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Orion Linear Binoviewer: Yes or No?

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#151 Sarkikos

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Posted 19 March 2024 - 09:11 PM

Updated list of binoviewer pairs.  I filled in more data and added the 15mm Celestron Spotting Scope Eyepiece.  They look like good contenders.  15mm focal length, effectively 25mm with the Kasai 0.66x Reducer.  Only 13.1mm field stop, so no vignetting.  62-degree AFOV, the same as the Delites.

 

Mike

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Edited by Sarkikos, 19 March 2024 - 09:18 PM.


#152 Sarkikos

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Posted 19 March 2024 - 09:37 PM

Here is a listing from Don's (Starman1's) 2023 Buyer's Guide to Eyepieces.  I've sorted by field stop, decreasing from 20.4mm.  I used the calculated field stop, because some of the manufacturers field stop data was missing.  

 

I have in mind to maximize AFOV and TFOV without vignetting.  Use of the 0.66x or 0.5x reducers would be options.  

 

Anything look interesting as bino pairs for the linear binoviewers?

 

Mike

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Edited by Sarkikos, 19 March 2024 - 09:42 PM.


#153 betacygni

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Posted 19 March 2024 - 10:31 PM

The 18.2mm Delites would be my pick, I think Televue comes in as the undisputed champion in the edge correction realm for fast systems, especially as was pointed out prior when you throw the reducer in there. The 18mm APM UFF would an interesting choice too. I’ve had both the Delites and UFF, very good eyepieces for binoviewing.

Edited by betacygni, 19 March 2024 - 10:33 PM.

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#154 Sarkikos

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Posted 20 March 2024 - 12:34 PM

The 18.2mm Delites would be my pick, I think Televue comes in as the undisputed champion in the edge correction realm for fast systems, especially as was pointed out prior when you throw the reducer in there. The 18mm APM UFF would an interesting choice too. I’ve had both the Delites and UFF, very good eyepieces for binoviewing.

I have the 3 and 7mm Delites and I like them.   Light weight, relatively small, good outer field correction, moderately wide AFOV.   Comparatively expensive, though.  A pair of 18.2 Delites would be $538.  That's about $200 more than the linear binoviewers cost me, shipped.  I intend to get a pair of the 18.2 Delites someday, but not today.  grin.gif

 

For now, I'm considering less expensive pairs, or adding a second eyepiece to ones I already have.  

 

I have an 18mm Paradigm.   The Paradigms have a 60-degree AFOV, nearly as wide as the 62 degrees of the Delites.  The eye relief is shorter at 13mm, while the Delites have 20mm eye relief.  But I don't need a lot of eye relief, even when I'm wearing glasses.  In the past, I liked the 8 and 12mm Paradigms as bino pairs for planet/lunar.   Some experienced observers - e.g., BillP - liked them for monoviewing deep sky.   The Starguider branding is available now for $70.  shocked.gif   Yep.  Guess what I'm going to do.  grin.gif

 

I have a 12.5 Docter.  Would I get a second to make a bino pair?  thinking1.gif  Well, there's the high price, which has increased even more lately.  And the weight:  a pair would be 2-1/3 lbs.  Nope.  That's a hard nope.  grin.gif

 

How about ordering another 14 XW for a pair?   They are 59mm wide.  Yeah, that is wide.  My IPD is 65mm, so I guess I could handle them.  A pair would be 1-2/3 lbs.  The outer field correction is not great for fast scopes, even worse with a reducer.  So:  nope.  

 

Years ago, I had a pair of 14mm ES 82-Degrees for my Burgess Binoviewer.  Now I wish I'd kept them.  

 

The 18mm APM UFF are only about $129 at APM.  65-degree AFOV.  Flat field.  My eyes no longer accommodate for focus, so I do appreciate flat field optics.  Something to consider.   Any decent brandings of this eyepiece in the US market?  I see Agena Astro discontinued theirs.  AliExpress has them for $85!  shocked.gif   But it looks like they're out of stock now.  I'm sure a lot of CNers bought them up.  Am I wrong?  lol.gif

 

The 14mm Angeleyes 70-degree flat field is $85.  I have a pair of the 22mm Oberwerk version, but the field stop is about 27mm.  I don't know what the field stop is for the 14mm.  

 

Mike


Edited by Sarkikos, 20 March 2024 - 12:57 PM.


#155 Doug Culbertson

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Posted 20 March 2024 - 12:49 PM

The Svbony 18mm UFF appears to be the exact same eyepiece as the APM. https://www.amazon.c...d/dp/B08Z2ZW7MK

There’s also the Celestron Ultima Edge https://www.bhphotov...e_eyepiece.html
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#156 Takuan

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Posted 20 March 2024 - 02:10 PM

The 18UFF are fixed in the case of my binoviewer.
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#157 Sarkikos

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Posted 20 March 2024 - 07:10 PM

I just now ordered a pair of the Svbony 18mm UFF's.  :grin:

 

Mike


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#158 jprideaux

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Posted 21 March 2024 - 07:27 PM

The Svbony 18mm UFF appears to be the exact same eyepiece as the APM. https://www.amazon.c...d/dp/B08Z2ZW7MK

There’s also the Celestron Ultima Edge https://www.bhphotov...e_eyepiece.html

I've used the 10mm Celestron Ultima Edge eyepieces for when I wanted a little more power with my Linear.  Otherwise I tend to use my Baader 18mm orthoscopic eyepiece pairs.



#159 nof

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Posted 23 March 2024 - 06:35 PM

I ordered the Explore Scientific Eyepiece 52° LER 20mm from astroshop.eu for €40 each a few weeks ago. But now the price has returned to normal and is twice as much. Still waiting for ship date, they said the delivery to them is delayed, but I’m not in a rush

#160 jprideaux

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Posted 24 March 2024 - 06:25 AM

I ordered the Explore Scientific Eyepiece 52° LER 20mm from astroshop.eu for €40 each a few weeks ago. But now the price has returned to normal and is twice as much. Still waiting for ship date, they said the delivery to them is delayed, but I’m not in a rush


Those should be a nice choice. Kasai Trading (one provider of the BV) recommended eyepieces where the focal-length (in mm) times AFOV (in degrees) was around 1000 or less so the BV would not be the limiting factor. 20x52 is around 1000.

#161 Sarkikos

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Posted 24 March 2024 - 07:21 AM

I ordered the Explore Scientific Eyepiece 52° LER 20mm from astroshop.eu for €40 each a few weeks ago. But now the price has returned to normal and is twice as much. Still waiting for ship date, they said the delivery to them is delayed, but I’m not in a rush

I have the 30mm ES 52-Degrees.  I bought it about five years ago.  The price at ES is now $149, much too high for what it is.  Mine was less expensive when I bought it.  To my eyes, the outer field astigmatism in that eyepiece is pretty obvious.  The astigmatism is from the eyepiece, not my eye or the telescope.  I don't see astigmatism in a 24 Pan or 13 Ethos in the same f/4.8 Petzval telescope.

 

The 25 and 30mm ES 52-Degrees are just four elements in two groups.   Probably Plossls.   The 20mm is five elements in three groups, so maybe it's better corrected than the 25 and 30mm. 

 

Why do you call it LER (Long Eye Relief)?   I don't see LER on the eyepiece or in the name anywhere.    Is it a different eyepiece?   

 

OK, here's a link to the 30 ES 52-Degrees at astroshop.eu:  https://www.astrosho...m-1-25-/p,61716   This vendor calls the line of eyepieces "LER," but at the ES website, they are not called "LER."

 

Mike


Edited by Sarkikos, 24 March 2024 - 08:09 AM.


#162 Sarkikos

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Posted 24 March 2024 - 07:36 AM

Those should be a nice choice. Kasai Trading (one provider of the BV) recommended eyepieces where the focal-length (in mm) times AFOV (in degrees) was around 1000 or less so the BV would not be the limiting factor. 20x52 is around 1000.

So, did you just find out about this recommendation or where you hiding it under your hat?   I could have used it in determining which eyepieces to use in my linear binoviewer, which pairs to buy and which to avoid.  poke.gif :lol:

 

Mike



#163 Sarkikos

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Posted 24 March 2024 - 07:44 AM

To everyone who was making recommendations for pairs of eyepieces:   Did you ever try your recommendations in a linear binoviewer, or where you going from your experience with them in a binoviewer with a wider clear aperture?   The main theme of this thread is the linear binoviewers.  I'm trying to avoid vignetting in the linears, people.  grin.gif

 

For instance, the SVbony 18mm UFF's which I recently ordered would come out at 1170 (18x65).   That's cutting it close, actually going over the edge, according to Kasai, who recommends 1000 or less for focal length times AFOV.  But I've seen different specs for this eyepiece.   The field stop varies.  So does the AFOV.   Looking at APM now, the product description page for the APM 18mm UFF says the AFOV is 60-degrees.  But the tecnical data page says the AFOV is 65-degrees.  18x60=1080.  Which is correct?

 

When I receive them, I'll definitely post in this thread saying whether they vignette or not in the linears.   If they vignette in the linears, maybe they won't in my Burgess Binoviewers, which have a little more clear aperture at 20mm compared to 17mm.   

 

Mike


Edited by Sarkikos, 24 March 2024 - 08:10 AM.


#164 Sarkikos

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Posted 24 March 2024 - 08:14 AM

The 18.2mm Delites would come out at about 1128 (18.2x62).   They are across the border as well, but not by much.

 

I only paid $164.98 for the pair of Svbony 18 UFF.   A pair of 18.2 Delites would have cost me $538.   The Svbony's should give me an indication if I should buy the Delites or not.  

 

Mike


Edited by Sarkikos, 24 March 2024 - 08:19 AM.


#165 betacygni

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Posted 24 March 2024 - 09:27 AM

The 1000 number seems like just another way to calculate that the eyepiece field stop doesn’t go much past the limiting factor of the Linears 17mm or so clear aperture. But if you’re going for max FOV still exceeding that by a bit probably makes some sense, as then for sure the eyepiece isn’t limiting you.

Either way you are being a very good guinea pig for the rest of us! hamsterdance.gif grin.gif

Edited by betacygni, 24 March 2024 - 09:29 AM.

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#166 sanbai

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Posted 24 March 2024 - 10:47 AM

Either way you are being a very good guinea pig for the rest of us! hamsterdance.gif grin.gif

I think this may be more of a weeder. I think the most valid information can be given also in mono-use (e.g. aberrations). For binoviewing use, other things come into consideration that may be much more personal. The comfort has a big role in binowviewing, in my opinion.

One thing, though, that may be very interesting and not that personal is how the eyepieces interact with the binoviewer in terms of internal reflections. For me, this is one of the weakest point of the Linear Binoviewers.


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#167 Sarkikos

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Posted 24 March 2024 - 12:34 PM

Either way you are being a very good guinea pig for the rest of us! hamsterdance.gif grin.gif

Yeah, that's what I figured.  But in my case, the guinea pig gets to choose which parts of the maze he runs through.  grin.gif

 

Mike


Edited by Sarkikos, 24 March 2024 - 12:36 PM.

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#168 Sarkikos

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Posted 24 March 2024 - 12:39 PM

When I have time, I'll compare the results I saw for vignetting in the eyepieces I tested, with the Kasai calculation.   I might add that as a column to my binoviewer spreadsheet.

 

Mike



#169 nof

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Posted 24 March 2024 - 03:21 PM

I happened to see these on sale and thought they could be good for the linears. The price was excellent so I didn’t hesitate. Your survey is very helpful, thanks. I have many ES eyepieces which are all very good to excellent so I assume these will be good, too.

So, did you just find out about this recommendation or where you hiding it under your hat? I could have used it in determining which eyepieces to use in my linear binoviewer, which pairs to buy and which to avoid. poke.gif :lol:

Mike


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#170 jprideaux

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Posted 26 March 2024 - 10:04 PM

Yeah, the 1000 is merely a different way of running the numbers for the field-stop of 17.4. The 1000 is useful if you are considering eyepieces that don’t publish their field-stop but do publish their AFOV. Whether you want to go over 1000 is personal in how much you prefer a sharp edge.
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#171 Sarkikos

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Posted 28 March 2024 - 11:00 AM

Today I checked another bino pair with the linear binoviewer.  They are 18mm Paradigms.  60-degree AFOV.  18.8mm field stop.   Actually, one is an 18mm Starguider, but they are different brandings of the same eyepiece.

 

Comparing the AFOV's with one of the eyepieces in the linear binoviewer and the other eyepiece held up directly to the other eye, the AFOV's were nearly the same.  The eyepiece in the linear had a slighly smaller AFOV.  I could see that the linear was vignetting.  There was a narrow darkish ring of hard vignetting surrounding the field of view.  I got the same result no matter which eyepiece of the pair was in the binoviewer.  The Kasai Number would be 18 x 60 = 1080.  

 

This small level of vignetting would be acceptable to me.  

 

I'm still waiting for the SVbony 18mm UFF's.  Their Kasai Number would be 1170 (18 x 65).  If their AFOV is actually 60 degrees, which some sources say it is, the number would be 1080, the same as the 18 Paradigms.  When I receive the Svbonys, I can compare their AFOV with the 18 Paradigms and my 7 Delite to get a better idea of the Svbonys' actual AFOV.

 

The 18.2 Delites' Kasai Number would be about 1128 (18.2 x 62).

 

Mike


Edited by Sarkikos, 28 March 2024 - 11:10 AM.


#172 jprideaux

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Posted 29 March 2024 - 07:38 AM

The "1000" that Kasai Trading came up with can easily be calculated in the following way and also generalized for any binoviewer.

 

Here I use the following terms:

 

TFOV = true field of view

AFOV = apparent field of view

TFL = telescope focal length

EFL = eyepiece focal length

FS = field stop (can be of either the eyepiece or Binivoewer)

pi = 3.1415...

MAG = magnification = TFL / EFL

 

Standard equation for TFOV using AFOV

TFOV = AFOV / MAG = AFOV / ( TFL / EFL )

 

Alternative equation for TFOV using FS

TFOV = ( 180 / pi ) ( FS / TFL )

 

Setting these equal:

 

AFOV / ( TFL / EFL ) = ( 180 / pi ) ( FS / TFL ) 

 

cancelling out TFL and rearranging terms

 

AFOV x EFL = 180 FS / pi

 

To test where the FS of the binoviewer starts to become the limiting factor, plug in the FS of the biniviewer in the above equation.  

In the case of the Linear, the FS = 17.4 so the equations becomes the following:

 

AFOV x EFL = 180 (17.4) / 3.1415927 = 997  (about 1000)

 

You could also use this equation with any other binoviewer if you knew that binoviewer's internal FS. 


Edited by jprideaux, 29 March 2024 - 07:42 AM.

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#173 Sarkikos

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Posted 29 March 2024 - 12:04 PM

The "1000" that Kasai Trading came up with can easily be calculated in the following way and also generalized for any binoviewer.

 

Here I use the following terms:

 

TFOV = true field of view

AFOV = apparent field of view

TFL = telescope focal length

EFL = eyepiece focal length

FS = field stop (can be of either the eyepiece or Binivoewer)

pi = 3.1415...

MAG = magnification = TFL / EFL

 

Standard equation for TFOV using AFOV

TFOV = AFOV / MAG = AFOV / ( TFL / EFL )

 

Alternative equation for TFOV using FS

TFOV = ( 180 / pi ) ( FS / TFL )

 

Setting these equal:

 

AFOV / ( TFL / EFL ) = ( 180 / pi ) ( FS / TFL ) 

 

cancelling out TFL and rearranging terms

 

AFOV x EFL = 180 FS / pi

 

To test where the FS of the binoviewer starts to become the limiting factor, plug in the FS of the biniviewer in the above equation.  

In the case of the Linear, the FS = 17.4 so the equations becomes the following:

 

AFOV x EFL = 180 (17.4) / 3.1415927 = 997  (about 1000)

 

You could also use this equation with any other binoviewer if you knew that binoviewer's internal FS. 

Nice!  :waytogo:

 

I see two flies in the ointment.   Or rather, a different fly in each ointment.  :grin:

 

The Kasai calculation assumes an accurate number for the AFOV.   Often this is exaggerated a bit.  Sometimes there are different numbers given for the AFOV, depending on which product description or specs you read.  

 

The calculation based on the field stop assumes an accurate number for the field stop.  The main problem here is that often the field stop size is not given at all.   

 

Mike



#174 DRodrigues

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Posted 30 March 2024 - 10:17 AM

...

I have a 12.5 Docter. 

...

 

It would be interesting to know if the Docter vignette with the LBV... wink.gif



#175 Sarkikos

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Posted 30 March 2024 - 07:40 PM

It would be interesting to know if the Docter vignette with the LBV... wink.gif

I would need a second one to determine that.   Anyone want to send me the second one?  grin.gif

 

A pair of Docters would weigh 2-1/3 lbs.   sumo.gif sumo.gif

 

Mike


Edited by Sarkikos, 30 March 2024 - 07:41 PM.



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