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To Prism or not to Prism?

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#1 AtmosFearIC

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Posted 25 April 2019 - 10:32 PM

With a recent thread on 2" diagonals it got me thinking about what I currently have, the telescopes I've got and doing a lot of reading on CN. I've slowly making up a list of things I need to order and one of those is a T2 to 1.25" click lock.

 

I currently have a 2" Baader Dielectric that I'm planning on selling as I don't have any 2" eye pieces. I also have a T2 Baader BBHS that I use with my Baader MkV binoviewer. I've been reading the diagonal views from Bill Paolini and he put prisms above mirrors when it came to views of Jupiter in particular but also says that the BBHS is a step up from the dielectrics.

 

My two visual instruments are a FC100DL F/9 and Mewlon250 F/10 so neither of them are fast. One of the bigger differences between the BBHS and prism diagonals with binoviewers is the shorter light path with the prisms. I'm wondering if there is anyone that has done a visual comparison between the BBHS and Baader/Zeiss prism?

 

Or are they going to be much of a muchness, too close for it to matter.


Edited by AtmosFearIC, 25 April 2019 - 10:32 PM.


#2 agmoonsolns

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Posted 25 April 2019 - 10:46 PM

The BBHS prism is slightly brighter than the standard Baader prism, but also has slightly more light scatter. Just as the difference in brightness is slight, but noticeable, so is the scatter. If you're primarily a planetary observer with slow systems, an upgrade to the BBHS prism might not be worth it. The longevity might not be quite as good with the BBHS versions, but I have never heard of the coatings on one going bad and so I would imagine they're a pretty safe bet.


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#3 clusterbuster

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Posted 25 April 2019 - 11:38 PM

I have compared my 2" ZIESS PRISM Diagonal to my 99% Electrolyte Mirror Diagonal in more than one Telescope and I like the Views through the PRISM better !

Mark


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#4 greenstars3

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Posted 26 April 2019 - 12:48 AM

I have the Baader T2 prism in the 1 1/4" and use it on my 180 Mewlon. It has a built in focuser  on the eyepiece side and works very well for me. I have heard on CN that the Baader 1 1/4 with the Ziess prism is better but have never used one, some of the non Ziess Baader 1 1/4" diagonals had some collimation issues in the past but I have had no problems with mine, I ordered it this year.

 

Robert  



#5 Fomalhaut

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Posted 26 April 2019 - 07:36 AM

Based on own observation, I agree T2 1 1/4" Prism is better for planetary than Dielectric Multilayer even with f/6.4. 

 

But how about same Prism versus BBHS-mirror with f/6.4?

 

Or IOW: Would BBHS-mirror equal or even improve the planetary views of T2 Prism with my f/6.4 triplet apo? 

 

Chris


Edited by Fomalhaut, 26 April 2019 - 07:40 AM.


#6 mikeDnight

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Posted 26 April 2019 - 11:39 AM

The sketch of Jupiter below was made using a Takahashi FC100DL and a 1.25" Baader prism.

 

IMG_0645.JPG

 

 

 

 


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#7 mikeDnight

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Posted 26 April 2019 - 11:41 AM

This second sketch was made using a Takahashi FC100DC and 1.25" Takahashi prism.

 

IMG_0646.JPG

 

 


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#8 RAKing

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Posted 26 April 2019 - 12:00 PM

I have both the Baader T-2 Zeiss prism and the T-2 BBHS mirror diagonal.  Frankly, I cannot tell much difference between the two with my Tak FC-100DC or any other scope I have used. 

 

But I prefer the Zeiss prism because of the slightly shorter light path and... well, it's a ZEISS prism that I have loved for many, many years.  Nothing says I have to be rational about this.  I love that little diagonal and that's that.  cool.gif 

 

Cheers,

 

Ron


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#9 Chucky

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Posted 26 April 2019 - 03:17 PM

Great drawing Mike.!


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#10 Kunama

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Posted 26 April 2019 - 05:32 PM

Colin, 

The views are so close it really makes no difference....

The Baader Zeiss prism has the BBHS coating on the hypotenuse face (since the late 1990s).

The BBHS T2 mirror is overcoated to protect the silver.

The Light path difference is 4.5mm, prism being 38.5mm, mirror 43mm.


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#11 AtmosFearIC

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Posted 27 April 2019 - 06:13 AM

The DL really does bring out those final details Mike, well sketched :)

Thanks for the thoughts all. After my attempt to binoview with the Mewlon last night and my inability to focus with the 1.7x GPC, I’m thinking I might get the prism purely for that extra 4.5mm, every mm counts when I’m already struggling to achieve focus.
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#12 Peter Besenbruch

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Posted 28 April 2019 - 07:27 PM

Or are they going to be much of a muchness, too close for it to matter.

I compared the Takahashi prism to the Baader BBHS mirror diagonal. The Tak had a bit less scatter, but not enough to really matter. Compared to the 1.25" Baader diagonal, the Tak won easily.



#13 Mitrovarr

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Posted 28 April 2019 - 07:31 PM

You saw that much detail in a 4" telescope? Wow.

 

I'm really tempted to get a prism but it's hard because they're so expensive. The Baader one has gotten more and more expensive as they seem to know they're close to the only game in town, and the Takahashi one has mixed reviews.


Edited by Mitrovarr, 28 April 2019 - 07:33 PM.


#14 Tyson M

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Posted 28 April 2019 - 07:36 PM

The way I see it, it is a bit of an expensive risk to try.  It could end up as good as a dielectric or just slightly better, but it could produce scatter that is obtrusive and degrade the image. 

 

Whereas an Everbrite, Maxbright or BBHS-mirror you will know is awesome and top notch.

 

That being said- I still want to try once I have more disposable money. Anything to potentially improve the viewing experience....brick.gif



#15 agmoonsolns

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Posted 28 April 2019 - 08:58 PM

How was the Takahashi better than the Baader prism and by how much? What criteria did you use to come to this conclusion? Just saying one is better than another leaves out an awful lot of helpful information. Please tell us more.

 

I compared the Takahashi prism to the Baader BBHS mirror diagonal. The Tak had a bit less scatter, but not enough to really matter. Compared to the 1.25" Baader diagonal, the Tak won easily.



#16 Peter Besenbruch

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Posted 29 April 2019 - 01:00 AM

How was the Takahashi better than the Baader prism and by how much? What criteria did you use to come to this conclusion? Just saying one is better than another leaves out an awful lot of helpful information. Please tell us more.

By a lot. On the Maksutov, the magnification topped out at 200x with the Baader, whereas the Takahashi prism passed 300x easily that night. I could see a lot more fine detail with the Tak, festoons, tiny swirls, and the like on Jupiter that simply weren't there in the Baader.

 

I haven't tested the Baader beyond checking star positioning in it compared to the known good Takahashi and GSO. That seemed OK. People have complained about the collimation of the Baader in online reviews, however.


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#17 agmoonsolns

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Posted 29 April 2019 - 01:04 AM

Wow, great information, thank you!

 

Has anyone else compared the Takahashi prism diagonals to the Baader versions? The solution might be to get a Takahashi instead.



#18 Peter Besenbruch

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Posted 29 April 2019 - 06:07 PM

Wow, great information, thank you!

As far as it goes. I own two Tak prisms and one Baader. That's a sample size of one, with additional inputs from online reviews.



#19 agmoonsolns

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Posted 29 April 2019 - 06:18 PM

If you don't mind me asking, which versions and sizes of Takahashi prisms do you have? Some have said 2" prisms tend to introduce slightly more chromatic aberration than the 1.25" versions. I would love to get one of the Takahashi prism diagonals to compare with my 1.25" Baader prism. I could then sell my other 1.25" diagonals if they didn't quite measure up. The thing is, I really like the mechanical construction of the Baader with the rotating/focusing eyepiece holder and so I would probably keep it.

 

I am also thinking about trying to find one of the older 2" prism diagonals made by Zeiss in Germany before everything was turned over to Baader. There have been many posts talking about how much better they are over the later Baader versions. It would be interesting to get several different brands of high-end prism diagonals together for a proper comparison - Zeiss, Baader, Takahashi, and ???



#20 YAOG

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Posted 29 April 2019 - 06:36 PM

If you don't mind me asking, which versions and sizes of Takahashi prisms do you have? Some have said 2" prisms tend to introduce slightly more chromatic aberration than the 1.25" versions. I would love to get one of the Takahashi prism diagonals to compare with my 1.25" Baader prism. I could then sell my other 1.25" diagonals if they didn't quite measure up. The thing is, I really like the mechanical construction of the Baader with the rotating/focusing eyepiece holder and so I would probably keep it.

 

I am also thinking about trying to find one of the older 2" prism diagonals made by Zeiss in Germany before everything was turned over to Baader. There have been many posts talking about how much better they are over the later Baader versions. It would be interesting to get several different brands of high-end prism diagonals together for a proper comparison - Zeiss, Baader, Takahashi, and ???

The Baader BBHS 36mm and 47.5mm prisms are Zeiss prisms.  The Baader BBHS 36mm T-2 prism is better than the regular Baader 32mm T-2 prism. The Baader 32mm T-2 prism is a better built but optically equivalent to the Takahashi 1.25" prism which is a good standard prism in an uncharacteristic cheap plastic body. 

 

Unfortunately the only way to know if your scope will benefit optically from using a premium prism is to try it. The build quality is obvious when you handle a Baader prism vs Takahashi prism.   


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#21 agmoonsolns

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Posted 29 April 2019 - 07:19 PM

I really wish manufacturers provided optical specification data like what many do with telescopes (i.e. all better than 1/6th wave, 96% Strehl, etc.). As it is, it's really hard picking out the best without actually buying and comparing them which can be a very expensive prospect.

 

I was told the older Zeiss prisms from the 1990s were made to higher tolerances with smoother surfaces than the later Baader prisms. This was part of Baader's cost cutting to streamline production and make them as cost efficient/profitable as possible after taking over the Zeiss line. I think these are still made by many of the same people at the same place (for now, Baader is planning on having everything made in China in the future), but they have replaced much of the final work that was done by hand with machine polishing and lowered the specs to match what their machines could produce quickly, efficiently, and repeatedly. It isn't much of a change and no one will tell me how much they lowered it. They claim that while it's a decrease, I wouldn't be able to tell the difference. Probably so, but seeing is believing.

 

Yes, I can see a difference and my telescopes do benefit from using premium diagonals (I already have several), but like most of you here, I am always looking for better and want to use the best I can find.

 

If Takahashi prisms are as good as or better than Baader, then it might be interesting to consider one of their turrets with the included prism.

 

I wish we could all magically appear at the same location on a night of terrific seeing so we could all compare our diagonals and learn from each other. Comparing is the only way I see to find the best and even then, these are all so good, it would be more down to differences in individual units and less a statement of who makes the best.


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#22 Kunama

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Posted 29 April 2019 - 08:03 PM

Colin, 

Are you using the Baader Ultra Short visual back on the Mewlon?  I am about to order another one for my M210 to be able to use my Zeiss binoviewers without a GPC.  It will shorten the light path by about 20mm. I have also the M71>M72 adapter as well as a M71>M68 adapter. I will use the latter directly with the Ultra Short VB.

 

I have both the mirror and prism versions of the T2 Baader diagonals as well as the Tak 2” mirror. Let me know if you want to borrow any to test.


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#23 YAOG

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Posted 29 April 2019 - 08:04 PM

I really wish manufacturers provided optical specification data like what many do with telescopes (i.e. all better than 1/6th wave, 96% Strehl, etc.). As it is, it's really hard picking out the best without actually buying and comparing them which can be a very expensive prospect.

 

I was told the older Zeiss prisms from the 1990s were made to higher tolerances with smoother surfaces than the later Baader prisms. This was part of Baader's cost cutting to streamline production and make them as cost efficient/profitable as possible after taking over the Zeiss line. I think these are still made by many of the same people at the same place (for now, Baader is planning on having everything made in China in the future), but they have replaced much of the final work that was done by hand with machine polishing and lowered the specs to match what their machines could produce quickly, efficiently, and repeatedly. It isn't much of a change and no one will tell me how much they lowered it. They claim that while it's a decrease, I wouldn't be able to tell the difference. Probably so, but seeing is believing.

 

Yes, I can see a difference and my telescopes do benefit from using premium diagonals (I already have several), but like most of you here, I am always looking for better and want to use the best I can find.

 

If Takahashi prisms are as good as or better than Baader, then it might be interesting to consider one of their turrets with the included prism.

 

I wish we could all magically appear at the same location on a night of terrific seeing so we could all compare our diagonals and learn from each other. Comparing is the only way I see to find the best and even then, these are all so good, it would be more down to differences in individual units and less a statement of who makes the best.

Where did you read that the Baader Zeiss prisms are not made the same way by the same people? Only the better Baader 36mm and 47.5mm Zeiss spec prisms have BBHS reflective coating and better AR coatings than the standard 32mm Baader prisms. The small 32mm standard Baader prisms are not BBHS coated, only AR coated, these are the same class of prism as the standard Takahashi 1.25" prisms. All of the Baader prisms are not equal, the BBHS coated Zeiss spec prisms are the better item. 

 

We gather all the time to observe and trade information, experiences and equipment. You need to find a big club or a better observing group and then show up and contribute to the group, don't be shy. 

 

Cheers/Chip



#24 agmoonsolns

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Posted 29 April 2019 - 08:57 PM

From talking with dealers and finally from communicating with Baader. They try really hard to answer most questions, but can get really cagey with the important stuff. They were very happy to discuss how they had "improved" the manufacturing process by replacing people with machines.

 

I am very familiar with the differences between BBHS and the various standard coatings. When it comes to coatings, the BBHS and the Phantom-type coatings are some of the best in the world with Astro-Physics coatings very close.

 

I do go to gatherings of the closest astronomical society in Olympia to share and contribute, but that's one heck of a long drive from here (about 5 hours round trip) and so I don't do it as often as I would like. I am in the middle of nowhere surrounded by ancient rain forests, Olympic mountains, and the Sound and ocean. Getting to the Seattle Astronomical Society and the Olympic Astronomical Society isn't so easy although the ferry rides to Seattle are fun. Hey, if you're in western Washington, come to the Hurricane Ridge star party this summer and we can compare diagonals. Being shy isn't one of my problems. Being the opposite of shy is. :-)

 

Where did you read that the Baader Zeiss prisms are not made the same way by the same people? Only the better Baader 36mm and 47.5mm Zeiss spec prisms have BBHS reflective coating and better AR coatings than the standard 32mm Baader prisms. The small 32mm standard Baader prisms are not BBHS coated, only AR coated, these are the same class of prism as the standard Takahashi 1.25" prisms. All of the Baader prisms are not equal, the BBHS coated Zeiss spec prisms are the better item. 

 

We gather all the time to observe and trade information, experiences and equipment. You need to find a big club or a better observing group and then show up and contribute to the group, don't be shy. 

 

Cheers/Chip



#25 SteveG

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Posted 29 April 2019 - 09:17 PM

I've read many posts over the years on these forums, stating the Tak 1.25" prism is excellent optically, and not-so-great mechanically. I have not used one, ever, so YMMV. The diagonal has a twist lock, and a lot of plastic.




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