Why Binoculars, Cameras, & Alternatives Telescopes Aren’t Always The Answer

Why Binoculars, Cameras, & Alternatives Telescopes Aren’t Always The Answer

There is no doubt that telescopes are great for studying the stars.  They are so incredibly powerful that people even use them for studying and photographing distant birds and other wildlife right here on Earth.  There is hardly a telephoto lens available that compares favorably to a decent telescope. 

          If you are terrified of heights, you can be standing safely on the ground in Yosemite Park, watching some crazy person free-climb El Capitan, yet feeling like you're right next to them.  Fair warning: it might still make your hands sweaty!

Let There Be Light

          Seeing is all about light-gathering; without light, there is no vision.  Deep-sea creatures often don't have eyes since there is insufficient light below 200 meters for even plants to grow, and none at all below 1000 meters, hence the name midnight zone.

          So, if a nice pair of binoculars is in your future, make sure you select a pair with relatively large objective lenses.  For clarity, the objective lenses are the ones closest to the object you’re looking at, thus the ones farthest from your eyes.

          Now, why is that important?  Your eye’s light-gathering pupil has an aperture in dim light of about 6 mm (say, about ¼ of an inch), whereas a good pair of binoculars has an aperture of about 50 mm (~2 inches).  Πr2 is the formula for calculating a circle’s surface area, so we can work out that 3.14 × 32 = 28 mm2 (for your eye) but 3.14 × 252 = 1963 mm2 (for the lens) which means that a 50 mm lens gathers 1963/28, or 70 times more light than the human eye.

What Do the Numbers Mean?

          There are quite a collection of numbers from 4×21, 4×30, 7×18, 7×21, 7×35, 7×42, 7×50, 8×25, 8×30, 8×42, 10×25, 10×30, 10×42, 10×50, or generally the biggest, 12×50.  The first number is the magnification (where × means magnification, or more commonly “power”), meaning that what you see will be 4, 7, 8, 10, or 12 times larger than what your eye sees.

The second number tells you the aperture, or light gathering ability, of the instrument.  So, should you get a 12×50 for maximum power and light?  Not necessarily! 

You see, the more magnification you have, the harder it is to hold it still enough to be able to see something.  The slightest jitter will make everything slip and slide around.  Anything more powerful than 12× undoubtedly needs a tripod or stand.  Some people even use them with 10× or 8×.

Another factor to consider is that the more powerful the magnification, the smaller the field of view (FOV).  Now, of course, that can be offset with a bigger objective lens, but there are limits.

A binocular has a very wide field of view but a small objective size.  These are ideal for watching daytime horse races or football/baseball/soccer matches.  and are suitable for watching a play, opera, or other theater-based activity.  and 10× are suited to wildlife watching and general use or viewing concerts from the very cheap seats.  When you get to 10×, 12×, and 16×, you're into Birding, and/or Varmint/Game hunting pursuits.

Which One for Astronomy?

In short, …all of them!  It depends on what you are doing.  If you're looking at the Full Moon, you most certainly do not want 50 mm objective lenses.  That is just painfully bright.  A 7×21 or 10×25 would provide good magnification, be reasonably easy to keep steady, and not be too bright. 

Now, on the other hand, when you are looking at the (unlighted) New Moon, the surface is still visible, even without any sunlight reflecting from it.  A 12×50 would allow you to look at craters and mountains, or study the limbs (edges) because light reflected from Earth provides a surprising amount of light on the “dark” New Moon…

At the other end of the spectrum, a pair of 4×21 or 7×18 would be usable for those people who refuse to believe that meteor showers are best enjoyed without any instrument.  Yes, if you locate the exact radiant point of the meteors (where they all seem to originate), you can see quite a few.  The truth is, however, that you will miss just as many, or more, by confining your observations to a small patch of sky.

Cameras

          Camera apertures can be much larger than the average binocular; you may get a tiny field of view, but remarkable light-gathering capabilities.  You could rival a small telescope!  Lenses are essentially the same in all optical instruments, and the same aperture rules apply.  The single most significant decision you make may simply be which camera you choose.  For some useful tips, take a look at our article [Author’s Note: insert a link to Astrophotography article here] called Astrophotography.

For example, the Digital Single Lens Reflex (DSLR) cameras with mirror locks, or mirrorless (non-reflex) cameras are preferred.  This eliminates the shaking from operating the shutter, or from multiple shots.  

They are also much less expensive than using photographic film.  When you add in the waiting-time-anxiety of getting it developed and returned, just to see if you actually obtained a useful image, it just doesn’t seem worth the hassle.  Besides, digital cameras have surpassed film cameras in many ways, including resolution. 

The most critical choice, irrespective of camera brand, is to record in RAW format and never in JPG/JPEG format.  The latter saves space, but that is because the camera is using "judgment" that was programmed in by some engineer at a far off electronics company who has no idea what you are using your camera for.

It was optimized to take pictures with idealized skin tones or to reflect the hues and tints in a lovely flower.  It was not programmed to take mainly black images with just a few pixels of light here and there.  Never trust an engineer to do the job of a photographer.

Pictures of the Sun

          Could you take a photo of the Sun?  Well, it would destroy the film, and almost certainly damage optics of a digital device, so can it be done?  Only a fool would stare at a solar eclipse without protection, despite all the warnings…because it can do permanent damage to your eyes.  The secret to seeing such an event without danger is to go Old School.

          When Galileo Galilei (1564–1642) first discovered "sunspots," he did it by direct observation, but he didn't go blind as some silly internet stories would have you believe.  He went blind somewhere around age 72, a good two decades after he made his solar observations, and the cause was glaucoma and cataracts.

          He performed all his observations at sunrise and sunset when the sun was still far too dim to do damage.  Later on, he did it by way of a helioscope, invented by Benedetto Castelli (1578-1643).

For you, the best way to observe the Sun is to go to the local dollar store and buy a couple of sheets of Bristol board, which is a relatively heavy colored cardboard.  One must be white.  Place the white sheet on the ground, and with a pin, poke a single smooth hole in the middle of the other sheet.  With the Sun behind you, hold the sheet-with-the-hole in such a way that its shadow falls on the white sheet.

You will notice that an image of the Sun forms as its light passes through the tiny hole you made.  You can change the size of the picture by getting closer or farther away.  When the image is the size you want, take a rough measurement of that distance.  You can now build a wooden frame to hold the sheets that distance apart permanently.  If you enclose the frame, the image of the Sun will appear even brighter, and the details will be seen more easily. 

          If you have a camera handy, you can take all the pictures you want of the image you have created!  Before we had cameras, they would simply put a piece of paper under the image and trace all of the features with a pencil.

The Takeaway

          Artistic photography and solar observation do not require the use of a telescope.  If you want a picture of the Horse Head Nebulae, which is inside the Orion nebula, then you are going to need a telescope and a good camera.

          If you want lunar photographs, or pinwheels of stars spinning overhead, or a record of all the meteors during a shower, a simple camera is all that is necessary.  All of these are things that can be done without hundreds of dollars of investment in a superfluous telescope.

      

    That being said, everyone should take an opportunity to look through a telescope at least once in their life to see what they might be missing.  The odds are that you will want to do it again…because once you start down the Dark Path… forever will it rule your destiny…

 Yoda

Leave a comment

Please note, comments must be approved before they are published