----------------------------------- nobody 20 Dec 2014 21:58 ----------------------------------- Alea 3 grade trebuie ca sunt ori grade Fahrenheit, ori grade de libertate. Altfel nu are nici un fel de noima, oricum, la fel cu ceea ce afiseaza producatorul: Apparent Field of View 3° :shock: There are considerable differences in advertised eye relief, fov & coatings with reality. Field of View -- TFOV ­ AFOV Celestron 25x100 Skymaster is specified as 3.0°. It measures 2.45°. Afov = 61°. Inter­Pupilary Distance & Eye Relief Celestron 25x100 eye relief is measured at 15mm, but there is a 6mm recess to the lens, so effective usable eye relief is only 9mm. That's very short. When used with my glasses on, I have to look around a little to see the very edges of the field. This deeply recessed eye lens is very similar to that found on the Fujinon 16x70, one that also requires I look around to see the entire field of view inside. With these two binoculars, looking straight into the eyepiece while wearing glasses cuts off about 10% of the field of view. That could be considered substantial for an eyeglass wearer. Considering the Tfov is only 2.45°, the net field of view due to short eye relief is only about 2.2°. Tilting the head slightly allows seeing out to either edge of the field. Baffles and Blackening I did not see any baffles in any of these other binoculars. Optical and Mechanical Deficiencies The Celestron 25x100 showed some slight ghost images on bright objects. This would indicate there are some internal reflections. This is consistent with surfaces that are not FMC. Collimation The Celestron 25x100 was out of collimation by 1 arc minute. That doesn't seem like much but at 25x, some may find it annoying. Most of the time I don't see it, but I had a difficult time focusing on Jupiter and I thought this might be part of the problem. I made no attempt to realign this binocular. The Celestron does not have readily accessible adjustment screws. They are very likely right under the coating, but that means cutting or poking thru it to get at the screws. I decided not to. Antireflection Coatings The Celestron Skymaster 25x100 has objective coatings that appear purple/green with little reflection off the objective lens. However, the objective prism face and the eye lens in the Celestron 25x100 shows a light blue reflection. The eye lens and prism coatings on the Celestron 25x100 appear like they might be single coated MgF. Sharpness Across the Field of View In the Celestron 25x100 sharpness of image is fair at 70% out from center, but then it drops off very quickly beyond 70%. By 80% out it gets rather poor. The Celestron has a problem with one barrel of the binocular that won't allow it to reach pinpoint focus as well as the other side. The Celestron 25x100, when observing a 14" double, was very clear at 50%, still good at 60% but poor at 70%, all the way around. Doubles of 21'' and 22'' could still be seen at 70­75% out from center. A 29'' double was the limit at 80%. Magnitude Loss in Outer Field of View Both the Celestron and the Oberwerk 100mm binoculars lost about a half magnitude in the fov area beyond 50% out from center. Chromatic Aberration In the Celestron 25x100, Saturn produced no CA at all. No CA was seen in Venus on­ axis, but blue and sometimes a purple or green was seen off­axis. Very little CA is seen on Jupiter out to about 50­60% from center. Beyond that, Jupiter produces blue CA on the inside edge and yellow/green on the outer edge. CA on the moon was green towards the outer edge. Mai sunt si testele deepsky ... dar ma opresc aici: SUMMARY A doublet binocular in a lower quality constructed housing. Gets high marks for IPD range, illumination and (current) price. Fair marks for collimation, diopter, fov and limited CA. Lower marks for pinpoint focus (lens aberration), eye relief, coatings, resolution on­axis, outer field sharpness, contrast, mounting post and nylon case. Currently the least expensive of these binoculars. P.S. Senzatia de "fereastra circular ovala" poate fi de la "Misalignment of the Field of View". Vezi la pagina 15.