Eyeco 10x50 Porro Binoculars for Adults with Case, BAK-4 Prism/ Multi-Coated Lens, for Stargazing Bird Watching Hiking Outdoor Sports

I wanted binoculars for star gazing and as a novice with geekish tendencies I spent some time on the internet researching. I thought I would share my findings (I don't claim to be an expert).10x mag, 50mm objective lens binoculars are generally regarded as the biggest you can use without a tripod - bigger objectives create too much weight, and higher magnification creates a jittery image. The 10x50 gives a 5mm exit pupil (50/10) which is a good match for a middle aged person whose iris can only reach 5-6mm in low light. Youngsters whose iris's can open larger (and thus receive more light) might benefit from 10x60 or 12x70 but handling is an issue.For star gazing I wanted a wide field of view to see as much of a constellation as possible. Magnification is less important for star gazing because stars are still pinpoints under high magnification. Higher magnification does let you see some galaxies as smudges rather than pinpoints, some planetary features and moons, as well as better detail of our moon. A telescope, rather than higher power binoculars might be better for this work.There are many Chinese manufacturers of these size glasses ranging from £10 to £50. Above £50 you can start to consider branded (but still Chinese) products. These clone binoculars are often built with the same components, and possibly in the same factory. Some are made into rogue copies of expensive brands.These Eyeco branded pair were the cheapest I could find that claimed BAK-4 prisms. BAK-4 is a Chinese version of a Schott glass standard (and apparently not nearly as good) but are better than the BK-7 fitted to cheaper binoculars. The BAK-4 refracts the light at a different angle and gives a brighter image (particularly important for low light/ wide angle). To verify BAK-4 were fitted I held the binoculars at arms length and the exit pupils were fairly round (I have some Japanese made Tasco's and the exit pupils are square indicating BK7). The Field of View specified gives a prism angle of 8.1 degrees which is stated on the specs of other BAK-4 Chinese binoculars.Both the objective and eyepiece lenses appear to be coated blue. Some internet sources state Red coating is best for daylight use. Other sources state Blue is a single coating system and green is a superior multi-coat system. You want the coating to be on all the lenses ('Full'). There are probably other limitations with the use of cheap optics that hide the subtle differences between the coatings.I wear glasses but much prefer to use these without - the image is more immersive.The first set of binoculars I received had debris in one lens and I returned them. If you buy a cheap pair give them a good shake when you test them to dislodge any rubbish in the optics. The box claimed them to be waterproof which wasn't mentioned in the description - but it could just be a generic box. I was sufficiently impressed with the image quality to order a replacement pair.