Problem with Sunagor Super Zoom binoculars
Some time ago I asked you for some advice on buying a Tasco telescope for which I found valuable indeed however it has developed a fault and I am now going to buy a powerful set of binoculars. The spec for these are Sunagor 18-100x30mm super zoom advertised as the world’s most powerful compact zoom binoculars.

I would really appreciate any advice you can offer.

                     regards    John H

How about “don’t touch with a bargepole” for advice?

I can think of nothing worse for astronomy, or indeed any purpose, than 18-100 x 30. This means that the binoculars have a magnification range from 18 to 100 and lenses 30 mm across. This might sound rather a useful range for astronomy, but there is a lot more to it than that. The trouble is that 30 mm lenses are very small for such a magnification.

Actually, I am amazed that anyone would sell binoculars with such a useless specification. I couldn’t believe you had it right, so I checked on the web and found them. 30 mm binoculars are OK up to a power of about 8, and indeed 8 x 30s are fairly common. They have the advantage of being lightweight, though they don't give very bright images. But take such an image and double the power to over twice as much and you have a really dim image which is very hard to hold steady, and in addition will give such a small field of view that it will be hard to find any object, particularly at night.

Increase that power even more and the results will be very hard to see, even if the optics are perfect. Given that this is unlikely – Sunagor are not exactly Leitz or Zeiss – and with the extra glass needed to provide a zoom facility, the combination is unthinkable.

If you want light binoculars, get 8 x 30s. If you want a brighter image, more suitable for astronomy, get 8 x 40 or if you don't mind heavier bioculars try 7 x 50 or 10 x 50. Go into a shop that has them all and insist on looking through them at a distant object (not in the shop), ideally with a high contrast such as a TV aerial against a bright sky (well away from the Sun!). Look for false colour and distortion around the edges of the aerial, when it is not just in the centre but near the edges as well. You should not have to refocus as it gets towards the edges of the field of view.

Start with good quality binoculars such as Pentax, Nikon, Olympus, Canon or Minolta. Then you will know what a reasonably good image looks like, and then try lower down the range and see the difference. Don’t even bother with zoom binoculars. You should be able to get a good instrument for considerably less than £100.

Binoculars are ideally suited to low-power use, and it is a waste of time trying to get high magnifications out of them. You might as well get a decent telescope.

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