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An SCT will have enough focuser travel to accommodate a binoviewer natively but will introduce some spherical aberration by doing so. As such you may find you prefer to use a barlow element to reduce the required in focus. 

Which objects you can view with the binoviewer depends on the the resulting magnifications, fields of view and exit pupils that can be achieved with your preferred combination. 

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30 minutes ago, Ricochet said:

An SCT will have enough focuser travel to accommodate a binoviewer natively but will introduce some spherical aberration by doing so. As such you may find you prefer to use a barlow element to reduce the required in focus. 

Which objects you can view with the binoviewer depends on the the resulting magnifications, fields of view and exit pupils that can be achieved with your preferred combination. 

When you say 'Barlow element' - is that just putting a Barlow before the bino-viewer (I have a 2x barlow). Thanks.

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16 minutes ago, Bino Pete said:

When you say 'Barlow element' - is that just putting a Barlow before the bino-viewer (I have a 2x barlow). Thanks.

The optics part, minus the extension tube.  Many barlows have removeable optical nosepieces that are filter threaded and can be screwed onto the front of the binoviewer.  The optical path through the binoviewer replaces the original barlow extension tube.  I use the nosepiece from a Meade 140 2x barlow for this purpose.

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1 hour ago, Bino Pete said:

Are they only useful for viewing the moon/planets?

I would say most useful.  They are useful on any bright or high contrast object.  They would not be recommended for detecting faint galaxies at the limits of perception, for instance.

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51 minutes ago, Louis D said:

The optics part, minus the extension tube.  Many barlows have removeable optical nosepieces that are filter threaded and can be screwed onto the front of the binoviewer.  The optical path through the binoviewer replaces the original barlow extension tube.  I use the nosepiece from a Meade 140 2x barlow for this purpose.

As my barlow is a 2" one will this be able to be used on a bino-viewer or would I need a 1.25 Barlow? Thanks.

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Having used my binoviewers in my cpc800 and cpc1100 then I agree that you need a 1.25" diagonal.

you do not need the barlow, the sct has plenty of infocus (you will need several turns of the focus knob to reach focus). The Barlow will just give you loads of unwanted magnification.

i really enjoyed my binos on the CPC on all targets not just planets.

it is my opinion that binos allow you to stay at the eyepiece for longer (than one eye viewing) and this allows more to be seen, add in the fact that your brain is also engaged when using two eyes then I found it really hard to compare single and two eye viewing results. It's not clear cut that two eyes are no good on dso - certainly that was not my experience.

i guess it also depends on which binoviewer you are intending to use?

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16 hours ago, alanjgreen said:

Having used my binoviewers in my cpc800 and cpc1100 then I agree that you need a 1.25" diagonal.

you do not need the barlow, the sct has plenty of infocus (you will need several turns of the focus knob to reach focus). The Barlow will just give you loads of unwanted magnification.

i really enjoyed my binos on the CPC on all targets not just planets.

it is my opinion that binos allow you to stay at the eyepiece for longer (than one eye viewing) and this allows more to be seen, add in the fact that your brain is also engaged when using two eyes then I found it really hard to compare single and two eye viewing results. It's not clear cut that two eyes are no good on dso - certainly that was not my experience.

i guess it also depends on which binoviewer you are intending to use?

What eyepieces do you use with your viewer?

I was looking at this - http://www.rothervalleyoptics.co.uk/celestron-stereo-binocular-viewer-125.html - are these classed as cheaper end models (as I've just seen what viewer you have!!). Is the Celestron one ok?

Thanks

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The binoviewers are foremostly distinguished by their prism size. Only the very expensive binos use 30mm prisms which allow the full aperture of 1.25" eyepieces. Buy cheaper and the prisms get cheaper and smaller meaning vignette of the eyepiece (not full width of view)

I would buy a decent pair second hand to start off, see how you get on with them, upgrade to premium later if you find you use them a lot.

Three things to learn about and get exact spec for:

1. Prism size (less than 28mm means vignetting)

2. Lightpath added by binoviewer (you need to get it all back to achieve focus in non-SCT scopes)

3. Connectivity to diagonal and other scopes (T2 is most flexible)

 

best second hand options 

- Baader maxbrights (out of production, new model expected 2018)

- William Optics (as have eyepieces and Barlow included)

 

Premium options (30mm prism)

- TeleVue Binoview (Nice but lack connectivity flexibility & not the shortest lightpath)

- Baader MarkV (I own a pair of these, big prism, small lightpath, great connectivity = fantastic!)

 

Both Baader units are the most flexible because they have T2 connections allowing direct connection to diagonals, scopes and other accessories. This is the key area to worry about as it determines if you can reach focus without barlow of glass path corrector. A T2 connection can save 10mm of light path and with refractors this is crucial.

This link shows all the Baader options and parts...

https://www.teleskop-express.de/shop/index.php/language/en/manufacturers_id/5/filter_id/60/astro/Baader.html

here is a link to T2 diagonals, you will need a 1.25 inch 30mm one or you get more lost light...

https://www.teleskop-express.de/shop/index.php/language/en/manufacturers_id/5/filter_id/9/astro/Baader.html

 

First thing is to buy the binoviewer. You may or may not need accessories to make them work but this is best sorted after you get the binos.

Now, the Celestron binoviewer...

Spec says 22mm prisms so you will get vignetting on lower power EPs

They are exact same as the William Optics according to this article

https://www.cloudynights.com/topic/511998-review-binoviewers-zeiss-baader-william-optics-siebert-denkmeier/

The William optics version comes supplied with a pair of eyepieces and a Barlow

second hand set http://www.astrobuysell.com/uk/propview.php?view=132127

new https://www.firstlightoptics.com/misc/william-optics-binoviewer.html

or wait for the new Baader Maxbrights. If you email teleskop-express then they will tell you what they know? They are great company, don't worry that they are in Germany, they speak good English and delivery is super quick :) 

What eyepieces to use?

Your best bet is to test the binos with one eyepiece that you already own (using one eye), if all is well (comparable to when you remove the binos ) then buy a second one to match. It's an expensive job to buy pairs in one go. You also need eyepieces that are not too wide or your nose will not fit in between them! Again, some bino specs will quote IPD range (distance between your eyes).

First job, is to see how much you use them then think about upgrades to premium lifetime binos and EPs... :) 

Alan

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