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Orion Linear Binoviewer: Yes or No?

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#126 Sarkikos

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Posted 13 March 2024 - 12:57 PM

Hi Mike

 

Did you prefer one combination over the others? Please keep us posted as you try them with your other scopes too.

 

Jim

Here are the eyepiece pairs and specs:

 

- 35 Ultrascopic (28.9mm field stop), 3.2-degree TFOV, 15.4x, 6.5mm exit pupil

- 32 Celestron Omni Plossl (27mm field stop), 2.6-degree TFOV, 16.9x, 6mm exit pupil

- 24 Pan (27mm field stop), 3-degree TFOV, 22.5x, 4.5mm exit pupil

- 24 Pan, Kasai 0.66x Reducer, 4.3-degree TFOV, 15.8x, 6.4mm exit pupil

- 18 Tak LE (15.8mm field stop), 1.7-degree TFOV, 30x, 3.4mm exit pupil

- 18 Tak LE, Kasai 0.66x Reducer, 2.5-degree, TFOV, 21x 4.8mm exit pupil

 

The 35 Ultrascopic and 32 Omni Plossl yielded a wider exit pupil than I usually like.  A 6mm or 6.5mm exit pupil makes the background too washed out for my taste.   I'd only put them in if I'm trying to chase a wider TFOV for large objects.

 

I liked the 24 Pan without reducer, and 18 Tak LE with or without reducer, best.

 

But judging from what I saw that night, I'd probably just leave the reducer out to make things quicker and easier.  I don't have to take the binoviewer out of the diagonal to switch eyepieces.  I do have to take it out to screw the reducer on or off.  I like simple and easy, because I'm mostly lazy.  :grin:

 

Mike


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#127 DRodrigues

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Posted 14 March 2024 - 07:29 PM

Here are the eyepiece pairs and specs:

 

- 35 Ultrascopic (28.9mm field stop), 3.2-degree TFOV, 15.4x, 6.5mm exit pupil

- 32 Celestron Omni Plossl (27mm field stop), 2.6-degree TFOV, 16.9x, 6mm exit pupil

- 24 Pan (27mm field stop), 3-degree TFOV, 22.5x, 4.5mm exit pupil

- 24 Pan, Kasai 0.66x Reducer, 4.3-degree TFOV, 15.8x, 6.4mm exit pupil

...

The LBV performance is really dependent of the all optical combo but I'm surprised that you didn't noticed any vignetting with these large TFOV eps...scratchhead2.gif
 



#128 betacygni

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Posted 14 March 2024 - 07:36 PM

The LBV performance is really dependent of the all optical combo but I'm surprised that you didn't noticed any vignetting with these large TFOV eps...scratchhead2.gif

I’m very surprised too. Are you sure they were not hitting a hard vignette, creating a more narrow field? Would be interesting to use them with the binoviewer, then swap them to mono with the same star field , to see if there is a reduction.
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#129 Sarkikos

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Posted 14 March 2024 - 08:19 PM

I’m very surprised too. Are you sure they were not hitting a hard vignette, creating a more narrow field? Would be interesting to use them with the binoviewer, then swap them to mono with the same star field , to see if there is a reduction.

Would a hard vignette give a different appearance to the edge of field than the regular appearance of the field stop without hard vignetting?  Or would they be indistinguishable?  

 

Swapping back and forth between binoviewing two specific eyepieces and monoviewing with one of the eyepieces would not be an easy task.  There would be too much of a time lag to easily see a reduction in the TFOV.   It's not something that would give me a confident judgment of the results.

 

One way to make it easier would be to first compare the monoviewing field with the Scope Display for that scope/eyepiece combination in SkySafari, and then compare the binoviewing field with the same Scope Display.   This would appeal to my way of doing things rather than sitting out in the dark timing how long it takes for a star to cross the field of view, though that is an option.  

 

All I can say is, if anyone with a linear binoviewer thinks a particular scope/eyepiece combination is showing a hard vignette, how do you know it is?   

 

Mike



#130 sanbai

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Posted 14 March 2024 - 10:19 PM

I like a Plössl 40mm for white solar observing with my C8. I looked for another one in my club so I could try binoviewing with such eyepiece. I found one, but the combination had bad vignetting. I was disappointed, but I then remembered that this was to be expected. My fault.

A nagler 13t6 doesn't vignette, although I don't like naglers-t6 that much for solar in that scope (they do better in my 80ed refractor).

I haven't tried the Plössl 40mm at night in the binoviewer, or a 32 mm which has the same field stop. It may be more forgiving, but this is a combinatiom I don't see using it.

Naglers do well at night and I prefer it over a Plössl. However, I prefer mono for deep sky, at least under my not so good sky. I'll give a try to my two 25mm Plössl, though. Ideally, I should try something in the 60-70 degrees AFOV, but I'm not up to spending more money in binoviewing at this time.
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#131 betacygni

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Posted 15 March 2024 - 01:04 AM

Would a hard vignette give a different appearance to the edge of field than the regular appearance of the field stop without hard vignetting? Or would they be indistinguishable?

Swapping back and forth between binoviewing two specific eyepieces and monoviewing with one of the eyepieces would not be an easy task. There would be too much of a time lag to easily see a reduction in the TFOV. It's not something that would give me a confident judgment of the results.

One way to make it easier would be to first compare the monoviewing field with the Scope Display for that scope/eyepiece combination in SkySafari, and then compare the binoviewing field with the same Scope Display. This would appeal to my way of doing things rather than sitting out in the dark timing how long it takes for a star to cross the field of view, though that is an option.

All I can say is, if anyone with a linear binoviewer thinks a particular scope/eyepiece combination is showing a hard vignette, how do you know it is?

Mike

Only time I’ve experienced a hard vignette is with my solar setup, where it was quite obvious the field of view was way less than it should have been when I switched to the vignette setup, but other than the new vignette “field stop” being a bit fuzzy, it looked just like a normal eyepiece view would, just more narrow. Depending on how severe it is the reduced field might not be super obvious at first glance, especially under night conditions.

Perhaps you could time drift a star across the field in the binoviewers then again in mono, the percentage quicker the star takes to go from edge to edge in the binoviewer would be the reduced FOV I would think. If the star takes 100 seconds to go from edge to edge in mono, then 75 seconds in the binoviewer, your FOV has been cut by 25% for example.

Edited by betacygni, 15 March 2024 - 01:10 AM.

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#132 Sarkikos

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Posted 15 March 2024 - 09:23 AM

I like a Plössl 40mm for white solar observing with my C8. I looked for another one in my club so I could try binoviewing with such eyepiece. I found one, but the combination had bad vignetting. I was disappointed, but I then remembered that this was to be expected. My fault.

A nagler 13t6 doesn't vignette, although I don't like naglers-t6 that much for solar in that scope (they do better in my 80ed refractor).

I haven't tried the Plössl 40mm at night in the binoviewer, or a 32 mm which has the same field stop. It may be more forgiving, but this is a combinatiom I don't see using it.

Naglers do well at night and I prefer it over a Plössl. However, I prefer mono for deep sky, at least under my not so good sky. I'll give a try to my two 25mm Plössl, though. Ideally, I should try something in the 60-70 degrees AFOV, but I'm not up to spending more money in binoviewing at this time.

I prefer monoviewing for deep sky if I'm trying to locate and view relatively faint objects.  I never thought that a binoviewer was the best tool for that job.  Doesn't binoviewing dim the image?  Why would an observer binoview if their purpose is to detect objects toward the limit of their telescope's light grasp?  That never made sense to me.  But I can see how binoviewing would be nice for appreciating the brighter eye candy objects.

 

Binoviewing is great for comparatively bright DSO, planets and the Moon.   Many binoview the Sun.  Some binoview double stars.  I don't have experience binoviewing those objects.  But I wouldn't opt for a binoviewer if I'm trying to see faint galaxies.  

 

Mike


Edited by Sarkikos, 15 March 2024 - 09:36 AM.


#133 Sarkikos

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Posted 15 March 2024 - 09:34 AM

Only time I’ve experienced a hard vignette is with my solar setup, where it was quite obvious the field of view was way less than it should have been when I switched to the vignette setup, but other than the new vignette “field stop” being a bit fuzzy, it looked just like a normal eyepiece view would, just more narrow. Depending on how severe it is the reduced field might not be super obvious at first glance, especially under night conditions.

Perhaps you could time drift a star across the field in the binoviewers then again in mono, the percentage quicker the star takes to go from edge to edge in the binoviewer would be the reduced FOV I would think. If the star takes 100 seconds to go from edge to edge in mono, then 75 seconds in the binoviewer, your FOV has been cut by 25% for example.

Night conditions are the only ones I'd be using a binoviewer.  I don't do solar (yet! grin.gif) and I don't do any terrestrial viewing. 

 

That sounds like a simple, straight-forward method of detecting a reduction in the FOV.  Has any other observers with linear binoviewers - or even standard binoviewers - used this method?  

 

I'm not sure that the term "vignetting" is the one that we should be using here.  Didn't Eddgie say that the linear binoviewer does not vignette, it's the eyepieces that vignette?  But if the binoviewer sets up a condition in the optical stack that allows the eyepieces to vignette, what's the difference?  shrug.gif   If not vignetting, what term should we be using when talking about the linear binoviewer?  It's a distinction without a difference, isn't it?

 

Mike


Edited by Sarkikos, 15 March 2024 - 08:05 PM.

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#134 Hwunkzeep

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Posted 15 March 2024 - 07:30 PM

Good choice! But relying entirely on reviews from others goes just so far --- trying (and even buying) for yourself are the true arbiter. Learning to use tools takes time and patience. Proper eye placement is something that most amateurs are not good at, not even the majority of astronomy buffs... and unwilling to research and practice. The Linears do indeed take some extra effort, skill and understanding.

 

I came up with some tutorial material... but I guess it's just ~over the heads or willingness~ of most amateurs. At work (B&L, ITT, L3Harris, etc.) --- the optical techs loved the Linear design and utility. But (admittedly) the professional optical technicians (military and industrial) are truly skilled observers.    Tom

Your illustration there was extremely educational.  Thank you.


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#135 Sarkikos

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Posted 15 March 2024 - 07:50 PM

TOMDEY said about the linear binoviewers that "Proper eye placement is something that most amateurs are not good at, not even the majority of astronomy buffs... and unwilling to research and practice. The Linears do indeed take some extra effort, skill and understanding.take some extra effort, skill and understanding."   

 

But as I said in post # 122:

 

Another thing I noticed when using the linears, is that I didn't have any problem getting the images to merge.  In my old Burgess, I had to struggle a bit every time I switched eyepiece pairs, trying to seat them optimally for merging.  This was true with the original thumbscrews and to a lesser degree with the collet replacements I got later for the Burgess.  No problem like this with the linears.  With the linears, I just insert the eyepieces, adjust the IPD and diopter, make sure the binoviewer is horizontal in relation to my eyes, and I'm good to go.  With the Burgess, I had to do all these things PLUS struggle with seating the eyepieces properly.

Am I an outlier? shrug.gif

 

Since I also didn't notice any obvious vignetting, maybe I'm an outlier on two data points?  shrug.gif shrug.gif

 

In any case, so far I'm liking the linears!  grin.gif

 

Mike


Edited by Sarkikos, 15 March 2024 - 08:03 PM.


#136 Hwunkzeep

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Posted 15 March 2024 - 09:54 PM

Going back to the root question - Yes!

 

When I bought mine it was a pretty stupid financial decision.  And I questioned that decision a lot while waiting for delivery, and the word "resale" (after me playing around a bit) was heavily on my mind.

 

I'll never sell this thing now until/unless I physically can't observe anymore...


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#137 jprideaux

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Posted 16 March 2024 - 03:29 AM

One easy experiment to check the tfov of the linear with your chosen eyepieces with or without reducer as compared to mono (not using BV) is to view a brick wall (or brick chimney) and count bricks in the daytime. Do it with the linear. Then do it mono. See if you get the same count. Try adding a reducer for both set-ups. It is also a good way to see if there is any field curvature. Note that if the brick wall is fairly close, you may need to add in an extension tube to reach focus.
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#138 Takuan

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Posted 16 March 2024 - 05:15 AM

I prefer monoviewing for deep sky if I'm trying to locate and view relatively faint objects. I never thought that a binoviewer was the best tool for that job. Doesn't binoviewing dim the image? Why would an observer binoview if their purpose is to detect objects toward the limit of their telescope's light grasp? That never made sense to me. But I can see how binoviewing would be nice for appreciating the brighter eye candy objects.

Binoviewing is great for comparatively bright DSO, planets and the Moon. Many binoview the Sun. Some binoview double stars. I don't have experience binoviewing those objects. But I wouldn't opt for a binoviewer if I'm trying to see faint galaxies.

Mike

Binoviewing dim the image, yes, but I can live with it.
Where I notice this effect the most is in the stars. One magnitude less is clearly perceptible. In galaxies and nebulae, in my experience, not so much.
For me, the experience of using both eyes makes up for the loss of light. When I use BV for deepsky I don't think about the light I'm losing, I just enjoy what I see. It seems obvious and simple, but it's not..

Edit: According to your reasoning, the Linear would not be the most appropriate tool for the moon and planets (I don't know about solar), because, in my experience, the image at high magnifications is less sharp.

Edited by Takuan, 16 March 2024 - 07:23 AM.

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#139 Bintang13

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Posted 16 March 2024 - 08:59 AM

I recall other reviewers that mentioned using the 24 Pan without experiencing vignetting with the linears. I will have to try them and see. My experience was with 26mm Celestron Silvertops it was like looking in a tunnel, the light at the end of the tunnel was surrounded by a very prominent and dark ring no slight drop off. I believe that the reason for the reducer being offered is due to the physical limitation of the 17mm clear aperture of the linears. Like the 20mm clear aperture of the WO binoviewers will allow use of 32mm eyepieces showing lower power, it will not show a larger TFOV than designed ( 20mm eyepiece with 66degree ). You most likely are not gaining any TFOV with lower powers, the tests mentioned will verify. It will be very interesting to read  your experiences as you use the linears with other scopes. i can’t imagine any scope design that would overcome that limitation though.

 

Jim



#140 Sarkikos

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Posted 16 March 2024 - 01:07 PM

Binoviewing dim the image, yes, but I can live with it.
Where I notice this effect the most is in the stars. One magnitude less is clearly perceptible. In galaxies and nebulae, in my experience, not so much.
For me, the experience of using both eyes makes up for the loss of light. When I use BV for deepsky I don't think about the light I'm losing, I just enjoy what I see. It seems obvious and simple, but it's not..

Edit: According to your reasoning, the Linear would not be the most appropriate tool for the moon and planets (I don't know about solar), because, in my experience, the image at high magnifications is less sharp.

M81 and M82 did look very nice when I was binoviewing them through the linears in my NP-101is.  waytogo.gif

 

I had heard that planet/lunar might not be as sharp through the linears as through a decent standard type of binoviewer.   I haven't used my linears on planet/lunar yet.  Maybe I'll compare the view of a bright planet or the Moon through the StellaLyra linears vs my old standard Burgess Binoviewer. 

 

 doah.gif   More work for me.  sweaty.gif  

 

grin.gif

Mike


Edited by Sarkikos, 16 March 2024 - 01:07 PM.

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#141 Sarkikos

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Posted 16 March 2024 - 01:15 PM

One easy experiment to check the tfov of the linear with your chosen eyepieces with or without reducer as compared to mono (not using BV) is to view a brick wall (or brick chimney) and count bricks in the daytime. Do it with the linear. Then do it mono. See if you get the same count. Try adding a reducer for both set-ups. It is also a good way to see if there is any field curvature. Note that if the brick wall is fairly close, you may need to add in an extension tube to reach focus.

An even easier experiment would be to put one eyepiece in one side of the binoviewer and look through that eyepiece while looking through its twin held in the other hand.  Superimpose the images from the two eyepieces.  You should be able to tell if the AFOV appears to be narrower through the eyepiece that's in the binoviewer.  If so, there is vignetting ... or loss of outer field illumination or reduction of effective clear aperture or whatever the optical mavens want to call it on whatever day you're doing the experiment.

 

I've done this many times when trying to determine the AFOV of an eyepiece, by comparing it with eyepieces that have known AFOV's.  

 

P.S.:  There are no brick walls or brick chimneys in my neighborhood, at least none within sight of my yard.  :grin:

 

Mike


Edited by Sarkikos, 16 March 2024 - 05:00 PM.


#142 DRodrigues

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Posted 17 March 2024 - 08:29 AM

...

P.S.:  There are no brick walls or brick chimneys in my neighborhood, at least none within sight of my yard.  grin.gif

...

You can use a measuring tape or ruler on a wall, fence, ...

Do the test during daylight and all vignetting will be easily noticeable.

Your experience might indicate that flat-field telescopes might be great for the LBV use - these incorporate a focal reducer that my experience showed to be good for the use of the LBV https://www.cloudyni...r-fov-increase/ 
 


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#143 Sarkikos

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Posted 17 March 2024 - 08:22 PM

OK, today I tried the technique I mentioned in post # 141:

 

An even easier experiment would be to put one eyepiece in one side of the binoviewer and look through that eyepiece while looking through its twin held in the other hand.  Superimpose the images from the two eyepieces.  You should be able to tell if the AFOV appears to be narrower through the eyepiece that's in the binoviewer.  If so, there is vignetting ... or loss of outer field illumination or reduction of effective clear aperture or whatever the optical mavens want to call it on whatever day you're doing the experiment.

In fact, I'm doing this right now at my desk.  You can't get any easier than that!  grin.gif

 

I'm already three beers through my obligatory six beers for St. Patrick's Day, so hopefully there won't be too many typos.  Erin go bragh!  waytogo.gif  I'm placing my current beer safely out of the way.  

 

Since for binoviewing you're always going to have a pair of eyepieces, it should be no problem putting one in the binoviewer and holding the other eyepiece in a hand.  

 

I'm putting one eyepiece in the right eyepiece holder of the binoviewer while looking through it with my left eye and holding the binoviewer with my left hand.  I put the other eyepiece of the pair in my right hand and look through that eyepiece with my right eye.  I compare the apparent size of each eyepiece field of view.  That's all there is to it.  No brick walls, rulers or clocks necessary for the testing.  Not even a telescope.

 

Results:

 

35 Ultrascopic (28.9mm field stop):  AFOV obviously narrower through linears.  About 20% smaller, maybe a bit smaller than that.

32 Omni Plossl (27mm field stop):  AFOV obviously narrower through linears.  About 20% smaller.

24 Pan (27mm field stop):  AFOV obviously narrower through linears.  Again, about 20% smaller.

18 Tak LE (15.8mm field stop):  AFOV the same size through linears as through eyepiece held in the hand. 

 

It was difficult for me to estimate accurately the decrease in AFOV.  But in all three cases, the decrease was obvious.  This technique is simpler and more accurate than trying to remember how large the field is supposed to be in these eyepieces as you're looking through the binoviewer in the telescope.  (That did not work for me.)   A direct, immediate comparison in real time is always best if you can manage it.

 

I did not see any change in AFOV with the Kasai 0.66x Reducer on the linears.  (I didn't expect there to be any.)  So, I doubt if using a reducer is in any real way an effective cheat to get around the vignetting that is taking place with eyepieces which have field stops much wider than 17mm.  Maybe I'm wrong.  Increase in field, of course, will be in the true field of view.

 

The next test will be to go through my other binoviewer pairs and see if I can determine the maximum field stop where vignetting starts to become easily visible.   My easy prediction is it will be somewhere between 27mm and 17mm, and closer to the 17mm end of the range.  grin.gif

 

So, what is causing the vignetting?  The linear binoviewer or the eyepieces?  Guess which answer I'd give.  lol.gif

 

Mike


Edited by Sarkikos, 17 March 2024 - 08:47 PM.

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#144 Sarkikos

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Posted 18 March 2024 - 12:25 PM

Here is a screen shot of my spreadsheet page which shows my binoviewer pairs.  I've excluded pairs that are mediocre to bad eyepieces I received when I bought telescopes in the past.  

 

I'll select the following for further testing in the linear binoviewer:

 

28 Edmund RKE

26 Celestron Silver Top Plossl

25 Sterling Plossl

24 Brandon

8-24 Baader Hyperion Zoom Mark III

 

Mike

Attached Thumbnails

  • bv eps.jpg

Edited by Sarkikos, 18 March 2024 - 01:29 PM.


#145 Bintang13

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Posted 18 March 2024 - 01:15 PM

Just something else to factor in. The TV 101 is f5.4 reduced its f3.6. Because no amplifier is being used you won’t get the same performance from Plossl like eyepieces unless matched with slower scopes like Maks. There was a noticeable performance difference with Delites using a Dob f4.7.

 

Jim


Edited by Bintang13, 18 March 2024 - 01:16 PM.

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#146 Sarkikos

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Posted 18 March 2024 - 01:56 PM

Just something else to factor in. The TV 101 is f5.4 reduced its f3.6. Because no amplifier is being used you won’t get the same performance from Plossl like eyepieces unless matched with slower scopes like Maks. There was a noticeable performance difference with Delites using a Dob f4.7.

 

Jim

By amplifier, you mean Barlow, correct?  The two columns for "FL @ 1.9" and FL @ 3" represent the effective focal length of the eyepiece with specific Barlows or OCS's in the system when I used my Burgess Binoviewer.  For this binoviewer, I should also include columns for "FL @ 0.5" and "FL @ 0.66" to represent the two reducers I have now.  (I cancelled the order for a 0.6x reducer and 10mm MonoCentric from Siebert Optics.)

 

At this point, I'm not so much concerned about the niceties of optical performance, beyond whether or not there is vignetting.  

 

Mike


Edited by Sarkikos, 18 March 2024 - 02:02 PM.

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#147 Bintang13

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Posted 18 March 2024 - 03:29 PM

Yes, in essence a Barlow. Just pointing out that eyepieces designed close to the scopes f ratio will be more important and sharing some of my own hard knocks. I am very much enjoying reading about your experiences so please keep us posted.

 

Jim


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#148 Sarkikos

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Posted 18 March 2024 - 08:26 PM

Tests from this evening, in the comfort of my home, sitting at my desk (no beers were consumed during the course of these tests :grin:):

 

28 Edmund RKE (23.3mm field stop):  AFOV obviously narrower through linears.

26 Celestron Silver Top Plossl (22.5mm field stop):  AFOV obviously narrower through linears.

25 Sterling Plossl (23.2mm field stop):  AFOV obviously narrower through linears.

24 Brandon (21.4mm field stop):  AFOV obviously narrower through linears.

8-24 Baader Hyperion Zoom Mark III (17.6mm field stop):  AFOV the same size through linears as through eyepiece held in the hand.

 

I also tested my bino pairs which had field stops between the 21.4mm of the 24 Brandon and the 17.6mm of the Baader Zoom:

 

20 Photo-20 (from a couple baby Maks, 20.1mm field stop):  AFOV's the same size.

25 Celestron Plossl (black with orange letters, 21.1mm field stop):  AFOV obviously narrower through linears.

Orion Explorer II Kellner (21.1mm field stop):  AFOV obviously narrower through linears.

Sky-Watcher LET/LER (21.2mm field stop):  AFOV obviously narrower through linears.

 

From these results, I'd say that if you want to avoid vignetting with the linear binoviewers, don't use eyepieces with field stops any wider than about 20mm.  At 21mm, you've already gone too wide.  

 

Keep in mind that for these last four pairs, the field stops were calculated from the focal length and AFOV.  For the 24 Brandon, however, I used the field stop (21.4mm) that is given in available specifications.  The 24 Brandon showed an AFOV that was obviously narrower through the linears.

 

Mike


Edited by Sarkikos, 18 March 2024 - 08:29 PM.

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#149 vkhastro1

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Posted 18 March 2024 - 09:43 PM

Excellent report, much appreciated.

I purchased an Orion version recently from my local Astro store in Montreal (La Maison de l’Astronomie) - in stock item.

They still have one available in stock (for anyone interested in purchasing).

 

Definitely a little learning curve compared to my Zeiss units.

Overall very impressed with the views especially with no OCS required.

Already ordered the Orion 1.25” pentaprism for normal daytime viewing (RACI).

For the lowest magnification viewing tried the following with my Mewlon 180B as well as a TeleVue Genesis SDF:

20mm Sterling Plossl 

18.2mm TeleVue DeLite

16mm Explore Scientific 16mm 68°

14mm Denkmeier 65° (actually 15.3mm)
 

All of the above had no issues with vignetting.

Especially impressed with the 18.2mm DeLite and 14mm Denkmeier.

I really found the eye relief very tight on the ES 16mm 68° - will not use them with the linear binoviewer in the future.


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#150 jprideaux

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Posted 19 March 2024 - 05:25 AM

I have enjoyed using my Baader orthoscopic 18mm FL (16.8 mm field-stop) with my linear in my fast refractor. These are also fairly inexpensive. Yes, you don’t want to pay for field-stop in an eyepiece that you can’t use.

Edited by jprideaux, 19 March 2024 - 05:26 AM.

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