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Review of the 18” f/5 Otte binodobson

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#1 PeterDob

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Posted 26 September 2016 - 10:58 AM

Sometimes, aperturefever can lead to a severe case of brain damage. The kind that compels you tomake a purchase that by all acceptable standards would be considered insane.Such is the case for those who decide to buy a gigantic binoscope. Already muchhas been said about the huge disadvantages of the binodobson. After all, theremust be a reason why almost no telescope manufacturing company offers them. Butare these prejudices true or are they merely based on assumptions without anyreal experience to back them up? In order to find out, me and my friends of theastronomical society of Trentino in northern Italy have put my new 18”binodobson to the test.


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#2 Astrojensen

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Posted 26 September 2016 - 11:47 AM

A scope like this has been on my wish list for quite some time. 

 

 

Clear skies!
Thomas, Denmark


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#3 denis0007dl

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Posted 26 September 2016 - 04:21 PM

OMG, what amazing setup!


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#4 Fmhiggins

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Posted 26 September 2016 - 04:50 PM

Just beautiful!  Thanks for sharing!

Clear skies!  

Mike

Parker CO



#5 Randolph Jay

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Posted 26 September 2016 - 08:59 PM

Beautiful instrument, beautiful observing site and I loved reading your review.  Your stunning sketches and now your introduction and review of this magnificent instrument have just blown me away with respect to what is possible in visual astronomy!  Thanks Peter.  Ok...now when I can I drop by for a look?  :)

Regards,

Randolph



#6 turtle86

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Posted 26 September 2016 - 11:46 PM

Really enjoyed your review. Awesome scope! Think you've really given a lot of us something to think about...



#7 jcruse64

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Posted 27 September 2016 - 08:18 AM

Beautiful scope! Only addition I would like to see on the review is a picture or two, up close, of the viewer and someone at the viewer.


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#8 The Ardent

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Posted 27 September 2016 - 12:21 PM

a fine instrument!!!
For me I'd want f/3.7 max focal ratio. No reason to have it f/5, it's already heavy and bulky enough without adding height.

#9 StellarOne

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Posted 27 September 2016 - 06:57 PM

The secondaries in a binoscope have to be larger in order to push the focal plane out sufficiently to allow the tertiary mirrors to fold the light path up to the eyepieces.  At f/3.7 for an 18" instrument they would be quite large:  around 5.2" (or possibly as much as 5.7" when using a Paracorr after the tertiary) - doable but moving into Schmidt-Cassegrain territory for obstruction ratios.

 

Another useful exercise is to work out the lowest power eyepiece that will not exceed the size of your dark-adapted pupils at various focal ratios (and that are not too large lest they bump into each other).  For most of us who are not very young, our pupils will be smaller than the oft-quoted 7 mm.


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#10 gillmj24

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Posted 27 September 2016 - 08:38 PM

This might give the heralded AP155edf binoscope a run for its money :)



#11 PeterDob

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Posted 28 September 2016 - 03:22 AM

Thanks guys!

As I mentioned in the review, the main reason why going below f/5 in a binoscope creates big difficulties is collimation and alignment. Slightly miscollimating an f/5 to obtain perfect alignment is no big deal. Slightly miscollimating an f/3,7 is a whole different story!

Cheers and you're all welcome to drop by when you're visiting Italy!

Peter
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#12 Shneor

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Posted 29 September 2016 - 01:31 AM

This is a very nice binoscope. But just so you know, five portable 22" binoscopes were constructed about 10 years ago. Two reside in Australia, two in Texas, and one at the home of the designer and builder near Auburn, California. Here's the web page describing them:

http://www.brucesayre.net


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#13 Solar storm

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Posted 29 September 2016 - 07:51 AM

My dream (if money were no object) would be to have one of these huge binoscopes and couple it with 2 night vision monoculars.  That would be deep space Nirvana.  


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#14 Shneor

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Posted 30 September 2016 - 01:43 AM

The first time I observed with one of the 22" binoscopes I targeted M31. The eyepieces were 30mm 80* and clones of an APM design. With both eyes a number of globular clusters were clearly visible as tiny disks. So of course, I closed one eye, and the disks disappeared, to become stellar objects.


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#15 Chopin

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Posted 30 September 2016 - 02:19 AM

Otte is one of my telescope heroes. To say I am envious would be an understatement. Every time I read of someone's experience with a well designed bino-dob it gets my gears turning for that next project...

 

Fantastic report, and a beautiful instrument. 



#16 PeterDob

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Posted 01 October 2016 - 01:01 PM

Thanks guys! :)

@Shneor: I've heard about the Sayre binoscopes and extensively read everything I could find about them before buying mine. But as I said in the review, very few telescope builders offer them... unfortunately...

Cheers!

Peter

#17 clay1022

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Posted 02 October 2016 - 11:44 PM

congrats!! great review, sounds like you are in for a lifetime of enjoyment.

Clay



#18 stefang

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Posted 03 October 2016 - 09:33 PM

Congratulations on a marvellous project. inspiring! sG



#19 ratnamaravind

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Posted 06 October 2016 - 05:45 PM

More of a bison than a binodobson :)

 

I would not hesitate to get one as long as it is for some sort of a permanent setup.



#20 TOMDEY

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Posted 10 October 2016 - 07:04 PM

Wonderful review; thanx so much! I have the JMI RB-16s, which are probably the only competing commercial giant binos? Your findings regarding collimation, zenith (non) access, light grasp and contrast all agreed. I think most folks talk themselves out of giant binos because of the cost and complexity. But once you are at the eyepieces... there's no going back unless you lose an eye. PS: I have added TWO I3 Night Vision eyepieces to mine with 6nm Ha filters. Now even the Horsehead looks like the CCD pictures!  Tom


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#21 martl

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Posted 14 October 2016 - 04:28 PM

Very interesting review. As formerly active ATM (have built a 10"  f5 binoscope in my younger days) I just take my hat off for that marvellous engineering. No thing like using 2 eyes. You better get a pair of 13 or 17mm Ethos soon!

CS

Martin


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#22 Lilvipa

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Posted 23 October 2016 - 06:08 PM

Quelle bête! I got to say, when I see monsters like this, it makes you wonder why we can't pool our money for sweet town observatories.  Un jour!


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#23 Fox1971

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Posted 31 October 2016 - 07:06 PM

When I look at the photos of this wonderful scope and then look at my little 8" SCT, I get seriously depressed. Congratulations on the scope of a lifetime. 


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#24 faackanders2

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Posted 06 November 2016 - 02:21 PM

Congrats and enjoy!  Truly a work of art.  Would have loved to see a photo where the eyepieces are at and directed from both dobs.


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#25 delgado39

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Posted 29 December 2016 - 04:44 PM

Yep, your insane alright . . . but we all are to some degree or other.  Enjoy yourself !!!  


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