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Comment by SoulMan | Hacker News Reader

I get this question all the time - "I am want to get started with Astronomy - which telescope should I buy ?"

Its so important to make people realize , one does not need to have telescope right way. A decent pair of binocular (and probably a book with sky charts) is enough to spot the 1st few objects in the sky. If the hunger for celestial objects then one can go for the telescope else there is high chance the telescope will eat dust at home.

The other problem with hastily buy a telescope is that we end up buying a beginners one with low budget which is is usually no better than good binoculars of same power. (magnification and light gathering). It is netter wait and have a decent budget to buy a good telescope later on.

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Another thing I commonly get is (after explaining that decent telescopes have the ability to swap eyepieces (If you're lucky it'll take 2" ones without vignetting)) is which eyepieces will "get the most zoom." People seem to be under the impression that because most objects in the sky are far away, they are also really "small." So if misguided they'll go buy 4mm Kellners with huge coma, have a painful time trying to get their scope aligned on any DSO, strain to see anything because everything looks dim in them, and squint because the eye relief is terrible. If somebody still wants a scope with high magnification because they're into planetary observing it's usually best to stick with a scope with a long focal length that brings it to f/12 or higher, then get some wide-FOV EPs for that.

In english?

You seem to be giving good advice to newbees, but the language is incomprehensible to that audience.

There's a little context involved:

- The magnification you get from a telescope/eyepiece combination is F_t/F_ep, where F_t is the telescope's focal length, and F_ep is the eyepiece's focal length.

- There are different kinds of eyepieces, and not all of them perform equally well on all targets. Broadly, you have "Planetary" targets, which are the planets, and DSOs, or "Deep-Sky Objects". The latter category includes galaxies, nebulae, and the like.

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Essentially, what GP is saying is, "Don't rush into buying equipment, look around and pick the right tool for the job".

There are two problems in Astronomy:

1. Objects are distant so you only have so many photons from them that reach your current location. This means they appear "faint". The solution to that is a large aperture scope which collects more light.

2. Objects still appear relatively small even after collecting more photons. This can be improved somewhat by using an eyepiece to "zoom up" the image.

But just like magnifying a lower resolution image on a computer, the image through your scope gets fuzzy as you blow it up since you are still only collecting so many photons. So a good eyepiece doesn't help as much as beginners think it will.

The equipment that is sold for "this lets you do amazing things" is the worst equipment for general purpose use. In this particular comment, the magnification of a telescope is the ratio of the primary (mirror or lens) focal length divided by the secondary (eyepiece). An entry level scope might include a low magnification 25mm lens and a high magnification 10mm lens, but going down to 4mm will mean that the field of view is tiny making it hard to track objects. Also, higher magnification requires more light, so it will be dim on a small scope, and usually has a more limited range of eye relief, in other words, how carefully you have to move your head to just the right spot to see through it.

Kellner, EP: I think these are kinds of eyepieces, defined by the stacking of convex and concave lenses. DSO: Deep space object. FOV: field of view 2": the larger of two standard eyepiece form factors

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