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Mark9473
Postmaster


Reged: 07/21/05
Posts: 6459
Loc: 51N 4E
Review of my Swift Satellite 20x80 new
      #674933 - 11/06/05 05:26 PM Attachment (395 downloads)

About 15 years ago, I took a long good look at a mag 6.5 sky through a pair of 80mm binoculars and was immediately convinced I needed to own one of these. Then 8 years ago I had an opportunity to buy a pair of Swift Satellite 20x80s for less than half of the regular price in local retail for similar models, and didn't have to think twice. It did not take long for these to become my favourite instrument for astronomical observation - I own four other (smaller) binoculars as well as 60 and 90 mm refractors.

The Swift Satellite 20x80 has the following specifications:
- fully coated optics
- true field of view 3.5 degrees
- center focus
- IPD labelled between 60 and 70 mm, measured at 58.5 to 74.5 mm
- weight 2.27 kg (5 lbs)
- eye relief 14 mm (not verified)
- close focus distance 18 m (60 ft) (not verified)

They came with a solid heavy-duty metal L-bracket for mounting on a tripod, perfectly fitting eyepiece and objective caps, a nice hard case for storage, and a quality card-board box that's been diverted to other good uses.

These are no longer featuring on the Swift website, so I suppose they're discontinued. A lot of Google links are turning up empty.

I've seen them advertised with BAK-4 prisms, but mine are not. The exit pupil when viewed at a distance shows the tell-tale square shading - though I can only see two of the four sides - could be an eye placement artifact. Viewed from the objective end, the exit pupil appears round, so the prisms are not undersized as far as I can tell.

I use these 20x80's on an admittedly light camera tripod, so they regularly bump into my brow (mainly because of the tripod's rubber feet and me using it on two legs) and then need refocussing. I'm a focus fiddler anyway. Probably an IF model would cure me of that, but for any binoculars potentially used for daylight viewing (you should see the view in these of the coast of England when standing on the coast of France) or by family members, I still prefer a CF model. Anyway, what I like about these as far as focussing goes, is that I'm not tempted into fiddling with the right eyepiece dioptre setting to improve focus, unlike with some other binoculars.

They are labelled as 'fully coated' which I do not expect to mean fully multi-coated. Either way, coatings and baffling are sufficiently effective to reduce glare and ghost images on bright objects like the Moon to a minimum. I noticed this immediately after I bought them, compared to my previous 12x50s and 10x50s they are a big improvement. Yes I'm losing some light by not having a superior multicoating (and BAK-4 prisms), but actually the variations in sky transparency and observer preception are much larger, and we don't spend our time complaining about these either.

Chromatic aberration has never bothered me in these 20x80s. The Moon has a thin coloured edge, and that's it. On other bright objects like planets and the brightest stars, other aberrations seem to degrade the image more than CA does. There is some radial spiking on the brightest stars, preventing pin-point refractor-like sharp focus. It took me a night of super-steady seeing and Sirius as a target to conclusively pin this down as radial spiking. On stars fainter than say mag 5 or 6 I can't notice anything and these are as sharp as I could expect.

What radial spiking seems to do, is increase the sensitivity of the image to seeing. On nights with very steady seeing the spiking seems less, and on such occasions I've seen the fourth star in the Trapezium, or the rings of Saturn. So I would conclude that center sharpness is at least of an acceptable level. I have little interest in double star observing with binoculars, so I can't really report on performance there.

The field of view I've measured at over 3 degrees 25 arcminutes, so they're as close to spec as I can tell. This makes the apparent field of view 70 degrees just like on my 8.5x44 Swift Audubons. The FOV gives the appearance of being sharp to the edge, but of course it is not. The image processor in our brain helps us here: we generally have a sharp field of view of about 50 to 60 degrees, so our brain sort of ignores some degree of unsharpness beyond that. In the Swift Satellite 20x80, the edge unsharpness is such that the brain (mine at least) can largely ignore it - this in contrast with the 8,5x44 where the edge fuzziness is more distinct and really annoying me. But when I really look directly at a bright star close to the edge of the FOV in my 20x80s, it gives a pretty convincing impression of a seagull.

To quantify edge sharpness, I've looked at the image of the Full Moon, as I've reported earlier on this forum. I found the Moon to appear in focus anywhere up to slightly less than one lunar diameter from the edge, and to appear out of focus when placed at the very edge (not that adjusting focus helped anything). From this I judged the sharp area to be 75-80% of the FOV. This does not mean that the Moon is still not a bit sharper in the center than it is at say 60% out.

What I noticed in the Full Moon test, and have since confirmed on double stars, is that the bottom edge is sharper than the other three. To me this is a bonus as my view is slightly lower than center whenever I'm looking high in the sky. One of the double stars I recently investigated, was the one at the heart of open cluster NGC 1502; both stars are mag 6.9 and they are separated by 17.8 arcseconds. In 20-power binoculars, this double star therefore allows a measurement of where in the field of view the apparent resolution drops below 356 arcseconds - this is about twice of what a good night-time visual acuity provides.

Looking at this particular double star just a few evenings ago, and taking note of where the double was in relation to the field edge when it became too fuzzy to be separated, I determined that the 356 arcseconds of apparent resolution was reached at about 35 arcminutes from the top, left and right edges, and about 20 arcminutes from the bottom edge.

There is however also something about a pair of 20x80s with 3.5 degree field of view that cannot be captured easily in specs and measurements. They open a whole new sky beyond what is visible in 10x50 class instruments, both in depth and in resolution. At the same time the field is still sufficiently wide, and the binoculars sufficiently light, to allow for a pleasant spontaneous use with moderate demands on mounting. A next step up in performance would be something like a 25x100, and these would be substantially heavier and more difficult (expensive) to mount, while also the FOV of about 2.5 degrees or less means more difficulty in locating targets and, for many objects - not the least of which the Pleiades - a loss of detachment from the background.

These 20x80s routinely reach fainter than mag 11 on any decent night, and coupled with the resolution of a 20-power glass this means that many open clusters become partly resolved that are just hazy patches in 10x50s if they are seen at all. For me, the natural targets of any instrument are those that (start to) reveal their true nature, and in 20x80s in my skies that means open clusters.

Despite some shortcomings on specifications and performance, I like these Swift 20x80s immensely. They are a pure joy to use. Every object is seen at a scale, depth and resolution way beyond my other binoculars. I would not hesitate to recommend a pair of 20x80s to any amateur astronomer with a basic level of experience..

Attachment

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Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet


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KennyJ
The British Flash


Reged: 04/27/03
Posts: 20139
Loc: Lancashire UK
Re: Review of my Swift Satellite 20x80 new [Re: Mark9473]
      #674943 - 11/06/05 05:35 PM

Mark ,

Congratulations on your first official " Bino Review " to this forum .

I'd been looking forward to this for quite a while and was not disappointed !

Kenny

--------------------


Milton Wilcox R.I.P






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Mark9473
Postmaster


Reged: 07/21/05
Posts: 6459
Loc: 51N 4E
Re: Review of my Swift Satellite 20x80 new [Re: KennyJ]
      #674946 - 11/06/05 05:38 PM

thanks Kenny.

--------------------
Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet


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jekincaid
member


Reged: 02/21/05
Posts: 13
Loc: IL, USA
Re: Review of my Swift Satellite 20x80 new [Re: Mark9473]
      #674981 - 11/06/05 06:09 PM

Great review Mark, your comments about the 20x80 characteristics and specifications (BK7 prisms, fully coated) apply to the 15x60 Vanguards as well. Solid performers (at least for me) out of the box. I went through several pairs of 15x70 Barskas, various 50mm Nikon AEs, and Pentax DCPs prior to purchasing the 15x60s at a closeout price. I've not looked back or wished to upgrade. Mine were in perfect collimation too, which cannot be said for several examples of the other brands. Also, decent color correction, contrast, with minimal ghosting or CA. I team them up with Zeiss 10x40 ClassiC's when not in the mood to drag the scopes out. Clear Skies!

--------------------
John
Parks 6" F/6 and 10" F/5
Celestron C-5



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Anonymous
Unregistered




Re: Review of my Swift Satellite 20x80 new [Re: jekincaid]
      #675736 - 11/07/05 09:17 AM

Good review Mark. This should make a nice addition to our growing review library.

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johnno
scholastic sledgehammer


Reged: 05/03/04
Posts: 807
Re: Review of my Swift Satellite 20x80 [Re: KennyJ]
      #675785 - 11/07/05 09:55 AM

Hi All,

Mark,

I totally agree with Kenny's comments.
A very well written,AND very Informative review.

Well Done.
Regards.John


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Littlegreenman
Carpal Tunnel


Reged: 05/09/05
Posts: 2730
Loc: Southern California
Re: Review of my Swift Satellite 20x80 new [Re: Mark9473]
      #677205 - 11/08/05 02:07 AM

Thank you. I see various older Swift Models for sale used in the usual places. I vaguely remember reading that they can be decent. Seeing how these are 8 years old, I'm guessing these were made in Japan. Do you have any info on where they were made?

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Mark9473
Postmaster


Reged: 07/21/05
Posts: 6459
Loc: 51N 4E
Re: Review of my Swift Satellite 20x80 new [Re: Littlegreenman]
      #677220 - 11/08/05 02:54 AM

yes they are made in Japan.

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Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet


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Simon S
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Reged: 01/07/07
Posts: 2206
Loc: Crawley West Sussex UK
Re: Review of my Swift Satellite 20x80 new [Re: Mark9473]
      #1481886 - 03/14/07 05:55 PM

Just bought a pair myself secondhand. They needed collimating, but after that the view was great. They do suffer from CA to a degree but not as bad as some i have seen. I would love to know if mine have BAK4 prisms or the basic BK3's. I don't think I have ever looked through a duff pair of swifts to date.....

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All binocular repairs are undertaken at your own risk. I cannot be held responsible for any damage to any instrument resulting from my suggestions.
My binocular collection
Binoculars by date of addition
Binoculars in Alphabetical order


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Mark9473
Postmaster


Reged: 07/21/05
Posts: 6459
Loc: 51N 4E
Re: Review of my Swift Satellite 20x80 new [Re: Simon S]
      #1481928 - 03/14/07 06:14 PM

Simon, look at the exit pupils: if they are round and evenly clear you've got BAK4 prisms, if there's dimmer sections as if in a shade, and the brightest part is reduced to a square, like in mine, you've got BK7 prisms.

--------------------
Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet


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pcad
Carpal Tunnel


Reged: 01/17/05
Posts: 2447
Loc: Connecticut
Re: Review of my Swift Satellite 20x80 new [Re: Mark9473]
      #1482049 - 03/14/07 07:01 PM

Hi Mark,

Nice review of the Swift Satellite 20x80. It's refreshing to read a positive report of a binocular with BK7 prisms. Seems that as long as it's well designed and executed BK7 prisms can be acceptable. Thanks for taking the time and effort to share your findings with us.

Peter

--------------------
Peter

Telescopes 25 - 318 mm
Binoculars 12 - 100 mm
Microscope 50x - 1000x


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Mark9473
Postmaster


Reged: 07/21/05
Posts: 6459
Loc: 51N 4E
Re: Review of my Swift Satellite 20x80 new [Re: pcad]
      #1482095 - 03/14/07 07:16 PM

Thank you Peter, I just re-read it now on occasion of Simon having dug it up from the mists of time. That was really not too bad for my first review, wasn't it?

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Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet


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pcad
Carpal Tunnel


Reged: 01/17/05
Posts: 2447
Loc: Connecticut
Re: Review of my Swift Satellite 20x80 new [Re: Mark9473]
      #1482116 - 03/14/07 07:24 PM

Oh, I don't think 11/05 is all that long ago. Besides, if I did read it back then, I didn't remember the details and it wouldn't kill me to read it again. Ya done good, no matter whether it's new or old.

Peter

--------------------
Peter

Telescopes 25 - 318 mm
Binoculars 12 - 100 mm
Microscope 50x - 1000x


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