I'm not sure what eyepieces come with the Celestron FirstScope. I have the very similar Orion FunScope, which came with 2 eyepieces: 20mm and 10mm focal length, yielding 15x and 30x respectively. I have found that the 10mm is around the upper limit of what this telescope's optics will support, and would not recommend any eyepiece giving higher magnification. In fact, most of the time, I use only the 20mm because the views are better.
Small telescopes like these are generally not capable of very high magnifications. To get a satisfactory view of the planets you need to spend more than $50. This telescope is fine for what it does, wide field views of the Moon, planets, and large deep sky objects, but simply is not capable of the magnifications (150x to 250x) needed for good planetary views. For that you need at least a 4-inch refractor or a 6-inch reflector.
Telescopes (and binoculars) are, primarily, light-concentrating devices. I get the impression that most people unfamiliar with telescopes think of a telescope as a "microscope pointing upwards". It is no such thing; a microscope's purpose is to magnify the image of a small object, and it uses a "strong" backlight for illuminating the object under the eyepiece. On the other hand, a telescope "funnels" the available light from the object itself (which might be feeble); the amplification of the image comes second, in that respect, so if you amplify an image you're spreading the same light over a wider area. Remember that when buying a telescope from a vendor claiming "large magnifications" (read: "unreasonable expectations").
With that idea of telescope/binoculars as light-funneling-devices in mind, the very first thing I'd suggest (since you're starting out) is that you buy binoculars instead of a telescope. The usually recommended binoculars are 7x50, 8x50 or 10x50 (to the left of the x is the magnification, to the right of the x is the diameter (in milimeters) of the objective, where light goes in). Anything smaller doesn't capture that much light; anything bigger than that becomes too heavy and unwieldy, both for you and for your kid. Since he's still young I'd recommend a lighter 7x50 which is still quite good.
There are several reasons for picking binoculars instead of a telescope.
- They're comparatively less expensive. This is a plus, especially if you remember that most first-time telescope buyers spend about 10-15 minutes with them before putting it in the attic for the rest of their lives (or selling on e-Bay).
- They're much more portable than a telescope; that's a plus. It can also find application when you go out camping for example, because you can carry it in the back pack to watch animal life.
- It's usual for small children to have trouble closing one eye and looking through a telescope's ocular (even though there are attachments which split the light, thus costing more). A binoculars makes it easier for them because they don't have to make extra effort.
- Many first-timers become confused when they pick a telescope because the image on the ocular is inverted; they push the telescope to the right hoping to see something "on the right" and instead the image goes left, they push the telescope up and the image "goes down". There is no such problem with binoculars since it has image-correcting prisms (it takes up a substancial amount of the binoculars' weight).
- When you don't know the night sky (constellations, etc), finding something on the sky without knowing your way arround is a good and fast way to frustration (and throwing the telescope into the attic). If you buy the binoculars and a good guide, it'll be better than spending your budget on the telescope (and no guide).
However, if you insist on buying a telescope, I suggest that you start out with something relatively inexpensive. There are two instruments that I can suggest for a small child.
- Celestron FirstScope.
- Orion FunScope.
I'm suggesting these because they're "tabletop" telescopes, meaning you just have to put them on a flat, level surface: it comes with its own "mount" so that you don't have to spend more money buying an equatorial mount (although there's nothing wrong with that and it's perfectly possible).
You can consider buying a larger telescope when both you and your child find out you want to take this hobby more seriously. These two are also relatively inexpensive and easily manageable. They'll allow you to view the larger features on the Moon, identify satellites around Jupiter, identify Saturn's ring. You won't see much details though, but it's still good for starting up.
If you spend a few good nights with that, you'll gradually want to progress further -- either choosing a telescope or a binoculars. But those are a good compromise between not being sure if you want to take it past one or two tries, or getting used to "what it feels like" before going for something more ambitious.
In any case, I also recommend two more things.
- Get a good sky guide. Example: Turn Left At Orion.
- Look for local astronomy clubs. This is very important if you want to develop your skills and learn. The other members have gone through what you've gone through and will be patient in teaching you and letting you pass the first hurdles.
One final important advice. I don't presume you'd overlook this, but never point and look with a telescope (or binoculars) at the Sun. (Hint: Have you ever burnt ants with a magnifying glass? That's what I'm talking about.) If you're observing at night you should be safe about this (for obvious reasons) but during the daylight you'll have to watch your boy so that he doesn't accidentally look to the Sun (e.g. when spotting an animal on a tree).
Best Answer
I'd recommend getting to know the telescope before adding a bunch of accessories. A few things I'd recommend:
• NightWatch by Terence Dickinson (Firefly). This is by far the best beginner's book on astronomy, and contains an excellent set of star charts for finding objects in the night sky.
• 10x50 binoculars. Useful in themselves, but also excellent to scout a new part of the sky before exploring with the telescope. I use my 10x50s as much as I use my telescope. Orion Scenix 10x50s are excellent, and are currently on sale.
• A good star atlas. My favourite is the Sky & Telescope Pocket Sky Atlas (Sky).
• A red flashlight.
• A solar filter. The best ones are made by Jim Kendrick using Baader AstroSolar film, better optically than Orion's glass filters: http://www.kendrickastro.com/astro/solarfilters.html
• The supplied eyepieces are a good match for this telescope. There isn't much to look at that requires a wider field of view than the 17mm, and the 6mm is about as high as you can go with a 4.5" telescope. Any more magnification than 75x would be "empty magnification." For the same reason, I wouldn't recommend a Barlow. By the way, the "Shorty Plus" is twice as good as the "Shorty"!