Most die-hard astronomers (or geeks as we're otherwise known) will own a selection of telescopes at any one time, each performing a different role. You'll have the little refractor that's easy to transport and take on holidays, you'll have the larger refractor that gives great views of the moon and planets, you'll have the big boy Dobsonian that lifts the limits of how far you can peer into the cosmos and you may even have a special wide field scope for astrophotography.
It is this diversity that allows a 6x30 finderscope to fill a niche and remain useful even among it's bigger and more powerful cousins.
Before going further allow me to explain a little about the technical aspects of the finderscope before going on to explain where it has it's uses.
Firstly it is made by Celestron which is a good start, Celestron use quality glassses in all their optical systems and the 6x30 is no exception. When gazed through, expect clear and unblemished views, aiding you in tracking down your astronomical quarry.
For reference, the number 6 corresponds to the amount of magnification provided, this number generally doesn't need to be large in a finderscope as it's primary use is in navigation not observation. 30 is the important number, this is the amount of light gathering the system offers over the naked eye, without doubt the higher this number is the more useful the finderscope will be, however this number also has a direct bearing on price so at times a balance may need to be struck.
The finderscope is a stylish metallic blue but Celestron also offer white and black for the vain astronomer. It's just over 6 inches long and around 1.5 inches at it's fattest making it very portable.
A black cross intersects the lens precisely at it's center making a handy X in which to center any celestial object ensuring a high level of accuracy.
As a finderscope it works well but for deep sky work or operating in highly light polluted areas the 30 times light grasp isn't quite enough and perhaps a 50x or higher would be more useful. The 9x30 fills a good gap though, for me my 6x30 sits on top of a large refractor and as such it is ideal for lunar and planetary work. The finderscope is powerful enough to bag even Neptune the faintest planet from my fairly typical suburban skies. It provides me with enough light grasp for solar system observation without the high prices that would come with a more powerful (and frankly redundant) finderscope.
The Celestron 6x30 excels where high power isn't a necessity, striking a perfect balance between performance and price. For lunar and planetary work (as well as one or two of the very brightest deep space objects) or from impeccably dark skies the 6x30 is a must have finder. If you desire more distant fare or are limited in what you can see by the high powered street lights that plague the suburban observer then I'm afraid higher power and more money will be a definite requisite to successful observation. Thankfully Celestron manufacture a good quality 9x50 so if you're used to the Celestron brand you need not stray too far.A 6x50 finder will cost around £25 (£40) expect to pay double for a 9x50, in my opinion both products are well worth the price.
A good finderscope will ensure that frustrations are kept low and to that end there is no sense in skimping on this front, always try to buy the best finderscope you can afford but if this is the best finderscope you can afford you can certainly do a hell of a lot worse, highly recommended.