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Nagler-like performance...

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#26 ronharper

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Posted 08 May 2008 - 11:12 AM

Thanks for a very interesting thread. I like 7x50s and have always been curious about the Prostar.

Since somebody asked, the Fujinon 7x50 is no great shakes in this department. The field is rather curved, about 2 diopters from center to edge. Despite it's narrower apparent field, the edge is quite a bit softer than the 10x50.

Henry Link has reported in other forums that the optical train of the Prostar (and its 10x70 sibling) and FMT are very similar except the Prostar has an extra convex lens cemented to the output end of the prisms. Very interesting! Comments, BillC or Henry?

While the Prostar is apparently supreme for edge correction, it's apparent field is only 53 degrees. Several of the second-place binos provide 60-67 degrees. If these were field-stopped to 53 degrees, Ed, would it be a different story?

Ron

#27 BillC

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Posted 08 May 2008 - 11:29 AM

I have owned 4 Prostars . . . AND WILL AGAIN. But, I have never noticed this extra lens. I treat my binos well, so I doubt I will ever have a reason to go inside. But, I have repaired them for others and still don't recall it. But then, my memory . . .

The only one I can remember with a separate field-flattener was the old Swift Commodore. This was a good bino--for the money--but Swift's lack of ability to really promote it killed it off.

Cheers,

Bill

#28 Rich N

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Posted 08 May 2008 - 11:52 AM

The Zeiss 7x42FL has a 450 foot true field at 1000 yards.

The Nikon 7x50 ProStar has a 383 foot true field at 1000 yards.

It would be interesting to see how sharp the Zeiss is at the true field of the Nikon.

#29 EdZ

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Posted 08 May 2008 - 12:10 PM

I've now have test data on 7 different 7x50s. The Prostar has an Afov of 53°. None of the other 7x50s are wider than that. Most of the others are between 52° and 49° and this is normal for a 7x50. One of them has a 45° Afov.

The Prostar 7x50 also has the widest Tfov of all 7x50s tested. It's not until you get into 8x binoculars that you start seeing wider Afov eyepieces and Tfov wider than 7.0° to 7.5°. But even with that, in fact only 3 out of 11 of the 8x binoculars that I've measured have a wider Tfov than the Prostar 7x50.

FWIW, I just checked my data files. 19 out of 36 small binoculars tested have Afov 54° or smaller. 14 of them have a narrower Afov than the Prostar. Prostar is just about right in the middle of Afov and is near the top in Tfov of 36 different binoculars tested.

So as it turns out, in the grand scheme of things, the Prostar Afov of 53° is NOT really all that narrow compared to many other binoculars ranging from 7x to 12x, and as far as comparison to 7x and 8x binoculars, it has a wider Tfov than 3/4ths of all 7s or 8s I've measured.

edz

#30 Rich N

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Posted 08 May 2008 - 12:24 PM

The older classic Zeiss 7x42 also had a 450 foot true field at 1000 yards.

It would be interesting to set out two small lights separated by 383 feet and get back 1000 yards to see how sharp they are in the Zeiss.

#31 EdZ

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Posted 08 May 2008 - 12:32 PM

a far better test than that would be

take the closest observable double star pair that can be seen at the edge of the Prostar and try to observe it in the other binocs. Starting with the double placed on the extreme edge, slowly move it inward until it can be seen and record the position. Try Alya, theta Serpens; an even magnitude 22" pair. I saw theta Serpens all the way out at 90%+ of fov in the Prostar.

FWIW, there are some 8x binoculars I've tested in which I cannot even see theta Serpens beyond dead center.

edz

#32 Neil Weiner

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Posted 08 May 2008 - 12:37 PM

Advertised TFOV: Prostar 7.3, Fujinon 7.5.

A few years ago I won a perfect Prostar on auction at a very fair price. I took my time comparing it to my Fujinon Meibo for Terrestrial (yes) viewing. I sold the Prostar and kept the Meibo.

The Prostar felt somewhat tunnel-view , the Fujinon felt natural. The Prostar was especially clunky to hold steady, the Fujinon (rubber armored), easier to hold steady--though still a big, heavy 7x50.

So despite the technical, optical excellence of the Prostar, I was seeing and enjoying more, Terrestrially, with the Fujinon.

Of course this is off topic regarding Nagler, but yet another reminder that bino "better" and "best" are not absolute, but relative to for-what and to-whom.

#33 EdZ

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Posted 08 May 2008 - 12:39 PM

Advertised TFOV: Prostar 7.3, Fujinon 7.5.


Actual measured TFOV: Prostar 7.5

edz

#34 Henry Link

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Posted 08 May 2008 - 12:41 PM

You can see the extra element in this internal view supplied by jrweisner in a thread last year:

http://rchamon.iies....ikon/7x50sp.jpg

Notice that it's placed in front of the objective focal plane and does not move with the eyepiece elements, so I think it should be considered a third objective element. My guess is that it's designed to correct field curvature by making the field curvatures of the objective and the eyepiece nearly complimentary. I agree with Ron that other so called "field flatteners" (Fujinon FMT-SX, Nikon SE, Pentax PIF) appear to correct astigmatism, but not field curvature.

#35 Rich N

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Posted 08 May 2008 - 12:44 PM

From the Zeiss UK site...
http://www.zeiss.co....1256f27003e957a

Zeiss 7x42 T FL has a 60 deg APOV
Zeiss 8x42 T FL has a 61.8 deg APOV
Zeiss 10x42 T FL has a 63 deg APOV

#36 Rich N

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Posted 08 May 2008 - 01:17 PM

Here is a link showing the internal view of the Zeiss Victory series.

http://www.zeiss.co....1256F27003F46D2

No. I don't work for Zeiss. ;)

#37 EdZ

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Posted 08 May 2008 - 01:26 PM

I agree with Ron that other so called "field flatteners" (Fujinon FMT-SX, Nikon SE, Pentax PIF) appear to correct astigmatism, but not field curvature.


Seems to agree with what I've found. Examples:
Fujinon FMT-SX 10x50, all or nearly all of the outer field aberration is field curvature.
Nikon SE 10x42, approx 80% of all outer field aberration is due to field curvature.
Nikon SE 12x50, approx 75% of all outer field aberration is due to field curvature.

Note, these binoculars outer filed total aberration is very well controlled, it's just being pointed out here how much of what is there is due to curvature.

Nikon Prostar 7x50, close to zero.

edz

#38 Rick

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Posted 08 May 2008 - 04:36 PM

The term "Nagler-like" generally means a WIDE AFOV in additon to edge sharpness. Most OEMs consider their binos to be WIDE if the AFOV > 65°. So I am suprised no one has mention the Nikon 8x30 E2 with its 70° AFOV (8.8° TFOV). Generally still available in most of the world ex USA for some silly reason. :confused:

clear skies,
Rick

#39 BillC

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Posted 08 May 2008 - 05:11 PM

Thanks for the drawing, Henry. You saved me 20 minutes of work, and possibly a scratched screw head or two.

Cheers,

Bill

#40 StarStuff1

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Posted 08 May 2008 - 06:00 PM

This afternoon, by sheer coincidence, I was shown a nearly 40 year old Nikon 9x35 porro with an afov of 66°, tfov of 7.3°. While not "Nagler like" in fov this rather small and light bino was remarkably sharp across the field. It was owned by a birder (naturally)who had ordered it from Europe since that model was not sold here. He said it cost about $135 in 1970 and the import duties was almost that, too. A well worn but very nice and compact instrument that was still in decent collimation.

#41 EdZ

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Posted 08 May 2008 - 06:41 PM

The term "Nagler-like" generally means a WIDE AFOV in additon to edge sharpness. Most OEMs consider their binos to be WIDE if the AFOV > 65°. So I am suprised no one has mention the Nikon 8x30 E2 with its 70° AFOV (8.8° TFOV). Generally still available in most of the world ex USA for some silly reason. :confused:

clear skies,
Rick


I have data on over 60 different binoculars in my database. A wide variety from 7x35 to 25x100, and many many small sizes and large sizes in between.

Less than 10 binoculars have Afov of 65°. I would say a 65°+ Afov is quite uncommon in binoculars. Only 4 of them handle the wide field well, so less than 7% of 60 binoculars have a GOOD wide field 65° or larger.

There are just as many in the data that have 50° or less as there are that are 65° or greater.

Half of all binoculars range from 60° to 65°

More than 20 binoculars have Afov of 53° or less. We sometimes hear people describe this as tunnel like, yet more than 1/3 of binoculars have eyepieces with these narrow field stops. Only 3 of these handle outer Afov sharpness poorly.

More than 15 binoculars have Afov of 64° or greater. Of these, 10 handle outer Afov sharpness poorly.

edz

#42 davidmcgo

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Posted 08 May 2008 - 09:05 PM

Maybe "Panoptic Like" is more typical than "Nagler Like", but Nagler designed the Panoptic! I am suprised no one mentioned the Canon 15x50IS in this discussion. The rectilinear distortion and slight lateral color allowed to maintain perfect focus out to edge in the Canons is very similar design philosophy I think, and performance on night sky is very similar in feel to a small refractor with a Panoptic eyepiece.

Dave

#43 Wes James

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Posted 09 May 2008 - 10:34 AM

Hmmm... reading back on this and some of the other recent posts, seems like a head-to-head shoot-out between the Nikon 7x50 Prostar, Fujinon 7x50 FMT-SX and Orion Resolux 7x50 would make for an interesting comparison...
Wes

#44 BillC

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Posted 09 May 2008 - 12:52 PM

Prostar #1
FMT #4
Orion #5

Bill

#45 Wes James

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Posted 09 May 2008 - 03:13 PM

Prostar #1
FMT #4
Orion #5

Bill


And #'s 2 & 3 would be??
Sorry- I also meant to add the WO 7x50 into the mix as well... as EdZ noted in a different thread- on the Resolux 10x50's-

The WO 7050:
has the finest resolution of any small binocular I've tested, so far. ...has the greatest illumance of any small binocular I've tested so far.


There seems to be enough top quality binoculars, and close enough in many aspects that to just place arbitrary numbers on them without the comments to go along with them is selling them short. It'd be nice, when looking at the upper end binoculars in any given class, what the differences are before making a purchasing decision. I, for one, live where the best bino's I can walk into a store and compare are in the $100-$200 range. Top quality bino's? I have to take a shot in the dark based upon what tests and reviews I can find- mail order them and hope for the best. And if one reads a review from one source- and then later another one from another source, by someone else, it's still not really as accurate a comparison as if the same person reviews them all at the same time and under the same conditions. EdZ has been exceptionally invaluable to us all here (Thank You, EdZ! :bow: ) in providing computer-like accurate and meaningful comparisons and tests. Would simply love to see him do a shoot-out between the top, say- 7x50's (as they seem to be a particular hot topic of interest at the present time) then, perhaps 10x50's, etc.
Wes

#46 EdZ

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Posted 09 May 2008 - 04:48 PM

as I said, Small Binocular Series - the 7x50s is underway.

edz

#47 BillC

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Posted 09 May 2008 - 06:05 PM

#2 and #3 have been intentionally left blank out of respect for the Prostar.

Cheers,

Bill

#48 BobinKy

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Posted 09 May 2008 - 07:26 PM

EdZ wrote Small Binocular Series - the 7x50s is underway.

EdZ, as a new owner of a Fujinon FMT-SX 7x50, I am looking forward to your test results.

#49 BobinKy

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Posted 09 May 2008 - 07:39 PM

Wes James wrote: I, for one, live where the best bino's I can walk into a store and compare are in the $100-$200 range. Top quality bino's? I have to take a shot in the dark based upon what tests and reviews I can find- mail order them and hope for the best. And if one reads a review from one source- and then later another one from another source, by someone else, it's still not really as accurate a comparison as if the same person reviews them all at the same time and under the same conditions. EdZ has been exceptionally invaluable to us all here (Thank You, EdZ! ) in providing computer-like accurate and meaningful comparisons and tests. Would simply love to see him do a shoot-out between the top, say- 7x50's (as they seem to be a particular hot topic of interest at the present time)


I agree, EdZ's test are the best comparisons going.

then, perhaps 10x50's


I would like to see the Pentax DCF ED 10x50 added to one of EdZ's exhaustive tests.

#50 BobinKy

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Posted 09 May 2008 - 07:44 PM

BillC wrote:Prostar #1
FMT #4 (#2)
Orion #5 (#3)



Bill, of course, we look forward to your supporting documentation for the above ratings. ;)


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