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Advice regarding mm

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I am fairly new to gazing. It's currently 5AM, and from 2;30 until 4;30 I have been able to both see mars and saturn. Saturn's rings were visible, but barely. The sky was clear, but the view was very very small. I used my "super 10mm" which came with the scope, whenever I tried to use the "super 25mm wide angle long eye relief"  saturn would only appear as a dot. Therefore,  my personal conclusion would be, if I get a smaller mm, 4mm for example,  I should be able to get a larger view of Saturn's rings? Would love some help and advice.

My telescope is the Skywatcher Mercury 705 AZ3.

So essentially my question is, which lens do I have to buy for me to get a larger view of Saturn.

Thank you kindly in advance.

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Yes the smaller the number theoretically the larger the view. However, other factors affect whether image will show more detail or not... You may have a large faint image or one with no clarity. Also, with the best will in the world, a planet is always going to be smallish, even at higher power. The focal length of the scope will give 50x magnification and 20x magnification. The highest practical magnification for that scope is 140x. I'd try something around a 5mm to give 100x magnification. A 4mm would give 125x magnification so nearing the limit but may still be useable. 

As an aside, my first views of Saturn came at 50x magnification and I saw the rings fine. It was higher in the sky back then in 2008 - a factor that affects clarity of view. 


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In my 8" telescope, I find that a 12mm eyepiece shows much more detail on Jupiter than a 5mm one does. It's a weird concept, as you would think that magnification would show the same detail just bigger. I would go for a 6mm eyepiece if I were you, but be aware that it will still be small, just bigger.

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