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Equipment Discussions >> Binoviewers

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bratislav
sage


Reged: 09/07/06

Re: WO vs DenkII's new [Re: Eddgie]
      #5878983 - 05/22/13 08:03 PM

My brief experience with Denk II's and C11 shows that even with a 2" diagonal and added motorised Crayford focuser (over 280mm BFL) there is no reduction of aperture at all. Not even one millimeter. C11 retains its full 279mm aperture (measured). The f-ratio does go up of course, but that just accounts for higher magnification, not light loss.
Maybe smaller SCTs are affected, but it seems that at least C11 is not. (this is classic C11, not Edge)


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bratislav
sage


Reged: 09/07/06

Re: WO vs DenkII's new [Re: bratislav]
      #5878999 - 05/22/13 08:15 PM

PS Denks are far superior to WOs in many ways. They can be collimated, there is less of color shift between sides, prisms are much larger, self centering collets are much better than set screw (which can and often does tilt or shift the eyepiece), interpupilary and diopter adjustment is smoother and far more positive, bottom "plate" perfectly squares the bino to the diagonal unlike WO, list goes on.
I never stopped fiddling with WOs, Denk just goes out of the way.
True, once set up properly, there will be little difference between WOs and Denks. But, at least for me, the part of "setting up" was much longer and more painful with WOs.


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Eddgie
Postmaster
*****

Reged: 02/01/06

Re: WO vs DenkII's new [Re: bratislav]
      #5879134 - 05/22/13 09:42 PM

The C11 has the most open baffles of the Celestron line.

The C14 on the other hand has very tight baffles, as does the C8.

The C14 starts loosing aperture at 200mm of back focus.

The C8 starts loosing aperture at about 190mm of back focus.

The EdgeHD 8" looses apeterture even with only 165mm of back focus, which is to say that it is almost impossible for it to work at full aperture with a binoviewer with a long light path (New Denk 27s for example).

The OP has an 8" scope, and my own belief is that because the Meade is dimensionally similar to the C8, with 245mm of back focus, he is likely loosing aperture.

So was really directing my remarks to him.

Had you asked, I would have said that the C11 is OK with a longer light path.

But most likely not the OPs scope.


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bratislav
sage


Reged: 09/07/06

Re: WO vs DenkII's new [Re: Eddgie]
      #5879170 - 05/22/13 10:05 PM

Hmm. Something new every day! I'm surprised that C14 is not designed with more liberal baffles.
OTOH, no surprises with 8" SCTs. There is very little room left between opposite design goals of keeping the obstruction at sane levels, full baffling and a decent BFL.

Bottom line, it seems like C11 is a SCT of choice for binoviewers.


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rockethead26
Post Laureate
*****

Reged: 10/21/09

Loc: Arizona, USA
Re: WO vs DenkII's new [Re: pftarch]
      #5879636 - 05/23/13 07:12 AM

Quote:

You still need to use the corrector, it's just that the Denk newtonian corrector will work on your dob, and their refractor corrector will work on your refractor. (You may need to get two correctors, one for the dob and one for the refractor, I'm not 100% sure how Denk works it.)




Denk makes a Multi OCS which works with all scopes. My multi works with my Dob, my refractor and my Lunt solar scope.


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Eddgie
Postmaster
*****

Reged: 02/01/06

Re: WO vs DenkII's new [Re: bratislav]
      #5879735 - 05/23/13 08:31 AM

Well, if you think about it, the C14 is f/11, and the obstruction is the smallest of any of the SCTs by percentage of aperture.

Aperture loss starts at 200mm of back focus.

The C11 uses the same size baffle (though a bit bigger percentage of obstruction) so that makes sense that it would tolerate more back focus.

The EdgeHD 11 though apparently has more restricted baffles too. The C11 used to have better field illumination than the C14, but according to Celestron, they are the same now.

And the EdgeHD 8" is much worse than the old C8.

I have ray traces for the standard Celestron scopes and if you would like to see them, just PM me and I will send you the PDF.


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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: WO vs DenkII's new [Re: bcuddihee]
      #5879814 - 05/23/13 09:22 AM

So I'm looking at this photo it appears that you have the diagonal screwed right to the back and not needing an OTA? My tube is 2" long. Who's diagonal are you using and is that a small fan in it?

Also, nice set of pairs you have there, which ones do you use most? Can you see the whole FOV with the 32 Brandons?

Thanks,

Bob


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bcuddihee
Carpal Tunnel
*****

Reged: 11/04/06

Loc: Cincinnati Ohio
Re: WO vs DenkII's new [Re: REC]
      #5882278 - 05/24/13 01:08 PM Attachment (20 downloads)

This is a William optics 2" dielectric diagonal with the optional 2" sct to ota adapter. It makes for a shortened light path. It screws on tho the back of the ota and onto the diagonal. I have installed a fan in it which extracts air through the baffle tube. I have installed 6 small vents in the fron t of the ota as shown. With the fan on I have active air circulation and extraction from the ota resulting in much quicker cool down times. Yes also shown are my 32 brandons..I use them to keep from having to use my power swith "not shown in the above photo" due to the reduction in aperture issues related to using it. I can see out to the field stops but right before the fierld stops you can see a bit of vignetting. Not a lot but there is some. Hope this helps...the next pic shows the vent holes and the power switch installed. I don't use the reduction mode in the power switch much unless I'm trying to get the entire double cluster in the fov.

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bcuddihee
Carpal Tunnel
*****

Reged: 11/04/06

Loc: Cincinnati Ohio
Re: WO vs DenkII's new [Re: bcuddihee]
      #5882281 - 05/24/13 01:09 PM Attachment (23 downloads)

another..

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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: WO vs DenkII's new [Re: bcuddihee]
      #5882330 - 05/24/13 01:29 PM

Holey CATs, Batman- that is now a cool kitty!


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SkyGibbon
super member


Reged: 02/09/13

Loc: Las Vegas, Nevada
Re: WO vs DenkII's [Re: Mike B]
      #5885770 - 05/26/13 03:25 PM

I have a set of the WO binoviewers. Many of the issues some have stated here are a reason I am looking to upgrade. The eyepiece shifting from the lock screw is a pain. Having to basically redo the diopter adjustment with each eyepiece set change. I basically set focus with left eye, adjust diopter with right, then release locking screws and the image snaps in. The eyepiece holders seem very tight also. Having to do multiple barlow voodoo antics to come to work on certain setups. Saying that, the views are great when it is working and I don't regret my first binoviewer purchase.

It comes to focus with no attachments on both my refractors and my Mak if I put it straight in the focuser, although I do have a nice 2" and a nice 1.25" diagonal if I choose that route. Extremely bright and nice views. To mag it up, I just put in a 4" extender and screw my 1.6x and 2x barlow lens elements straight to the nosepiece of the binoviewer. One or the other, both together. Usually 95x is about all I need though. On my dob though I have to screw 2 filter rings (filters out) between the nosepiece and the ocs to get my 1.6 to focus with the shortest lightpath. 2x works fine screwing it directly into the nosepiece.


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