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Denk Binotron rollout

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#51 Jim7728

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Posted 04 January 2013 - 04:18 PM

If I was starting from scratch, I certainly would buy the new model.


Same here. Introduction price is a nice deal, but I'm not about to sell my Standard PX and TV Bino-vue for them.

FWIW, I like the power switch for Solar, Lunar and Planets. Gotta find that mod thread for mating the TV Bino-vue to the Denk PX.

#52 teskridg

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Posted 05 January 2013 - 09:27 AM

What I like to know is that the Denk II still loses the aperture for the other two magnification factor (not the reduction arm is used): I think it is 1.2X and 2.8X.



Remember, this problem is somewhat unique to telescopes with moving mirror focusing and baffles, though it could be encountered in some refractors if the in-focus allows the front of the focuser tube to cut into the light cone, which is a very real possibility in some cases.

To answer the question though, in the case of the MCT, I was loosing apeture in reduced mode (severe aperture loss) and staight through mode (minor loss).

This has to do with the fact that the Super-system I used was based on the use of a 2" diagonal.

The C14 and C8 both start to loose aperture once the back focus goes past about 200mm. The C9.25 I think starts loosing aperture once the back focus goes above about 170mm and the falloff is quick.

As an example, in my C5, as measured directly, I am using a back focus of 203mm, and the 127mm scope is being reduced to 122mm.


The Denkmeier System I used was based on a 2" diagonal, and the entire back focus required to use it was about 230mm or so.

With 230mm of back focus, the C14 is working at slighly less than 14" of apeture (Maybe 13.75") and the C8 would be working at about7.7". The plot that I have for the C9 suggests that the 230mm of back focus would give an aperture of 8.75".

Because the aperture is reduced, the central obstruction becomes bigger by percentage of aperture so the contrast is further lowered.

This is in straight through mode.

With the High Power arm in, the back focus requirment is reduced. I don't know how much it changes, but this would mean that the high power arm will give the system more apeture than straight though, because the mirror needs to be moved back slighly to re-position the focal plane.

Now I can only be fair about this and say that many people (perhaps most people) will not care about this very slight loss in performance.

So, it only matter if it matters, but for those that want to get the absolute best performance from their SCT or refractor, they want to make sure that they are not working with a reduced aperture.

If the new Denkmeier can be attached to a Baader Prism or other device that will shorten the light path, aperture loss can be reduced or prevented in SCTs, MCTs, and many refractors that were not designed to allow a full apeture when the focuser was fully racked in (and this is not at all unusual, though after the Stellarvue debacle 10 years ago, I think it doesn't happen so much anymore).

Again, the back focus is the issue, and the point where aperture loss is very model specific (The C11 has the loosest baffle of the Celstron SCTs).

But if the back focus is over 200mm, most SCTs will start loosing aperture, which means in straight through or reducer mode, many will work at reduced aperture. With the high power arm in, the amount of apeture reduction will either be reduced, or in some cases, perhaps even eliminated.

The key to doing this in these scopes is the Baader approach where the binoviewer attaches directly to the top of the diagonal and keeping the connection to the telescope as short as possible.

If someone wanted to use the new Denkmeier in an SCT and keep the system working at full apeture, they would need to go to a Baader type diagonal with a short connector (Like the Baader SCT connector which only adds 15mm of back focus) and the Prism, which only adds I think 38mm of back focus. The Mark V binos add about 120mm of back focus, so this system will have a total requirement of about 173mm.

But in my Denkmeier, the power-switch alone added 18mm of back focus, so right there, if you go with a standard 2" SCT adapter and a standard lenght 2" nose, even if you used a Baader type diagonal, you are well over 200mm, which is the point that many SCT models will start to loose aperture.

Here are the numbers....

The Baader SCT adapter requires 15mm of back focus.

The Baader Prism requires about 38mm of back focus.

the Power Switch requires about 18mm of back focus (unless they have made it thinner).

A large prism bino will require about 120mm of back focus (this is what the Mark v requries).

Add this up and you get 191mm. If someone wants to use a powerswitch and avoid aperture loss with a moving mirror scope even in straight though mode, this will be the best configuration to use.

A 2" diagonal alone will put you well over 200mm, even if it is the Baader 2" diagonal.


Thanks a lot, Eddgie! I might not have cared about the effective aperture loss at low power switch setting in my CPC-1100 if you hadn't started this some months ago. Seriously, I'm willing to trade this aperture reduction at low power for the wider field for certain DSO's like M35. In addition, Eddgie, you can get customized high power lenses for the Denks and Earthwins that are less powerful and more convenient perhaps for you. I'm curious to find out from the first users of this new system if the extra mm of clear aperture renders less vignetting with 24mm Panoptics in the reduced power x switch setting than presently with 26mm clear aperture binoviewers. Tim

#53 Space Dragon

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Posted 05 January 2013 - 12:57 PM

I use the Earthwin PFS-B with Power/Filter switch [the model optimised for Newts] in a CPC 925. It was a great price.
In this configuration, the barlow acts as a reducer but not as reduced as the reducer itself.
I also have a 2x Barlow OCS which screws into the nosepiece.
There's about 7 turns of the focuser between each point.
I did consider changing out this glass from the powerswitch for one that would act as a barlow but I've found that I use the less reduced option a lot as the vignetting is hardly noticed and on the rare occasions I want to Barlow, screwing the OCS on only takes seconds.
I use the Baader T2 Diagonal with the 10mm SCT connection and a T2 - 2" adapter on the other side.[It's not ideal but the nosepiece on the Binos is not removable].
The vignetting is noticeable with 24mm Pans in full reducer mode, less so in half reducer and not in straight through or Barlow mode.
I did do the aperture flashlight test and did notice some loss with both reducers but not as much as I'd expected.

#54 faackanders2

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Posted 05 January 2013 - 08:57 PM

Thanks a lot, Eddgie! I might not have cared about the effective aperture loss at low power switch setting in my CPC-1100 if you hadn't started this some months ago. Seriously, I'm willing to trade this aperture reduction at low power for the wider field for certain DSO's like M35. In addition, Eddgie, you can get customized high power lenses for the Denks and Earthwins that are less powerful and more convenient perhaps for you. I'm curious to find out from the first users of this new system if the extra mm of clear aperture renders less vignetting with 24mm Panoptics in the reduced power x switch setting than presently with 26mm clear aperture binoviewers. Tim


You can purchase the 45mm clear aperture 1.2x Multipurpose OCS seperately.

#55 Jeff B

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Posted 06 January 2013 - 09:12 AM

I wonder if the power switch inlet becomes the limiting diameter now.

#56 beatlejuice

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Posted 15 January 2013 - 10:05 PM

Had an informative talk with Russ today and finally purchased my first binoviewer: The Binotron-27. Will probably be over a month before it arrives so now the anticipation and waiting begins.

Eric

#57 dajebriza

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Posted 16 January 2013 - 05:36 AM

I bought one too. I sold my Denk II supersystem with filter switch (hardly used it) for the price of the Binotron-27 supersystem sale, so it was break-even for me to upgrade. Looking forward to getting it!

#58 t.r.

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Posted 16 January 2013 - 11:50 AM

This is quite an offer for those just getting in...I'll have to stick with my Denk II's though, nothing to gain.

#59 ckwastro

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Posted 17 January 2013 - 09:14 AM

I've got the Denk standards, and have been debating whether or not to upgrade to the Denk II or the Mark V. Now I'm considering the Binotron or the Mark V. Decisions, decisions........

#60 denis0007dl

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Posted 17 January 2013 - 10:29 AM

I've got the Denk standards, and have been debating whether or not to upgrade to the Denk II or the Mark V. Now I'm considering the Binotron or the Mark V. Decisions, decisions........


Binotron sounds really good, but he has 26mm Clear Aperture prisms, while Mark V has 28mm! I really like my MkV :)

#61 ckwastro

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Posted 17 January 2013 - 11:17 AM

I've got the Denk standards, and have been debating whether or not to upgrade to the Denk II or the Mark V. Now I'm considering the Binotron or the Mark V. Decisions, decisions........


Binotron sounds really good, but he has 26mm Clear Aperture prisms, while Mark V has 28mm! I really like my MkV :)


Optically the Mark Vs are my front-runners. My concern is whether or not I will tire of constantly changing out the Glasspath Compensators. I know there can be some minor vignetting issues with the Power Switch, but the convenience of being able to change magnifications without switching configurations or getting up from the scope to change eyepieces is very nice.

My decision problem is that I'm very picky about optics, but I have limited time for observing these days, so convenience becomes more of an issue than I would prefer. :gve:

#62 crazyqban

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Posted 17 January 2013 - 05:07 PM

Optically the Mark Vs are my front-runners. My concern is whether or not I will tire of constantly changing out the Glasspath Compensators. I know there can be some minor vignetting issues with the Power Switch, but the convenience of being able to change magnifications without switching configurations or getting up from the scope to change eyepieces is very nice.


You can always use a Denk PowerSwitch with your Mark Vs. Here is how I did it...

FrankenBino

Eventually though, I was not totally happy with the Power Switch's low power setting so I got a Siebert 1.3X Multi Mag OCA and a few more bino pairs of eyepieces. I also tested the 1.7 Newtonian Glasspath Compensatoer but at 1.7X magnification, the less amount of wide view was not working for me. I now just change eyepieces and the 1.25x Glasspath Compensator stays in the Mark V's for the most part. The only time I remove the 1.25X Glasspath is when I need a little less magnification. At first I thought that it would be a pain in the rear end but it's not too bad once you get used to it.

#63 ckwastro

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Posted 17 January 2013 - 08:10 PM

Thanks Sergio. These give me some more possible solutions, but I'm actually leaning towards your suggestion of just leaving in the 1.25x and adding EP pairs. Appreciate the link and ideas! :grin:

#64 beatlejuice

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Posted 01 February 2013 - 03:11 AM

Here is the link to the B27-manual If you have the time to read it, any comments on the collimation procedure?

Eric

#65 teckpro

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Posted 14 April 2013 - 03:20 PM

I have the meade lx200 12" gps.
When using the denk binos with power switch system.


What will I see/ not see when my aperature is being
reduced??

Thanks.






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