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Binoviewer eyepieces


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I am getting ready to buy my first binoviewer and was thinking about suitable eyepieces. I love my Morpheus eyepieces and was thinking about 2 x 17.5mm or 12.5mm, or should I be looking for something lighter?

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Personally I would go for lighter as binoviewers are heavy to start with! The Morpheus are ~350g(?), and you'll need two so added to the weight of the Binoviewers you're talking maybe a kilogramme on the end of your scope. Much depends on how easily you can adjust the balance of your scope on your mount and what your mount is. I find my setup is definitely more shaky with the Binoviewers on.

Malcolm 

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If you are going to be using a 2x Barlow nosepiece operating at that or even a higher power, you can get away with using lighter, cheaper eyepieces.  I've found Svbony 20mm UWAs work really well at 3x (f/18 in my scopes).  I can't get my nose between fat eyepieces like the Morpheus.  That, and two of them plus the BV weigh a lot.

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Hi, 

I suppose it might also depend on what you want to observe with them. I pretty much exclusively use binoviewers now. For planetary and lunar viewing I just use Televue Plossls which are very sharp but for deeper sky I mostly use the Panoptics (19s and 24s) which work very well will the Binoviewers, Naglers up to about 16mm also work well.

IPD is the big thing with binoviewers, my IPD is pretty narrow so rules out most wide barrel eyepieces. I have a friend who swears by the Baader Mark IV zooms for his binoviewers but I could not use them.

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Thanks folks. I was concerned about the weight of two Morpheus or similar eyepieces so I’ll be definitely going lighter. I was also thinking of the Baader classic 18mm or the televue plossl’s as previously mentioned. Has anyone tried the 18mm Baader classics?

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3 hours ago, bosun21 said:

I am getting ready to buy my first binoviewer and was thinking about suitable eyepieces. I love my Morpheus eyepieces and was thinking about 2 x 17.5mm or 12.5mm, or should I be looking for something lighter?

Don't forget the eyepieces will act like eyepieces with a shorter focal length, based on the magnification factor of the optical corrector assembly (OCA) on the binoviewers.

An 18mm eyepiece may function as a 9mm.  If the binoviewers are being used for lunar and planetary observing, that may be what you want.

The most popular pairs of eyepieces I see used in most binoviewers, though, are 32mm 50° and 24mm 68° because of magnification.

Those correctors come in many magnifications, though, and what eyepieces would be appropriate should be based on that.

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13 minutes ago, Don Pensack said:

Don't forget the eyepieces will act like eyepieces with a shorter focal length, based on the magnification factor of the optical corrector assembly (OCA) on the binoviewers.

An 18mm eyepiece may function as a 9mm.  If the binoviewers are being used for lunar and planetary observing, that may be what you want.

The most popular pairs of eyepieces I see used in most binoviewers, though, are 32mm 50° and 24mm 68° because of magnification.

Those correctors come in many magnifications, though, and what eyepieces would be appropriate should be based on that.

Thanks Don, when you are talking about the OCA are you referring to the additional accessories that usually come with the binoviewer? ie: the barlows, or are you referring to an internal component of the binoviewer? I was taking into consideration the eyepiece focal length being reduced by whichever size the OCA being used. For instance a 20mm eyepiece with a 2x OCA would be a 10mm equivalent. Is my grasp of this correct? Thanks 

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4 hours ago, Neil P said:

Hi, 

I suppose it might also depend on what you want to observe with them. I pretty much exclusively use binoviewers now. For planetary and lunar viewing I just use Televue Plossls which are very sharp but for deeper sky I mostly use the Panoptics (19s and 24s) which work very well will the Binoviewers, Naglers up to about 16mm also work well.

IPD is the big thing with binoviewers, my IPD is pretty narrow so rules out most wide barrel eyepieces. I have a friend who swears by the Baader Mark IV zooms for his binoviewers but I could not use them.

 

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I can highly recommend the APM 15mm ultra flats.

Good value and they compliment the 19mm / 24mm Panoptics very nicely.

Agree with MalcolmM : smaller glass is generally better suited for binoviewing.

As said, a 1 to 1.5kg load can get rather unwieldy and will cause balancing issues as well as asking questions of your focuser.

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19 minutes ago, Space Hopper said:

I can highly recommend the APM 15mm ultra flats.

Good value and they compliment the 19mm / 24mm Panoptics very nicely.

Agree with MalcolmM : smaller glass is generally better suited for binoviewing.

As said, a 1 to 1.5kg load can get rather unwieldy and will cause balancing issues as well as asking questions of your focuser.

I already have the 18mm and 10mm ultra flat eyepieces although with the SVbony label. I looked at the 15mm APM and it has a similar form factor to the 10mm which is small and neat which I like. So is this the sort of focal length I should be aiming at? What about the Baader Classic 18mm?

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3 minutes ago, bosun21 said:

 So is this the sort of focal length I should be aiming at? What about the Baader Classic 18mm?

Depends on the focal length of your scope really.

My APM 15's give me 170x magnification, which is generally more than enough for most nights under grotty UK sky's.

I've never used the Baader classic ortho's as i already use 19mm Pans which are ideal. I'm sure the Baader classics are great though, although i'd find the 52º fov a bit narrow.

I like 65º fov best for two eyed viewing : its a 'Goldilocks' type thing its just right 😀

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I forgot to mention I need to wear eyeglasses when observing with exit pupils larger than 1mm, so that limits my choices.  Microscope eyepieces intended for eyeglass wearers are also a good choice if you can get the proper barrel adapters.  They are generally compact and designed to be very sharp at f/18.  If you don't need to wear eyeglasses, you have many more options.

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No glasses required for me I’m glad to say. My focal lengths are in the same ballpark as yourself @Space Hopper so the 15mm APM’s look quite inviting. Thanks for the input folks, it’s much appreciated.

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The type of binoviewer you are buying will also determine whether you can use wider eyepieces at all - the cheaper Chinese units mostly use small prisms, which will vignette widefield EPs. The good news is that if they are collimated well, they give on-axis views on a par with far more expensive binoviewers with larger prisms. But important to check this before you make final decisions about BV/EP pairings.

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10 hours ago, bosun21 said:

Thanks Don, when you are talking about the OCA are you referring to the additional accessories that usually come with the binoviewer? ie: the barlows, or are you referring to an internal component of the binoviewer? I was taking into consideration the eyepiece focal length being reduced by whichever size the OCA being used. For instance a 20mm eyepiece with a 2x OCA would be a 10mm equivalent. Is my grasp of this correct? Thanks 

Yes.  OCA = Glass Path corrector (GPC) = effectively a barlow, but often compensating for the CA of the binoviewer itself.

In the case of the Norin binoviewer (William Optics et.al.) the 2x OCA ADDS CA instead of solving for it.  Pure garbage, that one.

And yes, the multiplying effect of an OCA will act just like a Barlow.

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7 hours ago, bosun21 said:

I already have the 18mm and 10mm ultra flat eyepieces although with the SVbony label. I looked at the 15mm APM and it has a similar form factor to the 10mm which is small and neat which I like. So is this the sort of focal length I should be aiming at? What about the Baader Classic 18mm?

The 18mm BCOs make a nice binoviewer pair if you don't mind them only having a 50° field. However, you shouldn't buy any new eyepieces until you have your binoviewer and have found a barlow that will allow you to focus and have calculated the effective multiplication that it gives when paired with the binoviewer. Once you have that you can calculate the eyepiece focal lengths you need, rather than buying a pair of eyepieces that may or may not be of use to you. 

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11 hours ago, Second Time Around said:

What is your IPD please, Neil?

I had never measured it before but had a go this morning, looks to be 58mm.

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Hi Neil,

Just seen this thread..😊.

To answer your original questions, I've binoviewed with both Baader Classic Ortho 18mm and Morpheus 17.5mm pairs.

Optically I much preferred the Morphs, due to the much wider fov. A few salient points to add though:

- I don't need to use a ocs or Barlow in my Tak FS128, as by using  Baader adapters and T2 prisms I can get native focus with several pairs, so that the eps operate at their actual focal length..this includes the Morpheus 17.5mms although I currently only have one of these at the moment (long story). So, for me, not having to use an OCS is a major plus.

- note that the Morph 17.5mms are the smallest and lightest in the Morpheus line.

- you need a strong 2" focuser on your scope to use pairs of sizeable eps like the Morphs..

- you need to be able to find a stable balance point with your scope loaded with a Binoviewer and pair of eps..this is obviously easier with refractors than with Dobs etc..and I find a 5" OTA easier to balance than a 4".

- you don't need high end eps to bv successfully: as @mikeDknight, a very talented and respected SGL planetary observer has often said..quite cheap pairs will often outperform single high end eps on certain targets, especially moon and major planets eg Mars, Jupiter and Saturn.. this seems to be due to our brains being used to two eyed viewing as a normal state, and the views can often seem more 3 dimensional..but this doesn't seem to work for everyone the same way.

Coming back to the Baader Classic orthos..they are great eps for the price..my preference for the Morpheus ' was simply that the BCOs are 52 degree fov vs the 76deg of the Morphs..I recently bought an 18mm BCO for my son in laws 120mm achro and it's great👍.

Good luck with your ep pairs choices Neil🔭😂

Dave

 

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3 hours ago, F15Rules said:

Hi Neil,

Just seen this thread..😊.

To answer your original questions, I've binoviewed with both Baader Classic Ortho 18mm and Morpheus 17.5mm pairs.

Optically I much preferred the Morphs, due to the much wider fov. A few salient points to add though:

- I don't need to use a ocs or Barlow in my Tak FS128, as by using  Baader adapters and T2 prisms I can get native focus with several pairs, so that the eps operate at their actual focal length..this includes the Morpheus 17.5mms although I currently only have one of these at the moment (long story). So, for me, not having to use an OCS is a major plus.

- note that the Morph 17.5mms are the smallest and lightest in the Morpheus line.

- you need a strong 2" focuser on your scope to use pairs of sizeable eps like the Morphs..

- you need to be able to find a stable balance point with your scope loaded with a Binoviewer and pair of eps..this is obviously easier with refractors than with Dobs etc..and I find a 5" OTA easier to balance than a 4".

- you don't need high end eps to bv successfully: as @mikeDknight, a very talented and respected SGL planetary observer has often said..quite cheap pairs will often outperform single high end eps on certain targets, especially moon and major planets eg Mars, Jupiter and Saturn.. this seems to be due to our brains being used to two eyed viewing as a normal state, and the views can often seem more 3 dimensional..but this doesn't seem to work for everyone the same way.

Coming back to the Baader Classic orthos..they are great eps for the price..my preference for the Morpheus ' was simply that the BCOs are 52 degree fov vs the 76deg of the Morphs..I recently bought an 18mm BCO for my son in laws 120mm achro and it's great👍.

Good luck with your ep pairs choices Neil🔭😂

Dave

 

Thanks for heads up regarding the Baader Morpheus and classics. By the way my name is Ian @bosun21. I am also thinking of using the Baader T2 prism and click lock as it would be a more secure way of mounting the binoviewer. Decisions, Decisions 🤔

    ATB  

       Ian 

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What about a pair of Nirvana 16mm eyepieces? Or would they vignette badly in most of the cheaper binoviewers? What sort of money would you have to spend for the binoviewer to accept the 16mm Nirvanas without vignetting?

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According to Ernest's measurements, the 16mm Levenhuk Ra UWA 82° branding of the 16mm Nirvana 82° has a 25mm diameter field lens and a 21.2mm field stop.  Technically, it wouldn't vignette based on the field stop alone, but since the field lens is slightly larger than the BV's clear aperture (~22mm), there might be a bit of vignetting at the edge.  Since you have to look in the center to hold both images, you'd be unlikely to see this level of vignetting in your peripheral vision, though.

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Posted (edited)
4 hours ago, Louis D said:

According to Ernest's measurements, the 16mm Levenhuk Ra UWA 82° branding of the 16mm Nirvana 82° has a 25mm diameter field lens and a 21.2mm field stop.  Technically, it wouldn't vignette based on the field stop alone, but since the field lens is slightly larger than the BV's clear aperture (~22mm), there might be a bit of vignetting at the edge.  Since you have to look in the center to hold both images, you'd be unlikely to see this level of vignetting in your peripheral vision, though.

Louis does the binoviewer actually have a magnification factor on their own without an OCA or barlow? If so, then to what degree? Thanks  

     Ian 

Edited by bosun21
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23 hours ago, bosun21 said:

Louis does the binoviewer actually have a magnification factor on their own without an OCA or barlow? If so, then to what degree? Thanks  

     Ian 

None beyond what effect they have on SCTs and Maks in native focus mode without an OCA/Barlow.  That is, to reach focus with a BV in a catadioptric scope without an OCA/Barlow element requires about 100mm or more additional back focus.  To do this, the primary mirror must be shifted forward which increases the scope's focal length due to the magnification factor of the secondary mirror.  There are formulas for both types to calculate the added focal length based on added back focus.

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