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Denk Binotron rollout

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#26 bcuddihee

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Posted 01 January 2013 - 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.

#27 Denimsky

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Posted 01 January 2013 - 05:07 PM

Thank you very much Ed.

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

#28 Eddgie

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Posted 01 January 2013 - 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.

#29 GlennLeDrew

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Posted 01 January 2013 - 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.

#30 johnnyha

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Posted 01 January 2013 - 06:48 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.

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

#31 faackanders2

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Posted 01 January 2013 - 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.

#32 Eddgie

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Posted 01 January 2013 - 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.

#33 drprovi57

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Posted 01 January 2013 - 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

#34 GlennLeDrew

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Posted 01 January 2013 - 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.

#35 rick rian

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Posted 02 January 2013 - 08:56 AM

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 ...

#36 bcuddihee

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Posted 02 January 2013 - 09:10 AM

Eddgie, here is a pic of my config.

Attached Files



#37 Eddgie

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Posted 02 January 2013 - 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.

#38 johnnyha

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Posted 02 January 2013 - 01:29 PM

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

#39 DaveJ

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Posted 02 January 2013 - 02:01 PM

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.

#40 bcuddihee

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Posted 02 January 2013 - 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!

#41 johnnyha

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Posted 02 January 2013 - 04:17 PM

Thanks I will check that out!

#42 beatlejuice

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Posted 02 January 2013 - 05:25 PM

what happened to make this thread twice as wide as it was at the start? Annoying!

Eric

#43 GlennLeDrew

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Posted 02 January 2013 - 06:26 PM

The last post on page two has ridiculously long hyperlinks. They should have been shortened, as per the suggestions/guidelines posted at the tops of at least most Forums.

#44 bcuddihee

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Posted 02 January 2013 - 07:03 PM

Eric..i was simply trying to answer a question. Sorry for yor inconvienience.

#45 beatlejuice

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Posted 02 January 2013 - 08:41 PM

Eric..i was simply trying to answer a question. Sorry for yor inconvienience.




Isn't this convient link
the same link without the extra length?

Eric

#46 bcuddihee

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Posted 02 January 2013 - 08:48 PM

yes it is.. but isn't civility even more desirable.

#47 beatlejuice

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Posted 02 January 2013 - 08:56 PM

yes it is.. but isn't civility even more desirable.


No incivility implied on my part, I was just pointing out a better way of doing something as I am sure there are others who dislike having to scroll in both directions to read a thread. If you are not sure how to do it I would be happy to guide you.

Cheers

Eric

#48 panhard

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Posted 02 January 2013 - 08:57 PM

Shorter links are desired. :grin:

#49 drprovi57

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Posted 03 January 2013 - 10:03 PM

Thank you for the insights.. The CDK 12.5 has about 7" of back focus , so should work

Best
Jason

#50 Mr. Bill

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Posted 04 January 2013 - 01:19 PM

I have the Denk IIs....other than picking up 1mm of clear aperture with the Binotrons (and collimation adjustment) what would I gain with the new model that would justify buying?

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

:question:






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