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#1 Guest_**DONOTDELETE**_*

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Posted 04 August 2005 - 02:42 PM

Would the Fuji FMT-SX Polaris 7x50's be suitable for astronomical viewing? They really look like they reek of quality build and hand-holdability while at the same time being more economical, than say, the Nikon SE's. :question:

darkside

#2 Guest_**DONOTDELETE**_*

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Posted 04 August 2005 - 03:37 PM

The exit pupil size with these bins is not really ideal for astronomy. You certainly can use them, but some degree of contrast and effective aperature loss will occur. Read the "best of" section regarding exit pupil.

#3 lighttrap

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Posted 04 August 2005 - 03:47 PM

If you can make use of a 7mm exit pupil, the Fujinon FMT-SX 7x50s are amongst the best there is. But most folks will find better contrast by going to a smaller exit pupil.

#4 EdZ

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Posted 04 August 2005 - 03:56 PM

In general I find that my Fujinon 10x70s don't see any much more than any of my 10x50s, that is until I get them both to a location where the sky is mag 6.5-6.7. Then the 10x70 Fujinon jump out ahead of the 10x50s. of course my pupils are 6.5mm and 7mm, so I can use the full aperture of those 10x70s when the time comes.

If you don't get to very dark skies OR your pupils don't open to 7mm, then a binocular with a 7mm exit pupil is the wrong choice for you. But as Mike said, if you can meet the criteria I mention here, then the 7x50s are a great one to own.

edz

#5 BillC

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Posted 04 August 2005 - 04:49 PM

In general I find that my Fujinon 10x70s don't see any much more than any of my 10x50s, that is until I get them both to a location where the sky is mag 6.5-6.7. Then the 10x70 Fujinon jump out ahead of the 10x50s. of course my pupils are 6.5mm and 7mm, so I can use the full aperture of those 10x70s when the time comes.

If you don't get to very dark skies OR your pupils don't open to 7mm, then a binocular with a 7mm exit pupil is the wrong choice for you. But as Mike said, if you can meet the criteria I mention here, then the 7x50s are a great one to own.

edz


I agree with all EdZ has said. I have to. When I don't, he beats me. But, I would like to add a slight wrinkle.

The 7x50 Fujinon would be GREAT for folks who suffer from inordinate body tremors. If the exit pupil of the bino is matched exactly with the entrance pupil of the eye, the image may frequently "cut out" due to positional problems. Larger exit pupils give the observer some wiggle room.

Just a thought.

Bill

#6 mooreorless

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Posted 04 August 2005 - 06:19 PM

Hi Bill,I have been thinking of saying this for a while and I agree with you about the larger exit pupil being easier to "line" up with your eye entrance pupil esp. for new people. After reading the title >I am no expert.
Steve M

#7 BillC

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Posted 04 August 2005 - 06:39 PM

The Idea doesn't get much airplay. But, I have to keep up my reputation as a kurm . . . Kurmage . . . cormudgeo . . . jerk.

Cheers,

Bill

#8 Pinewood

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Posted 04 August 2005 - 08:24 PM

My first binocular for astronomy was a 7x50, although I did not buy it with astronomy in mind. It was a Leitz Marseptit, which revealed the moons of Jupiter when I pointed it at the planet. My second binoculars were also 7x50's, although I once again bought it for other reasons.

I wonder if navies chose the 7x50 because a young lookout could take advantage of the light gathering potential and an old skipper could keep the binocular on target.

Nowadays, I prefer an 8x40 in my hand or a 12x50 on a monopod.

Clear skies,
Arthur

#9 Guest_**DONOTDELETE**_*

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Posted 04 August 2005 - 08:46 PM

Thanks, guys. I think you've brought up a critical issue when you talk about my qualification re exit pupil. Ed, Mike, Bill, PW, NW et al., I'll be sixty soon and probably couldn't take advantage of the exit pupil. I wear glasses, but not for reading or looking through binos or scopes. You're point is well taken. I see after having read another thread in this forum that Eagle Optics now offers the 10x50's in the same line for about $15 more than the 7x. Although it weighs almost 50 oz. and may not be really hand-holdable, maybe it's something to consider? I already have Japanese Celestron Ultima 8x40's, and I find I use these much more than my Obie 20x80 DII's because of the weight factor, even though I have the latter mounted on a P-mount. So thanks again, fellas, you've given me plenty to think about. And Bill, I for one don't think you're a curmudgeon. :grin:

darkside

#10 Rich N

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Posted 04 August 2005 - 08:54 PM

Would the Fuji FMT-SX Polaris 7x50's be suitable for astronomical viewing? They really look like they reek of quality build and hand-holdability while at the same time being more economical, than say, the Nikon SE's. :question:

darkside


It's a very nice binocular.

However, here are my nit picks... they are a little heavy. The individual focus has its good points but I like to play with the focus a lot so I prefer a center focus binocular.

Maybe it is because I wear glasses when I look through a binocular but I find 7x just isn't quite enough magnification to make the view look the way I want. This is why I'm so happy there are so many different binoculars available. There is almost always one that will make you happy.

Rich

#11 Guest_**DONOTDELETE**_*

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Posted 04 August 2005 - 09:37 PM

Thanks, Rich. I've got plenty of time for information overload. Tax return time is a long way off! Unless I come into an inheritance, and I'm a little long in the tooth for that... . :smirk:

darkside

#12 brocknroller

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Posted 04 August 2005 - 10:35 PM

I saw those 7x50 Fujis on A-mart for $325 and was very tempted, but I talked myself out of it by using much of the same reasoning given on this thread. These posts confirm what I already knew, but it's nice to "hear" it from others, because the propaganda surrounding the 7x50 for astronomy in general, and the Fuji 7x50s in particular, is quite pervasive. Who hasn't been recommended a 7x50 when he/she first expressed interest in using binoculars to observe the night sky?

My skies are bright enough that I seriously doubt if my exit pupil gets larger than 4mm. The more moisture in the air, the brighter the skies, so summer skies are particularly bright on top of taking longer to get dark(er).

Although the exit pupil issue was discussed, we didn't crunch the numbers, but if I'm doing the math right, a 4mm exit pupil with a 7x50 binocular would only allow me to see 28mm of aperture, correct? (7x4=28). Granted I could bounce around more with 3mm room to move, as Bill mentioned, but I'd also have to hold a 48 oz. binocular to see 28mm of aperture while my 22 oz. 8X32 SE allows me an additional 1X and gives better contrast, the same TFOV, and views at least as sharp if not sharper. The SE has a wider AFOV (60* vs. 52.5*) for a more "open" view.

As far as the price difference, the 8X32 SE on A-Mart sold for just a bit more than the 7X50 FMT-SX, and unlike the Fuji, it has rubber armoring for better gripping and center focus, which makes them easier to use for birding, wildlife observation, and general use during the day. They aren't WP/FP but are "weather resistant", which for most environments is probably sufficient, at least for stargazing.

OTOH, if I were young w/ strong arms and lived in a rural area w/ dark skies and wasn't interested in birding or wildlife observation, those 7X50 Fujis would be on their way to me now.

#13 DJB

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Posted 05 August 2005 - 02:21 AM

Hello again, all,

I really have to agree with all that has been said concerning the FUJI 7x50 FMT-SX. I have owned mine for about 10-12 years. I'm a bit older now, but THIS 7x50 satisfies me most for astronomy. I think Mr. Bill hit the nail on the head.

Yes, they are heavy, but, then again, they are "built like a tank," as they say. I find them much easier to handhold than all of the lighter binos that I have. Perhaps the solid weight effect is helping me out here. I had an industrial accident and injured my back, so it is extremely difficult for me to steady anything when looking skyward, except for the FUJI.

Also, I've never seen finer coatings nor a flatter FOV than on my FUJI's. Haven't seen everything yet, tho.

Regards,

Dave.

#14 Guest_**DONOTDELETE**_*

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Posted 05 August 2005 - 10:40 AM

Good points about the SE, Brock. But if I were to consider the SE's I'd be tempted to buy, ( the 10 and 12x models), I'd have to bite my tongue because they're out of my reach. I already have the Ultima 8x40's. Maybe the Fuji 10x50's are looking a little better now, although they are quite heavy. It's nice to dream... . Like I said: plenty of time for paralysis by analysis.

darkside

#15 KennyJ

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Posted 08 August 2005 - 06:47 AM

< If the exit pupil of the bino is matched exactly with the entrance pupil of the eye, the image may frequently "cut out" due to positional problems. Larger exit pupils give the observer some wiggle room. >

Bill Cook is absolutely BANG ON THE BUTTON with this statement.

To my mind , it represents probably THE most underestimated advantage a larger exit pupil has over one which too closely matches pupil dilation.

This is considerably more important with binoculars , where two eyes are utilised , than with a telescope.


Even when binoculars are mounted , it doesn't stop a head moving ,a heart beating or a body trembling slightly , perhaps due to the cold.

Much of the best viewing , both terrestrial and celestial , is found in COLD conditions , here in the UK.

I think these unwanted bodily movements CAN be minimised , but at the price of UNNATURAL TENSION , which over longer ,more persistent viewing periods , can cause headaches and in some cases muscle spasm ,particularly if the viewing position is not ideal.

Furthermore , I think the emphasis on MINIMAL exit -pupil has OVERATED optical advantages in all kinds of seeing conditions , both by day and night.

Regards , Kenny

#16 gparkerson

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Posted 08 August 2005 - 08:51 AM

I too have failed to consider Bill's point, which sounds obvious once stated, but not so obvious that I thought of it! Of the binos I've tried for astro use, 10X50, 11X70 and 20X80, I use the 10X50s most as their weight permits comfortable hand held viewing and magnification appears to be my limit for hand held as well. I've assumed that I was wasting aperture with the 11X70s because my old pupils can now only manage 5mm or so. But, I hadn't considered the rigors of keeping my 5mm pupils exactly aligned with the 5mm exit pupil of the 10X50s. Sounds impossible now that you mention it.

Now if only I could find some 10X70s that weigh 2 lb. or less. Does anyone produce that animal?

#17 KennyJ

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Posted 08 August 2005 - 11:06 AM

< Now if only I could find some 10X70s that weigh 2 lb. or less. Does anyone produce that animal? >

No Gary -- or at least none which I'm aware of.

How I wish they DID !

For quite a while now ,I've been considering trying to swap the eyepieces in my Helios 15 x 70 for a pair with longer focal length , to provide between 9x and 12x magnification , for brighter image , greater depth of field , shorter close -focus , longer eye -relief , wider TRUE field of view , larger exit -pupil , less shake - factor and more comfortable viewing.

ALL factors which I much prefer about LOWER magnification.

Last time I tried to swap eps on a car boot " bargain " I ended up bu----ing up the right diopter adjustment.

In addition to that , " D.I.Y conditional alignment , let alone true collimation , seems not to be quite so simple with those Japanese 15 x 70s as with the Chinese ones Edz and others play around with.

The " little adjustable screws " are not in the same place to start with :-)

Regards , Kenny

#18 Mark9473

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Posted 08 August 2005 - 02:02 PM

< If the exit pupil of the bino is matched exactly with the entrance pupil of the eye, the image may frequently "cut out" due to positional problems. Larger exit pupils give the observer some wiggle room. >

To my mind , it represents probably THE most underestimated advantage a larger exit pupil has over one which too closely matches pupil dilation.

I happened to be thinking about this today at work.
From purely geometrical reasons, I would expect to get the same 'wiggle tolerance' with binoculars having an exit pupil SMALLER than the eye's pupil.

Would you agree or am I overlooking something?

#19 KennyJ

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Posted 08 August 2005 - 02:10 PM

Hello again Mark ,

I'm sure you are correct.

The smaller the exit - pupil from the binocular , the MORE this applies.

I wonder sometimes if I might happen to have freakishly OPEN entrance pupils in daylight.

This problem of " wiggling " is ever present when using the Swarovski 8 x 20 , regardless of time of day / natural brightness -- and MIGHT even be one of several niggling little annoyances I find when trying image stabilised binoculars with 3mm exit - pupils , and the reason why I can always tell the difference between a 4mm and 6mm exit -pupil in bright daylight :-)

Regards , Kenny

#20 Mark9473

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Posted 08 August 2005 - 02:19 PM

Hi Kenny,

I wonder sometimes if I might happen to have freakishly OPEN entrance pupils in daylight.

I'm sure the next police officer who pulls you over for a routine check will be happy to inform you about this, as he will next be enquiring about your possible use of certain substances.

This problem of " wiggling " is ever present when using the Swarovski 8 x 20 , regardless of time of day / natural brightness -- and MIGHT even be one of several niggling little annoyances I find when trying image stabilised binoculars with 3mm exit - pupils , and the reason why I can always tell the difference between a 4mm and 6mm exit -pupil in bright daylight :-)

Kenny, if it is true that there is a certain wiggle tolerance both for binocular exit pupils that are either oversized or undersized for the eye entrance pupil, then you would have to be experiencing these problems especially with binoculars having an exit pupil matching your eyes.

#21 KennyJ

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Posted 08 August 2005 - 02:56 PM

< Kenny, if it is true that there is a certain wiggle tolerance both for binocular exit pupils that are either oversized or undersized for the eye >

Mark ,

I NEVER said it happens when the exit - pupil from a bino is OVERSIZED.

Only when UNDERSIZED or the same size.

Kenny

#22 KennyJ

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Posted 08 August 2005 - 02:59 PM

< Would the Fuji FMT-SX Polaris 7x50's be suitable for astronomical viewing? >

Darkside ,

The answer to your original question is : -- YES .

Kenny

#23 Mark9473

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Posted 08 August 2005 - 04:15 PM

I NEVER said it happens when the exit - pupil from a bino is OVERSIZED.

Only when UNDERSIZED or the same size.

You're losing me here, Kenny.
You agreed with Bill Cook about the oversized exit pupils, and with me about the undersized. So what is it?

#24 KennyJ

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Posted 08 August 2005 - 06:18 PM

Mark,

I'm afraid YOU are losing ME here too ! :-)

Let's get this straight , for once and all.

WHAT I AM saying , always HAVE said , and probably always WILL say , is THIS :

If in doubt , go with a binocular with a LARGER exit -pupil.

IF -- for some reason -- you either misunderstand what I am trying to preach , or have evidence that I have ever indicated to the contrary , I would appreciate a nod in the right direction.

Regards ,

Kenny

#25 Guest_**DONOTDELETE**_*

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Posted 08 August 2005 - 07:55 PM

< Would the Fuji FMT-SX Polaris 7x50's be suitable for astronomical viewing? >

Darkside ,

The answer to your original question is : -- YES .

Kenny


Thanks, Kenny. I appreciate the input.

darkside


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