Eyepiece recommendation for 70mm Refractor

[patomlin76]

Hi

My first proper post at SGL..

I have an ETX-70, with which I have the 25mm, 9mm and 3x barlow lenses. Some are yet to arrive in the post, and in any case it's cloudy so no point going out!

In other sources on the web, I have heard about the maximum magnification that any scope can provide, depending on the focal length and aperture.

My scope is 350mm at f/5, so do I have the best range of eyepieces above? I was wondering about adding a 6mm eyepiece but am not sure what I would realistically gain from that addition.

I do know from previous experience, that I can get great detail on the moon with the 9mm + 3x barlow. Will 6mm + 3x barlow just give me a larger, fuzzier view?

Thanks for the help - just wanting to make sure I have the best eyepieces for my setup (telescope upgrade is definitely a no-go!)

Paul

[John]

The max on your scope will be around 100x as it is a fast (F/5) refractor and the chromatic abberation will limit it's usefulness above that. These F/5 refractors are best used as low to medium power scopes (20x - 60x).

The 9mm eyepiece used with the 3x barlow is giving you 117x. A 6mm eyepiece with a 3x barlow will give you 175x which would be far too much magnification - things will look larger but very fuzzy indeed.

I reckon you will get your best views of the planets at lower magnification than you are using on the Moon - something like 80x - 100x.

[patomlin76]

Thanks!