Moon Photography help needed (OMD)

150 on 4/3 is a bit short for a decent moon shot. You really need 300+mm.

If you already have a 4/3 to M43 adapter, you can pick up the Oly ZD 70-300 for around $200 on the used market. It works very well on the EM5, even AF's quickly.

At F16, you're hitting diffraction limitation and you will get a softer shot. Try F8 or lower. In fact, try a variety of apertures and shutter speeds. Try underexposing, with RAW, and use LR4 to bring the exposure back up.

I used an old MF Nikkor 400 3.5+ 2x TC + EM5 to get this moon shot, uncropped to give you an idea of what 400mm+2x TC does on a 4/3 sensor.