Astronomy with a Pocket Binocular.

Creating a new genre of amateur astronomy literature.

A work commenced November 11, Anno Domini 2019.

I’m a big fan of pocket binoculars; they’re tiny, elegant, and when decently made, are  very sharp shooters. Compared with standard-sized binoculars, ‘pockets’ are much less expensive and there is a good one available to suit most anyone’s budget. They can work well with kids, grand-parents and every one in between. Their extreme portability makes them very popular across a broad ecclesia of people; hikers, birders, sports spectators, hunters, theatre goers and general nature lovers. They’re as likely to be found near a window overlooking a garden as they are tucked away in a backpacker’s pouch. But what is less commonly known is that they can be used for casual astronomical viewing. Unlike telescopes, there is no set up required. Simply pick it up and off out you go! They’re so small that they are completely immune to the vagaries of the Earth’s atmosphere. It doesn’t matter if the seeing is horrid or immaculate, their small apertures and low magnification will show you the same view, under the same conditions, time and time again. Their very low carrying weight allow individuals to hold them to their eyes much longer than standard binoculars in the 40 to 50mm aperture class. And as soon as you’re done, they fold away in a pocket, hence the name.

Pocket binoculars are almost invariably not recommended for astronomy. Sure, they don’t provide those knock-out views you get with larger binos, but what if your only instrument were a pocket binocular? Is viewing the night sky anathema? Absolutely not! Even small glasses like these can bring a great deal of cosmic real estate to your eyeballs. And though their ability to gather faint starlight is limited, they will nonetheless greatly exceed the acuity of even the keenest, sharpest human eye.

I suspect that one of the main reasons why pocket binoculars are not spoken of much in astronomical circles is that most people live in big cities or towns, where light pollution drowns out much, if not all, the glory of the starry heaven. They are disconnected from the great natural light show provided by Amighty God, who reveals His majesty in every shooting star, every burning sun, every moon, planet, and galaxy scattered across the Universe. But if you take leave of the cities and drive out into the countryside, the night sky is transformed from a washed-out, featureless dome into a marvellous light show that can fill us with awe and re-unite us with the sacred, the mysterious and the infinite-eternal.

I have the immense good fortune to live in a beautiful place, far enough away from the large cities and towns that are home to the vast majority of people. I can step out of my back door and immediately engage with the sky. I take nothing for granted. For me, astronomy is not always connected with darkness. In Scotland, we enjoy many fabulous sunsets, painting radiant colours; brilliant oranges, sanguine reds, and even purple splashes across the heavens as the Sun makes its way toward the horizon. As dusk gives way to darkness, the night sky has a way of wrapping itself around you like a magic cloak. At first, only the brightest stars can be seen, but as full darkness falls upon the landscape, the great host of heaven come out to play. Being located on the western edge of northern Europe, beautiful auroral displays are common, colouring in the northern horizon in magnificent ribbons of incandescent light. Out here in the sticks, the great river of stars that constitute the Milky Way can be easily seen on a dark, Moonless night.

During  deepest winter, darkness rules. The Sun sets early(4pm) and rises late(8am). Many go to work in darkness and travel home in darkness. Yet in summer, the Sun rules the sky from 3.30am to after 9pm, and even then its shallow dip below the northeastern horizon never brings true darkness. In June and July, twilight rules the wee small hours. Still, whether it’s high summer or deepest winter, my pocket binoculars never fail to show me something new and exciting.

A mid-Summer’s night stroll; looking northeast at 2 minutes after midnight on June 22, 2019.

My quest to find a good pocket binocular encountered many unexpected twists and turns. I don’t live anywhere near a good binocular dealer, so I was not afforded the luxury of ‘trying before you buy,’ as it were. No, in my case, the best I could do was ‘buy-in and try.’ Some models promised the earth but fell well short of the mark. In other cases, I trusted the opinions of a number of so-called ‘experienced glassers’, but upon learning how to test such instruments myself, I discovered that many of these reviews were just not discriminating enough. It was like deja vu all over again from my telescope testing days( I have no interest in acquiring any new telescopes, as I already have all I could possibly wish for). Some models advertised as ‘premium’ turned out to be junk.

Premium junk.

In the end though, I settled on a couple of models – both 8 x 25  formats – made by reputable firms; Zeiss and Opticron. Unlike a swathe of pretenders, these were the real McCoys. Both models are very well made, with fully-multicoated optical components and phase corrected Schmidt-Pechan roof prisms. The Opticron has a wonderfully flat field of view, thanks to the incorporation of aspherical ocular lenses, but the size of the field is rather restricted as modern pocket binoculars go; just 5.2 angular degrees. In contrast, the Zeiss Terra has a significantly wider field – 6.8 degrees – but is not quite as sharp at the edges of the field as the Opticron. During daylight testing, I ascertained that the Zeiss Terra produced a slightly brighter image, due in most part to the employment of higher reflectivity dielectric coatings on the prisms. The Opticron, in contrast, has silver coated prisms, with slightly lower reflectivity.

My instruments of choice; the Zeiss Terra(left) and the Opticron Aspheric LE(right).

Both models display excellent control of stray light and do not produce annoying internal reflections and glare when pointed at bright objects like the full Moon, or during the day, when glassing strongly backlit scenes. This affords the highest levels of contrast in the images they produce. For astronomical use, where all the objects are effectively located at infinity, it is important for the field to remain as flat as possible from the centre right the way to the edge for aesthetic appeal. While many of the pretenders I tested were good on axis, their edge of field definition was less than desirable. And no one wants to see stars bloat to enormous sizes as they are moved off axis.

Both models have hermetically sealed optics, filled with dry nitrogen gas at a slighly higher pressure than the surrounding atmosphere. This prevents fogging of the optics in cold weather and slows down internal corrosion of the components. The slight pressure differential also creates a small outward force that helps keep dust and fungi  from entering the instruments. Ergonomically, the Zeiss is easier to use, as its slightly larger frame fits my hands that little bit better than the Opticron. Both focusers are buttery smooth with zero backlash when rotated clockwise or anti-clockwise, but this has proven more important during daylight observing than at night, where relatively little focusing adjustments are required, as for example, in moving from a target at low to high elevations above the horizon. The Opticron is the more elegant instrument; the Zeiss more rugged.

Mechanically, both the Zeiss and Opticron are very well endowed. The double-hinge design on both models has enough tension to maintain my particular inter-pupillary distance, and fold up with ease when not in use. The eye lenses are good and large on both instruments, allowing me to comfortably and swiftly engage with the entire field, with little or no guesswork or blackouts. The eyecups on both instruments are robust, comfortable and simple to deploy. Unlike other models which offer several positions, both the Zeiss and the Opticron only have two- either fully down or fully up. And both have the same eye relief; 16mm.

The Zeiss Terra Pocket(right) is a little wider and taller than the more conventional Opticron Aspheric(left), but both fold away when not in use.

The larger field of view of the Zeiss(6.8 degrees) is more useful for daytime applications, but at night, when observing the sky, even a 5.2 degree field is more than sufficient to frame the vast majority of targets I’m likely to study. I estimate that the limiting magnitude of both instruments to lie somewhere between +8.7 and +8.9. And with the same exit pupil – 3.1mm – they allow me to image targets with the sharpest part of my eye lenses.

A Walk through the Autumn Sky:

A favourite autumn  haunt.

November is perhaps my favourite month. It’s easy enough to justify. I entered the world in November, and have come to associate my experiences of it with the carefree days of my youth. While the trees begin their long winter slumber, I feel especially alive. All my senses go into overdrive. Maybe it’s the vibrant colours of autumn leaves that assault the eyes, or the sweet, musky aroma of decaying plant matter that infuses the misty air. Or could it be the crunching sound made by my feet as they wade through the rain-soaked leaf litter that creates a memory trace back to the innocence of childhood? Whatever it is, walking though the rural autumn landscape upwells deep feelings of reverence for the preternatural beauty of the wet and the wild.

The feeble light of November compels me to re-schedule the times of my walks, and usually I try to make the most of the daylight by venturing out around noon, when the Sun is at its highest in the sky. And though November nights can be mild, bitterly cold, and everything in between, the celestial treasures that attend a clear night with no Moon greatly warm the heart.

To help us find them, it pays to invest in a good literary guide and, in this capacity, I would heartily recommend  Ian Ridpath’s and Wil Tirion’s, Collins Stars & Planets, now in its fifth edition. In it the student of the starry heaven can find all kinds of useful information, packed full as it is with month-by-month maps of the entire night sky, as well as beautifully illustrated colour maps of all 88 constellations that grace the celestial sphere.

Good companions under the stars.

So without further ado, let’s begin our adventures with a pocket binocular. A great place to start is to seek out two amazing sights in the northern heavens; the glimmering Pleiads and imposing Hyads, both located near each other, and both well situated for observation, riding high in the sky after 9pm on mid-November evenings.

The constellation of Taurus.

Before we embark on our first celestial adventure, let’s get in the mood by reading the  celestial swangsong of Lord Byron(1788-1824):

‘Tis midnight! on the mountains brown

The cold round moon shines deeply down;

Blue roll the waters, blue the sky

Spreads like an ocean hung on high

Bespangled with those isles of light,

So wildly, spiritually bright.

Whoever gazed upon them shining,

And turn’d to earth without repining,

Nor wish for wings to flee away,

And mix with their eternal ray?

From Night at Sea by Lord Byron.

 

 

To be continued…………………………………..

 

De Fideli.

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