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< >CloudyNights Telescope Reviews 上的资深教授Edz对MS7x50的评价（国外称William Optic 7x50ED）</P>
<>I’ve have a William Optics 7x50 ED for testing and I’ve had it out just a little so far. So I can report some early findings. <BR><BR>This is a heavy binocular about 3.5 pounds, but not much different than the two other 7x50s I have in the house, both over 3#. I found it still pretty stable to hand hold. <BR><BR>The IPD range is 57.5 to 72mm. <BR><BR>The coatings are particularly impressive. I had to try very hard to see my reflection at all in the light bouncing off the objective lens. I compared to several other binoculars and this William Optic 7x50 ED shows so very little reflection it is comparable to the Nikon Superior E 12x50 and maybe even slightly better than the Fujinon FMT-SX 16x70. <BR><BR>This is an Individual Focus eyepiece binocular. For my eyeglass corrected eyes the diopter settings are near exact on zero from my evening of viewing stars at infinity. For my resolution readings at a distance of 125’, I found my eyeglass corrected diopter settings show a reading of +1. The diopter range extends from +6 to –6 and eyepiece travel is about 4.5mm in or out from the zero setting. <BR><BR>The aperture measures 50mm with no apparent stops. <BR><BR>There are no apparent edges of exit pupil cut off. They are nice and round. <BR><BR>I measured exit pupil several times and come up with about 7.2mm. That is within 1% of expected and could be measuring error. <BR><BR>Close Focus was measured at 23 feet, not the 4m as published. <BR><BR>Objective covers are captive. Rather than over caps, they are the stick in type. They are a poor fit and repeatedly came open of their own accord. I found them particularly annoying. <BR><BR>Eye guards are rubber fold down and when fully extended are a nice soft rubber that you can push up against your eye sockets. <BR><BR>The binocular L-bracket mounting hole is set back several mm behind a very narrow space in the prism housings. I have 8 different styles of binocular brackets. Only two would work, one was custom made and it is very non-standard and the other is the Orion Small L bracket. None of my deluxe binocular L brakets would work. Either you need a bracket with a 5mm extension nub at the binocular mount screw or you need a bracket that is only 7-8mm wide. None that I know of are that narrow. The narrow style Pentax L bracket is about 20mm wide and would only allow me to get the IPD in as close as 68mm. <BR><BR>Eye relief is very long. Exit pupil focus distance is 18mm behind the eyecups when they are folded down for use with glasses. Depth to the lens is 7.4mm. Pressing my eyeglasses hard up to the folded down eyecups would result in minor blackout. With the eyecups folded down for eyeglass viewing, handheld I needed to place my thumbs against my cheekbones to hold the binocular far enough out to prevent blackouts. That is similar to the Nikon 12x50 SE. This actually should bode well for those with thicker glasses, as I find I usually need only about 14mm with my thin glasses. I could almost see the entire fov while wearing my glasses even with the eyecups fully extended. <BR><BR>Resolution as tested with a USAF line pairs chart shows 13.5 arcseconds in subdued light and 12.1 arcsec in bright light. These results produce apparent resolution of 95 arcsec subdued and 85 arcsec in bright light. These readings are in line with almost every other binocular I’ve tested, as most other binoculars I’ve tested fall between 97 and 90 in bright light. While I have suspected seeing 85 arcsec apparent resolution with several other binoculars, with this binocular, I suspected seeing 76 arcsec apparent. I made no attempt to use supplemental magnification behind the lens. <BR><BR>Handheld, I found I was able to easily read 10mm tall x 2mm thick lettering at 125 feet. That’s less than 1 arcminute resolution or approx 6 arcminutes apparent resolution handheld. <BR><BR>The fov is stated as 7° 30’, or 7.5°. I measured the True field of view as 7.3° to 7.4°, very close to stated. That gives an eyepiece with an Afov of 52°. There was no feeling of a narrow Afov with these binoculars. In fact I was surprised at the nice wide field of view. The impression one gets handheld is a field of view sharp completely across the view. <BR><BR>Accurate measuring of sharpness of image across the field of view showed some problems. The sharpness is not balanced. 16 Cygni, a 6.0-6.1/39” double star could be seen clearly separated out to 90% of the field on the right side. However on the left side of the view, it became distorted beyond perception at 70% out from center. Both barrels produced the same error. The same error was noticed when observing the USAF resolution bar charts. <BR><BR>The right barrel shows some minor amount of astigmatism. This was seen on-axis as a bright star was defocused inside and outside of focus. The orientation of the out-of-focus image would flip 90° as I passed thru the precise focus point. <BR><BR>The binocular is stated as waterproof / shockproof. I can say that it seems very ruggedly built. I did not attempt a water immersion test. I appreciate waterproof binoculars since I often leave my equipment out overnight. Quite often, I find my equipment completely soaked with morning dew. I never get too concerned about my waterproof equipment, but always need to protect binoculars such as the Nikon SE. <BR><BR>This binocular uses some combination of ED glass. Chromatic Aberration is very well suppressed. I could not produce any false color on any astronomical objects anywhere in the field of view, including mag1 stars, mag –1.7 Mars and the near full moon. Also I could not produce any false color in daylight when viewing the edges of white porch posts in sunlight or when viewing sunlit tree limbs against a bright blue sky background. <BR><BR>Internal baffling is flat gray/black ridges in the barrels. I could not produce any ghosting or internal reflections with the moon off axis or just out of the edge of the field of view. <BR><BR>The binocular is complete wrapped in a 1.2mm thick rubber coated armor. The rubber armor is brown. <BR><BR>Collimation of star points was not seen to be in error by more than a very small amount, well within standards and easily merged. Collimation of the field overlap is off by several arcminutes. It is more noticeable in daylight viewing, where I would say field overlap is off by 10 to 12 inches at 200 feet. That represents about 15 arcminutes, or 3% of the field. There are no externally accessible prism adjustment screws found under the rubber armor. <BR><BR>The IPD hinge is solidly stiff and very smooth. The eyepieces likewise are solidly stiff, but move with a quiet smoothness. Nothing moves unless you intend to move it. <BR><BR>Night-sky observing impressions show a very clear bright view. At 7x, not much detail can be seen, but that impression is from one who spends a lot of time behind 16x70, 20x80, 25x100 and even 30x-40x100 binoculars. So I can’t very well compare this 7x binocular to some of the star counts I’ve done or to the density seen in clusters like the double cluster at 20x or 25x. I did find one particular object of interest last night. The moon was just rising and very low behind some thin clouds, so it didn’t much interfere. I scanned around (mounted) in the vicinity of M31 and had some pleasant views. I dropped down a little lower to search for M33 a much more difficult to see extended galaxy. At first I didn’t see it. Once I got out my charts and located the exact spot, I was then only able to see it with averted vision. As I would wiggle the binocular back and forth just a little, maybe a degree, I could see the diffuse background glow of this very extended face on galaxy. I was then able to confirm what I saw by moving away and coming back to the area. Using the same back and forth scan, I could pretty easily pick out M33 as just ever so slightly brighter against the background sky. I would consider this an indicator of good contrast. <BR><BR>This is a very nice binocular. Some users are content with low power views. It would not be my binocular of choice for astronomy, but it could be for any number of people who cherish those low powers wide swaths of sky. This particular binocular could provide you those views. It seems pretty comfortable to hand hold and produces no false color or internal reflections to speak of. If you have the large eye pupils to take advantage of this 7.2mm exit pupil, you would have a very bright image. This large exit pupil will also make it easy for you to hold onto the view in daylight, although your effective aperture would be much smaller. Still, the image seems crisp and daylight color rendition seems pretty natural. <BR><BR>The binocular sells for $299.00 from William Optics. <BR><BR>edz <BR></P> |
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