My first DIY Telescope. Help!

I am trying to prepare a telescope with the following lens combination. Can someone suggest if it is any good? I am intending to notice the planets and the moon in detail.

Objective: Plano convex - 50cm focal length
Eye-piece: The lens supplier suggested I use a Ramsden's eye-piece for this. Any other suggestions?

Also, would the thickness [diameter] of the objective lens make any difference to the telescope?

Regards
Depp.
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