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Equipment Discussions >> Binoviewers

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Eddgie
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Re: Denk Binotron rollout new [Re: johnnyha]
      #5599822 - 01/01/13 03:24 PM

I think that in a Newtonian, the benefits of the Powerswitch are far greater.

In an SCT, it entials a lot of compromise though, and since my primary scope is an SCT, the powerswitch simply did not work to my satisfaction.

But for a Newtonian, I am sure it is everything everyone says it is.

Also, I did not like it at all on my 6" APO. It put me into a high power box. With the reducer arm in, the view was so dim that it seemed like I was looking trough an 80mm refactor.

Also, to get the "Advertised" 1.3x from the Denk Supersystem in a refractor, you have to use the Denkmeier diagonal (or some other diagonal that has the same threads). Otherwise, the OCS yeilds about 1.4x rather than 1.3x. Denkmeier doesn't clearly say this on their web page, but in the User's Guide it explains that the benefit of the Denkmeier Diagonal is that it lowers the magnification factor from 1.4x to 1.3x.

Frankly, I didn't like finding that out. I felt kind of deceived by the web page.

Anyway, I did not find it to be all that useful in my 6" APO because I don't use that scope for planets, so the high power arm was of no particular benefit to me in that scope.

Again, I think in a Newt or a refactor that will reach focus without the OCS, this would be a great way to go!


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faackanders2
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5599870 - 01/01/13 03:53 PM

Newtonian reflectors definitely require OCS's to focus (believe the same is true for refractors as well).

Also believe star sweeper OCS can only be used by SCTs.


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Eddgie
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Re: Denk Binotron rollout new [Re: bcuddihee]
      #5599884 - 01/01/13 04:01 PM

Quote:

I did run a light protection test on my c8 with the power switch and the reducer reduced effective aperture to a hair over 6 inches. Straight through I was measuring around 7-3/8 effective aperture, the mag mode showed almost no aperture reduction. Just my results and in no way difinative other than that it did substantiate the effect of the power switch in the reduction of aperture. In addition...with the reduction of aperture with the CO being a constant, the CO percentage increases as well. Hope this helps.




Thanks for sharing this data.

Can you tell me what your configuration was, or do you happen to know the back focus for the entire system? I am collecting this info for reference to use when this topic comes up again.

I personally an not at all surprised by the numbers. I know that the first time I used the low power arm in my C14, something was seriously wrong. The view was nothing short of horrible! I remember thinking that it looked like I was looking though a C10!!! I did not do a measurment, but I estimate that the aperture was less than 11"!

Straight though, It was about 13.3". This does not sound like much, but I could see the difference (and this is about a 12% difference in image brightness so anyone should be able to see this. Eyepiece forum guys can see a 4% difference.. LOL).

Also, you might be interested to know that using the Baader diagonal and the Glee Telescopressor, AstroJensen was able to get his C8 to work with only 10mm aperture loss. This is about as good as it gets with an SCT and a reducer. I am not aware of another configuration that comes close to this. But he was also using the Maxbright Binoviewer, and while this unit has smaller prisms, it also has 10mm less light path than the Mark Vs and even the standard Denk. I suspect that the new Binotron will have at least as much as the mark V, and maybe more.

I do not know if he used the Baader SCT to T2 converter in his light path or not, but if he didn't this might improve the situation a bit. But again, he was using the Maxbrigth/T2 which is the shortest light path in the bino world that I know of.

But thanks for confirming this message. I don't want people to think I make this stuff up.. LOL.

Bottom line is that a focal reducer (low power arm) and binoviewer used with just about any SCT made will entail a pretty serious aperture reduction, and 2" based systems will often not work at full aperture on many SCTs even in straight through mode.

This is why I went to the Mark V/T2 Prism. It gives the shortest possible back focus in a large prism bino when used in an SCT.

And while some SCTs may still loose a bit of apeture, this will give them the largest possible aperture in a big prism bino. You only trade a couple of millimaters of aperture but this is compensated for by being able to use a 24mm Pan or similar so you can get reasonably larger true field.


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Eddgie
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5599938 - 01/01/13 04:43 PM

By the way.. No one should think that I am slamming the Binotron in any way. I think it is an exciting new product! Just want to make sure that the powerswitch issue was clearly and cleanly addressed. This is just an SCT issue, but an important one if you own an SCT.

And this.. If Denkmeier is smart, they will introduce a very short back focus solution, or list a dovetail adapter that would allow the use of the Baader prism on their web page.

Just going to the T2 prism can save anywhere from 15mm to 50mm of back focus.

And no one should use a 2" diagonal on a binoviewer in an SCT. Not only does it usually reduce the aperture, but it also makes a big increase in focal lenght, which raises magnificaiton and reduces field size.

This is what made the Mark V so attractive to me, and unless Denkmeier can counter, people that have done their homework may still move to the Mark V because of the shorter light path.

Home run for Newt onwers though. Beautiful unit. I am impressed.

Edited by Eddgie (01/01/13 04:44 PM)


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bcuddihee
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5599961 - 01/01/13 05:04 PM

I don't know the back focus numbers but I am using a William Optics 2" diagonal with a WO SCT threaded adapter to couple it to the visual back (no nose piece). The power switch is attached directly to the top of the diagonal(the S2 config),with binos with 2" adapter sitting on top. actually I got some heat on one of the threads for making a point of the aperture reduction issue, as if I was trying to put down SCT's or something. Nothing could be further from the case. The C8 I own is one of the best examples I've seen and I wouldn't part with it for a even 6"AP...........well maybe:)
bc


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bcuddihee
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Re: Denk Binotron rollout new [Re: bcuddihee]
      #5599969 - 01/01/13 05:06 PM

PS...I really like the convenience of power switch...you should be aware though of its limitations. I regularly use the barlow mode as it works well with the ep fl's I have chosen as my workhorses.

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Denimsky
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5599971 - 01/01/13 05:07 PM

Thank you very much Ed.

It was very useful to understand the big picture regarding the Binoviewer.


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Eddgie
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Re: Denk Binotron rollout new [Re: bcuddihee]
      #5600066 - 01/01/13 06:10 PM

Ok, these adapters look like they have about 30mm of back focus.

A 2" diagonal will usually have about 100mm from the front of the mirror box to the top of the eyepeice holder, but I am unsure from your discription if there is an eyepeice holder or if the switch somehow attaches directly or the eyepeice barrel is removed from the diagonal and the switch screws into it???

If it is a typical 2" diagonal and eyepiece though, the back focus will be 100mm.

The light switch I think is about 18 or 20mm.

The binoviwer is about 120mm.

About 270mm of back focus...

A picture would help me understand the configuration though.

But if you are using 260mm of back focus, the focal length of your system is about 2550mm.

You should see about converting to a Baader diagonal and SCT adapter. This can cut a couple of hundred millimeters off of your focal lenght and give you back some aperture in straight through mode.


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GlennLeDrew
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5600115 - 01/01/13 06:40 PM

It would be useful to include in the Binotron's specs on-line some detail on the user collimation feature. This could go some way toward alleviating doubt or skepticism among some, and swing over yet more prospective buyers. Based on the awfully brief and vague 'ad copy' on the matter so far, I do nonetheless feel it to be a most important feature which will ease the lot of all observers. I'm certain it's designed so that one cannot ever put it permanently out of whack.

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johnnyha
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Re: Denk Binotron rollout new [Re: bcuddihee]
      #5600132 - 01/01/13 06:48 PM

Quote:

PS...I really like the convenience of power switch...you should be aware though of its limitations. I regularly use the barlow mode as it works well with the ep fl's I have chosen as my workhorses.



Well it's certainly easier than switching out Baader Glasspath Correctors!


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faackanders2
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5600191 - 01/01/13 07:28 PM

"And no one should use a 2" diagonal on a binoviewer in an SCT. Not only does it usually reduce the aperture, but it also makes a big increase in focal lenght, which raises magnificaiton and reduces field size."

Could 1.25" diagonal be why I do not like binoviewing with solarmax 40mm, and only like binoviewing weith my large dobsonian? I don't own a refractor nor SCT.


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Eddgie
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Re: Denk Binotron rollout new [Re: faackanders2]
      #5600234 - 01/01/13 07:56 PM

The the size of the diagonal should not change the optical performance (except for very fast telescopes), but it does make the back focus requirement less than a 2" diagonal.

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drprovi57
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5600237 - 01/01/13 07:58 PM

I am currently waiting a delivery of a Planewave CDK 12.5 and I am interested in using the new Binotron 27 for some occasional visual observing. I would be interested in any thoughts or comments on binoviewers with a CDK.

Thanks
Jason


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GlennLeDrew
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Re: Denk Binotron rollout new [Re: drprovi57]
      #5600387 - 01/01/13 09:49 PM

If the CDK has the focus placed sufficiently far back so as to accommodate the considerable optical path length of the BV setup, it'll work well enough. The CDK's larger central obstruction will slightly impact fine scale contrast, but only in the higher magnification regime, where the exit pupil is getting down to close to 1mm.

The primary concern, really, is available back focus, as the CDK has its mirrors at fixed separation.


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rick rian
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Re: Denk Binotron rollout new [Re: GlennLeDrew]
      #5600866 - 01/02/13 08:56 AM

Quote:

It would be useful to include in the Binotron's specs on-line some detail on the user collimation feature. This could go some way toward alleviating doubt or skepticism among some, and swing over yet more prospective buyers. Based on the awfully brief and vague 'ad copy' on the matter so far, I do nonetheless feel it to be a most important feature which will ease the lot of all observers. I'm certain it's designed so that one cannot ever put it permanently out of whack.




Agreed! I'd be interested in the binos minus the power switch feature, I wonder if he'll offer that ...


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bcuddihee
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Re: Denk Binotron rollout new [Re: rick rian]
      #5600881 - 01/02/13 09:10 AM Attachment (73 downloads)

Eddgie, here is a pic of my config.

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Eddgie
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Re: Denk Binotron rollout new [Re: bcuddihee]
      #5601248 - 01/02/13 01:17 PM

That is about as short as you can get using a 2" diagonal i would say.

I would guess that the SCT connector is about 15mm. Pretty short. The light path though a 2" diagonal body is usually about 75mm. As I recall, the powerswitch itself is about 18mm. It looks like the eyepeice holder is about 35mm, and the light path though the bino is I think is about 120mm.

So, this is about 263mm of back focus.

According to Ken Hudchinson's SCT vignetting analysis, your scope would be working at right about 7.3" which is good to hear because it matches perfectly with your own measurment!!! I have had people question Ken's work, but in this case, it appears to agree quite well with an actual measured scope.


But you might be able to get even less if you can go to the Baader Prism.

Someone showed an adapter that they used to connect a Denk to a Baader prism.

This would save you about 35mm from the eyepeice holder, and at least 30mm from the diagonal light path.

If you could reduce the back focus this much, you would get your C8 to work at maybe 201mm, which would be a nice improvement.

And I was a bit conservative with my estimates, but you can always measure yourself to see if the savings would be worth it.

But this is why I like the Baader system so much, and don't like the Powerswitch on the SCT. Every millimater matters and the Baader/Mark V is right at 200mm in my current configuration.

Anyway, you could restore most of the aperture you are loosing now by going to the T2 diagonal and connecting the powerswitch directly to the T2.

I think Jonny showed an adapter for this not long ago.

Thanks for the picture, and if you ever get around to measuring the light path directly so we can get an accurate number, I would appreciate knowing it.

Edited by Eddgie (01/02/13 01:38 PM)


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johnnyha
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5601264 - 01/02/13 01:29 PM

Brendan - can you elaborate on the fan/diagonal? I've never sen that...

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DaveJ
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Re: Denk Binotron rollout new [Re: Eddgie]
      #5601305 - 01/02/13 02:01 PM

Quote:

But you might be able to get even less if you can go to the Baader Prism. This would save you about 35mm from the eyepeice holder, and at least 30mm from the diagonal light path.




Actually, he can cut out the 35mm wasted by the eyepiece holder/2" bino nosepiece by using the Denkmeier dovetail connector in place of the 2" nosepiece. See the two silver thumbscrews above the PowerXswitch? They are holding the 2" eyepiece holder in place. Instead of using that configuration, Denkmeier has a very shallow dovetail connector that screws to the bottom of the binoviewers instead of a 1.25" or 2" nosepiece. The random variable in this case is its use with the OCS and PowerXswitch configuration. They may require the 35mm of the 2" eyepiece holder to allow the system to come to focus.
For a photo & description of the aforementioned dovetail connector, go to the Denkmeier site and scroll about half-way to the end of the page until you come to the "About the Dovetail Connector" paragraph.


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bcuddihee
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Re: Denk Binotron rollout new [Re: DaveJ]
      #5601494 - 01/02/13 04:02 PM

Johnny, I don't want to hijack this thread but I did a write up on this active cooling mod a while back. I did this project in two parts..I'll attach both links. The mod BTW works great. Check it out

Venting an SCT questions??????

passive air vent

Edited to shorten the links. Thank you for the pointers Brendan!

Edited by Richard McC (01/03/13 02:04 AM)


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