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18mm ES vs 16mm Nagler vs 15mm Knightowl

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#1 droid

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Posted 21 September 2019 - 09:52 PM

I set out to see how my 16mm Nagler type 2 would fair against modern eyepieces.

 

The scope an f10 classic two lens refractor

 

The eye pieces are listed in the title above

 

The sky was average, and got worse to really bad quickly.

 

The test subject : M13 in Hercules

 

first up was the 18mm ES , Dark back ground , sharp stars out to the edge minus like 4 or 5 percent. Very nice presentation. Of course slightly less magnification, but I was really just comparing views.

 

Next up was the new to me 16mm Nagler t2 , tack sharp stars out toe edge, I could not see any defects at the edge. focuses way farther out than either of the other 2

 

And last but not least....the real surprise....the 15mm knightowl…..stars were sharp to very near the edge, background was a shade or so lighter than the Naglers view. I was surprised to say the least. Of course it was an f10 scope , it focused the furthest inward., this 15mm is the odd ball of the group., all the rest are straight cylindrical affairs, the 15mm is not. Id love to know what this is. http://www.owlastron...m/ultrawide.htm

 

the sky was average at best and deteriorating quikly, so these results are not what I had hoped for. Ill try again if and when I get good skies

 

 

 

 



#2 fcathell

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Posted 21 September 2019 - 10:55 PM

Very interesting!  I have the 11mm version and I've had it for a number of years and I like it.  It is one of my favorite eyepieces.  I'm pretty sure I got it from Knightowl for about $40.

 

I think this is the same eyepiece series: 

 

https://www.ebay.com...lYAAOSwSzdXCGiX

 

Frank



#3 CeleNoptic

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Posted 21 September 2019 - 11:17 PM

Id love to know what this is. http://www.owlastron...m/ultrawide.htm


These inexpensive EPs existing for ages under different brands. Nothing special, but probably not bad for very slow scopes.
 
https://www.ebay.com...oa=1&pg=2385738
 
 https://www.ebay.com...k-/191855623489
 
https://www.amazon.c...e/dp/B06X986WH9
 
https://telescopes.n.../80-99-fov.html



#4 agmoonsolns

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Posted 21 September 2019 - 11:42 PM

Is there any difference between the 2" and 1.25" versions of the 15mm 80° eyepieces other than being in different sized bodies?



#5 droid

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Posted 23 September 2019 - 12:51 PM

I set out to see how my 16mm Nagler type 2 would fair against modern eyepieces.

 

The scope an f10 classic two lens refractor

 

The eye pieces are listed in the title above

 

The sky was average, and got worse to really bad quickly.

 

The test subject : M13 in Hercules

 

first up was the 18mm ES , Dark back ground , sharp stars out to the edge minus like 4 or 5 percent. Very nice presentation. Of course slightly less magnification, but I was really just comparing views.

 

Next up was the new to me 16mm Nagler t2 , tack sharp stars out toe edge, I could not see any defects at the edge. focuses way farther out than either of the other 2

 

And last but not least....the real surprise....the 15mm knightowl…..stars were sharp to very near the edge, background was a shade or so lighter than the Naglers view. I was surprised to say the least. Of course it was an f10 scope , it focused the furthest inward., this 15mm is the odd ball of the group., all the rest are straight cylindrical affairs, the 15mm is not. Id love to know what this is. http://www.owlastron...m/ultrawide.htm

 

the sky was average at best and deteriorating quikly, so these results are not what I had hoped for. Ill try again if and when I get good skies

update: I took the 12 inch f4.9 out with these eps, the ES 18 did very well, but showed distortions about the last 20 percent or so. , the night owl which impressed me at f10, not so much at 4.9. probably the outer 3rd were smeared ,slightly at first and the closer you got to the edge, the worse it got., The 16mm Nagler was virtually perfect, accept for right at the edge where it started to smear . I do not use a paracor so.....

 

An interesting aside......the 16mm t2 at f10 was just normal ,at 4.9 it really caught my eye. large fields all pin points, no distortions. Its a sweet addition to my kit when using he 12 inch scope.


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#6 Miranda2525

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Posted 23 September 2019 - 12:58 PM

No surprise with the 15mm Night Owl, or many other types. You are at f/10. 

 

As you have discovered, at f/4.9, things REALLY change.


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#7 25585

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Posted 23 September 2019 - 05:55 PM

Is Knightowl related to Moonfish?  https://www.cloudyni...eyepieces-r1153



#8 droid

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Posted 23 September 2019 - 06:04 PM

Is Knightowl related to Moonfish?  https://www.cloudyni...eyepieces-r1153

I do not know, but if I had to guess...Id say probably not.



#9 John Huntley

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Posted 24 September 2019 - 06:48 PM

I think these are all based on the original Kokusai Kohki Widescan II and III's made in Japan. I used to have a set comprising 13mm, 16mm and 20mm in the 1.25 inch fitting and a 30mm in 2 inches. The stated AFoV of those is 84 degrees.

 

They were very nice in scopes down to F/8 but faster than that and the flocks of seagulls infested the outer half of the field. The 13mm was probably the best corrected.

 

post-753-0-81676200-1464263041.jpg

 

 

 

 


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#10 Jon Isaacs

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Posted 25 September 2019 - 04:11 AM

update: I took the 12 inch f4.9 out with these eps, the ES 18 did very well, but showed distortions about the last 20 percent or so. , the night owl which impressed me at f10, not so much at 4.9. probably the outer 3rd were smeared ,slightly at first and the closer you got to the edge, the worse it got., The 16mm Nagler was virtually perfect, accept for right at the edge where it started to smear . I do not use a paracor so.....

 

An interesting aside......the 16mm t2 at f10 was just normal ,at 4.9 it really caught my eye. large fields all pin points, no distortions. Its a sweet addition to my kit when using he 12 inch scope.

 

The advantages of the Naglers become more and more apparent with faster and faster focal ratios.  

 

Some years ago, a friend was observing with his 10 inch F/4.7 XT-10i and asked me if I could show him what coma looked like.  I used my 16mm T2 and the Paracorr (there was no 2 at the time.)  Without the Paracorr, it looked quite good but with the Paracorr, the edge stars were tight and round and then going back to the eyepiece alone, he could see the coma.

 

Jon



#11 macdonjh

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Posted 25 September 2019 - 10:52 AM

The advantages of the Naglers become more and more apparent with faster and faster focal ratios.  

 

Some years ago, a friend was observing with his 10 inch F/4.7 XT-10i and asked me if I could show him what coma looked like.  I used my 16mm T2 and the Paracorr (there was no 2 at the time.)  Without the Paracorr, it looked quite good but with the Paracorr, the edge stars were tight and round and then going back to the eyepiece alone, he could see the coma.

 

Jon

I have to admit, the Naglers I have are in my colleection for field of view only.  Almost all my scopes are slow enough I don't need the correction Uncle Al provides.  

 

My introduction to coma was with a friend's 12.5" f/5 Obsession Dobsonian and my 40mm Optiluxe, which I think is a Konig.  I really like that eye piece in my f/10 and slower scopes, but in my friend's f/5 the stars at the edge were just like a second grader's drawing of birds: a central dot with opposing arcs for wings.  It was terrible.  I think Rick had a Paracorr and we tried it.  It helped, but didn't cure the problem.



#12 Jon Isaacs

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Posted 26 September 2019 - 02:41 PM

I have to admit, the Naglers I have are in my colleection for field of view only.  Almost all my scopes are slow enough I don't need the correction Uncle Al provides.  

 

My introduction to coma was with a friend's 12.5" f/5 Obsession Dobsonian and my 40mm Optiluxe, which I think is a Konig.  I really like that eye piece in my f/10 and slower scopes, but in my friend's f/5 the stars at the edge were just like a second grader's drawing of birds: a central dot with opposing arcs for wings.  It was terrible.  I think Rick had a Paracorr and we tried it.  It helped, but didn't cure the problem.

 

The Optiluxe likely suffered from off-axis astigmatism so correcting the coma was only part of the battle.  One of the advantages of slow scopes is they are forgiving of eyepiece's.

 

The downside is you're limited to relative narrow TFoVs and generally smaller exit pupils.. 

 

Jon




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