Hey Mick,
Now we are getting somewhere
A 15mm eyepiece will give you 83X, which is not really enough for the planets.
You will need a 5mm EP to push things along to 250X, and then things with the planets will really change. Going any higher may prove tricky if your mount is stiff and jerky, as this makes doing small and fine movements of the scope difficult.
If you would like a recommendation for a very good but inexpensive 5mm EP, consider the TMB Planetary Type ii 5mm. You will find it much easier to use than your 15mm plossl - these TMB's all have the same big eye lens (the lens you look into of the eyepiece), and they all havd the same amount of generous eye relief meaning you don't need to park your cornea on the eye lens to look into it, unlike a 5mm plossl, and they all have a 58° apparent field of view (plossls have only 52°). The 5mm also does an outstanding job in Newts (dobs are Newtonian scopes on a dobsonian mount). For their price, these are outstanding eyepieces:
https://www.ebay.com.au/sch/i.html?_...ce+5mm&_sop=15
Of the 10 individual focal lengths in this range, all are excellent in refractors, SCTs and Maks. In Newts, they all do a good job, with the 7.5mm, 7mm, 5mm, 4mm and 2.5mm being the best performers in Newts. Just avoid the 3.2mm - I have looked through three of these 3.2mm and all have been unusable.
Yes there are other 5mm eyepieces, with a wider apparent field of view, and that are also outstanding in Newts, but for price alone these are really very good. I'm sure other people can recommend other EPs.
I actually have a few of these TMBs in my kit, and the 5mm is one of them too. These $45 TMBs sit beside $450 eyepieces in my kit, and I use them all according to the conditions of the night and the scope I'm using.
Alex.