons a hard time?

How about bino-viewers? You know, those great-looking appendages which double your eyepiece outlay. Do they correct the image, or do they just more or less replicate / split / whatever the reverse image for two eyes?

Just typing in thoughts here, not making an argument.

:happy11:

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I'm not making any argument either Mike - just kicking ideas around - which is fun :icon_biggrin:

 

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1 hour ago, John said:

When using a correct image prism diagonal the poor old photons are being really messed about after their long journey

Maybe it's the photons that don't mind this that are worth seeing - the lazy ones, well, they have their place.

:grin:

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7 minutes ago, iPeace said:

Maybe it's the photons that don't mind this that are worth seeing - the lazy ones, well, they have their place.

:grin:

 

But " every photon counts" so need as many as possible, even the lazy ones ?

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Nice post ipeace. 

Like men-only golf clubs, cheque books,  and five day cricket matches, maybe astronomers' upside down/reversed images of the night sky will be an anachronism by 2040

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23 minutes ago, Timebandit said:

But " every photon counts" so need as many as possible, even the lazy ones ?

Is that why all those dark-art AP imaging folk don't use diagonals at all?

:huh2:

It's my - limited - understanding that those who image go to considerable lengths to give all photons every possible opportunity, as well as plenty of time, to reach whatever it is that they eventually reach in order to create the digital image.

(Imagine that - you, the photon, go all that way, and don't even make it to an actual eyeball. You're eventually eaten by a machine. Bummer.)

:grin:

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2 minutes ago, Highburymark said:

Nice post ipeace. 

Like men-only golf clubs, cheque books,  and five day cricket matches, maybe astronomers' upside down/reversed images of the night sky will be an anachronism by 2040

Thanks.

:happy11:

Double-edged, this. I miss five day cricket matches. But I haven't bought or read a book printed on paper for years.

I do have great hopes for improvements in optical equipment for us to use. Make it lighter, less involved to use! Wouldn't it be great if a pair of digital eyeglasses would suffice?

Of course, DSO hunters would have to look like Elton John...just as well it would be after dark.

:grin:

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11 hours ago, Stu said:

Traitor! Expel the traitor!!! 

;);) 

Tee hee, nice report Mike. If you are going to get an Amici, may as well get the best! I've read that the Zeiss Amici is as good as a standard Zeiss Prism so I'm not totally surprised by your report.

I've got totally used to reversed images, infact when I use a correct image Prism in a scope I ended up pushing it the wrong way!

Now, as for upside down Newt images, you have to be seriously crazy to put up with them! ;) 

No worse: Send him to Twente.

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Just now, ronin said:

No worse: Send him to Twente.

Who says I don't already live there...?

Whoops...

:confused5:

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I am in the correct image camp for diagonals, I really can't get on with reversed images from mirror diagonals. The reason being they simply don't represent what the object looks like.

In a Newtonian the image is rotated 180 degrees so although it looks upside down the image is internally consistent and that is also fine with me I.e. if I stood on my head everything would look fine.

I got a Takahashi prism diagonal to try out and although  the quality is better than my stock sky watcher correct image diagonals, 95% of the time I go for the correct image diagonals in the field.

 

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I'll take the optical quality every time and handle the (for me minor) issue of the reversed left and right. I've sort of got used to it over the 35 years I've been using scopes with diagonals. I'd probably get confused if I changed to a fully corrected image in the main scope !

Also I can't see the point in using a top end objective and eyepiece and having something in between that is less than that :icon_scratch:

 

 

 

Edited by John
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7 minutes ago, John said:

I'll take the optical quality every time and handle the (for me minor) issue of the reversed left and right. I've sort of got used to it over the 35 years I've been using scopes with diagonals. I'd probably get confused if I changed to a fully corrected image in the main scope !

Also I can't see the point in using a top end objective and eyepiece and having something in between that is less than that :icon_scratch:

My quandary exactly. If it turns out that I have to make the choice between image orientation and image quality, well...

:rolleyes2:

Hopefully, my attempt to insert the best I can find between objective and eyepiece will make the choice moot, at least for me.

:happy11:

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23 minutes ago, John said:

I'll take the optical quality every time and handle the (for me minor) issue of the reversed left and right. I've sort of got used to it over the 35 years I've been using scopes with diagonals. I'd probably get confused if I changed to a fully corrected image in the main scope !

Also I can't see the point in using a top end objective and eyepiece and having something in between that is less than that :icon_scratch:

 

 

 

 

Yes I know there is no upside down in outer space ?, but give me quality of image every day, and this is especially true on planetary and lunar observing, where you are trying to pick out as much fine detail as possible .

The diagonal to many seems to be a bit of a infill and IMO there is no point putting effort and money into a great scope and eyepiece and then put a so so diagonal into link . As the quality of image is only as good as the weakest link in the optical chain. This is why I picked up a televues diagonal when one came up used to try and get a optical chain that was IMO equal in quality to each part in the link. Give me optical quality every time IMO. 

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33 minutes ago, John said:

Well John, that's the one I've had my eye on, but Baader have not had them in stock for some time now. I've sprung for this T-2 model:

http://www.baader-planetarium.com/en/accessories/optical-accessories/prism-and-mirror-star-diagonals/baader-t-2--90°-baader-roof-prism-with-bbhs-r-coating-(t-2-part-02).html

Don't see this one on the RVO site.

Have added 2" nosepiece and ClickLock for eyepieces. And the T-2 spacers for their usefulness, as you related elsewhere. :happy11:

The German description explicitly promotes it as the "astro quality" version. Whether it's as good as the other (the one you mention), who knows? It's produced to Zeiss standard.

Edited by iPeace

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