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Go Back   IceInSpace > Equipment > Eyepieces, Barlows and Filters

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  #1  
Old 17-06-2018, 07:05 AM
ghusko (Gordon)
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GSO Superview 2" eps and GSO 2x Barlow

Hi Peeps,
anyone had much experience with these and can comment on quality?


My 2" star diag (Bintel /GSO ) is on its way so its time to think about some 2" eps and a barlow to go with it. Think from memory they come in a 42mm , 30mm, 20mm I was going to get all 3.


Its all going on a Meade LX90 8" F10


Cheers Gordo.
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  #2  
Old 17-06-2018, 11:56 AM
SkyWatch (Dean)
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Hi Gordon,
They come in 15, 20, 30, 42 and 50mm fl's. The 15 is a 4-element design, and the rest are 5-element.
I have the 42mm version, and it works well in long FL scopes like yours. It is not entirely sharp to the edge, but the longer the FL the better it gets.
One issue to be aware of is that depending which site you read they have a claimed AFOV of 65-68°, apart from the 50mm which is claimed 60°. However, my 42mm doesn't have a true field stop: the lens retaining ring effectively acts as a field stop, and is around 41.5mm in diameter, but because this is inside the focal plane of the eyepiece it provides a fuzzy edge, and there is no clear field stop when you look through the eyepiece. (The field stop determines the true FOV: TFOV=field stop/focal length x 57.3) This corresponds to an AFOV of around 57°, not 65-68° as advertised...
I can't speak for the other focal lengths, but I believe they are generally good value for money in a scope like yours.
My only concern is whether you can move your scope to the vertical with a 2" diagonal. I believe others have said that it hits the base of the mount on the LX90 when trying to go above around 70° or so. This is something to check before you commit to extra eyepieces.
All the best, and happy viewing.

- Dean
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  #3  
Old 18-06-2018, 06:14 PM
Oddity (Andrew)
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Not a 2" ... but I compared the 1.25" GSO 15mm 68* and ES 16mm 68* last night in a short (731mm/f4.8) focal length scope.

I know there is a significant price difference but it's still an interesting comparison between the two. The GSO started to fuzz a little on stars about halfway out, whereas the ES kept it clean as far to the edge as I needed to look. Good for keeping things in view longer, reducing the need to move the scope in non-tracking mounts (or just want a quick look at planets in the backyard and don't want to hook up the power and align it).

Last edited by Oddity; 19-06-2018 at 12:36 AM.
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  #4  
Old 18-06-2018, 09:34 PM
Startrek (Martin)
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My 10” Bintel / GSO dob which I purchased 2 years ago included a number of eye pieces including a Bintel/GSO 30mm superview.

I can only comment on my initial reaction when it was dropped in the focuser which was “ wow” what a wide field sharp as a tac view.In comparison to my 2 other 50 deg Plössl eye pieces it was like looking at the whole night sky. But like most beginner visual astronomers you are eager to see better views sooner than later so within 2 years I decided to take a quantum leap and now I’m looking through Televue Delites, Delos and Ethos eye pieces ( enough said )

The Bintel/GSO 30mm Superview is certainly a great eyepiece in the 68 deg FOV range for value and quality.
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  #5  
Old 19-06-2018, 01:01 AM
ghusko (Gordon)
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Thanks

Thanks heaps for all your input looks like a worthwhile investment, especially over the standard Meade 4k series that came with it.



with the 2" diag was aware of that being an issue going vertical, but I have since acquired a wedge, so hopefully that will solve that issue


Was also not aware that they had the additional sizes as well...doh wife not going to be happy with the $$$


does anyone know if they sell a complete kit all eps?
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  #6  
Old 19-06-2018, 07:54 AM
mental4astro (Alexander)
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These Superview eyepieces are designed to work with scopes that produce a convex focal plane, refractors, SCT's and Maks. In Newts, concave focal plane, these eyepieces will show both field curvature and astigmatism because of the optical mismatch. The faster the Newt, the more significant the aberrations will appear. And as with all eyepieces, different focal lengths will perform differently. This EP design also performs better with a slower f/ratio refractor than a faster one. That's the design.

I have the 30mm and 15mm Superviews. The 30mm in my Newt is poorer in my Newts than the 15, showing a lot more astigmatism and field curvature. In my SCT, both EPs perform a whole lot better. But, despite the optical mismatch with Newts, for their price these represent excellent value for money and still do a good job. They are also very easy to use, especially for novices and as a first 2" eyepiece.

The 30mm was they first 2" eyepiece I bought for my Newt. Great to start out with, and my novice eyes didn't have any issues with it. I've bought and sold MANY 2" eyepieces since, but I never sold this 30mm, nor its 15mm little brother. I've kept these as they are excellent for outreach. Yes, these are not my first option EPs for my personal use anymore, but these have cemented their spot in my EP case.

A good mate of mine also bought his 15mm and 30mm Superviews at the same time as me, and uses them on his only scope, an f/4.5 Newt. To his good fortune he found his EP Nirvana with these, and has never felt motivated to change. Lucky devil! . He well knows of their short comings, but he's most happy with them.

These are not a "perfect" eyepiece either optically in refractors either, and not for everyone either. Some people wouldn't look sideways at them, but other people wouldn't change them either. They have a place in my kit today, and when they had pride place when I first bought them they served me well. If $ are a concern, these are a very good option. If you are starting out in astro these are a good place to start, and you may find these are all you need.

Alex.
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  #7  
Old 19-06-2018, 11:00 AM
mental4astro (Alexander)
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As far as a kit of the whole set of these Superviews, no, they are available just individually.

If you use the 42mm and 50mm under urban skies with your SCT, you will find that the shadow of the secondary mirror will become problematic. The issue is not the EP or scope, but the amount of light pollution. Has nothing to do with the design of the EPs either. A 50mm plossl will show the same shadow. Use these long EPs in your SCT under a dark sky, and the shadow won't be noticeable.

However, the 50mm won't show you more of the sky than the 42mm. Both will show you the same amount of sky, but the image of in the 50mm will be smaller in both magnification and in the diameter of the image. This is due to the limitation of the 2" barrel - it just can't show anymore sky than a certain amount. The 50mm may seem redundant then, but it does have a place with concentrating the image that little more which helps bring out some objects.

In a Newtonian, going longer in EP focal length than 30mm won't help you very much. As most Newt's are around f/5 and faster, the "exit pupil", or the size of the light beam coming out of the EP, when you use an EP longer than 30mm will be too large for all the light to enter our human eyes. So effectively you will be reducing the aperture of your scope as a result. This is not to say you can't use an EP longer than 30mm with your Newtonian, and a 42mm Superview will show you as much of the sky as a 2" barrel can give, just be aware that it you won't be maximizing the aperture capacity of your scope.

Exit pupil???

Think about the pupil of your eye. When it is open to its widest, in a young person this will be around 7mm in diameter. As we age, this reduces to around 6mm. So, to maximise the amount of light coming from your scope, you would want to get a beam of light coming out of the EP to be around the 7mm to 6mm range. The term "exit pupil" is a ratio given between the EP focal length and the scope's f/ratio. While the exit pupil generated by a scope can certainly be smaller than 6mm (as you increase magnification the exit pupil gets smaller, so all the light beam is entering your eye), normally you would want to max out the EP focal length FOR A GIVEN SCOPE, to best suit the scope's focal ratio.

Here's how it works:

We want a max exit pupil of 6mm - I'm older than 35years after all, so I need to be realistic about my eyes.

So, for the longest EP focal length, the equation is:

f/ratio of scope X 6mm = longest EP focal length

The scope is an f/10 SCT.

The longest focal length EP that will give me a 6mm exit pupil will be:

10 X 6 = 60mm

So with any EP shorter than 60mm, IN AN f/10 SCT, you know you will be getting all the light going into your eye.

If your scope is f/4.5 (and it doesn't matter if it's a Newt, SCT, refractor, etc, it's all the same here), then the longest focal length EP would be:

4.5 X 6 = 27mm

But there's no 27mm EPs!!!!

Exit pupil is just a guide. You need to be practical about these things, and the % loss between a 27mm and 30mm is not really that significant.

There is a way to counter-act this eyepiece focal length discrepancy. You could get an EP with a wider apparent field of view than 68° (Superviews have an AFOV of 68° - yes the 50mm is smaller, and I explained why). With an 82° eyepiece, the longest 2" eyepiece that will give you this is 30mm - you won't find a 40mm 2" EP with an 82° AFOV, that 2" barrel just can't do it. But you may feel that 30mm is still too long (and that's fine), so you can step things up by going to 100° eyepieces, in which case the longest focal length that will give you 100° AFOV is 21mm. In this way you know that you are both maximising the amount of light coming into your eyes, and maximizing the amount of sky that you scope is capable of showing.

HOWEVER, there's no free lunch here either...

100° eyepieces are not a panacea. There's pros and cons to all eyepieces, and these include $$$, ease of use, optical matching, personal preferences, your own eyeballs, and the such.

There is no "mandatory" reason as to why you somehow need to stick to a strict maximum exit pupil. If you understand what is going on, you may feel just fine with a scope/EP combination that gives a larger exit pupil. I have an 8" f/4 Newt. The longest EP for a 6mm exit pupil would be 24mm. I have a 24mm 82° EP, but I know I won't be getting all the sky this scope is capable to showing me. I could use a 21mm 100°, but I don't find this size AFOV practical. However, I am quite happy to use my 30mm 82° eyepiece with this f/4 scope. Sure the exit pupil is "too large", I know this, but I am also getting the largest amount of sky I can get with this scope, and I still very much enjoy the image this EP/scope combo gives me. And there are people who would never entertain the idea of doing this, and that's their personal preference, and that is ok too. Everyone is different.

And I bet you thought that "this is an eyepiece, and this is a scope, so it will work..."

That's how I thought about things too when I started in astro... 35 years ago...

Alex.
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  #8  
Old 19-06-2018, 06:05 PM
Saturnine (Jeff)
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Just to be picky Alex . There is the Televue 27mm Panoptic that's been around for a while now and a fine eyepiece. Suited to newts too, kicking myself for selling mine.



Quote:
Originally Posted by mental4astro View Post
As far as a kit of the whole set of these Superviews, no, they are available just individually.

If you use the 42mm and 50mm under urban skies with your SCT, you will find that the shadow of the secondary mirror will become problematic. The issue is not the EP or scope, but the amount of light pollution. Has nothing to do with the design of the EPs either. A 50mm plossl will show the same shadow. Use these long EPs in your SCT under a dark sky, and the shadow won't be noticeable.

However, the 50mm won't show you more of the sky than the 42mm. Both will show you the same amount of sky, but the image of in the 50mm will be smaller in both magnification and in the diameter of the image. This is due to the limitation of the 2" barrel - it just can't show anymore sky than a certain amount. The 50mm may seem redundant then, but it does have a place with concentrating the image that little more which helps bring out some objects.

In a Newtonian, going longer in EP focal length than 30mm won't help you very much. As most Newt's are around f/5 and faster, the "exit pupil", or the size of the light beam coming out of the EP, when you use an EP longer than 30mm will be too large for all the light to enter our human eyes. So effectively you will be reducing the aperture of your scope as a result. This is not to say you can't use an EP longer than 30mm with your Newtonian, and a 42mm Superview will show you as much of the sky as a 2" barrel can give, just be aware that it you won't be maximizing the aperture capacity of your scope.

Exit pupil???

Think about the pupil of your eye. When it is open to its widest, in a young person this will be around 7mm in diameter. As we age, this reduces to around 6mm. So, to maximise the amount of light coming from your scope, you would want to get a beam of light coming out of the EP to be around the 7mm to 6mm range. The term "exit pupil" is a ratio given between the EP focal length and the scope's f/ratio. While the exit pupil generated by a scope can certainly be smaller than 6mm (as you increase magnification the exit pupil gets smaller, so all the light beam is entering your eye), normally you would want to max out the EP focal length FOR A GIVEN SCOPE, to best suit the scope's focal ratio.

Here's how it works:

We want a max exit pupil of 6mm - I'm older than 35years after all, so I need to be realistic about my eyes.

So, for the longest EP focal length, the equation is:

f/ratio of scope X 6mm = longest EP focal length

The scope is an f/10 SCT.

The longest focal length EP that will give me a 6mm exit pupil will be:

10 X 6 = 60mm

So with any EP shorter than 60mm, IN AN f/10 SCT, you know you will be getting all the light going into your eye.

If your scope is f/4.5 (and it doesn't matter if it's a Newt, SCT, refractor, etc, it's all the same here), then the longest focal length EP would be:

4.5 X 6 = 27mm

But there's no 27mm EPs!!!!

Exit pupil is just a guide. You need to be practical about these things, and the % loss between a 27mm and 30mm is not really that significant.

There is a way to counter-act this eyepiece focal length discrepancy. You could get an EP with a wider apparent field of view than 68° (Superviews have an AFOV of 68° - yes the 50mm is smaller, and I explained why). With an 82° eyepiece, the longest 2" eyepiece that will give you this is 30mm - you won't find a 40mm 2" EP with an 82° AFOV, that 2" barrel just can't do it. But you may feel that 30mm is still too long (and that's fine), so you can step things up by going to 100° eyepieces, in which case the longest focal length that will give you 100° AFOV is 21mm. In this way you know that you are both maximising the amount of light coming into your eyes, and maximizing the amount of sky that you scope is capable of showing.

HOWEVER, there's no free lunch here either...

100° eyepieces are not a panacea. There's pros and cons to all eyepieces, and these include $$$, ease of use, optical matching, personal preferences, your own eyeballs, and the such.

There is no "mandatory" reason as to why you somehow need to stick to a strict maximum exit pupil. If you understand what is going on, you may feel just fine with a scope/EP combination that gives a larger exit pupil. I have an 8" f/4 Newt. The longest EP for a 6mm exit pupil would be 24mm. I have a 24mm 82° EP, but I know I won't be getting all the sky this scope is capable to showing me. I could use a 21mm 100°, but I don't find this size AFOV practical. However, I am quite happy to use my 30mm 82° eyepiece with this f/4 scope. Sure the exit pupil is "too large", I know this, but I am also getting the largest amount of sky I can get with this scope, and I still very much enjoy the image this EP/scope combo gives me. And there are people who would never entertain the idea of doing this, and that's their personal preference, and that is ok too. Everyone is different.

And I bet you thought that "this is an eyepiece, and this is a scope, so it will work..."

That's how I thought about things too when I started in astro... 35 years ago...

Alex.
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  #9  
Old 19-06-2018, 07:34 PM
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RobNevyn (Rob)
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Some good info in this thread, I am at the very early stages and waiting for my 10" Dob to arrive (please be before the weekend), and just now looking for some eyepieces to go with the stock 10 and 25mm Plossl's. So much to consider both product wise and what will and won't work with my scope.
Would there be anything wrong with going a ES 6.7mm 82° for my Dob at f/4.7 ?
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  #10  
Old 19-06-2018, 08:13 PM
ghusko (Gordon)
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Thanks heaps for all your input and experience great info, can't seem to find anything smaller than the 20mm in a 2 inch?


Keep searching...


And yes the 2" diag arrived today....doh pissing rain and cloudy can't test it out and yes it just hits the base...wedge on its way soon.

Thanks again.
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Old 19-06-2018, 11:24 PM
Oddity (Andrew)
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I use the 2" ES 30mm 82* in a f/4.8 Mak-Newt and it's stunning. I also use it in the 2" ES 2x focal extender (essentially their competitor to the powermate) to get the equivalent mag of a 15mm, and that's equally stunning.

Last edited by Oddity; 19-06-2018 at 11:35 PM.
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  #12  
Old 20-06-2018, 06:47 AM
AEAJR (Ed)
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I have the GSO 2" 2X barlow. Like it very much. Use it in my Orion XT8 with a 38 mm 2", 25mm 2" and my Baader Hyperion zoom using the 2" collar.
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  #13  
Old 20-06-2018, 06:49 AM
AEAJR (Ed)
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Cool

Quote:
Originally Posted by ghusko View Post
Thanks heaps for all your input and experience great info, can't seem to find anything smaller than the 20mm in a 2 inch?


Keep searching...


And yes the 2" diag arrived today....doh pissing rain and cloudy can't test it out and yes it just hits the base...wedge on its way soon.

Thanks again.
Plenty of 2" eyepieces under 20 mm. You would only need 2" if you want to be wider than 82 degrees. Otherwise 1.25 is smaller, lower cost and lighter in weight. But 2" are available.
https://agenaastro.com/eyepieces/2-e...0_degrees.html
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  #14  
Old 20-06-2018, 08:15 AM
Oddity (Andrew)
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That said, if you’re particular about getting the best out of your eyepieces, be sure to use a parallelizer or at least a self centering adapter.
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  #15  
Old 20-06-2018, 11:30 AM
mental4astro (Alexander)
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Quote:
Originally Posted by Saturnine View Post
Just to be picky Alex . There is the Televue 27mm Panoptic that's been around for a while now and a fine eyepiece. Suited to newts too, kicking myself for selling mine.
Thanks Jeff!
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