Astronomy

Choosing an Eyepiece



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Thinking of purchasing an eyepiece for that significant stargazer in your life? Well you couldn't have picked a better time to buy as the eyepiece market is bursting with quality made lenses at a fraction of what they used to cost. The most important question to ask yourself is what kind of observer is the person receiving the gift.

Do they exclusively observe objects within the solar system? Do they go in search of faint and elusive deep space objects like nebulae and galaxies? Or do they dabble in both? These questions amongst others can make the choice of eyepiece a confusing one, luckily these days there is a type of eyepiece for everyone, all you need to know is what to look for...

Plossl Power.

Let's start off with the best all rounder, perfect if you're not exactly sure what your friend or loved one likes to observe. Whatever that is there's a good chance they'll benefit from a good quality plossl. The secret of the plossls success is that it uses the least amount of lenses in it's design usually only 4 but sometimes 5 bits of glass are used. It's usually true to say in astronomy that the fewer lens elements you use the sharper the image will be.


Pros

.Plossls are amongst the cheapest eyepieces available

.They are a very diverse eyepiece that work incredibly well on a wide range of astronomical objects

.They are common meaning you won't have to scour the earth to get hold of one at a good price


Cons

.Only using 4 or 5 lenses means the plossl does not have a staggeringly wide field of view, 50-55 degrees is to be expected in the large majority of plossls



Plossls can be considered the workhorses of the eyepiece world, excellent examples can be found within a price range running from $30 right the way up to around $500. The average person will probably be looking to buy in the lower part of that range, some of the most pleasing plossls can be found for less than $100.


Planetary 'Pieces.

The most important single aspect of a good planetary eyepiece is a wide field of view. On an unmotorised scope it can become frustrating seeing your carefully positioned planet fly out of your field of view at a terrific pace. The wider your field of view the less time you have to spend fumbling with your telescope trying to recenter your target. Some astronomers say that a wider field allows you to actually see more detail in an object because it frees your mind from the boring repetitive process of constantly nudging your scope and allows you to focus 100% of your brain on pulling out fine details.

Pros

.Wide fields mean less fussing with readjustments

.Very good for studying the entirety of the lunar surface all at once

Cons

.Heavier than a similar non wide field eyepiece, so may cause your telescope to become unbalanced when swapping with lighter eyepieces

.Very large in size, due to the use of up to 4 extra lenses over a standard field eyepiece, can be important when portability is an issue

.Some astronomers find the extra lenses used can deteriorate image quality


Thankfully due to recent advances in glass quality it is possible to buy wide field eyepieces on a budget so you don't have to be flash with your cash to get a good eyepiece with a field of view over 80 degrees. If money is not such an issue then the Televue Ethos might be what you're looking for, it carries a hefty $800 price tag but for your money you get a whopping 110 degrees of unadulterated quality. For those who are on a budget then Williams Optics do a very satisfying array of wide fielders starting at around $150


Galaxy Hunters.


Finally, the deep space eyepieces. There is only one word that needs to be considered when choosing an excellent eyepiece for exploring the very depths of the cosmos and that word is contrast. Many objects outside the solar system are faint...really faint. So the issue is no longer about field of view but about how to spot an eyepiece that will squeeze every last bit of contrast out of those faint and fuzzy wisps. The best deep space eyepieces will have had the edges of their lenses blackened with a good quality matte black paint. They should also have their lens elements coated, a perfect way to check for this is to simply hold the eyepiece up to the light, what you will hope to see is an even green shine across the lenses surface.

For a great deep space eyepiece, pros and cons are not really applicable because a quality deep space eyepiece is not restricted to a single type or design. The only stipulations required are that the lens is multi coated and all of the internal elements of the eyepiece are coated in a dark matte paint, both these pieces of information will be printed on the box, other than that the worlds your oyster. Most Astronomers would recommend an eyepiece of low focal length, around 10-25mm. The more magnification (higher focal length) the dimmer an object will become, when your primary targets are very dim to begin with you'll want to try and maximise their brightness. 



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