After a series of gloomy overclouded days, with the sky like lead at 6pm, Clear Outside was offering this unlikely prediction for Saturday night:

Clear Outside (courtesy of First Light Optics)

Clear Outside (courtesy of First Light Optics)

Spot on.

It was never going to be a great observing evening, with a nearly full moon cluttering up the sky.  So I did a binocular test.  The 10x50s which I’ve been using for years (evident) have always been a bit of an issue, and I gave myself a small reward for being still standing, and bought two new pairs:  7×50 modest price, and 8×40 very cheap (with the thought in mind that I might return the cheap ones if they were rubbish).


Although the objective lenses are the same size in the 10×50 and 7×50 and so should have the same light-gathering capability, I did think that the old binoculars had a slightly brighter image.  But the reason I bought 7x50s is that the field of view is wider.  We all know that I am an idiot observer, and if I can only see three stars, I haven’t got a clue what I am looking at, stars having rather a tendency to look exactly the same.  But with five in the view, it is much easier to work out where you are, and to star hop on to the next part of the constellation.

The 8x40s were pretty much rubbish by daylight; the image looked dim and woolly at the edges by comparison with either of the larger pairs – a quality issue as much as light gathering.  But I thought I would do them the justice of a night comparison.  Somewhat to my surprise, they grew on me; of course the image was not so bright and some faint stars were lost, and they got fuzzy at the edges.  But 40mm is still much better at collecting light than the 7mm of even the best-adapted night vision.  The field of view was even wider than for the 7x50s; and the bins are much lighter – I could hold them one-handed, and it was longer before arm fatigue made the cosmos shake and dither.

So maybe I’ll keep both.  Retail therapy.


3 responses »

  1. I bought a retro-ish telescope from a market. It’s only 10x but we love sitting on a park bench looking through it. We manage not to go ‘ooh -arh!’ whenever we spot something. It’s usually not what we thought it was anyway!

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