Telescope Lenses

[bigdods]

Mods - not sure where to put this so please move as necessary

I have a Celestron nexstar telescope and for the first time last night was able to see jupiter and its moons. I want to increase the image size and clarity and the best bet seems to be a barlow x 2 - Any experts out there care to comment or advise me ? I have 25mm and 9mm eyepices, would a 4mm eyepice have a similar effect to a barlow x 2 ? And if I then add a barlow to the 4mm would that be even better ?

Cheers

[bobfather]

In simple terms the barlow x 2 will do exactly what it says it will do, your image will cover half as much area, it will double the size of objects within the visible space and will halve the image quality (resolution). The amount of information available is determined by the object lenses or mirror. A barlow x 2 only uses the information gathered from the centre 50% of your objective lens and expands that out to fill the image space, therefore image quality reduces because the barlow x 2 uses less of the information entering the telescope than you would see without a barlow x 2 fitted.

Good quality eye pieces should improve quality because most of the loss of quality is due to poor optics. You could get something near what you want by paying for a very high quality x2 eye piece but adding more optics by way of an additional barlow unit is counterproductive.

[bigdods]

cheers, thats pretty much what I thought. I'll go for a high quality 4mm eyepiece rather than the barlow see how I get on. This is purely for viewing planets , I'll stick with the 9 and 25 for stargazing.

This astronomy is worse than running the TVR. Every time I use the telescope I want to get something expensive to improve the experience !