[Wavytone]

That depends on the focal ratio of your scope and how good the objective is.

The maximum magnification to expect from a refractor is 2X per mm of aperture. So for mine, 200X. With a 700 mm focal length, I'd need a 3.5 mm eyepiece to get that magnification. In practice though the shortest I have is 8mm and the views through this are excellent.

At the other extreme, the lowest useful power is defined by the diameter of the exit pupil your eye can accommodate. I opted for 5mm (I'm not young) and this means the lowest useful magnification is the aperture of the lens divided by the exit pupil - in my case 20X. As before, with a 700mm focal length that means a 35mm focal length eyepiece. The nearest I have is a 30mm Vixen NLVW.

Between max and minimum you will need at least one, maybe two eyepieces (total 3 or 4), so that the ratio of focal lengths from one to the next is about 1:1.5 or 1:2. In my case I chose 8, 13, 22, 30 for this reason.

With my scope, the LVW 42mm eyepiece gives an exit pupil that is too big, so I saw no point in buying it. Conversely, I skipped the 17mm in the LVW series (too close to 13 or 22 mm), and I frankly don't need to push the refractor all the way to see Airy disks - the 8mm provides fine views of the planets at 142X.

Depending on your scope, you could go for say 6, 12, 24 or perhaps 6, 10, 18, 30 depending on what is available in the type you choose.

And yes using a small refractor for a "Rich Field" view with a widefield eypiece (in my case the 22 or 30) is always good for hours, even after 30 years of stargazing.

Lastly when buying really short focal length eyepieces below 15mm, stay away from the ones with really short eyerelief - such as orthos and plossls. Aside from being a pain to use, they are also a ***** to keep clean.

Even if you only buy one really good eyepiece, the long eye relief types (Vixen LV, LVW, Orion Stratus, Baader Hyperion) are well worth the extra $ in the short focal lengths.